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<chapter id="backup">
<title>Backup and Restore</title>
</para>
<para>
- Some versions of GNU <application>tar</> consider it an error if a file
- is changed while <application>tar</> is copying it. This case is normal,
- and not an error, when taking a base backup of an active database.
- Since ignoring all errors from <application>tar</> would be unwise,
- you should either manually inspect <application>tar</>'s messages or
- else use a different backup tool that does not complain about this case.
+ Some backup tools that you might wish to use emit warnings or errors
+ if the files they are trying to copy change while the copy proceeds.
+ This situation is normal, and not an error, when taking a base backup of
+ an active database; so you need to ensure that you can distinguish
+ complaints of this sort from real errors. For example, some versions
+ of <application>rsync</> return a separate exit code for <quote>vanished
+ source files</>, and you can write a driver script to accept this exit
+ code as a non-error case. Also,
+ some versions of GNU <application>tar</> consider it an error if a file
+ is changed while <application>tar</> is copying it. There does not seem
+ to be any very convenient way to distinguish this error from other types
+ of errors, other than manual inspection of <application>tar</>'s messages.
+ GNU <application>tar</> is therefore not the best tool for making base
+ backups.
</para>
<para>