How to check why a PostgreSQL server won't start

journalctl -u postgresql-15.service

Example output:

Dec 27 07:15:50 psl0part-prod-pgsql02.skead.no systemd[1]: Unit postgresql-15.service entered failed state.
Dec 27 07:15:50 psl0part-prod-pgsql02.skead.no systemd[1]: postgresql-15.service failed.
Dec 27 07:22:01 psl0part-prod-pgsql02.skead.no systemd[1]: Starting PostgreSQL 15 database server...
Dec 27 07:22:01 psl0part-prod-pgsql02.skead.no postmaster[65528]: 
2024-12-27 06:22:01.703 GMT [65528] 
LOG:  syntax error in file "/path/to/file/postgresql.auto.conf" line
Dec 27 07:22:01 psl0part-prod-pgsql02.skead.no systemd[1]: postgresql-15.service: main process exited, code=exited, status=1/FAILURE
Dec 27 07:22:01 psl0part-prod-pgsql02.skead.no systemd[1]: Failed to start PostgreSQL 15 database server.
Dec 27 07:22:01 psl0part-prod-pgsql02.skead.no systemd[1]: Unit postgresql-15.service entered failed state.
Dec 27 07:22:01 psl0part-prod-pgsql02.skead.no systemd[1]: postgresql-15.service failed.

In this case, the error seems to be in an error in the file postgresql.auto.conf.

How to use rsync between two servers

For example, to syncronize two servers so they get identical file structures: 

• Source server: server1.oric.no 
• Destination server: server2.oric.no 
• Execute as: root

target=server2.oric.no && rsync -vaz --delete /u01/app/myfiles ebsuser@$target:/u01/app

This will sync the entire "/u01/app/myfiles" folder + all subfolders.

The --delete flag in rsync ensures that files in the destination directory (ebsuser@$target:/u01/app) that are not present in the source directory (/u01/app/inst) are deleted. This helps keep the destination directory synchronized with the source directory.