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<chapter id="backup">

<title>Backup and Restore</title>

<para>

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

This situation is normal, and not an error, when taking a base backup

ofan 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. Fortunately, GNU

<application>tar</> versions 1.16 and later exit with <literal>1</>

if files changed during the backup, and <literal>2</> for other errors.

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 was truncated

while <application>tar</> is copying it. Fortunately, GNU

<application>tar</> versions 1.16 and later exits with <literal>1</>

if a file was changed during the backup, and <literal>2</> for other

errors.

</para>

<para>