restore from pg_basebackup

Issue

I made daily backups of a postgresql DB using the command

/usr/bin/pg_basebackup -D $outdir -Ft -x -z -w -R -v

Now I want to restore this DB on another server. I used the description on https://www.postgresql.org/docs/9.5/static/continuous-archiving.html#BACKUP-PITR-RECOVERY.

The recovery.conf file included in the backup has the following contents:

standby_mode = 'on'
primary_conninfo = 'user=postgres port=5432 sslmode=prefer sslcompression=1 krbsrvname=postgres'

The next step (8.) in the documentation says to start postgresql. This results in a failure due to a timeout:

3783 postgres: startup process   waiting for 0000000100000024000000B 

On the original server I don’t have this file. Is it possible to restore only the state of the pg_basebackup without using any WAL files? What should then be in the recovery.conf file?

Following the suggestion by @JosMac I moved the recovery.conf with this result:

shaun2:/var/lib/pgsql/data # service postgresql start
Job for postgresql.service failed because the control process exited with error code. See "systemctl status postgresql.service" and "journalctl -xe" for details.
shaun2:/var/lib/pgsql/data # service postgresql status
â postgresql.service - PostgreSQL database server
   Loaded: loaded (/usr/lib/systemd/system/postgresql.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Mon 2018-06-18 12:02:53 CEST; 12s ago
  Process: 1340 ExecStop=/usr/lib/postgresql-init stop (code=exited, status=0/SUCCESS)
  Process: 9355 ExecStart=/usr/lib/postgresql-init start (code=exited, status=1/FAILURE)
 Main PID: 1060 (code=exited, status=0/SUCCESS)

Jun 18 12:02:52 shaun2 postgres[9369]: [3-1] 2018-06-18 12:02:52 CEST   LOG:  invalid checkpoint record
Jun 18 12:02:52 shaun2 postgres[9369]: [4-1] 2018-06-18 12:02:52 CEST   FATAL:  could not locate required checkpoint record
Jun 18 12:02:52 shaun2 postgres[9369]: [4-2] 2018-06-18 12:02:52 CEST   HINT:  If you are not restoring from a backup, try removing the file "/var/lib/pgsql/data/backup_label".
Jun 18 12:02:52 shaun2 postgres[9367]: [2-1] 2018-06-18 12:02:52 CEST   LOG:  startup process (PID 9369) exited with exit code 1
Jun 18 12:02:52 shaun2 postgres[9367]: [3-1] 2018-06-18 12:02:52 CEST   LOG:  aborting startup due to startup process failure
Jun 18 12:02:53 shaun2 postgresql-init[9355]: pg_ctl: could not start server
Jun 18 12:02:53 shaun2 systemd[1]: postgresql.service: Control process exited, code=exited status=1
Jun 18 12:02:53 shaun2 systemd[1]: Failed to start PostgreSQL database server.
Jun 18 12:02:53 shaun2 systemd[1]: postgresql.service: Unit entered failed state.
Jun 18 12:02:53 shaun2 systemd[1]: postgresql.service: Failed with result 'exit-code'.

I suppose that PostgreSQL is still looking for the missing WAL file because of the contents of backup_label:

shaun2:/var/lib/pgsql/data # cat backup_label
START WAL LOCATION: 24/B0000028 (file 0000000100000024000000B0)
CHECKPOINT LOCATION: 24/B0000028
BACKUP METHOD: streamed
BACKUP FROM: master
START TIME: 2018-06-14 02:55:08 CEST
LABEL: pg_basebackup base backup

Result after moving backup_label away:

shaun2:/var/lib/pgsql/data # service postgresql status
â postgresql.service - PostgreSQL database server
   Loaded: loaded (/usr/lib/systemd/system/postgresql.service; enabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since Mon 2018-06-18 12:17:54 CEST; 4s ago
  Process: 1340 ExecStop=/usr/lib/postgresql-init stop (code=exited, status=0/SUCCESS)
  Process: 10401 ExecStart=/usr/lib/postgresql-init start (code=exited, status=1/FAILURE)
 Main PID: 1060 (code=exited, status=0/SUCCESS)

Jun 18 12:17:53 shaun2 postgres[10414]: [4-1] 2018-06-18 12:17:53 CEST   LOG:  invalid secondary checkpoint record
Jun 18 12:17:53 shaun2 postgres[10414]: [5-1] 2018-06-18 12:17:53 CEST   PANIC:  could not locate a valid checkpoint record
Jun 18 12:17:54 shaun2 postgres[10412]: [2-1] 2018-06-18 12:17:54 CEST   LOG:  startup process (PID 10414) was terminated by signal 6: Aborted

Solution

We use pg_basebackup for backups and also did several restorations so generally it works very well without problems.

But I would recommend you to use parameter -X stream instead of -x (meaning “-X fetch”). With this parameter pg_basebackup will catch and store WAL log segments created during the time of backup together with data files. These WAL logs will be stored in separate pg_xlog.tar or pg_wal.tar files (depending on PG version).

Full description of restoration can be find here – pg_basebackup / pg-barman – restore tar backup

Answered By – JosMac

This Answer collected from stackoverflow, is licensed under cc by-sa 2.5 , cc by-sa 3.0 and cc by-sa 4.0

Leave a Reply

(*) Required, Your email will not be published