PostgreSQL is an open source, community driven, standard compliant object-relational database system.
This document describes how to set up PostgreSQL. It also describes how to configure PostgreSQL to be accessible from a remote client. Among other applications, PostgreSQL can be substituted for MySQL as part of the LAMP web stack.
- 1 Installing PostgreSQL
- 2 Create your first database/user
- 3 Familiarize with PostgreSQL
- 4 Optional configuration
- 5 Administration tools
- 6 Setup HHVM to work with PostgreSQL
- 7 Upgrading PostgreSQL
- 8 Troubleshooting
Then, switch to the default PostgreSQL user postgres by executing the following command:
- If you have sudo and your username is in
$ sudo -u postgres -i
$ su # su -l postgres
Seeor for their usage.
Before PostgreSQL can function correctly, the database cluster must be initialized:
[postgres]$ initdb --locale $LANG -E UTF8 -D '/var/lib/postgres/data'
--localeis the one defined in the file
-Eis the default encoding of the database that will be created in the future;
-Dis the default location where the database cluster must be stored.
Many lines should now appear on the screen with several ending by
The files belonging to this database system will be owned by user "postgres". This user must also own the server process. The database cluster will be initialized with locale "en_GB.UTF-8". The default text search configuration will be set to "english". Data page checksums are disabled. fixing permissions on existing directory /var/lib/postgres/data ... ok creating subdirectories ... ok selecting default max_connections ... 100 selecting default shared_buffers ... 128MB selecting dynamic shared memory implementation ... posix creating configuration files ... ok creating template1 database in /var/lib/postgres/data/base/1 ... ok initializing pg_authid ... ok [...]
If these are the kind of lines you see, then the process succeeded. Return to the regular user using
Create your first database/user
Become the postgres user. Add a new database user using the createuser command:
[postgres]$ 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
-U database-username to the following command):
$ createdb myDatabaseName
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:
Configure PostgreSQL to be accessible from remote hosts
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
Edit the file
/var/lib/postgres/data/postgresql.conf. In the connections and authentications section, add the
listen_addresses line to your needs:
listen_addresses = 'localhost,my_local_ip_address' #You can use '*' to listen on all local addresses
Take a careful look at the other lines.
Host-based authentication is configured in
/var/lib/postgres/data/pg_hba.conf. This file controls which hosts are allowed to connect. Note that the defaults allow any local user to connect as any database user, including the database superuser. Add a line like the following:
# IPv4 local connections: host all all my_remote_client_ip_address/32 md5
my_remote_client_ip_address is the IP address of the 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
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
Some variables need to be overridden in the configuration, as described in Systemd#Editing provided units. First, run:
# systemctl edit postgresql.service
Systemctl will open a drop-in configuration file in your editor. Write the following in that file:
[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
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 |
- phpPgAdmin — Web-based administration tool for PostgreSQL.
- pgAdmin — GUI-based administration tool for PostgreSQL.
Setup HHVM to work with PostgreSQL
$ git clone https://github.com/PocketRent/hhvm-pgsql.git $ cd hhvm-pgsql
If you do not use a nightly build, then run this command (verified on HHVM 3.6.1) to avoid compile errors:
$ git checkout tags/3.6.0
Then build the extension (if you do not need an improved support for Hack language, then remove -DHACK_FRIENDLY=ON):
$ hphpize $ cmake -DHACK_FRIENDLY=ON . $ make
Then copy the built extension:
# cp pgsql.so /etc/hhvm/
Add to /etc/hhvm/server.ini:
extension_dir = /etc/hhvm hhvm.extensions[pgsql] = pgsql.so
Upgrading major PostgreSQL versions (i.e. from
9.y) requires some extra maintenance.
It is recommended to add the following to your
IgnorePkg = postgresql postgresql-libs
This will ensure you do not accidentally upgrade the database to an incompatible version. When an upgrade is available, pacman will notify you that it is skipping the upgrade because of the entry in
pacman.conf. Minor version upgrades (e.g. 9.0.3 to 9.0.4) are safe to perform. However, if you do an accidental upgrade to a different major version (e.g. 9.0.x to 9.1.x), 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.
For those wishing to use
pg_upgrade, a 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.
When you are ready, upgrade the following packages:
pg_upgrade, it is necessary to rename your existing data directory and migrate into a new directory. The new database must be initialized, as described near the top of this page.
# systemctl stop postgresql.service # su -l postgres -c 'mv /var/lib/postgres/data /var/lib/postgres/olddata' # su -l postgres -c 'initdb --locale en_US.UTF-8 -E UTF8 -D /var/lib/postgres/data'
The upgrade invocation will likely look something like the following. Do not run this command blindly without understanding what it does! Reference the upstream pg_upgrade documentation for details.
# su -l postgres -c 'pg_upgrade -d /var/lib/postgres/olddata/ -D /var/lib/postgres/data/ -b /opt/pgsql-9.4/bin/ -B /usr/bin/'
Manual dump and reload
You could also do something like this (after the upgrade and install of).
# systemctl stop postgresql.service # /opt/pgsql-9.4/bin/pg_ctl -D /var/lib/postgres/olddata/ start # /opt/pgsql-9.4/bin/pg_dumpall >> old_backup.sql # /opt/pgsql-9.4/bin/pg_ctl -D /var/lib/postgres/olddata/ stop # systemctl start postgresql.service # psql -f old_backup.sql postgres
Improve performance of small transactions
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'
Cannot connect to database through pg_connect()
php.ini file uncommenting the lines
extension=pgsql.so, then restart