WAL files are not copied

Question

I'm using postgres 9.3 on Ubuntu 14.04 and I'm currently setting up a WAL backup. These are my changes to the postgresql.conf: [as described here: http://www.postgresql.org/docs/9.3/static/continuous-archiving.html ]

# - Settings -
wal_level = archive                     # minimal, archive, or hot_standby
                                        # (change requires restart)
# - Archiving -
archive_mode = on               # allows archiving to be done
archive_command = 'cp %p /home/userName/Documents/WALS'             

I did a 'sudo service postgresql restart' after changing the config and there are wal files generated:

root@control:/var/lib/postgresql/9.3/main/pg_xlog# ls -hlrt
total 49M
-rw------- 1 postgres postgres  16M Dez  2 14:24 000000010000000000000002
-rw------- 1 postgres postgres  16M Dez  2 14:24 000000010000000000000003
drwx------ 2 postgres postgres 4,0K Dez  2 14:24 archive_status
-rw------- 1 postgres postgres  16M Dez  2 14:25 000000010000000000000004



root@control:/var/lib/postgresql/9.3/main/pg_xlog# ls archive_status/
000000010000000000000002.ready  000000010000000000000003.ready

I assume that the archive_status means that WAL segments 2 and 3 are ready to be archived. But I don't find anything in the Documents/WALS (which exists).

Could someone give me a hint?

Answer 1

The wal files are archived when they are no longer needed in the pg_xlog directory (usually when there are 16 segments and another one is needed - the one that is rolled over and reused is first archived). You can force the system to archive some files to verify manually if you want - to do this run the following:

select pg_start_backup('testing_archiving');
select pg_stop_backup();

Once pg_stop_backup() is finished, you should see a few files in the archive directory.

Postgres uses the archive status folder to record "notes" about archiving attempts and so on with regard to the WAL files.