e2image: add offset switches

Add -o and -O switches to specify the offset where the source
and destination filesystems start.  This is useful if you have
an image of a partitioned disk or wish to create one.

Signed-off-by: Phillip Susi <psusi@ubuntu.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/misc/e2image.8.in b/misc/e2image.8.in
index 78f0682..ba97ef8 100644 (file)
--- a/misc/e2image.8.in
+++ b/misc/e2image.8.in
@@ -10,6 +10,14 @@ e2image \- Save critical ext2/ext3/ext4 filesystem metadata to a file
 [
 .B \-rsIQa
 ]
+[
+.B \-o
+.I source_offset
+]
+[
+.B \-O
+.I dest_offset
+]
 .I device
 .I image-file
 .SH DESCRIPTION
@@ -201,6 +209,34 @@ give an image that is suitable to use to clone the entire FS or
 for backup purposes.  Note that this option only works with the
 raw or QCOW2 formats.
 .PP
+.SH OFFSETS
+Normally a filesystem starts at the beginning of a partition, and
+.B e2image
+is run on the partition.  When working with image files, you don't
+have the option of using the partition device, so you can specify
+the offset where the filesystem starts directly with the
+.B \-o
+option.  Similarly the
+.B \-O
+option specifies the offset that should be seeked to in the destination
+before writing the filesystem.
+.PP
+For example, if you have a
+.B dd
+image of a whole hard drive that contains an ext2 fs in a partition
+starting at 1 MiB, you can clone that fs with:
+.PP
+.br
+\      \fBe2image \-aro 1048576 img /dev/sda1\fR
+.br
+.PP
+Or you can clone a fs into an image file, leaving room in the first
+MiB for a partition table with:
+.PP
+.br
+\      \fBe2image -arO 1048576 /dev/sda1 img\fR
+.br
+.PP
 .SH AUTHOR
 .B e2image
 was written by Theodore Ts'o (tytso@mit.edu).

diff --git a/misc/e2image.c b/misc/e2image.c
index 4fb9a96..2f80eff 100644 (file)
--- a/misc/e2image.c
+++ b/misc/e2image.c
@@ -55,6 +55,7 @@ static char * device_name = NULL;
 static char all_data;
 static char output_is_blk;
 /* writing to blk device: don't skip zeroed blocks */
+blk64_t source_offset, dest_offset;
 
 static void lseek_error_and_exit(int errnum)
 {
@@ -87,7 +88,7 @@ static int get_bits_from_size(size_t size)
 
 static void usage(void)
 {
-       fprintf(stderr, _("Usage: %s [-rsIQaf] device image_file\n"),
+       fprintf(stderr, _("Usage: %s [-rsIQaf] [-o source_offset] [-O dest_offset] device image_file\n"),
                program_name);
        exit (1);
 }
@@ -1278,7 +1279,7 @@ int main (int argc, char ** argv)
        if (argc && *argv)
                program_name = *argv;
        add_error_table(&et_ext2_error_table);
-       while ((c = getopt(argc, argv, "rsIQaf")) != EOF)
+       while ((c = getopt(argc, argv, "rsIQafo:O:")) != EOF)
                switch (c) {
                case 'I':
                        flags |= E2IMAGE_INSTALL_FLAG;
@@ -1302,6 +1303,12 @@ int main (int argc, char ** argv)
                case 'f':
                        ignore_rw_mount = 1;
                        break;
+               case 'o':
+                       source_offset = strtoull(optarg, NULL, 0);
+                       break;
+               case 'O':
+                       dest_offset = strtoull(optarg, NULL, 0);
+                       break;
                default:
                        usage();
                }
@@ -1313,7 +1320,11 @@ int main (int argc, char ** argv)
                                         "with raw or QCOW2 images.");
                exit(1);
        }
-
+       if ((source_offset || dest_offset) && img_type != E2IMAGE_RAW) {
+               com_err(program_name, 0,
+                       "Offsets are only allowed with raw images.");
+               exit(1);
+       }
        device_name = argv[optind];
        image_fn = argv[optind+1];
 
@@ -1346,9 +1357,11 @@ int main (int argc, char ** argv)
                        goto skip_device;
                }
        }
-
-       retval = ext2fs_open (device_name, open_flag, 0, 0,
-                             unix_io_manager, &fs);
+       char *options;
+       asprintf (&options, "offset=%llu", source_offset);
+       retval = ext2fs_open2 (device_name, options, open_flag, 0, 0,
+                              unix_io_manager, &fs);
+       free (options);
         if (retval) {
                com_err (program_name, retval, _("while trying to open %s"),
                         device_name);
@@ -1367,6 +1380,11 @@ skip_device:
                        exit(1);
                }
        }
+       if (dest_offset)
+               if (ext2fs_llseek (fd, dest_offset, SEEK_SET) < 0) {
+                       perror("ext2fs_llseek");
+                       exit(1);
+               }
 
        if ((img_type & E2IMAGE_QCOW2) && (fd == 1)) {
                com_err(program_name, 0, "QCOW2 image can not be written to "