PostgreSQL is an open source, community driven, standard compliant object-relational database system.
Install the postgresql package. It will also create a system user called postgres.
You can now switch to the postgres user using a privilege elevation program.
[postgres]$in this article.
You can switch to the PostgreSQL user by executing the following command:
See sudo(8) or su(1) for their usage.
Before PostgreSQL can function correctly, the database cluster must be initialized:
[postgres]$ initdb -D /var/lib/postgres/data
-D is the default location where the database cluster must be stored (see #Change default data directory if you want to use a different one).
initdb accepts a number of extra arguments:
- By default, the locale and the encoding for the database cluster are derived from your current environment (using $LANG value). If this is not what you want, you can override the defaults using
--locale=locale(where locale is to be chosen amongst the system's available locales) and
--encoding=encoding(which must match the chosen locale). (Once the database is up, you can check which values were used with
[postgres]$ psql -l.)
- If your data directory resides on a file system without data checksumming, you may wish to enable PostgreSQL's built-in checksumming for increased integrity guarantees - add the
--data-checksumsargument to do so. Read #Enable data checksumming for more information. (Once the database is up, you can check if it is enabled with
[postgres]$ psql -c "SHOW data_checksums".)
- The trust authentication method is used by default, meaning that anyone on the host can connect as any database user. You can use
--auth-local=peer --auth-host=scram-sha-256for safer authentication methods.
- For more options, see
initdb --helpand official documentation.
[postgres]$ initdb --locale=C.UTF-8 --encoding=UTF8 -D /var/lib/postgres/data --data-checksums
Many lines should now appear on the screen with several ending by
The files belonging to this database system will be owned by user "postgres". This user must also own the server process. The database cluster will be initialized with locale "C.UTF-8". The default database encoding has accordingly been set to "UTF8". The default text search configuration will be set to "english". Data page checksums are disabled. fixing permissions on existing directory /var/lib/postgres/data ... ok creating subdirectories ... ok selecting default max_connections ... 100 selecting default shared_buffers ... 128MB selecting dynamic shared memory implementation ... posix creating configuration files ... ok running bootstrap script ... ok performing post-bootstrap initialization ... ok syncing data to disk ... ok WARNING: enabling "trust" authentication for local connections You can change this by editing pg_hba.conf or using the option -A, or --auth-local and --auth-host, the next time you run initdb. Success. You can now start the database server using: pg_ctl -D /var/lib/postgres/data -l logfile start
If these are the kind of lines you see, then the process succeeded. Return to the regular user using
WARNING, see #Restricts access rights to the database superuser by default.
/var/lib/postgres, you will have to edit the service file. If the root is under
home, make sure to set
- If the database resides on a Btrfs file system, you should consider disabling Copy-on-Write for the directory before creating any database.
- If the database resides on a ZFS file system, you should consult ZFS#Databases before creating any database.
Finally, start and enable the
Create your first database/user
Become the postgres user. Add a new database role/user using the createuser command:
[postgres]$ createuser --interactive
Create a new database over which the above user has read/write privileges using the createdb command (execute this command from your login shell if the database user has the same name as your Linux user, otherwise add
-O database-username to the following command):
$ createdb myDatabaseName
-U postgresto the previous command.
Familiarize with PostgreSQL
Access the database shell
Become the postgres user. Start the primary database shell, psql, where you can do all your creation of databases/tables, deletion, set permissions, and run raw SQL commands. Use the
-d option to connect to the database you created (without specifying a database,
psql will try to access a database that matches your username).
[postgres]$ psql -d myDatabaseName
Some helpful commands:
Connect to a particular database:
=> \c <database>
List all users and their permission levels:
Show summary information about all tables in the current database:
=> \q or CTRL+d
There are of course many more meta-commands, but these should help you get started. To see all meta-commands run:
The PostgreSQL database server configuration file is
postgresql.conf. This file is located in the data directory of the server, typically
/var/lib/postgres/data. This folder also houses the other main configuration files, including the
pg_hba.conf which defines authentication settings, for both local users and other hosts ones.
locateare not finding the configuration files.
Restricts access rights to the database superuser by default
pg_hba.conf allow any local user to connect as any database user, including the database superuser.
This is likely not what you want, so in order to restrict global access to the postgres user, change the following line:
# TYPE DATABASE USER ADDRESS METHOD # "local" is for Unix domain socket connections only local all all trust
# TYPE DATABASE USER ADDRESS METHOD # "local" is for Unix domain socket connections only local all postgres peer
You might later add additional lines depending on your needs or software ones.
Require password for login
/var/lib/postgres/data/pg_hba.conf and set the authentication method for each user (or "all" to affect all users) to
scram-sha-256 (preferred), or
md5 (less secure; should be avoided if possible):
# TYPE DATABASE USER ADDRESS METHOD # "local" is for Unix domain socket connections only local all user scram-sha-256
If you choose
scram-sha-256, you must also edit
/var/lib/postgres/data/postgresql.conf and set:
password_encryption = scram-sha-256
postgresql.service, and then re-add each user's password using
ALTER USER user WITH ENCRYPTED PASSWORD 'password';.
Configure PostgreSQL to be accessible exclusively through UNIX Sockets
In the connections and authentications section of your configuration, set:
listen_addresses = ''
This will disable network listening completely.
After this you should restart
postgresql.service for the changes to take effect.
Configure PostgreSQL to be accessible from remote hosts
In the connections and authentications section, set the
listen_addresses line to your needs:
listen_addresses = 'localhost,my_local_ip_address'
You can use
'*' to listen on all available addresses.
5432by default for remote connections. Make sure this port is open in your firewall and able to receive incoming connections. You can also change it in the configuration file, right below
Then add a line like the following to the authentication config:
# TYPE DATABASE USER ADDRESS METHOD # IPv4 local connections: host all all ip_address/32 md5
ip_address is the IP address of the remote client.
See the documentation for pg_hba.conf.
After this you should restart
postgresql.service for the changes to take effect.
For troubleshooting take a look in the server log file:
# journalctl -u postgresql.service
Configure PostgreSQL authenticate against PAM
PostgreSQL offers a number of authentication methods. If you would like to allow users to authenticate with their system password, additional steps are necessary. First you need to enable PAM for the connection.
For example, the same configuration as above, but with PAM enabled:
# IPv4 local connections: host all all my_remote_client_ip_address/32 pam
The PostgreSQL server is however running without root privileges and will not be able to access
/etc/shadow. We can work around that by allowing the postgres group to access this file:
# setfacl -m g:postgres:r /etc/shadow
Change default data directory
The default directory where all your newly created databases will be stored is
/var/lib/postgres/data. To change this, follow these steps:
Create the new directory and make the postgres user its owner:
# mkdir -p /pathto/pgroot/data # chown -R postgres:postgres /pathto/pgroot
Become the postgres user, and initialize the new cluster:
[postgres]$ initdb -D /pathto/pgroot/data
postgresql.service to create a drop-in file and override the
PIDFile settings. For example:
[Service] Environment=PGROOT=/pathto/pgroot PIDFile=/pathto/pgroot/data/postmaster.pid
If you want to use
/home directory for default directory or for tablespaces, add one more line in this file:
Change default encoding of new databases to UTF-8
-E UTF8or while using an UTF-8 locale, these steps are not required.
When creating a new database (e.g. with
createdb blog) PostgreSQL actually copies a template database. There are two predefined templates:
template0 is vanilla, while
template1 is meant as an on-site template changeable by the administrator and is used by default. In order to change the encoding of a new database, one of the options is to change on-site
template1. To do this, log into PostgreSQL shell (
psql) and execute the following:
First, we need to drop
template1. Templates cannot be dropped, so we first modify it so it is an ordinary database:
UPDATE pg_database SET datistemplate = FALSE WHERE datname = 'template1';
Now we can drop it:
DROP DATABASE template1;
The next step is to create a new database from
template0, with a new default encoding:
CREATE DATABASE template1 WITH TEMPLATE = template0 ENCODING = 'UNICODE';
template1 so it is actually a template:
UPDATE pg_database SET datistemplate = TRUE WHERE datname = 'template1';
Optionally, if you do not want anyone connecting to this template, set
UPDATE pg_database SET datallowconn = FALSE WHERE datname = 'template1';
Now you can create a new database:
[postgres]$ createdb blog
If you log back in to
psql and check the databases, you should see the proper encoding of your new database:
List of databases Name | Owner | Encoding | Collation | Ctype | Access privileges -----------+----------+-----------+-----------+-------+---------------------- blog | postgres | UTF8 | C | C | postgres | postgres | SQL_ASCII | C | C | template0 | postgres | SQL_ASCII | C | C | =c/postgres : postgres=CTc/postgres template1 | postgres | UTF8 | C | C |
Enable data checksumming
If your database files reside on a file system without checksumming, its data is suspectible to silent data corruption due to bit rot and broken hardware. While those events are rare, you might want to enable PostgreSQL's built-in data checksumming if you care about data integrity. This feature must be enabled on the cluster level, not per-database or per-table.
- There is a minimal performance impact, especially while reading large datasets from disk. In-memory operations are not affected.
- PostgreSQL is unable to repair corrupt data - it will only abort transactions reading from corrupt pages to prevent further damage or invalid execution results.
- Checksums cover on-disk data (row) pages only, not metadata or control structures. In-memory pages are not checksummed. Error-corrected storage and ECC memory is still beneficial.
- To enable checksumming during cluster creation, add the
- To verify whenever checksumming is enabled, run
[postgres]$ psql -c "SHOW data_checksums"(which should print
- To toggle checksumming on an existing cluster:
[postgres]$ pg_checksums --pgdata /var/lib/postgres/data --enable(or
--disableif you no longer want checksumming). Enabling checksums will rewrite all database pages, which will take a while for large database instances.
- phpPgAdmin — Web-based administration tool for PostgreSQL.
- pgAdmin — Comprehensive design and management GUI for PostgreSQL.
- https://www.pgadmin.org/ || pgadmin3AUR or pgadmin4
- pgModeler — Graphical schema designer for PostgreSQL.
For tools supporting multiple DBMSs, see List of applications/Documents#Database tools.
Upgrading major PostgreSQL versions (e.g. version 14.x to version 15.y) requires some extra maintenance.
Get the currently used database version via
# cat /var/lib/postgres/data/PG_VERSION
To ensure you do not accidentally upgrade the database to an incompatible version, it is recommended to skip updates to the PostgreSQL packages.
Minor version upgrades are safe to perform. However, if you do an accidental upgrade to a different major version, you might not be able to access any of your data. Always check the PostgreSQL home page to be sure of what steps are required for each upgrade. For a bit about why this is the case, see the versioning policy.
There are two main ways to upgrade your PostgreSQL database. Read the official documentation for details.
pg_upgrade utility attempts to copy over as much compatible data as possible between clusters and upgrading everything else. It is generally the fastest method to upgrade most instances, although it requires access to binaries for both source and target PostgreSQL versions. Read the pg_upgrade(1) man page to understand what actions it performs. For non-trivial instances (e.g. with streaming replication or log-shipping), read the upstream documentation first.
For those wishing to use
pg_upgrade, a postgresql-old-upgrade package is available that will always run one major version behind the real PostgreSQL package. This can be installed side-by-side with the new version of PostgreSQL. To upgrade from older versions of PostgreSQL there are AUR packages available, e.g. postgresql-12-upgradeAUR. (You must use the
pg_upgrade version packaged with the PostgreSQL version you are upgrading to.)
Note that the database cluster directory does not change from version to version, so before running
pg_upgrade, it is necessary to rename your existing data directory and migrate into a new directory. The new database cluster must be initialized using the same parameters as the old one.
When you are ready to begin the upgrade:
- While the old database cluster is still online, collect the
initdbarguments used to create it. Refer to #Initial configuration for more information.
postgresql.service. (Check the unit status to be sure that PostgresSQL was stopped correctly. If it failed,
pg_upgradewill fail too.)
- Upgrade postgresql, postgresql-libs, and postgresql-old-upgrade.
- Rename the old cluster directory, then create a new cluster and temporary working directory:
# mv /var/lib/postgres/data /var/lib/postgres/olddata # mkdir /var/lib/postgres/data /var/lib/postgres/tmp # chown postgres:postgres /var/lib/postgres/data /var/lib/postgres/tmp [postgres]$ cd /var/lib/postgres/tmp
- Initialize the new cluster using the same
initdbarguments as were used for the old cluster:
[postgres]$ initdb -D /var/lib/postgres/data --locale=C.UTF-8 --encoding=UTF8 --data-checksums
- Upgrade the cluster, replacing
PG_VERSIONbelow, with the old PostgreSQL version number (e.g.
[postgres]$ pg_upgrade -b /opt/pgsql-PG_VERSION/bin -B /usr/bin -d /var/lib/postgres/olddata -D /var/lib/postgres/dataNote: If necessary, adjust the configuration files of new cluster (e.g.
postgresql.conf) to match the old cluster.Note: If
The source cluster was not shut down cleanly, PostgreSQL was not stopped before attempting the upgrade. Stop it, then restart the cluster with old database binaries to recover old cluster files:
[postgres]$ /opt/pgsql-PG_VERSION/bin/pg_ctl start -D /var/lib/postgres/olddata && /opt/pgsql-PG_VERSION/bin/pg_ctl stop -D /var/lib/postgres/olddataYou can now safely retry the
pg_upgradecommand. If the upgrade process still fails, shut down any database processes, downgrade PostgreSQL packages to their previous versions, recover your previous cluster data from backups and restart the upgrade process.
- Optional: Run
[postgres]$ vacuumdb --all --analyze-in-stagesto recalculate query analyzer statistics, which should improve query performance shortly after the upgrade. (Adding
--jobs=NUMBER_OF_CPU_CORESargument may improve this command's performance.)
- Optional: Back up the
/var/lib/postgres/olddatadirectory in case you need to restore a previous PostgreSQL version.
- Delete the
/var/lib/postgres/olddatadirectory with old cluster data.
- Delete the
pg_upgrade is said to be tricky. On a talk in a recent postgresql conference, the presenter asked everyone that had used
to raise their hands, followed up by the next question - how many have used
pg_upgrade and it just worked on the first attempt without any errors? Very few hands to be seen on the second question. This section is intended to be a list of problems people have observed when upgrading PostgreSQL under Archlinux (problems should preferably be reported upstream, too).
- When upgrading from Postgresql 14 to Postgresql 15, old postgresql did not start - it insisted on fetching data from
/var/lib/postgres/data.oldand threw an error message that the directory was created with pg 15 and not pg 14. Moving the old directory to
/var/lib/postgres/dataand the new directory to
/var/lib/postgres/15did not help - then things were apparently freezing. What did help was to edit
data_directoryfrom that file. (Hm ... perhaps a user error to have that thing there at all, if the config file is in the data directory, obviously postgresql has already found the data directory and should not need that directive. Postgresql was installed through
puppetlabs-postgresqlpuppet module, it is managing the configuration).
Manual dump and reload
You could also do something like this (after the upgrade and install of postgresql-old-upgrade).
- Below are the commands for upgrading from PostgreSQL 14. You can find similar commands in
/opt/for your version of PostgreSQL cluster, provided you have matching version of postgresql-old-upgrade package installed.
- If you had customized your
pg_hba.conffile, you may have to temporarily modify it to allow full access to old database cluster from local system. After upgrade is complete set your customization to new database cluster as well and restart
# mv /var/lib/postgres/data /var/lib/postgres/olddata # mkdir /var/lib/postgres/data # chown postgres:postgres /var/lib/postgres/data [postgres]$ initdb -D /var/lib/postgres/data --locale=C.UTF-8 --encoding=UTF8 --data-checksums [postgres]$ /opt/pgsql-14/bin/pg_ctl -D /var/lib/postgres/olddata/ start # cp /usr/lib/postgresql/postgis-3.so /opt/pgsql-14/lib/ # Only if postgis installed [postgres]$ pg_dumpall -h /tmp -f /tmp/old_backup.sql [postgres]$ /opt/pgsql-14/bin/pg_ctl -D /var/lib/postgres/olddata/ stop
[postgres]$ psql -f /tmp/old_backup.sql postgres
Improve performance of small transactions
If you are using PostgresSQL on a local machine for development and it seems slow, you could try turning synchronous_commit off in the configuration. Beware of the caveats, however.
synchronous_commit = off
Prevent disk writes when idle
PostgreSQL periodically updates its internal "statistics" file. By default, this file is stored on disk, which prevents disks from spinning down on laptops and causes hard drive seek noise. It is simple and safe to relocate this file to a memory-only file system with the following configuration option:
stats_temp_directory = '/run/postgresql'
pgAdmin 4 issues after upgrade to PostgreSQL 12
If you see errors about
string indices must be integers when navigating the tree on the left, or about
column rel.relhasoids does not exist when viewing the data, remove the server from the connection list in pgAdmin and add a fresh server instance. pgAdmin will otherwise continue to treat the server as a PostgreSQL 11 server resulting in these issues.
PostgreSQL database unable to start after package update when using extensions
The cause in this case is mostly the existing package is not compiled for the newer version (and it may be up-to-date), the solution is rebuilding the package either manually or waiting for an update to the extension package.
Failing to start a PostgreSQL server with the older version of the database while upgrading to the newer version with extensions
This is caused because the old version of postgres from the package postgresql-old-upgrade does not have the required extensions (.so files) in its lib directory, the current solution is dirty, and might cause a lot of problems so keep a backup of the database just in case, basically copy the required extension .so files from
/opt/pgsql-XX/lib/ (remember to replace XX with the major version of postgresql-old-upgrade).
For example, for timescaledb
# cp /usr/lib/postgresql/timescaledb*.so /opt/pgsql-13/lib/
to know the exact files to copy, check the contant of the package of the extension using :
$ pacman -Ql package_name