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.TH "POSTGRESQL\-95\-RHEL7" "1" "February 22, 2017" "Container Image Pages" ""
.hy
.SH PostgreSQL Docker image
.PP
This repository contains Dockerfiles for PostgreSQL images for general
usage and OpenShift.
Users can choose between RHEL and CentOS based images.
.SS Environment variables and volumes
.PP
The image recognizes the following environment variables that you can
set during initialization by passing \f[C]\-e\ VAR=VALUE\f[] to the
Docker run command.
.PP
.TS
tab(@);
lw(26.7n) lw(43.3n).
T{
Variable name
T}@T{
Description
T}
_
T{
\f[C]POSTGRESQL_USER\f[]
T}@T{
User name for PostgreSQL account to be created
T}
T{
\f[C]POSTGRESQL_PASSWORD\f[]
T}@T{
Password for the user account
T}
T{
\f[C]POSTGRESQL_DATABASE\f[]
T}@T{
Database name
T}
T{
\f[C]POSTGRESQL_ADMIN_PASSWORD\f[]
T}@T{
Password for the \f[C]postgres\f[] admin account (optional)
T}
.TE
.PP
The following environment variables influence the PostgreSQL
configuration file.
They are all optional.
.PP
.TS
tab(@);
lw(15.7n) lw(37.6n) lw(16.7n).
T{
Variable name
T}@T{
Description
T}@T{
Default
T}
_
T{
\f[C]POSTGRESQL_MAX_CONNECTIONS\f[]
T}@T{
The maximum number of client connections allowed
T}@T{
100
T}
T{
\f[C]POSTGRESQL_MAX_PREPARED_TRANSACTIONS\f[]
T}@T{
Sets the maximum number of transactions that can be in the "prepared"
state.
If you are using prepared transactions, you will probably want this to
be at least as large as max_connections
T}@T{
0
T}
T{
\f[C]POSTGRESQL_SHARED_BUFFERS\f[]
T}@T{
Sets how much memory is dedicated to PostgreSQL to use for caching data
T}@T{
32M
T}
T{
\f[C]POSTGRESQL_EFFECTIVE_CACHE_SIZE\f[]
T}@T{
Set to an estimate of how much memory is available for disk caching by
the operating system and within the database itself
T}@T{
128M
T}
.TE
.PP
You can also set the following mount points by passing the
\f[C]\-v\ /host:/container\f[] flag to Docker.
.PP
.TS
tab(@);
l l.
T{
Volume mount point
T}@T{
Description
T}
_
T{
\f[C]/var/lib/pgsql/data\f[]
T}@T{
PostgreSQL database cluster directory
T}
.TE
.PP
\f[B]Notice: When mouting a directory from the host into the container,
ensure that the mounted directory has the appropriate permissions and
that the owner and group of the directory matches the user UID or name
which is running inside the container.\f[]
.SS Usage
.PP
For this, we will assume that you are using the
\f[C]openshift/postgresql\-92\-centos7\f[] image.
If you want to set only the mandatory environment variables and not
store the database in a host directory, execute the following command:
.IP
.nf
\f[C]
$\ docker\ run\ \-d\ \-\-name\ postgresql_database\ \-e\ POSTGRESQL_USER=user\ \-e\ POSTGRESQL_PASSWORD=pass\ \-e\ POSTGRESQL_DATABASE=db\ \-p\ 5432:5432\ openshift/postgresql\-92\-centos7
\f[]
.fi
.PP
This will create a container named \f[C]postgresql_database\f[] running
PostgreSQL with database \f[C]db\f[] and user with credentials
\f[C]user:pass\f[].
Port 5432 will be exposed and mapped to the host.
If you want your database to be persistent across container executions,
also add a \f[C]\-v\ /host/db/path:/var/lib/pgsql/data\f[] argument.
This will be the PostgreSQL database cluster directory.
.PP
If the database cluster directory is not initialized, the entrypoint
script will first run
\f[C]initdb\f[] (http://www.postgresql.org/docs/9.2/static/app-initdb.html)
and setup necessary database users and passwords.
After the database is initialized, or if it was already present,
\f[C]postgres\f[] (http://www.postgresql.org/docs/9.2/static/app-postgres.html)
is executed and will run as PID 1.
You can stop the detached container by running
\f[C]docker\ stop\ postgresql_database\f[].
.SS PostgreSQL auto\-tuning
.PP
When the PostgreSQL image is run with the \f[C]\-\-memory\f[] parameter
set and if there are no values provided for
\f[C]POSTGRESQL_SHARED_BUFFERS\f[] and
\f[C]POSTGRESQL_EFFECTIVE_CACHE_SIZE\f[] those values are automatically
calculated based on the value provided in the \f[C]\-\-memory\f[]
parameter.
.PP
The values are calculated based on the
upstream (https://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server)
formulas.
For the \f[C]shared_buffers\f[] we use 1/4 of given memory and for the
\f[C]effective_cache_size\f[] we set the value to 1/2 of the given
memory.
.SS PostgreSQL admin account
.PP
The admin account \f[C]postgres\f[] has no password set by default, only
allowing local connections.
You can set it by setting the \f[C]POSTGRESQL_ADMIN_PASSWORD\f[]
environment variable when initializing your container.
This will allow you to login to the \f[C]postgres\f[] account remotely.
Local connections will still not require a password.
.SS Changing passwords
.PP
Since passwords are part of the image configuration, the only supported
method to change passwords for the database user
(\f[C]POSTGRESQL_USER\f[]) and \f[C]postgres\f[] admin user is by
changing the environment variables \f[C]POSTGRESQL_PASSWORD\f[] and
\f[C]POSTGRESQL_ADMIN_PASSWORD\f[], respectively.
.PP
Changing database passwords through SQL statements or any way other than
through the environment variables aforementioned will cause a mismatch
between the values stored in the variables and the actual passwords.
Whenever a database container starts it will reset the passwords to the
values stored in the environment variables.
.SH AUTHORS
Red Hat.