diff options
| -rw-r--r-- | doc/src/sgml/backup.sgml | 25 |
1 files changed, 14 insertions, 11 deletions
diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml index b646c7c5987..cec8ff5fe2b 100644 --- a/doc/src/sgml/backup.sgml +++ b/doc/src/sgml/backup.sgml @@ -560,7 +560,8 @@ tar -cf backup.tar /usr/local/pgsql/data character in the command. The simplest useful command is something like: <programlisting> -archive_command = 'cp -i %p /mnt/server/archivedir/%f </dev/null' +archive_command = 'test ! -f /mnt/server/archivedir/%f && cp %p /mnt/server/archivedir/%f' # Unix +archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"' # Windows </programlisting> which will copy archivable WAL segments to the directory <filename>/mnt/server/archivedir</>. (This is an example, not a @@ -568,7 +569,7 @@ archive_command = 'cp -i %p /mnt/server/archivedir/%f </dev/null' <literal>%p</> and <literal>%f</> parameters have been replaced, the actual command executed might look like this: <programlisting> -cp -i pg_xlog/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065 </dev/null +test ! -f /mnt/server/archivedir/00000001000000A900000065 && cp pg_xlog/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065 </programlisting> A similar command will be generated for each new file to be archived. </para> @@ -597,17 +598,19 @@ cp -i pg_xlog/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900 preserve the integrity of your archive in case of administrator error (such as sending the output of two different servers to the same archive directory). + </para> + + <para> It is advisable to test your proposed archive command to ensure that it indeed does not overwrite an existing file, <emphasis>and that it returns - nonzero status in this case</>. We have found that <literal>cp -i</> does - this correctly on some platforms but not others. If the chosen command - does not itself handle this case correctly, you should add a command - to test for pre-existence of the archive file. For example, something - like: -<programlisting> -archive_command = 'test ! -f .../%f && cp %p .../%f' -</programlisting> - works correctly on most Unix variants. + nonzero status in this case</>. + The example command above for Unix ensures this by including a separate + <command>test</> step. On some Unix platforms, <command>cp</> has + switches such as <option>-i</> that can be used to do the same thing + less verbosely, but you should not rely on these without verifying that + the right exit status is returned. (In particular, GNU <command>cp</> + will return status zero when <option>-i</> is used and the target file + already exists, which is <emphasis>not</> the desired behavior.) </para> <para> |