Backing up the server
The following shell commands can be used for database backup and restore on a running PostgreSQL server in an Airtime system.
You can dump the entire database to a zipped file with the combination of the pg_dumpall command and gzip. The pg_dumpall command is executed as the user postgres, by using the sudo command and the -u switch. It is separated from the gzip command with the pipe symbol.
sudo -u postgres pg_dumpall | gzip -c > airtime-backup.gz
This command can be automated to run on a regular basis using the standard cron tool on your server.
When restoring a production database on a cleanly installed Airtime system, it may be necessary to drop the empty database that was created during the new installation, by using the dropdb command. Again, this command is executed with sudo as the user postgres:
sudo -u postgres dropdb airtime
This dropdb command above is necessary to avoid 'already exists' errors on table creation when overwriting an empty Airtime database in the next step. These errors might prevent some data from being restored, such as user account data.
To restore, first unzip the backup file with gunzip, then use the psql command as the postgres user:
gunzip airtime-backup.gz sudo -u postgres psql -f airtime-backup postgres
You should now be able to log in to the Airtime web interface in the usual way.
For safety reasons, your regular database backups should be kept in a directory which is backed up by your storage backup tool of choice; for example, the /srv/airtime/database_backups directory. This should ensure that a storage restore can be made along with a matching and complete version of the Airtime database from the day that the storage backup was made.
Backing up the Airtime database with pg_dumpall will not back up the Airtime media storage server, which is likely to need a great deal more backup space. Creating a compressed file from hundreds of gigabytes of storage server contents is likely to take a very long time, and may have little benefit for the amount of CPU power used, if the media files are already stored in a highly compressed format. It is also impractical to copy very large backup files across the network on a daily basis.
Instead, it is preferable to use an incremental backup technique to synchronise the production Airtime server storage with a backup server each day or night. If the backup server also contains an Airtime installation, it should be possible to switch playout to this second machine relatively quickly, in case of a hardware failure or other emergency on the production server.
A standard incremental backup tool on GNU/Linux servers is rsync (http://rsync.samba.org/) which can be installed using the package manager of your GNU/Linux distribution. However, incremental backup alone cannot help in the scenario where a file which later proves to be important has been deleted by an administrator. For backups that can be rolled back to restore from an earlier date than the current backup, the tool rdiff-backup (http://www.nongnu.org/rdiff-backup/) can be deployed.