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postgresql [2017/02/13 14:41]
mstraub [Backups]
postgresql [2020/07/15 09:42] (current)
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 # set a password # set a password
 \password \password
 +# make an existing user superuser (or remove superuser rights)
 +sudo -u postgres psql -c "ALTER USER theuser WITH SUPERUSER;"​
 +sudo -u postgres psql -c "ALTER USER theuser WITH NOSUPERUSER;"​
 # create a restricted user with password (long and short version) # create a restricted user with password (long and short version)
Line 58: Line 62:
 ==== Setting a password for user postgres ==== ==== Setting a password for user postgres ====
 <code sql> <code sql>
-alter user postgres ​with password '​password';​+\password ​postgres
 </​code>​ </​code>​
Line 126: Line 130:
 -- list all users -- list all users
 \du \du
 -- list all schemas -- list all schemas
 \dn \dn
--- list all tables ​(and views) in the current database / show details of table+ 
 +-- list tables
 \d \d
 \d+  -- (also show comments) \d+  -- (also show comments)
-\d tablename +\d tablename ​-- show details of a table 
--- list all tables of a certain schema + 
-\dt schemaname.*+-- list all tables / tables of a certain schema 
 +\dt *.* -- list all tables in DB 
 +\dt schemaname.* ​-- list all tables in a certain schema 
 +-- list all views 
 +\dv *.* -- list all views in DB 
 -- list all databases on the host -- list all databases on the host
 \l \l
 -- connect to a database -- connect to a database
 \c dbname \c dbname
 -- execute a command on the Linux shell (as-is) -- execute a command on the Linux shell (as-is)
 \! command \! command
 -- quit -- quit
 \q \q
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 ====== Backups ====== ====== Backups ======
 +There are many options available on how to back up your databases. Postgres already contains some tools itself:
 +  * ''​pg_dump'':​ per-database dumping of db contents
 +  * ''​pg_basebackup'':​ binary backup of whole postgres clusters (per db backup is not possible)
 +However, especially for larger databases (hundreds of GB) more powerful third-party tools featuring parallelism ​ and incremental backups are [[http://​​2017/​02/​03/​pg-phriday-getting-back-up|recommended]]:​
 +  * [[https://​|pgBackRest]]
 +  * [[https://​|pgBarman]]
 +===== pg_dump =====
 It makes sense to use the postgres user It makes sense to use the postgres user
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 # └───────────────────────── min (0 - 59) # └───────────────────────── min (0 - 59)
 </​code>​ </​code>​
 +===== pg_basebackup =====
 +see e.g. [[https://​​2016/​02/​15/​how-to-perform-base-postgresql-backup-using-pg_basebackup-utility|this tutorial]]
 +===== pgBackRest =====
 +A typical use of pgBackRest would be to install a backup server that backs up several DB servers. For now we only use a simpler approach: pgBackRest backing up on localhost. For more see the [[https://​​user-guide.html|excellent user guide]] or [[https://​​2018/​01/​04/​introduction_to_pgbackrest.html|this good introduction blog post]].
 +Install from postgres repo:
 +<code bash>
 +sudo add-apt-repository "deb http://​​pub/​repos/​apt/​ xenial-pgdg main"
 +wget --quiet -O - https://​​media/​keys/​ACCC4CF8.asc | sudo apt-key add -
 +sudo apt update
 +sudo apt install pgbackrest
 +==== Incremental Backups on Localhost ====
 +In addition to the global section, where e.g. retention is configured, you must add a so-called "​stanza"​ for each cluster you want to back up. Make sure the repo1-path exists and is owned by user postgres.
 +<file - /​etc/​pgbackrest/​pgbackrest.conf>​
 +Then adjust the postgres config to allow for proper backups
 +<file - /​etc/​postgresql/​9.5/​main/​postgresql.conf>​
 +listen_addresses = '​*'​
 +wal_level = hot_standby ​
 +archive_mode = on 
 +archive_command = '​pgbackrest --stanza=STANZANAME archive-push %p'
 +max_wal_senders = 3
 +log_line_prefix = ''​
 +Reload the cluster (or the complete postgres server) to activate changes
 +  sudo systemctl restart postgresql@9.5-CLUSTERNAME
 +  ​
 +Create and test the pgbackrest stanza
 +  sudo -u postgres pgbackrest --stanza=STANZANAME --log-level-console=info stanza-create
 +  sudo -u postgres pgbackrest --stanza=STANZANAME --log-level-console=info check
 +Make backups manually (e.g. from a cronjob)
 +  sudo -u postgres pgbackrest --stanza=STANZANAME --type=full --log-level-console=detail backup
 +  sudo -u postgres pgbackrest --stanza=STANZANAME --type=incr --log-level-console=detail backup
 +Make **regular backups via cronjob**
 +<file - /​etc/​cron.d/​pgbackrest>​
 +#minute hour day-of-month month day-of-week user command
 +0 4 * * 0   ​postgres pgbackrest --type=full --stanza=STANZANAME backup
 +0 4 * * 1-6 postgres pgbackrest --type=diff --stanza=STANZANAME backup
 +**Restore latest backup.** The cluster must be stopped and the cluster directory must exist and be empty.
 +  sudo systemctl stop postgresql@9.5-CLUSTERNAME
 +  sudo mv /​var/​lib/​postgresql/​9.5/​CLUSTERNAME /​opt/​backups/​CLUSTERNAME_backup
 +  sudo -u postgres mkdir /​var/​lib/​postgresql/​9.5/​CLUSTERNAME
 +  sudo chmod 0700 /​var/​lib/​postgresql/​9.5/​CLUSTERNAME
 +  sudo -u postgres pgbackrest --stanza=STANZANAME --log-level-console=detail restore
 +  sudo systemctl start postgresql@9.5-CLUSTERNAME
 +To **restore a specific backup** use ''​%%--set%%''​ with the name of a folder in ''/​var/​lib/​pgbackrest/​backup/​STANZANAME'',​ e.g.:
 +  sudo -u postgres pgbackrest --set=20180724-144511F --stanza=STANZANAME --log-level-console=detail restore
 +You can also copy the contents of ''/​var/​lib/​pgbackrest''​ to a different device and restore it there.
 +Log files can be found in ''/​var/​log/​pgbackrest''​.
 ====== Performance Tuning ====== ====== Performance Tuning ======
postgresql.1486993317.txt.gz · Last modified: 2017/02/13 14:41 by mstraub