.\" and System V IPC (as well as various other) additions from
.\" Michael Kerrisk <mtk.manpages@gmail.com>
.\"
+.\" %%%LICENSE_START(GPLv2+_DOC_FULL)
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
-.\" License along with this manual; if not, write to the Free
-.\" Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111,
-.\" USA.
+.\" License along with this manual; if not, see
+.\" <http://www.gnu.org/licenses/>.
+.\" %%%LICENSE_END
.\"
.\" Modified 1995-05-17 by faith@cs.unc.edu
.\" Minor changes by aeb and Marty Leisner (leisner@sdsp.mc.xerox.com).
.\" to see what information could be imported from that file
.\" into this file.
.\"
-.TH PROC 5 2010-10-30 "Linux" "Linux Programmer's Manual"
+.TH PROC 5 2014-05-28 "Linux" "Linux Programmer's Manual"
.SH NAME
-proc \- process information pseudo-file system
+proc \- process information pseudo-filesystem
.SH DESCRIPTION
The
.I proc
-file system is a pseudo-file system which is used as an interface to
+filesystem is a pseudo-filesystem which provides an interface to
kernel data structures.
It is commonly mounted at
.IR /proc .
Most of it is read-only, but some files allow kernel variables to be
changed.
.LP
-The following outline gives a quick tour through the
+The following list describes many of the files and directories under the
.I /proc
hierarchy.
.PD 1
The format is one \fIunsigned long\fP ID
plus one \fIunsigned long\fP value for each entry.
The last entry contains two zeros.
-.\" FIXME Describe /proc/[pid]/cgroup and
-.\" /proc/[pid]/task/[tid]/cgroup
-.\" Info in Documentation/cgroups.txt
-.\" Added in 2.6.24
-.\" CONFIG_CGROUPS
+.TP
+.IR /proc/[pid]/cgroup " (since Linux 2.6.24)"
+.\" Info in Documentation/cgroups/cgroups.txt
+This file describes control groups to which the process/task belongs.
+For each cgroup hierarchy there is one entry containing
+colon-separated fields of the form:
+.nf
+.ft CW
+
+ 5:cpuacct,cpu,cpuset:/daemons
+.ft
+.fi
+.IP
+The colon-separated fields are, from left to right:
+.RS 11
+.IP 1. 3
+hierarchy ID number
+.IP 2.
+set of subsystems bound to the hierarchy
+.IP 3.
+control group in the hierarchy to which the process belongs
+.RE
+.IP
+This file is present only if the
+.B CONFIG_CGROUPS
+kernel configuration option is enabled.
+.TP
+.IR /proc/[pid]/clear_refs " (since Linux 2.6.22)"
+.\" commit b813e931b4c8235bb42e301096ea97dbdee3e8fe (2.6.22)
+.\" commit 398499d5f3613c47f2143b8c54a04efb5d7a6da9 (2.6.32)
+.\" commit 040fa02077de01c7e08fa75be6125e4ca5636011 (3.11)
.\"
-.\" FIXME Describe /proc/[pid]/clear_refs
-.\" Added in 2.6.22
.\" "Clears page referenced bits shown in smaps output"
-.\" write-only
-.\" CONFIG_PROC_PAGE_MONITOR
+.\" write-only, writable only by the owner of the process
+
+This is a write-only file, writable only by owner of the process.
+
+The following values may be written to the file:
+.RS
+.TP
+1 (since Linux 2.6.22)
+.\" Internally: CLEAR_REFS_ALL
+Reset the PG_Referenced and ACCESSED/YOUNG
+bits for all the pages associated with the process.
+(Before kernel 2.6.32, writing any nonzero value to this file
+had this effect.)
+.TP
+2 (since Linux 2.6.32)
+.\" Internally: CLEAR_REFS_ANON
+Reset the PG_Referenced and ACCESSED/YOUNG
+bits for all anonymous pages associated with the process.
+.TP
+3 (since Linux 2.6.32)
+.\" Internally: CLEAR_REFS_MAPPED
+Reset the PG_Referenced and ACCESSED/YOUNG
+bits for all file-mapped pages associated with the process.
+.RE
+.IP
+Clearing the PG_Referenced and ACCESSED/YOUNG bits provides a method
+to measure approximately how much memory a process is using.
+One first inspects the values in the "Referenced" fields
+for the VMAs shown in
+.IR /proc/[pid]/smaps
+to get an idea of the memory footprint of the
+process.
+One then clears the PG_Referenced and ACCESSED/YOUNG bits
+and, after some measured time interval,
+once again inspects the values in the "Referenced" fields
+to get an idea of the change in memory footprint of the
+process during the measured interval.
+If one is interested only in inspecting the selected mapping types,
+then the value 2 or 3 can be used instead of 1.
+
+A further value can be written to affect a different bit:
+.RS
+.TP
+4 (since Linux 3.11)
+Clear the soft-dirty bit for all the pages associated with the process.
+.\" Internally: CLEAR_REFS_SOFT_DIRTY
+This is used (in conjunction with
+.IR /proc/[pid]/pagemap )
+by the check-point restore system to discover which pages of a process
+have been dirtied since the file
+.IR /proc/[pid]/clear_refs
+was written to.
+.RE
+.IP
+Writing any value to
+.IR /proc/[pid]/clear_refs
+other than those listed above has no effect.
+
+The
+.IR /proc/[pid]/clear_refs
+file is present only if the
+.B CONFIG_PROC_PAGE_MONITOR
+kernel configuration option is enabled.
.TP
.I /proc/[pid]/cmdline
This holds the complete command line for the process,
.nf
.ft CW
-.RB "$" " (cat /proc/1/environ; echo) | tr \(aq\e000\(aq \(aq\en\(aq"
+.RB "$" " strings /proc/1/environ"
.fi
.ft P
.in
.I \-inum
option can be used to locate the file.
.TP
-.I /proc/[pid]/fd
+.I /proc/[pid]/fd/
This is a subdirectory containing one entry for each file which the
process has open, named by its file descriptor, and which is a
symbolic link to the actual file.
-Thus, 0 is standard input, 1 standard output, 2 standard error, etc.
+Thus, 0 is standard input, 1 standard output, 2 standard error, and so on.
-.\" The following was still true as at kernel 2.6.13
+For file descriptors for pipes and sockets,
+the entries will be symbolic links whose content is the
+file type with the inode.
+A
+.BR readlink (2)
+call on this file returns a string in the format:
+
+ type:[inode]
+
+For example,
+.I socket:[2248868]
+will be a socket and its inode is 2248868.
+For sockets, that inode can be used to find more information
+in one of the files under
+.IR /proc/net/ .
+
+For file descriptors that have no corresponding inode
+(e.g., file descriptors produced by
+.BR epoll_create (2),
+.BR eventfd (2),
+.BR inotify_init (2),
+.BR signalfd (2),
+and
+.BR timerfd (2)),
+the entry will be a symbolic link with contents of the form
+
+ anon_inode:<file-type>
+
+In some cases, the
+.I file-type
+is surrounded by square brackets.
+
+For example, an epoll file descriptor will have a symbolic link
+whose content is the string
+.IR "anon_inode:[eventpoll]" .
+
+.\"The following was still true as at kernel 2.6.13
In a multithreaded process, the contents of this directory
are not available if the main thread has already terminated
(typically by calling
.BR open (2)).
The files in this directory are readable only by the owner of the process.
-.\" FIXME document /proc/[pid]/io
-.\" .TP
-.\" .IR /proc/[pid]/io " (since kernel 2.6.20)"
+.\" FIXME
+.\" Certain file types include additional info; see
+.\" Documentation/filesystems/proc.txt
+.\"
+.\" Especially interesting is this:
+.\"
+.\" commit ab49bdecc3ebb46ab661f5f05d5c5ea9606406c6
+.\" Author: Cyrill Gorcunov <gorcunov@openvz.org>
+.\" Date: Mon Dec 17 16:05:06 2012 -0800
+.\"
+.\" Basically, the /proc/PID/fdinfo/ entry for an inotify FD
+.\" includes the file handles for all watched FDs
+.\"
+.TP
+.IR /proc/[pid]/io " (since kernel 2.6.20)"
+.\" commit 7c3ab7381e79dfc7db14a67c6f4f3285664e1ec2
+This file contains I/O statistics for the process, for example:
+.in +4n
+.nf
+
+.RB "#" " cat /proc/3828/io"
+rchar: 323934931
+wchar: 323929600
+syscr: 632687
+syscw: 632675
+read_bytes: 0
+write_bytes: 323932160
+cancelled_write_bytes: 0
+.fi
+.in
+
+The fields are as follows:
+.RS
+.TP
+.IR rchar ": characters read"
+The number of bytes which this task has caused to be read from storage.
+This is simply the sum of bytes which this process passed to
+.BR read (2)
+and similar system calls.
+It includes things such as terminal I/O and
+is unaffected by whether or not actual
+physical disk I/O was required (the read might have been satisfied from
+pagecache).
+.TP
+.IR wchar ": characters written"
+The number of bytes which this task has caused, or shall cause to be written
+to disk.
+Similar caveats apply here as with
+.IR rchar .
+.TP
+.IR syscr ": read syscalls"
+Attempt to count the number of read I/O operations\(emthat is,
+system calls such as
+.BR read (2)
+and
+.BR pread (2).
+.TP
+.IR syscw ": write syscalls"
+Attempt to count the number of write I/O operations\(emthat is,
+system calls such as
+.BR write (2)
+and
+.BR pwrite (2).
+.TP
+.IR read_bytes ": bytes read"
+Attempt to count the number of bytes which this process really did cause to
+be fetched from the storage layer.
+This is accurate for block-backed filesystems.
+.TP
+.IR write_bytes ": bytes written"
+Attempt to count the number of bytes which this process caused to be sent to
+the storage layer.
+.TP
+.IR cancelled_write_bytes :
+The big inaccuracy here is truncate.
+If a process writes 1MB to a file and then deletes the file,
+it will in fact perform no writeout.
+But it will have been accounted as having caused 1MB of write.
+In other words: this field represents the number of bytes which this process
+caused to not happen, by truncating pagecache.
+A task can cause "negative" I/O too.
+If this task truncates some dirty pagecache,
+some I/O which another task has been accounted for
+(in its
+.IR write_bytes )
+will not be happening.
+.RE
+.IP
+.IR Note :
+In the current implementation, things are a bit racy on 32-bit systems:
+if process A reads process B's
+.I /proc/[pid]/io
+while process B is updating one of these 64-bit counters,
+process A could see an intermediate result.
.TP
.IR /proc/[pid]/limits " (since kernel 2.6.24)"
This file displays the soft limit, hard limit, and units of measurement
for each of the process's resource limits (see
.BR getrlimit (2)).
-The file is protected to only allow reading by the real UID of the process.
+Up to and including Linux 2.6.35,
+this file is protected to allow reading only by the real UID of the process.
+Since Linux 2.6.36,
+.\" commit 3036e7b490bf7878c6dae952eec5fb87b1106589
+this file is readable by all users on the system.
+.TP
+.IR /proc/[pid]/map_files/ " (since kernel 3.3)
+.\" commit 640708a2cff7f81e246243b0073c66e6ece7e53e
+This subdirectory contains entries corresponding to memory-mapped
+files (see
+.BR mmap (2)).
+Entries are named by memory region start and end
+address pair (expressed as hexadecimal numbers),
+and are symbolic links to the mapped files themselves.
+Here is an example, with the output wrapped and reformatted to fit on an 80-column display:
+.in +4n
+.nf
+
+.RB "$" " ls -l /proc/self/map_files/"
+lr\-\-\-\-\-\-\-\-. 1 root root 64 Apr 16 21:31
+ 3252e00000\-3252e20000 \-> /usr/lib64/ld-2.15.so
+\&...
+.fi
+.in
+
+Although these entries are present for memory regions that were
+mapped with the
+.BR MAP_FILE
+flag, the way anonymous shared memory (regions created with the
+.B MAP_ANON | MAP_SHARED
+flags)
+is implemented in Linux
+means that such regions also appear on this directory.
+Here is an example where the target file is the deleted
+.I /dev/zero
+one:
+.in +4n
+.nf
+
+.RB
+lrw\-\-\-\-\-\-\-. 1 root root 64 Apr 16 21:33
+ 7fc075d2f000\-7fc075e6f000 \-> /dev/zero (deleted)
+.fi
+.in
+
+This directory appears only if the
+.B CONFIG_CHECKPOINT_RESTORE
+kernel configuration option is enabled.
.TP
.I /proc/[pid]/maps
A file containing the currently mapped memory regions and their access
permissions.
+See
+.BR mmap (2)
+for some further information about memory mappings.
-The format is:
+The format of the file is:
+.in -7n
.nf
.ft CW
-address perms offset dev inode pathname
-08048000-08056000 r-xp 00000000 03:0c 64593 /usr/sbin/gpm
-08056000-08058000 rw-p 0000d000 03:0c 64593 /usr/sbin/gpm
-08058000-0805b000 rwxp 00000000 00:00 0
-40000000-40013000 r-xp 00000000 03:0c 4165 /lib/ld-2.2.4.so
-40013000-40015000 rw-p 00012000 03:0c 4165 /lib/ld-2.2.4.so
-4001f000-40135000 r-xp 00000000 03:0c 45494 /lib/libc-2.2.4.so
-40135000-4013e000 rw-p 00115000 03:0c 45494 /lib/libc-2.2.4.so
-4013e000-40142000 rw-p 00000000 00:00 0
-bffff000-c0000000 rwxp 00000000 00:00 0
.ft
+.I "address perms offset dev inode pathname"
+00400000-00452000 r-xp 00000000 08:02 173521 /usr/bin/dbus-daemon
+00651000-00652000 r--p 00051000 08:02 173521 /usr/bin/dbus-daemon
+00652000-00655000 rw-p 00052000 08:02 173521 /usr/bin/dbus-daemon
+00e03000-00e24000 rw-p 00000000 00:00 0 [heap]
+00e24000-011f7000 rw-p 00000000 00:00 0 [heap]
+\&...
+35b1800000-35b1820000 r-xp 00000000 08:02 135522 /usr/lib64/ld-2.15.so
+35b1a1f000-35b1a20000 r--p 0001f000 08:02 135522 /usr/lib64/ld-2.15.so
+35b1a20000-35b1a21000 rw-p 00020000 08:02 135522 /usr/lib64/ld-2.15.so
+35b1a21000-35b1a22000 rw-p 00000000 00:00 0
+35b1c00000-35b1dac000 r-xp 00000000 08:02 135870 /usr/lib64/libc-2.15.so
+35b1dac000-35b1fac000 ---p 001ac000 08:02 135870 /usr/lib64/libc-2.15.so
+35b1fac000-35b1fb0000 r--p 001ac000 08:02 135870 /usr/lib64/libc-2.15.so
+35b1fb0000-35b1fb2000 rw-p 001b0000 08:02 135870 /usr/lib64/libc-2.15.so
+\&...
+f2c6ff8c000-7f2c7078c000 rw-p 00000000 00:00 0 [stack:986]
+\&...
+7fffb2c0d000-7fffb2c2e000 rw-p 00000000 00:00 0 [stack]
+7fffb2d48000-7fffb2d49000 r-xp 00000000 00:00 0 [vdso]
.fi
+.in
-where "address" is the address space in the process that it occupies,
-"perms" is a set of permissions:
+The
+.I address
+field is the address space in the process that the mapping occupies.
+The
+.I perms
+field is a set of permissions:
.nf
.in +5
.fi
.in
-"offset" is the offset into the file/whatever, "dev" is the device
-(major:minor), and "inode" is the inode on that device.
+The
+.I offset
+field is the offset into the file/whatever;
+.I dev
+is the device
+(major:minor);
+.I inode
+is the inode on that device.
0 indicates that no inode is associated with the memory region,
-as the case would be with BSS (uninitialized data).
+as would be the case with BSS (uninitialized data).
+
+The
+.I pathname
+field will usually be the file that is backing the mapping.
+For ELF files,
+you can easily coordinate with the
+.I offset
+field by looking at the
+Offset field in the ELF program headers
+.RI ( "readelf\ \-l" ).
+
+There are additional helpful pseudo-paths:
+.RS 12
+.TP
+.IR [stack]
+The initial process's (also known as the main thread's) stack.
+.TP
+.IR [stack:<tid>] " (since Linux 3.4)"
+.\" commit b76437579d1344b612cf1851ae610c636cec7db0
+A thread's stack (where the
+.IR <tid>
+is a thread ID).
+It corresponds to the
+.IR /proc/[pid]/task/[tid]/
+path.
+.TP
+.IR [vdso]
+The virtual dynamically linked shared object.
+.TP
+.IR [heap]
+The process's heap.
+.in
+.RE
+.IP
+If the
+.I pathname
+field is blank,
+this is an anonymous mapping as obtained via the
+.BR mmap (2)
+function.
+There is no easy way to coordinate this back to a process's source,
+short of running it through
+.BR gdb (1),
+.BR strace (1),
+or similar.
Under Linux 2.0 there is no field giving pathname.
.TP
(3)
major:minor: value of
.I st_dev
-for files on file system (see
+for files on filesystem (see
.BR stat (2)).
.TP
(4)
-root: root of the mount within the file system.
+root: root of the mount within the filesystem.
.TP
(5)
mount point: mount point relative to the process's root.
separator: marks the end of the optional fields.
.TP
(9)
-file system type: name of file system in the form "type[.subtype]".
+filesystem type: name of filesystem in the form "type[.subtype]".
.TP
(10)
-mount source: file system-specific information or "none".
+mount source: filesystem-specific information or "none".
.TP
(11)
-super options: per-super block options.
+super options: per-superblock options.
.RE
.IP
Parsers should ignore all unrecognized optional fields.
For more information on mount propagation see:
.I Documentation/filesystems/sharedsubtree.txt
-in the kernel source tree.
+in the Linux kernel source tree.
.TP
.IR /proc/[pid]/mounts " (since Linux 2.4.19)"
-This is a list of all the file systems currently mounted in the
+This is a list of all the filesystems currently mounted in the
process's mount namespace.
The format of this file is documented in
.BR fstab (5).
Since kernel version 2.6.15, this file is pollable:
after opening the file for reading, a change in this file
-(i.e., a file system mount or unmount) causes
+(i.e., a filesystem mount or unmount) causes
.BR select (2)
to mark the file descriptor as readable, and
.BR poll (2)
(or "nodevice" if there is no corresponding device).
.TP
(2)
-The mount point within the file system tree.
+The mount point within the filesystem tree.
.TP
(3)
-The file system type.
+The filesystem type.
.TP
(4)
Optional statistics and configuration information.
-Currently (as at Linux 2.6.26), only NFS file systems export
+Currently (as at Linux 2.6.26), only NFS filesystems export
information via this field.
.RE
.IP
-This file is only readable by the owner of the process.
+This file is readable only by the owner of the process.
+.TP
+.IR /proc/[pid]/ns/ " (since Linux 3.0)"
+.\" See commit 6b4e306aa3dc94a0545eb9279475b1ab6209a31f
+This is a subdirectory containing one entry for each namespace that
+supports being manipulated by
+.BR setns (2).
+For information about namespaces, see
+.BR clone (2).
+.TP
+.IR /proc/[pid]/ns/ipc " (since Linux 3.0)"
+Bind mounting this file (see
+.BR mount (2))
+to somewhere else in the filesystem keeps
+the IPC namespace of the process specified by
+.I pid
+alive even if all processes currently in the namespace terminate.
+
+Opening this file returns a file handle for the IPC namespace
+of the process specified by
+.IR pid .
+As long as this file descriptor remains open,
+the IPC namespace will remain alive,
+even if all processes in the namespace terminate.
+The file descriptor can be passed to
+.BR setns (2).
+.TP
+.IR /proc/[pid]/ns/net " (since Linux 3.0)"
+Bind mounting this file (see
+.BR mount (2))
+to somewhere else in the filesystem keeps
+the network namespace of the process specified by
+.I pid
+alive even if all processes in the namespace terminate.
+
+Opening this file returns a file handle for the network namespace
+of the process specified by
+.IR pid .
+As long as this file descriptor remains open,
+the network namespace will remain alive,
+even if all processes in the namespace terminate.
+The file descriptor can be passed to
+.BR setns (2).
+.TP
+.IR /proc/[pid]/ns/uts " (since Linux 3.0)"
+Bind mounting this file (see
+.BR mount (2))
+to somewhere else in the filesystem keeps
+the UTS namespace of the process specified by
+.I pid
+alive even if all processes currently in the namespace terminate.
+
+Opening this file returns a file handle for the UTS namespace
+of the process specified by
+.IR pid .
+As long as this file descriptor remains open,
+the UTS namespace will remain alive,
+even if all processes in the namespace terminate.
+The file descriptor can be passed to
+.BR setns (2).
.TP
.IR /proc/[pid]/numa_maps " (since Linux 2.6.14)"
See
A positive score increases the likelihood of this
process being killed by the OOM-killer;
a negative score decreases the likelihood.
+.IP
The default value for this file is 0;
a new process inherits its parent's
.I oom_adj
A process must be privileged
.RB ( CAP_SYS_RESOURCE )
to update this file.
+.IP
+Since Linux 2.6.36, use of this file is deprecated in favor of
+.IR /proc/[pid]/oom_score_adj .
.TP
.IR /proc/[pid]/oom_score " (since Linux 2.6.11)"
.\" See mm/oom_kill.c::badness() in the 2.6.25 sources
.IP
The
.I oom_score
-also reflects the bit-shift adjustment specified by the
+also reflects the adjustment specified by the
+.I oom_score_adj
+or
.I oom_adj
setting for the process.
+.TP
+.IR /proc/[pid]/oom_score_adj " (since Linux 2.6.36)"
+.\" Text taken from 3.7 Documentation/filesystems/proc.txt
+This file can be used to adjust the badness heuristic used to select which
+process gets killed in out-of-memory conditions.
+
+The badness heuristic assigns a value to each candidate task ranging from 0
+(never kill) to 1000 (always kill) to determine which process is targeted.
+The units are roughly a proportion along that range of
+allowed memory the process may allocate from,
+based on an estimation of its current memory and swap use.
+For example, if a task is using all allowed memory,
+its badness score will be 1000.
+If it is using half of its allowed memory, its score will be 500.
+
+There is an additional factor included in the badness score: root
+processes are given 3% extra memory over other tasks.
+
+The amount of "allowed" memory depends on the context
+in which the OOM-killer was called.
+If it is due to the memory assigned to the allocating task's cpuset
+being exhausted,
+the allowed memory represents the set of mems assigned to that
+cpuset (see
+.BR cpuset (7)).
+If it is due to a mempolicy's node(s) being exhausted,
+the allowed memory represents the set of mempolicy nodes.
+If it is due to a memory limit (or swap limit) being reached,
+the allowed memory is that configured limit.
+Finally, if it is due to the entire system being out of memory, the
+allowed memory represents all allocatable resources.
+
+The value of
+.I oom_score_adj
+is added to the badness score before it
+is used to determine which task to kill.
+Acceptable values range from \-1000
+(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).
+This allows user space to control the preference for OOM-killing,
+ranging from always preferring a certain
+task or completely disabling it from OOM-killing.
+The lowest possible value, \-1000, is
+equivalent to disabling OOM-killing entirely for that task,
+since it will always report a badness score of 0.
+
+Consequently, it is very simple for user space to define
+the amount of memory to consider for each task.
+Setting a
+.I oom_score_adj
+value of +500, for example,
+is roughly equivalent to allowing the remainder of tasks sharing the
+same system, cpuset, mempolicy, or memory controller resources
+to use at least 50% more memory.
+A value of \-500, on the other hand, would be roughly
+equivalent to discounting 50% of the task's
+allowed memory from being considered as scoring against the task.
+
+For backward compatibility with previous kernels,
+.I /proc/[pid]/oom_adj
+can still be used to tune the badness score.
+Its value is
+scaled linearly with
+.IR oom_score_adj .
+
+Writing to
+.IR /proc/[pid]/oom_score_adj
+or
+.IR /proc/[pid]/oom_adj
+will change the other with its scaled value.
.\" FIXME Describe /proc/[pid]/pagemap
.\" Added in 2.6.25
.\" CONFIG_PROC_PAGE_MONITOR
.TP
.I /proc/[pid]/root
UNIX and Linux support the idea of a per-process root of the
-file system, set by the
+filesystem, set by the
.BR chroot (2)
system call.
This file is a symbolic link that points to the process's
-root directory, and behaves as exe, fd/*, etc. do.
+root directory, and behaves in the same way as
+.IR exe ,
+and
+.IR fd/* .
.\" The following was still true as at kernel 2.6.13
In a multithreaded process, the contents of this symbolic link
.\" CONFIG_SCHEDSTATS
.TP
.IR /proc/[pid]/smaps " (since Linux 2.6.14)"
-.\" CONFIG_PROC_PAGE_MONITOR
This file shows memory consumption for each of the process's mappings.
-For each of mappings there is a series of lines such as the following:
+For each mapping there is a series of lines such as the following:
.in +4n
.nf
-08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
-Size: 464 kB
-Rss: 424 kB
-Shared_Clean: 424 kB
-Shared_Dirty: 0 kB
-Private_Clean: 0 kB
-Private_Dirty: 0 kB
+00400000-0048a000 r-xp 00000000 fd:03 960637 /bin/bash
+Size: 552 kB
+Rss: 460 kB
+Pss: 100 kB
+Shared_Clean: 452 kB
+Shared_Dirty: 0 kB
+Private_Clean: 8 kB
+Private_Dirty: 0 kB
+Referenced: 460 kB
+Anonymous: 0 kB
+AnonHugePages: 0 kB
+Swap: 0 kB
+KernelPageSize: 4 kB
+MMUPageSize: 4 kB
+Locked: 0 kB
.fi
.in
for the mapping in
.IR /proc/[pid]/maps .
The remaining lines show the size of the mapping,
-the amount of the mapping that is currently resident in RAM,
+the amount of the mapping that is currently resident in RAM ("Rss"),
+the process' proportional share of this mapping ("Pss"),
the number of clean and dirty shared pages in the mapping,
and the number of clean and dirty private pages in the mapping.
+"Referenced" indicates the amount of memory currently marked as
+referenced or accessed.
+"Anonymous" shows the amount of memory
+that does not belong to any file.
+"Swap" shows how much
+would-be-anonymous memory is also used, but out on swap.
+
+The "KernelPageSize" entry is the page size used by the kernel to back a VMA.
+This matches the size used by the MMU in the majority of cases.
+However, one counter-example occurs on PPC64 kernels
+whereby a kernel using 64K as a base page size may still use 4K
+pages for the MMU on older processors.
+To distinguish, this
+patch reports "MMUPageSize" as the page size used by the MMU.
+
+The "Locked" indicates whether the mapping is locked in memory
+or not.
+
+"VmFlags" field represents the kernel flags associated with
+the particular virtual memory area in two letter encoded manner.
+The codes are the following:
+
+ rd - readable
+ wr - writable
+ ex - executable
+ sh - shared
+ mr - may read
+ mw - may write
+ me - may execute
+ ms - may share
+ gd - stack segment grows down
+ pf - pure PFN range
+ dw - disabled write to the mapped file
+ lo - pages are locked in memory
+ io - memory mapped I/O area
+ sr - sequential read advise provided
+ rr - random read advise provided
+ dc - do not copy area on fork
+ de - do not expand area on remapping
+ ac - area is accountable
+ nr - swap space is not reserved for the area
+ ht - area uses huge tlb pages
+ nl - non-linear mapping
+ ar - architecture specific flag
+ dd - do not include area into core dump
+ sd - soft-dirty flag
+ mm - mixed map area
+ hg - huge page advise flag
+ nh - no-huge page advise flag
+ mg - mergeable advise flag
-This file is only present if the
-.B CONFIG_MMU
-kernel configuration
-option is enabled.
+The
+.IR /proc/[pid]/smaps
+file is present only if the
+.B CONFIG_PROC_PAGE_MONITOR
+kernel configuration option is enabled.
+.TP
+.IR /proc/[pid]/stack " (since Linux 2.6.29)"
+.\" 2ec220e27f5040aec1e88901c1b6ea3d135787ad
+This file provides a symbolic trace of the function calls in this
+process's kernel stack.
+This file is provided only if the kernel was built with the
+.B CONFIG_STACKTRACE
+configuration option.
.TP
.I /proc/[pid]/stat
Status information about the process.
.RS
.TP 12
\fIpid\fP %d
-The process ID.
+(1) The process ID.
.TP
\fIcomm\fP %s
-The filename of the executable, in parentheses.
+(2) The filename of the executable, in parentheses.
This is visible whether or not the executable is swapped out.
.TP
\fIstate\fP %c
-One character from the string "RSDZTW" where R is running, S is
+(3) One character from the string "RSDZTW" where R is running, S is
sleeping in an interruptible wait, D is waiting in uninterruptible
disk sleep, Z is zombie, T is traced or stopped (on a signal),
and W is paging.
.TP
\fIppid\fP %d
-The PID of the parent.
+(4) The PID of the parent.
.TP
\fIpgrp\fP %d
-The process group ID of the process.
+(5) The process group ID of the process.
.TP
\fIsession\fP %d
-The session ID of the process.
+(6) The session ID of the process.
.TP
\fItty_nr\fP %d
-The controlling terminal of the process.
+(7) The controlling terminal of the process.
(The minor device number is contained in the combination of bits
31 to 20 and 7 to 0;
the major device number is in bits 15 to 8.)
.TP
\fItpgid\fP %d
.\" This field and following, up to and including wchan added 0.99.1
-The ID of the foreground process group of the controlling
+(8) The ID of the foreground process group of the controlling
terminal of the process.
.TP
\fIflags\fP %u (%lu before Linux 2.6.22)
-The kernel flags word of the process.
+(9) The kernel flags word of the process.
For bit meanings,
-see the PF_* defines in
-.IR <linux/sched.h> .
+see the PF_* defines in the Linux kernel source file
+.IR include/linux/sched.h .
Details depend on the kernel version.
.TP
\fIminflt\fP %lu
-The number of minor faults the process has made which have not
+(10) The number of minor faults the process has made which have not
required loading a memory page from disk.
.TP
-.\" field 11
\fIcminflt\fP %lu
-The number of minor faults that the process's
+(11) The number of minor faults that the process's
waited-for children have made.
.TP
\fImajflt\fP %lu
-The number of major faults the process has made which have
+(12) The number of major faults the process has made which have
required loading a memory page from disk.
.TP
\fIcmajflt\fP %lu
-The number of major faults that the process's
+(13) The number of major faults that the process's
waited-for children have made.
.TP
\fIutime\fP %lu
-Amount of time that this process has been scheduled in user mode,
+(14) Amount of time that this process has been scheduled in user mode,
measured in clock ticks (divide by
-.IR sysconf(_SC_CLK_TCK) .
+.IR sysconf(_SC_CLK_TCK) ).
This includes guest time, \fIguest_time\fP
(time spent running a virtual CPU, see below),
so that applications that are not aware of the guest time field
do not lose that time from their calculations.
.TP
\fIstime\fP %lu
-Amount of time that this process has been scheduled in kernel mode,
+(15) Amount of time that this process has been scheduled in kernel mode,
measured in clock ticks (divide by
-.IR sysconf(_SC_CLK_TCK) .
+.IR sysconf(_SC_CLK_TCK) ).
.TP
\fIcutime\fP %ld
-Amount of time that this process's
+(16) Amount of time that this process's
waited-for children have been scheduled in user mode,
measured in clock ticks (divide by
-.IR sysconf(_SC_CLK_TCK) .
+.IR sysconf(_SC_CLK_TCK) ).
(See also
.BR times (2).)
This includes guest time, \fIcguest_time\fP
(time spent running a virtual CPU, see below).
.TP
\fIcstime\fP %ld
-Amount of time that this process's
+(17) Amount of time that this process's
waited-for children have been scheduled in kernel mode,
measured in clock ticks (divide by
-.IR sysconf(_SC_CLK_TCK) .
+.IR sysconf(_SC_CLK_TCK) ).
.TP
\fIpriority\fP %ld
-(Explanation for Linux 2.6)
+(18) (Explanation for Linux 2.6)
For processes running a real-time scheduling policy
.RI ( policy
below; see
.\" And back in kernel 1.2 days things were different again.
.TP
\fInice\fP %ld
-The nice value (see
+(19) The nice value (see
.BR setpriority (2)),
a value in the range 19 (low priority) to \-20 (high priority).
.\" Back in kernel 1.2 days things were different.
-.TP
.\" .TP
.\" \fIcounter\fP %ld
.\" The current maximum size in jiffies of the process's next timeslice,
.\" \fItimeout\fP %u
.\" The time in jiffies of the process's next timeout.
.\" timeout was removed sometime around 2.1/2.2
+.TP
\fInum_threads\fP %ld
-Number of threads in this process (since Linux 2.6).
+(20) Number of threads in this process (since Linux 2.6).
Before kernel 2.6, this field was hard coded to 0 as a placeholder
for an earlier removed field.
.TP
-.\" field 21
\fIitrealvalue\fP %ld
-The time in jiffies before the next
+(21) The time in jiffies before the next
.B SIGALRM
is sent to the process due to an interval timer.
Since kernel 2.6.17, this field is no longer maintained,
and is hard coded as 0.
.TP
\fIstarttime\fP %llu (was %lu before Linux 2.6)
-The time in jiffies the process started after system boot.
+(22) The time the process started after system boot.
+In kernels before Linux 2.6, this value was expressed in jiffies.
+Since Linux 2.6, the value is expressed in clock ticks (divide by
+.IR sysconf(_SC_CLK_TCK) ).
.TP
\fIvsize\fP %lu
-Virtual memory size in bytes.
+(23) Virtual memory size in bytes.
.TP
\fIrss\fP %ld
-Resident Set Size: number of pages the process has in real memory.
+(24) Resident Set Size: number of pages the process has in real memory.
This is just the pages which
count toward text, data, or stack space.
This does not include pages
which have not been demand-loaded in, or which are swapped out.
.TP
\fIrsslim\fP %lu
-Current soft limit in bytes on the rss of the process;
+(25) Current soft limit in bytes on the rss of the process;
see the description of
.B RLIMIT_RSS
in
-.BR getpriority (2).
+.BR getrlimit (2).
.TP
\fIstartcode\fP %lu
-The address above which program text can run.
+(26) The address above which program text can run.
.TP
\fIendcode\fP %lu
-The address below which program text can run.
+(27) The address below which program text can run.
.TP
\fIstartstack\fP %lu
-The address of the start (i.e., bottom) of the stack.
+(28) The address of the start (i.e., bottom) of the stack.
.TP
\fIkstkesp\fP %lu
-The current value of ESP (stack pointer), as found in the
+(29) The current value of ESP (stack pointer), as found in the
kernel stack page for the process.
.TP
\fIkstkeip\fP %lu
-The current EIP (instruction pointer).
+(30) The current EIP (instruction pointer).
.TP
-.\" field 31
\fIsignal\fP %lu
-The bitmap of pending signals, displayed as a decimal number.
+(31) The bitmap of pending signals, displayed as a decimal number.
Obsolete, because it does not provide information on real-time signals; use
.I /proc/[pid]/status
instead.
.TP
\fIblocked\fP %lu
-The bitmap of blocked signals, displayed as a decimal number.
+(32) The bitmap of blocked signals, displayed as a decimal number.
Obsolete, because it does not provide information on real-time signals; use
.I /proc/[pid]/status
instead.
.TP
\fIsigignore\fP %lu
-The bitmap of ignored signals, displayed as a decimal number.
+(33) The bitmap of ignored signals, displayed as a decimal number.
Obsolete, because it does not provide information on real-time signals; use
.I /proc/[pid]/status
instead.
.TP
\fIsigcatch\fP %lu
-The bitmap of caught signals, displayed as a decimal number.
+(34) The bitmap of caught signals, displayed as a decimal number.
Obsolete, because it does not provide information on real-time signals; use
.I /proc/[pid]/status
instead.
.TP
\fIwchan\fP %lu
-This is the "channel" in which the process is waiting.
-It is the
-address of a system call, and can be looked up in a namelist if you
-need a textual name.
-(If you have an up-to-date
-.IR /etc/psdatabase ,
-then
-try \fIps \-l\fP to see the WCHAN field in action.)
+(35) This is the "channel" in which the process is waiting.
+It is the address of a location in the kernel where the process is sleeping.
+The corresponding symbolic name can be found in
+.IR /proc/[pid]/wchan .
.TP
\fInswap\fP %lu
+(36)
.\" nswap was added in 2.0
Number of pages swapped (not maintained).
.TP
\fIcnswap\fP %lu
+(37)
.\" cnswap was added in 2.0
Cumulative \fInswap\fP for child processes (not maintained).
.TP
\fIexit_signal\fP %d (since Linux 2.1.22)
-Signal to be sent to parent when we die.
+(38) Signal to be sent to parent when we die.
.TP
\fIprocessor\fP %d (since Linux 2.2.8)
-CPU number last executed on.
+(39) CPU number last executed on.
.TP
\fIrt_priority\fP %u (since Linux 2.5.19; was %lu before Linux 2.6.22)
-Real-time scheduling priority, a number in the range 1 to 99 for
+(40) Real-time scheduling priority, a number in the range 1 to 99 for
processes scheduled under a real-time policy,
or 0, for non-real-time processes (see
.BR sched_setscheduler (2)).
.TP
-.\" field 41
\fIpolicy\fP %u (since Linux 2.5.19; was %lu before Linux 2.6.22)
-Scheduling policy (see
+(41) Scheduling policy (see
.BR sched_setscheduler (2)).
Decode using the SCHED_* constants in
.IR linux/sched.h .
.TP
\fIdelayacct_blkio_ticks\fP %llu (since Linux 2.6.18)
-Aggregated block I/O delays, measured in clock ticks (centiseconds).
+(42) Aggregated block I/O delays, measured in clock ticks (centiseconds).
.TP
\fIguest_time\fP %lu (since Linux 2.6.24)
-Guest time of the process (time spent running a virtual CPU
+(43) Guest time of the process (time spent running a virtual CPU
for a guest operating system), measured in clock ticks (divide by
-.IR sysconf(_SC_CLK_TCK) .
+.IR sysconf(_SC_CLK_TCK) ).
.TP
\fIcguest_time\fP %ld (since Linux 2.6.24)
-Guest time of the process's children, measured in clock ticks (divide by
-.IR sysconf(_SC_CLK_TCK) .
+(44) Guest time of the process's children, measured in clock ticks (divide by
+.IR sysconf(_SC_CLK_TCK) ).
.RE
.TP
.I /proc/[pid]/statm
.in +4n
.nf
-size total program size
+size (1) total program size
(same as VmSize in \fI/proc/[pid]/status\fP)
-resident resident set size
+resident (2) resident set size
(same as VmRSS in \fI/proc/[pid]/status\fP)
-share shared pages (from shared mappings)
-text text (code)
+share (3) shared pages (i.e., backed by a file)
+text (4) text (code)
.\" (not including libs; broken, includes data segment)
-lib library (unused in Linux 2.6)
-data data + stack
+lib (5) library (unused in Linux 2.6)
+data (6) data + stack
.\" (including libs; broken, includes library text)
-dt dirty pages (unused in Linux 2.6)
+dt (7) dirty pages (unused in Linux 2.6)
.fi
.in
.TP
Command run by this process.
.IP *
.IR State :
-Current state of the process. One of
+Current state of the process.
+One of
"R (running)",
"S (sleeping)",
"D (disk sleep)",
Thread ID (see
.BR gettid (2)).
.IP *
+.IR PPid :
+PID of parent process.
+.IP *
.IR TracerPid :
PID of process tracing this process (0 if not being traced).
.IP *
.IR Uid ", " Gid :
-Real, effective, saved set, and file system UIDs (GIDs).
+Real, effective, saved set, and filesystem UIDs (GIDs).
.IP *
.IR FDSize :
Number of file descriptor slots currently allocated.
.IR Threads :
Number of threads in process containing this thread.
.IP *
+.IR SigQ :
+This field contains two slash-separated numbers that relate to
+queued signals for the real user ID of this process.
+The first of these is the number of currently queued
+signals for this real user ID, and the second is the
+resource limit on the number of queued signals for this process
+(see the description of
+.BR RLIMIT_SIGPENDING
+in
+.BR getrlimit (2)).
+.IP *
.IR SigPnd ", " ShdPnd :
Number of signals pending for thread and for process as a whole (see
.BR pthreads (7)
(typically by calling
.BR pthread_exit (3)).
.TP
+.IR /proc/[pid]/wchan " (since Linux 2.6.0)"
+The symbolic name corresponding to the location
+in the kernel where the process is sleeping.
+.TP
.I /proc/apm
Advanced power management version and battery information when
.B CONFIG_APM
.B CONFIG_PCMCIA
is set at kernel compilation time.
.TP
+.IR /proc/[pid]/timers " (since Linux 3.10)"
+.\" commit 5ed67f05f66c41e39880a6d61358438a25f9fee5
+.\" commit 48f6a7a511ef8823fdff39afee0320092d43a8a0
+A list of the POSIX timers for this process.
+Each timer is listed with a line that started with the string "ID:".
+For example:
+
+.in +4n
+.nf
+ID: 1
+signal: 60/00007fff86e452a8
+notify: signal/pid.2634
+ClockID: 0
+ID: 0
+signal: 60/00007fff86e452a8
+notify: signal/pid.2634
+ClockID: 1
+.fi
+.in
+
+The lines shown for each timer have the following meanings:
+.RS
+.TP
+.I ID
+The ID for this timer.
+This is not the same as the timer ID returned by
+.BR timer_create (2);
+rather, it is the same kernel-internal ID that is available via the
+.I si_timerid
+field of the
+.IR siginfo_t
+structure (see
+.BR sigaction (2)).
+.TP
+.I signal
+This is the signal number that this timer uses to deliver notifications
+followed by a slash, and then the
+.I sigev_value.sival_ptr
+value supplied to the signal handler.
+Valid only for timers that notify via a signal.
+.TP
+.I notify
+The part before the slash specifies the mechanism
+that this timer uses to deliver notifications,
+and is one of "thread", "signal", or "none".
+Immediately following the slash is either the string "tid" for timers
+with
+.B SIGEV_THREAD_ID
+notification, or "pid" for timers that notify by other mechanisms.
+Following the "." is the PID of the process that will be delivered
+a signal if the timer delivers notifications via a signal.
+.TP
+.I ClockID
+This field identifies the clock that the timer uses for measuring time.
+For most clocks, this is a number that matches one of the user-space
+.BR CLOCK_*
+constants exposed via
+.IR <time.h> .
+.B CLOCK_PROCESS_CPUTIME_ID
+timers display with a value of -6
+in this field.
+.B CLOCK_THREAD_CPUTIME_ID
+timers display with a value of -2
+in this field.
+.RE
+.TP
.I /proc/bus/pccard/drivers
.TP
.I /proc/bus/pci
.IR "make config" ,
or similar).
The file contents are compressed; view or search them using
-.BR zcat (1),
-.BR zgrep (1),
-etc.
+.BR zcat (1)
+and
+.BR zgrep (1).
As long as no changes have been made to the following file,
the contents of
.I /proc/config.gz
.in +4n
.nf
-cat /lib/modules/$(uname -r)/build/.config
+cat /lib/modules/$(uname \-r)/build/.config
.fi
.in
.IP
.I /proc/config.gz
-is only provided if the kernel is configured with
+is provided only if the kernel is configured with
.BR CONFIG_IKCONFIG_PROC .
.TP
.I /proc/cpuinfo
during kernel initialization.
SMP machines have information for
each CPU.
+The
+.BR lscpu (1)
+command gathers its information from this file.
.TP
.I /proc/devices
Text listing of major numbers and device groups.
.TP
.IR /proc/diskstats " (since Linux 2.5.69)"
This file contains disk I/O statistics for each disk device.
-See the kernel source file
+See the Linux kernel source file
.I Documentation/iostats.txt
for further information.
.TP
is defined during kernel compilation.
.TP
.I /proc/filesystems
-A text listing of the file systems which are supported by the kernel,
-namely file systems which were compiled into the kernel or whose kernel
+A text listing of the filesystems which are supported by the kernel,
+namely filesystems which were compiled into the kernel or whose kernel
modules are currently loaded.
(See also
.BR filesystems (5).)
-If a file system is marked with "nodev",
+If a filesystem is marked with "nodev",
this means that it does not require a block device to be mounted
-(e.g., virtual file system, network file system).
+(e.g., virtual filesystem, network filesystem).
Incidentally, this file may be used by
.BR mount (8)
-when no file system is specified and it didn't manage to determine the
-file system type.
-Then file systems contained in this file are tried
+when no filesystem is specified and it didn't manage to determine the
+filesystem type.
+Then filesystems contained in this file are tried
(excepted those that are marked with "nodev").
.TP
.I /proc/fs
.BR uptime (1)
and other programs.
The fourth field consists of two numbers separated by a slash (/).
-The first of these is the number of currently executing kernel
-scheduling entities (processes, threads);
-this will be less than or equal to the number of CPUs.
+The first of these is the number of currently runnable kernel
+scheduling entities (processes, threads).
The value after the slash is the number of kernel scheduling entities
that currently exist on the system.
The fifth field is the PID of the process that was most
.TP
.IR /proc/malloc " (only up to and including Linux 2.2)"
.\" It looks like this only ever did something back in 1.0 days
-This file is only present if
+This file is present only if
.B CONFIG_DEBUG_MALLOC
was defined during compilation.
.TP
to report the amount of free and used memory (both physical and swap)
on the system as well as the shared memory and buffers used by the
kernel.
+Each line of the file consists of a parameter name, followed by a colon,
+the value of the parameter, and an option unit of measurement (e.g., "kB").
+The list below describes the parameter names and
+the format specifier required to read the field value.
+Except as noted below,
+all of the fields have been present since at least Linux 2.6.0.
+Some fields are displayed only if the kernel was configured
+with various options; those dependencies are noted in the list.
+.RS
+.TP
+.IR MemTotal " %lu"
+Total usable RAM (i.e., physical RAM minus a few reserved
+bits and the kernel binary code).
+.TP
+.IR MemFree " %lu"
+The sum of
+.IR LowFree + HighFree .
+.TP
+.IR Buffers " %lu"
+Relatively temporary storage for raw disk blocks that
+shouldn't get tremendously large (20MB or so).
+.TP
+.IR Cached " %lu"
+In-memory cache for files read from the disk (the page cache).
+Doesn't include
+.IR SwapCached .
+.TP
+.IR SwapCached " %lu"
+Memory that once was swapped out, is swapped back in but
+still also is in the swap file.
+(If memory pressure is high, these pages
+don't need to be swapped out again because they are already
+in the swap file.
+This saves I/O.)
+.TP
+.IR Active " %lu"
+Memory that has been used more recently and usually not
+reclaimed unless absolutely necessary.
+.TP
+.IR Inactive " %lu"
+Memory which has been less recently used.
+It is more eligible to be reclaimed for other purposes.
+.TP
+.IR Active(anon) " %lu (since Linux 2.6.28)"
+[To be documented.]
+.TP
+.IR Inactive(anon) " %lu (since Linux 2.6.28)"
+[To be documented.]
+.TP
+.IR Active(file) " %lu (since Linux 2.6.28)"
+[To be documented.]
+.TP
+.IR Inactive(file) " %lu (since Linux 2.6.28)"
+[To be documented.]
+.TP
+.IR Unevictable " %lu (since Linux 2.6.28)"
+(From Linux 2.6.28 to 2.6.30,
+\fBCONFIG_UNEVICTABLE_LRU\fP was required.)
+[To be documented.]
+.TP
+.IR Mlocked " %lu (since Linux 2.6.28)"
+(From Linux 2.6.28 to 2.6.30,
+\fBCONFIG_UNEVICTABLE_LRU\fP was required.)
+[To be documented.]
+.TP
+.IR HighTotal " %lu"
+(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
+Total amount of highmem.
+Highmem is all memory above ~860MB of physical memory.
+Highmem areas are for use by user-space programs,
+or for the page cache.
+The kernel must use tricks to access
+this memory, making it slower to access than lowmem.
+.TP
+.IR HighFree " %lu
+(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
+Amount of free highmem.
+.TP
+.IR LowTotal " %lu
+(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
+Total amount of lowmem.
+Lowmem is memory which can be used for everything that
+highmem can be used for, but it is also available for the
+kernel's use for its own data structures.
+Among many other things,
+it is where everything from
+.I Slab
+is allocated.
+Bad things happen when you're out of lowmem.
+.TP
+.IR LowFree " %lu
+(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
+Amount of free lowmem.
+.TP
+.IR MmapCopy " %lu (since Linux 2.6.29)"
+.RB ( CONFIG_MMU
+is required.)
+[To be documented.]
+.TP
+.IR SwapTotal " %lu"
+Total amount of swap space available.
+.TP
+.IR SwapFree " %lu"
+Amount of swap space that is currently unused.
+.TP
+.IR Dirty " %lu"
+Memory which is waiting to get written back to the disk.
+.TP
+.IR Writeback " %lu"
+Memory which is actively being written back to the disk.
+.TP
+.IR AnonPages " %lu (since Linux 2.6.18)"
+Non-file backed pages mapped into user-space page tables.
+.TP
+.IR Mapped " %lu"
+Files which have been mapped into memory (with
+.BR mmap (2)),
+such as libraries.
+.TP
+.IR Shmem " %lu (since Linux 2.6.32)"
+[To be documented.]
+.TP
+.IR Slab " %lu"
+In-kernel data structures cache.
+.TP
+.IR SReclaimable " %lu (since Linux 2.6.19)"
+Part of
+.IR Slab ,
+that might be reclaimed, such as caches.
+.TP
+.IR SUnreclaim " %lu (since Linux 2.6.19)"
+Part of
+.IR Slab ,
+that cannot be reclaimed on memory pressure.
+.TP
+.IR KernelStack " %lu (since Linux 2.6.32)"
+Amount of memory allocated to kernel stacks.
+.TP
+.IR PageTables " %lu (since Linux 2.6.18)"
+Amount of memory dedicated to the lowest level of page tables.
+.TP
+.IR Quicklists " %lu (since Linux 2.6.27)"
+(\fBCONFIG_QUICKLIST\fP is required.)
+[To be documented.]
+.TP
+.IR NFS_Unstable " %lu (since Linux 2.6.18)"
+NFS pages sent to the server, but not yet committed to stable storage.
+.TP
+.IR Bounce " %lu (since Linux 2.6.18)"
+Memory used for block device "bounce buffers".
+.TP
+.IR WritebackTmp " %lu (since Linux 2.6.26)"
+Memory used by FUSE for temporary writeback buffers.
+.TP
+.IR CommitLimit " %lu (since Linux 2.6.10)"
+Based on the overcommit ratio ('vm.overcommit_ratio'),
+this is the total amount of memory currently available to
+be allocated on the system.
+This limit is adhered to
+only if strict overcommit accounting is enabled (mode 2 in
+.IR /proc/sys/vm/overcommit_ratio ).
+The
+.I CommitLimit
+is calculated using the following formula:
+
+ CommitLimit =
+ ([total RAM pages] - [total huge TLB pages]) *
+ overcommit_ratio / 100 + [total swap pages]
+
+For example, on a system with 1GB of physical RAM and 7GB
+of swap with a
+.I overcommit_ratio
+of 30, this formula yields a
+.I CommitLimit
+of 7.3GB.
+For more details, see the memory overcommit documentation
+in the kernel source file
+.IR Documentation/vm/overcommit-accounting .
+.TP
+.IR Committed_AS " %lu"
+The amount of memory presently allocated on the system.
+The committed memory is a sum of all of the memory which
+has been allocated by processes, even if it has not been
+"used" by them as of yet.
+A process which allocates 1GB of memory (using
+.BR malloc (3)
+or similar), but touches only 300MB of that memory will show up
+as using only 300MB of memory even if it has the address space
+allocated for the entire 1GB.
+This 1GB is memory which has been "committed" to by the VM
+and can be used at any time by the allocating application.
+With strict overcommit enabled on the system (mode 2
+.IR /proc/sys/vm/overcommit_memory ),
+allocations which would exceed the
+.I CommitLimit
+(detailed above) will not be permitted.
+This is useful if one needs to guarantee that processes will not
+fail due to lack of memory once that memory has been successfully allocated.
+.TP
+.IR VmallocTotal " %lu"
+Total size of vmalloc memory area.
+.TP
+.IR VmallocUsed " %lu"
+Amount of vmalloc area which is used.
+.TP
+.IR VmallocChunk " %lu"
+Largest contiguous block of vmalloc area which is free.
+.TP
+.IR HardwareCorrupted " %lu (since Linux 2.6.32)"
+(\fBCONFIG_MEMORY_FAILURE\fP is required.)
+[To be documented.]
+.TP
+.IR AnonHugePages " %lu (since Linux 2.6.38)"
+(\fBCONFIG_TRANSPARENT_HUGEPAGE\fP is required.)
+Non-file backed huge pages mapped into user-space page tables.
+.TP
+.IR HugePages_Total " %lu"
+(\fBCONFIG_HUGETLB_PAGE\fP is required.)
+The size of the pool of huge pages.
+.TP
+.IR HugePages_Free " %lu"
+(\fBCONFIG_HUGETLB_PAGE\fP is required.)
+The number of huge pages in the pool that are not yet allocated.
+.TP
+.IR HugePages_Rsvd " %lu (since Linux 2.6.17)"
+(\fBCONFIG_HUGETLB_PAGE\fP is required.)
+This is the number of huge pages for
+which a commitment to allocate from the pool has been made,
+but no allocation has yet been made.
+These reserved huge pages
+guarantee that an application will be able to allocate a
+huge page from the pool of huge pages at fault time.
+.TP
+.IR HugePages_Surp " %lu (since Linux 2.6.24)"
+(\fBCONFIG_HUGETLB_PAGE\fP is required.)
+This is the number of huge pages in
+the pool above the value in
+.IR /proc/sys/vm/nr_hugepages .
+The maximum number of surplus huge pages is controlled by
+.IR /proc/sys/vm/nr_overcommit_hugepages .
+.TP
+.IR Hugepagesize " %lu"
+(\fBCONFIG_HUGETLB_PAGE\fP is required.)
+The size of huge pages.
+.RE
.TP
.I /proc/modules
A text list of the modules that have been loaded by the system.
.TP
.I /proc/mounts
Before kernel 2.4.19, this file was a list
-of all the file systems currently mounted on the system.
+of all the filesystems currently mounted on the system.
With the introduction of per-process mount namespaces in
Linux 2.4.19, this file became a link to
.IR /proc/self/mounts ,
.TP
.I /proc/mtrr
Memory Type Range Registers.
-See the kernel source file
+See the Linux kernel source file
.I Documentation/mtrr.txt
for details.
.TP
socket and Path is the bound path (if any) of the socket.
.TP
.I /proc/partitions
-Contains major and minor numbers of each partition as well as number
-of blocks and partition name.
+Contains the major and minor numbers of each partition as well as the number
+of 1024-byte blocks and the partition name.
.TP
.I /proc/pci
This is a listing of all PCI devices found during kernel initialization
.\" .IR /proc/sched_debug " (since Linux 2.6.23)"
.\" See also /proc/[pid]/sched
.TP
+.IR /proc/profile " (since Linux 2.4)"
+This file is present only if the kernel was booted with the
+.I profile=1
+command-line option.
+It exposes kernel profiling information in a binary format for use by
+.BR readprofile (1).
+Writing (e.g., an empty string) to this file resets the profiling counters;
+on some architectures,
+writing a binary integer "profiling multiplier" of size
+.IR sizeof(int)
+sets the profiling interrupt frequency.
+.TP
.I /proc/scsi
A directory with the
.I scsi
initialization.
Reading these files will usually show driver and host configuration,
-statistics, etc.
+statistics, and so on.
Writing to these files allows different things on different hosts.
For example, with the \fIlatency\fP and \fInolatency\fP commands,
.I /proc/self
This directory refers to the process accessing the
.I /proc
-file system,
+filesystem,
and is identical to the
.I /proc
directory named by the process ID of the same process.
.TP
.I /proc/slabinfo
Information about kernel caches.
-Since Linux 2.6.16 this file is only present if the
+Since Linux 2.6.16 this file is present only if the
.B CONFIG_SLAB
kernel configuration option is enabled.
The columns in
.IR sysconf(_SC_CLK_TCK)
to obtain the right value),
.\" 1024 on Alpha and ia64
-that the system spent in user mode,
-user mode with low priority (nice), system mode, and the
-idle task, respectively.
+that the system spent in various states:
+.RS
+.TP
+.I user
+(1) Time spent in user mode.
+.TP
+.I nice
+(2) Time spent in user mode with low priority (nice).
+.TP
+.I system
+(3) Time spent in system mode.
+.TP
+.I idle
+(4) Time spent in the idle task.
.\" FIXME Actually, the following info about the /proc/stat 'cpu' field
-.\" does not seem to be quite right (at least in 2.6.12)
-The last value should be USER_HZ times the
-second entry in the uptime pseudo-file.
-
-In Linux 2.6 this line includes three additional columns:
-.I iowait
-\- time waiting for I/O to complete (since 2.5.41);
-.I irq
-\- time servicing interrupts (since 2.6.0-test4);
-.I softirq
-\- time servicing softirqs (since 2.6.0-test4).
-
-Since Linux 2.6.11, there is an eighth column,
-.I steal
-\- stolen time, which is the time spent in other operating systems when
+.\" does not seem to be quite right (at least in 2.6.12 or 3.6):
+.\" the idle time in /proc/uptime does not quite match this value
+This value should be USER_HZ times the
+second entry in the
+.I /proc/uptime
+pseudo-file.
+.TP
+.IR iowait " (since Linux 2.5.41)"
+(5) Time waiting for I/O to complete.
+.TP
+.IR irq " (since Linux 2.6.0-test4)"
+(6) Time servicing interrupts.
+.TP
+.IR softirq " (since Linux 2.6.0-test4)"
+(7) Time servicing softirqs.
+.TP
+.IR steal " (since Linux 2.6.11)"
+(8) Stolen time, which is the time spent in other operating systems when
running in a virtualized environment
-
-Since Linux 2.6.24, there is a ninth column,
-.IR guest ,
-which is the time spent running a virtual CPU for guest
+.TP
+.IR guest " (since Linux 2.6.24)"
+(9) Time spent running a virtual CPU for guest
operating systems under the control of the Linux kernel.
.\" See Changelog entry for 5e84cfde51cf303d368fcb48f22059f37b3872de
.TP
+.IR guest_nice " (since Linux 2.6.33)"
+.\" commit ce0e7b28fb75cb003cfc8d0238613aaf1c55e797
+(10) Time spent running a niced guest (virtual CPU for guest
+operating systems under the control of the Linux kernel).
+.RE
+.TP
\fIpage 5741 1808\fP
The number of pages the system paged in and the number that were paged
out (from disk).
\fIintr 1462898\fP
This line shows counts of interrupts serviced since boot time,
for each of the possible system interrupts.
-The first column is the total of all interrupts serviced;
-each subsequent column is the total for a particular interrupt.
+The first column is the total of all interrupts serviced
+including unnumbered architecture specific interrupts;
+each subsequent column is the total for that particular numbered interrupt.
+Unnumbered interrupts are not shown, only summed into the total.
.TP
\fIdisk_io: (2,0):(31,30,5764,1,2) (3,0):\fP...
(major,disk_idx):(noinfo, read_io_ops, blks_read, write_io_ops, blks_written)
This directory (present since 1.3.57) contains a number of files
and subdirectories corresponding to kernel variables.
These variables can be read and sometimes modified using
-the \fI/proc\fP file system, and the (deprecated)
+the \fI/proc\fP filesystem, and the (deprecated)
.BR sysctl (2)
system call.
.TP
.IR /proc/sys/abi " (since Linux 2.4.10)"
This directory may contain files with application binary information.
.\" On some systems, it is not present.
-See the kernel source file
+See the Linux kernel source file
.I Documentation/sysctl/abi.txt
for more information.
.TP
.TP
.I /proc/sys/fs
This directory contains the files and subdirectories for kernel variables
-related to file systems.
+related to filesystems.
.TP
.I /proc/sys/fs/binfmt_misc
Documentation for files in this directory can be found
-in the kernel sources in
+in the Linux kernel sources in
.IR Documentation/binfmt_misc.txt .
.TP
.IR /proc/sys/fs/dentry-state " (since Linux 2.2)"
.BR RLIMIT_NOFILE ,
on the number of files it may open.)
If you get lots
-of error messages about running out of file handles,
+of error messages in the kernel log about running out of file handles
+(look for "VFS: file-max limit <number> reached"),
try increasing this value:
.br
.br
.nf
.ft CW
-echo 100000 > /proc/sys/fs/file-max
+ echo 100000 > /proc/sys/fs/file-max
.fi
.ft
imposes an upper limit on the value that may be placed in
.IR file-max .
-If you increase
-.IR /proc/sys/fs/file-max ","
-be sure to increase
-.I /proc/sys/fs/inode-max
-to 3-4 times the new
-value of
-.IR /proc/sys/fs/file-max ","
-or you will run out of inodes.
+Privileged processes
+.RB ( CAP_SYS_ADMIN )
+can override the
+.I file-max
+limit.
.TP
.I /proc/sys/fs/file-nr
-This (read-only) file gives the number of files presently opened.
-It contains three numbers: the number of allocated file handles;
-the number of free file handles; and the maximum number of file handles.
-The kernel allocates file handles dynamically, but it
-doesn't free them again.
-If the number of allocated files is close to the
+This (read-only) file contains three numbers:
+the number of allocated file handles
+(i.e., the number of files presently opened);
+the number of free file handles;
+and the maximum number of file handles (i.e., the same value as
+.IR /proc/sys/fs/file-max ).
+If the number of allocated file handles is close to the
maximum, you should consider increasing the maximum.
-When the number of free file handles is
-large, you've encountered a peak in your usage of file
-handles and you probably don't need to increase the maximum.
-.TP
-.I /proc/sys/fs/inode-max
+Before Linux 2.6,
+the kernel allocated file handles dynamically,
+but it didn't free them again.
+Instead the free file handles were kept in a list for reallocation;
+the "free file handles" value indicates the size of that list.
+A large number of free file handles indicates that there was
+a past peak in the usage of open file handles.
+Since Linux 2.6, the kernel does deallocate freed file handles,
+and the "free file handles" value is always zero.
+.TP
+.IR /proc/sys/fs/inode-max " (only present until Linux 2.2)"
This file contains the maximum number of in-memory inodes.
-On some (2.4) systems, it may not be present.
This value should be 3-4 times larger
than the value in
.IR file-max ,
since \fIstdin\fP, \fIstdout\fP
and network sockets also need an inode to handle them.
When you regularly run out of inodes, you need to increase this value.
+
+Starting with Linux 2.4,
+there is no longer a static limit on the number of inodes,
+and this file is removed.
.TP
.I /proc/sys/fs/inode-nr
This file contains the first two values from
.IR nr_inodes ,
.IR nr_free_inodes ,
.IR preshrink ,
-and four dummy values.
+and four dummy values (always zero).
+
.I nr_inodes
is the number of inodes the system has allocated.
-This can be slightly more than
-.I inode-max
-because Linux allocates them one page full at a time.
+.\" This can be slightly more than
+.\" .I inode-max
+.\" because Linux allocates them one page full at a time.
.I nr_free_inodes
represents the number of free inodes.
+
.I preshrink
is nonzero when the
.I nr_inodes
>
.I inode-max
-and the system needs to prune the inode list instead of allocating more.
+and the system needs to prune the inode list instead of allocating more;
+since Linux 2.4, this field is a dummy value (always zero).
.TP
.IR /proc/sys/fs/inotify " (since Linux 2.6.13)"
This directory contains files
These files
allow you to change the value of the fixed UID and GID.
The default is 65534.
-Some file systems only support 16-bit UIDs and GIDs, although in Linux
+Some filesystems support only 16-bit UIDs and GIDs, although in Linux
UIDs and GIDs are 32 bits.
-When one of these file systems is mounted
+When one of these filesystems is mounted
with writes enabled, any UID or GID that would exceed 65535 is translated
to the overflow value before being written to disk.
.TP
display the contents of this file after assigning a value to it.
The minimum value that can be assigned to this file is the system page size.
.TP
+.IR /proc/sys/fs/protected_hardlinks " (since Linux 3.6)"
+.\" commit 800179c9b8a1e796e441674776d11cd4c05d61d7
+When the value in this file is 0,
+no restrictions are placed on the creation of hard links
+(i.e., this is the historical behaviour before Linux 3.6).
+When the value in this file is 1,
+a hard link can be created to a target file
+only if one of the following conditions is true:
+.RS
+.IP * 3
+The caller has the
+.BR CAP_FOWNER
+capability.
+.IP *
+The filesystem UID of the process creating the link matches
+the owner (UID) of the target file
+(as described in
+.BR credentials (7),
+a process's filesystem UID is normally the same as its effective UID).
+.IP *
+All of the following conditions are true:
+.RS 4
+.IP \(bu 3
+the target is a regular file;
+.IP \(bu
+the target file does not have its set-user-ID permission bit enabled;
+.IP \(bu
+the target file does not have both its set-group-ID and
+group-executable permission bits enabled; and
+.IP \(bu
+the caller has permission to read and write the target file
+(either via the file's permissions mask or because it has
+suitable capabilities).
+.RE
+.RE
+.IP
+The default value in this file is 0.
+Setting the value to 1
+prevents a longstanding class of security issues caused by
+hard-link-based time-of-check, time-of-use races,
+most commonly seen in world-writable directories such as
+.IR /tmp .
+The common method of exploiting this flaw
+is to cross privilege boundaries when following a given hard link
+(i.e., a root process follows a hard link created by another user).
+Additionally, on systems without separated partitions,
+this stops unauthorized users from "pinning" vulnerable set-user-ID and
+set-group-ID files against being upgraded by
+the administrator, or linking to special files.
+.TP
+.IR /proc/sys/fs/protected_symlinks " (since Linux 3.6)"
+.\" commit 800179c9b8a1e796e441674776d11cd4c05d61d7
+When the value in this file is 0,
+no restrictions are placed on following symbolic links
+(i.e., this is the historical behaviour before Linux 3.6).
+When the value in this file is 1, symbolic links are followed only
+in the following circumstances:
+.RS
+.IP * 3
+the filesystem UID of the process following the link matches
+the owner (UID) of the symbolic link
+(as described in
+.BR credentials (7),
+a process's filesystem UID is normally the same as its effective UID);
+.IP *
+the link is not in a sticky world-writable directory; or
+.IP *
+the symbolic link and its parent directory have the same owner (UID)
+.RE
+.IP
+A system call that fails to follow a symbolic link
+because of the above restrictions returns the error
+.BR EACCES
+in
+.IR errno .
+.IP
+The default value in this file is 0.
+Setting the value to 1 avoids a longstanding class of security issues
+based on time-of-check, time-of-use races when accessing symbolic links.
+.TP
.IR /proc/sys/fs/suid_dumpable " (since Linux 2.6.13)"
.\" The following is based on text from Documentation/sysctl/kernel.txt
The value in this file determines whether core dump files are
produced for set-user-ID or otherwise protected/tainted binaries.
Three different integer values can be specified:
-.sp
+.RS
+.TP
\fI0\ (default)\fP
This provides the traditional (pre-Linux 2.6.13) behavior.
A core dump will not be produced for a process which has
.BR setgid (2),
or similar, or by executing a set-user-ID or set-group-ID program)
or whose binary does not have read permission enabled.
-.sp
+.TP
\fI1\ ("debug")\fP
All processes dump core when possible.
-The core dump is owned by the file system user ID of the dumping process
+The core dump is owned by the filesystem user ID of the dumping process
and no security is applied.
This is intended for system debugging situations only.
Ptrace is unchecked.
-.sp
+.TP
\fI2\ ("suidsafe")\fP
Any binary which normally would not be dumped (see "0" above)
is dumped readable by root only.
another or other files.
This mode is appropriate when administrators are
attempting to debug problems in a normal environment.
+.IP
+Additionally, since Linux 3.6,
+.\" 9520628e8ceb69fa9a4aee6b57f22675d9e1b709
+.I /proc/sys/kernel/core_pattern
+must either be an absolute pathname
+or a pipe command, as detailed in
+.BR core (5).
+Warnings will be written to the kernel log if
+.I core_pattern
+does not follow these rules, and no core dump will be produced.
+.\" 54b501992dd2a839e94e76aa392c392b55080ce8
+.RE
.TP
.I /proc/sys/fs/super-max
This file
controls the maximum number of superblocks, and
-thus the maximum number of mounted file systems the kernel
+thus the maximum number of mounted filesystems the kernel
can have.
-You only need to increase
+You need increase only
.I super-max
-if you need to mount more file systems than the current value in
+if you need to mount more filesystems than the current value in
.I super-max
allows you to.
.TP
.I /proc/sys/fs/super-nr
This file
-contains the number of file systems currently mounted.
+contains the number of filesystems currently mounted.
.TP
.I /proc/sys/kernel
This directory contains files controlling a range of kernel parameters,
.IR lowwater ,
and
.IR frequency .
-If BSD-style process accounting is enabled these values control
+If BSD-style process accounting is enabled, these values control
its behavior.
-If free space on file system where the log lives goes below
+If free space on filesystem where the log lives goes below
.I lowwater
-percent accounting suspends.
+percent, accounting suspends.
If free space gets above
.I highwater
-percent accounting resumes.
+percent, accounting resumes.
.I frequency
determines
how often the kernel checks the amount of free space (value is in
if 4% or more space is free; consider information about amount of free space
valid for 30 seconds.
.TP
+.IR /proc/sys/kernel/cap_last_cap " (since Linux 3.2)"
+See
+.BR capabilities (7).
+.TP
.IR /proc/sys/kernel/cap-bound " (from Linux 2.2 to 2.6.24)"
This file holds the value of the kernel
.I "capability bounding set"
ever reaches the kernel tty layer, and it's up to the program
to decide what to do with it.
.TP
-.I /proc/sys/kernel/hotplug
-This file
-contains the path for the hotplug policy agent.
-The default value in this file is
-.IR /sbin/hotplug .
+.IR /proc/sys/kernel/dmesg_restrict " (since Linux 2.6.37)"
+The value in this file determines who can see kernel syslog contents.
+A value of 0 in this file imposes no restrictions.
+If the value is 1, only privileged users can read the kernel syslog.
+(See
+.BR syslog (2)
+for more details.)
+Since Linux 3.4,
+.\" commit 620f6e8e855d6d447688a5f67a4e176944a084e8
+only users with the
+.BR CAP_SYS_ADMIN
+capability may change the value in this file.
.TP
.IR /proc/sys/kernel/domainname " and " /proc/sys/kernel/hostname
can be used to set the NIS/YP domainname and the
.BR hostname (1)
man page.
.TP
+.I /proc/sys/kernel/hotplug
+This file
+contains the path for the hotplug policy agent.
+The default value in this file is
+.IR /sbin/hotplug .
+.TP
.I /proc/sys/kernel/htab-reclaim
(PowerPC only) If this file is set to a nonzero value,
the PowerPC htab
is pruned
each time the system hits the idle loop.
.TP
+.IR /proc/sys/kernel/kptr_restrict " (since Linux 2.6.38)"
+.\" 455cd5ab305c90ffc422dd2e0fb634730942b257
+The value in this file determines whether kernel addresses are exposed via
+.I /proc
+files and other interfaces.
+A value of 0 in this file imposes no restrictions.
+If the value is 1, kernel pointers printed using the
+.I %pK
+format specifier will be replaced with zeros unless the user has the
+.BR CAP_SYSLOG
+capability.
+If the value is 2, kernel pointers printed using the
+.I %pK
+format specifier will be replaced with zeros regardless
+of the user's capabilities.
+The initial default value for this file was 1,
+but the default was changed
+.\" commit 411f05f123cbd7f8aa1edcae86970755a6e2a9d9
+to 0 in Linux 2.6.39.
+Since Linux 3.4,
+.\" commit 620f6e8e855d6d447688a5f67a4e176944a084e8
+only users with the
+.BR CAP_SYS_ADMIN
+capability can change the value in this file.
+.TP
.I /proc/sys/kernel/l2cr
(PowerPC only) This file
contains a flag that controls the L2 cache of G3 processor
This file contains the path for the kernel module loader.
The default value is
.IR /sbin/modprobe .
-The file is only present if the kernel is built with the
-.B CONFIG_KMOD
+The file is present only if the kernel is built with the
+.B CONFIG_MODULES
+.RB ( CONFIG_KMOD
+in Linux 2.6.26 and earlier)
option enabled.
-It is described by the kernel source file
+It is described by the Linux kernel source file
.I Documentation/kmod.txt
-(only present in kernel 2.4 and earlier).
+(present only in kernel 2.4 and earlier).
+.TP
+.IR /proc/sys/kernel/modules_disabled " (since Linux 2.6.31)"
+.\" 3d43321b7015387cfebbe26436d0e9d299162ea1
+.\" From Documentation/sysctl/kernel.txt
+A toggle value indicating if modules are allowed to be loaded
+in an otherwise modular kernel.
+This toggle defaults to off (0), but can be set true (1).
+Once true, modules can be neither loaded nor unloaded,
+and the toggle cannot be set back to false.
+The file is present only if the kernel is built with the
+.B CONFIG_MODULES
+option enabled.
.TP
-.I /proc/sys/kernel/msgmax
+.IR /proc/sys/kernel/msgmax " (since Linux 2.2)"
This file defines
a system-wide limit specifying the maximum number of bytes in
a single message written on a System V message queue.
.TP
-.I /proc/sys/kernel/msgmni
+.IR /proc/sys/kernel/msgmni " (since Linux 2.4)"
This file defines the system-wide limit on the number of
message queue identifiers.
-(This file is only present in Linux 2.4 onward.)
.TP
-.I /proc/sys/kernel/msgmnb
+.IR /proc/sys/kernel/msgmnb " (since Linux 2.2)"
This file defines a system-wide parameter used to initialize the
.I msg_qbytes
setting for subsequently created message queues.
setting specifies the maximum number of bytes that may be written to the
message queue.
.TP
+.IR /proc/sys/kernel/ngroups_max " (since Linux 2.6.4)"
+This is a read-only file that displays the upper limit on the
+number of a process's group memberships.
+.TP
.IR /proc/sys/kernel/ostype " and " /proc/sys/kernel/osrelease
These files
give substrings of
.I /proc/sys/kernel/panic
This file gives read/write access to the kernel variable
.IR panic_timeout .
-If this is zero, the kernel will loop on a panic; if nonzero
+If this is zero, the kernel will loop on a panic; if nonzero,
it indicates that the kernel should autoreboot after this number
of seconds.
When you use the
and then panics.
If the
.I /proc/sys/kernel/panic
-file is also nonzero then the machine will be rebooted.
+file is also nonzero, then the machine will be rebooted.
.TP
.IR /proc/sys/kernel/pid_max " (since Linux 2.5.34)"
This file specifies the value at which PIDs wrap around
(i.e., the value in this file is one greater than the maximum PID).
+PIDs greater than this value not allocated;
+thus, the value in this file also acts as a system-wide limit
+on the total number of processes and threads.
The default value for this file, 32768,
results in the same range of PIDs as on earlier kernels.
On 32-bit platforms, 32768 is the maximum value for
.BR random (4)
for further information.
.TP
+.IR /proc/sys/kernel/random/uuid " (since Linux 2.4)"
+Each read from this read-only file returns a randomly generated 128-bit UUID,
+as a string in the standard UUID format.
+.TP
.I /proc/sys/kernel/real-root-dev
-This file is documented in the kernel source file
+This file is documented in the Linux kernel source file
.IR Documentation/initrd.txt .
.TP
.IR /proc/sys/kernel/reboot-cmd " (Sparc only) "
(Only in kernels up to and including 2.6.7.)
This file shows the number POSIX real-time signals currently queued.
.TP
+.IR /proc/sys/kernel/sched_rr_timeslice_ms " (since Linux 3.9)"
+See
+.BR sched_rr_get_interval (2).
+.TP
+.IR /proc/sys/kernel/sched_rt_period_us " (Since Linux 2.6.25)"
+See
+.BR sched (7).
+.TP
+.IR /proc/sys/kernel/sched_rt_runtime_us " (Since Linux 2.6.25)"
+See
+.BR sched (7).
+.TP
.IR /proc/sys/kernel/sem " (since Linux 2.4)"
This file contains 4 numbers defining limits for System V IPC semaphores.
These fields are, in order:
.BR SG_BIG_BUFF .
However, there shouldn't be any reason to change this value.
.TP
-.I /proc/sys/kernel/shmall
+.IR /proc/sys/kernel/shm_rmid_forced " (since Linux 3.1)"
+.\" commit b34a6b1da371ed8af1221459a18c67970f7e3d53
+.\" See also Documentation/sysctl/kernel.txt
+If this file is set to 1, all System V shared memory segments will
+be marked for destruction as soon as the number of attached processes
+falls to zero;
+in other words, it is no longer possible to create shared memory segments
+that exist independently of any attached process.
+.IP
+The effect is as though a
+.BR shmctl (2)
+.B IPC_RMID
+is performed on all existing segments as well as all segments
+created in the future (until this file is reset to 0).
+Note that existing segments that are attached to no process will be
+immediately destroyed when this file is set to 1.
+Setting this option will also destroy segments that were created,
+but never attached,
+upon termination of the process that created the segment with
+.BR shmget (2).
+.IP
+Setting this file to 1 provides a way of ensuring that
+all System V shared memory segments are counted against the
+resource usage and resource limits (see the description of
+.B RLIMIT_AS
+in
+.BR getrlimit (2))
+of at least one process.
+.IP
+Because setting this file to 1 produces behavior that is nonstandard
+and could also break existing applications,
+the default value in this file is 0.
+Only set this file to 1 if you have a good understanding
+of the semantics of the applications using
+System V shared memory on your system.
+.TP
+.IR /proc/sys/kernel/shmall " (since Linux 2.2)"
This file
contains the system-wide limit on the total number of pages of
System V shared memory.
.TP
-.I /proc/sys/kernel/shmmax
+.IR /proc/sys/kernel/shmmax " (since Linux 2.2)"
This file
can be used to query and set the run-time limit
on the maximum (System V IPC) shared memory segment size that can be
This value defaults to
.BR SHMMAX .
.TP
-.I /proc/sys/kernel/shmmni
-(available in Linux 2.4 and onward)
+.IR /proc/sys/kernel/shmmni " (since Linux 2.4)"
This file
specifies the system-wide maximum number of System V shared memory
segments that can be created.
0 - disable sysrq completely
1 - enable all functions of sysrq
- >1 - bitmask of allowed sysrq functions, as follows:
+ >1 - bit mask of allowed sysrq functions, as follows:
2 - enable control of console logging level
4 - enable control of keyboard (SAK, unraw)
8 - enable debugging dumps of processes etc.
16 - enable sync command
32 - enable remount read-only
- 64 - enable signalling of processes (term, kill, oom-kill)
+ 64 - enable signaling of processes (term, kill, oom-kill)
128 - allow reboot/poweroff
256 - allow nicing of all real-time tasks
-This file is only present if the
+This file is present only if the
.B CONFIG_MAGIC_SYSRQ
kernel configuration option is enabled.
-For further details see the kernel source file
+For further details see the Linux kernel source file
.IR Documentation/sysrq.txt .
.TP
.I /proc/sys/kernel/version
This directory may be empty.
.TP
.I /proc/sys/sunrpc
-This directory supports Sun remote procedure call for network file system
+This directory supports Sun remote procedure call for network filesystem
(NFS).
On some systems, it is not present.
.TP
cache management.
.TP
.IR /proc/sys/vm/drop_caches " (since Linux 2.6.16)"
-Writing to this file causes the kernel to drop clean caches, dentries and
+Writing to this file causes the kernel to drop clean caches, dentries, and
inodes from memory, causing that memory to become free.
+This can be useful for memory management testing and
+performing reproducible filesystem benchmarks.
+Because writing to this file causes the benefits of caching to be lost,
+it can degrade overall system performance.
+
+To free pagecache, use:
+
+ echo 1 > /proc/sys/vm/drop_caches
+
+To free dentries and inodes, use:
+
+ echo 2 > /proc/sys/vm/drop_caches
-To free pagecache, use
-.IR "echo 1 > /proc/sys/vm/drop_caches" ;
-to free dentries and inodes, use
-.IR "echo 2 > /proc/sys/vm/drop_caches" ;
-to free pagecache, dentries and inodes, use
-.IR "echo 3 > /proc/sys/vm/drop_caches" .
+To free pagecache, dentries and inodes, use:
-Because this is a nondestructive operation and dirty objects
+ echo 3 > /proc/sys/vm/drop_caches
+
+Because writing to this file is a nondestructive operation and dirty objects
are not freeable, the
user should run
.BR sync (8)
Note this is not supported for a few types of pages, like kernel internally
allocated data or the swap cache, but works for the majority of user pages.
.IP 0: 4
-Only unmap the corrupted page from all processes and only kill a process
-who tries to access it.
+Only unmap the corrupted page from all processes and kill only a process
+that tries to access it.
.RE
.IP
The kill is performed using a
.BR sigaction (2)
for more details.
-This feature is only active on architectures/platforms with advanced machine
+This feature is active only on architectures/platforms with advanced machine
check handling and depends on the hardware capabilities.
Applications can override the
then the kernel normally panics when out-of-memory happens.
However, if a process limits allocations to certain nodes
using memory policies
-.RB ( mbind (2)
+.RB ( mbind (2)
.BR MPOL_BIND )
or cpusets
.RB ( cpuset (7))
Writing a character to this file triggers the same SysRq function as
typing ALT-SysRq-<character> (see the description of
.IR /proc/sys/kernel/sysrq ).
-This file is normally only writable by
+This file is normally writable only by
.IR root .
-For further details see the kernel source file
+For further details see the Linux kernel source file
.IR Documentation/sysrq.txt .
.TP
.I /proc/sysvipc
Subdirectory containing the pseudo-files
-.IR msg ", " sem " and " shm "."
+.IR msg ", " sem " and " shm "."
These files list the System V Interprocess Communication (IPC) objects
(respectively: message queues, semaphores, and shared memory)
that currently exist on the system,
.BR svipc (7)
provides further background on the information shown by these files.
.TP
+.IR /proc/timer_list " (since Linux 2.6.21)"
+.\" commit 289f480af87e45f7a6de6ba9b4c061c2e259fe98
+This read-only file exposes a list of all currently pending
+(high-resolution) timers,
+all clock-event sources, and their parameters in a human-readable form.
+.TP
+.IR /proc/timer_stats " (since Linux 2.6.21)"
+.\" commit 82f67cd9fca8c8762c15ba7ed0d5747588c1e221
+.\" Date: Fri Feb 16 01:28:13 2007 -0800
+.\" Text largely derived from Documentation/timers/timer_stats.txt
+This is a debugging facility to make timer (ab)use in a Linux
+system visible to kernel and user-space developers.
+It can be used by kernel and user-space developers to verify that
+their code does not make undue use of timers.
+The goal is to avoid unnecessary wakeups,
+thereby optimizing power consumption.
+
+If enabled in the kernel
+.RB ( CONFIG_TIMER_STATS ),
+but not used,
+it has almost zero runtime overhead and a relatively small
+data-structure overhead.
+Even if collection is enabled at runtime, overhead is low:
+all the locking is per-CPU and lookup is hashed.
+
+The
+.I /proc/timer_stats
+file is used both to control sampling facility and to read out the
+sampled information.
+
+timer_stats collects information about the timer events which are fired in a
+Linux system over a sample period:
+
+- the pid of the task(process) which initialized the timer
+- the name of the process which initialized the timer
+- the function where the timer was initialized
+- the callback function which is associated to the timer
+- the number of events (callbacks)
+
+The timer_stats functionality is inactive on bootup.
+A sampling period can be started using the following command:
+
+ # echo 1 > /proc/timer_stats
+
+The following command stops a sampling period:
+
+ # echo 0 > /proc/timer_stats
+
+The statistics can be retrieved by:
+
+ $ cat /proc/timer_stats
+
+While sampling is enabled, each readout from /proc/timer_stats will see
+newly updated statistics.
+Once sampling is disabled, the sampled information
+is kept until a new sample period is started.
+This allows multiple readouts.
+
+Sample output from
+.IR /proc/timer_stats :
+
+.nf
+.RS -4
+.RB $ " cat /proc/timer_stats"
+Timer Stats Version: v0.3
+Sample period: 1.764 s
+Collection: active
+ 255, 0 swapper/3 hrtimer_start_range_ns (tick_sched_timer)
+ 71, 0 swapper/1 hrtimer_start_range_ns (tick_sched_timer)
+ 58, 0 swapper/0 hrtimer_start_range_ns (tick_sched_timer)
+ 4, 1694 gnome-shell mod_delayed_work_on (delayed_work_timer_fn)
+ 17, 7 rcu_sched rcu_gp_kthread (process_timeout)
+\&...
+ 1, 4911 kworker/u16:0 mod_delayed_work_on (delayed_work_timer_fn)
+ 1D, 2522 kworker/0:0 queue_delayed_work_on (delayed_work_timer_fn)
+1029 total events, 583.333 events/sec
+
+.fi
+.RE
+.IP
+The output columns are:
+.RS
+.IP * 3
+a count of the number of events,
+optionally (since Linux 2.6.23) followed by the letter \(aqD\(aq
+.\" commit c5c061b8f9726bc2c25e19dec227933a13d1e6b7 deferrable timers
+if this is a deferrable timer;
+.IP *
+the PID of the process that initialized the timer;
+.IP *
+the name of the process that initialized the timer;
+.IP *
+the function where the timer was initialized; and
+.IP *
+(in parentheses)
+the callback function that is associated with the timer.
+.RE
+.TP
.I /proc/tty
Subdirectory containing the pseudo-files and subdirectories for
tty drivers and line disciplines.
.\" .SH ACKNOWLEDGEMENTS
.\" The material on /proc/sys/fs and /proc/sys/kernel is closely based on
.\" kernel source documentation files written by Rik van Riel.
-.SH "SEE ALSO"
+.SH SEE ALSO
.BR cat (1),
.BR dmesg (1),
.BR find (1),
.BR mount (8),
.BR netstat (8),
.BR procinfo (8),
-.BR route (8)
-.br
-The kernel source files:
-.IR Documentation/filesystems/proc.txt ,
-.IR Documentation/sysctl/vm.txt
+.BR route (8),
+.BR sysctl (8)
+
+The Linux kernel source files:
+.IR Documentation/filesystems/proc.txt
+.IR Documentation/sysctl/fs.txt ,
+.IR Documentation/sysctl/kernel.txt ,
+.IR Documentation/sysctl/net.txt ,
+and
+.IR Documentation/sysctl/vm.txt .
+.SH COLOPHON
+This page is part of release 3.68 of the Linux
+.I man-pages
+project.
+A description of the project,
+information about reporting bugs,
+and the latest version of this page,
+can be found at
+\%http://www.kernel.org/doc/man\-pages/.
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