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Sunday, July 14, 2019

How to Install PostgreSQL and pgAdmin on CentOS 7

Install PostgreSQL and pgAdmin on CentOS 7

PostgreSQL (or Postgres) is a free and open-source, relational database management system (RDBMS) emphazing on extensibility and technical standards compliance. PostgreSQL is developed by the PostgreSQL Global Development Group. It is the default database for MacOS server but also available for other platforms.

pgAdmin is the most popular open source and feature enrich web interface for administration of PostgreSQL database servers. Currently pgAdmin 4 has been released and available via PostgreSQL yum repository.

In this article, we are installing PostgreSQL 11 and pgAdmin 4 on CentOS 7 server. The article is broken down into three sections, first we will install PostgreSQL, then we will configure PostgreSQL for remote access and finally we will install pgAdmin web interface.

This article is for setting up a PostgreSQL 11 database server with pgAdmin 4 web interface. However, if you want to learn PostgreSQL 11 in detail then you should read Mastering PostgreSQL 11: Expert techniques to build scalable, reliable, and fault-tolerant database applications, 2nd Edition by Packt Publishing.

Read Also: Setup PostgreSQL Database Server on Rocky Linux 9

Install PostgreSQL and pgAdmin on CentOS 7

Table of Contents:


Environment Specification:

We have configured a CentOS 7 virtual machine with following specifications.

  • CPU - 3.4 Ghz (2 cores)
  • Memory - 2 GB
  • Storage - 20 GB
  • Operating System - CentOS 7.6
  • Hostname - postgresql-01.example.com
  • IP Address -


Installing PostgreSQL 11 on CentOS 7:

Connect with postgresql-01.example.com using ssh as root user.

In CentOS 7.6, PostgreSQL 9.2 is available in standard yum repositories.

But we are required to install latest version of PostgreSQL i.e. 11. Therefore, we have to add PostgreSQL yum repository in our CentOS 7 server and then we will be able to install PostgreSQL 11.

Yum repositories for various Linux distros can be obtained from PostgreSQL official download page.

Install PostgreSQL yum repository using following command.

# yum install -y https://download.postgresql.org/pub/repos/yum/reporpms/EL-7-x86_64/pgdg-redhat-repo-latest.noarch.rpm

Disable old version PostgreSQL yum repositories.

# yum-config-manager --disable pgdg10 pgdg94 pgdg95 pgdg96

Build cache for yum repositories.

# yum makecache fast
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
 * base: ftp3.isra.edu.pk
 * extras: ftp3.isra.edu.pk
 * updates: ftp3.isra.edu.pk
base                                                     | 3.6 kB     00:00
extras                                                   | 3.4 kB     00:00
pgdg11                                                   | 3.6 kB     00:00
updates                                                  | 3.4 kB     00:00
Metadata Cache Created

Install PostgreSQL 11 client and server packages using yum command.

# yum install -y postgresql11 postgresql11-server

Initialize PostgreSQL database instance as follows.

# /usr/pgsql-11/bin/postgresql-11-setup initdb
Initializing database ... OK

Enable and start PostgreSQL service.

# systemctl enable postgresql-11.service
Created symlink from /etc/systemd/system/multi-user.target.wants/postgresql-11.service to /usr/lib/systemd/system/postgresql-11.service.
# systemctl start postgresql-11.service

Connect as postgres user and set admin password.

# su - postgres
-bash-4.2$ psql
psql (11.4)
Type "help" for help.

postgres=# ALTER USER postgres WITH PASSWORD '123';
postgres=# \q
-bash-4.2$ exit

PostgreSQL 11 server has been installed on our CentOS 7 server.


Configuring PostgreSQL Remote Access on CentOS 7:

By default, PostgreSQL service runs locally on port 5432/tcp. However, if required we can configure it for remote access from other computers in our network.

Edit PostgreSQL configuration file.

# vi /var/lib/pgsql/11/data/postgresql.conf

Find and set following directive in this file.

listen_addresses = '*'

Allow network clients to access PostgreSQL service in pg_hba.conf file.

# echo "host all all md5" >> /var/lib/pgsql/11/data/pg_hba.conf

Restart PostgreSQL service to apply changes.

# systemctl restart postgresql-11.service

Allow PostgreSQL service in Linux firewall.

# firewall-cmd --permanent --add-service=postgresql
# firewall-cmd --reload

Our PostgreSQL service is configured for remote access.


Installing pgAdmin 4 Web Interface on CentOS 7:

To ease the process of Database Administration of PostgreSQL, we are installing a popular SQL web interface i.e. pgAdmin 4 on our CentOS 7 server.

pgAdmin 4 is available in the same PostgreSQL 11 yum repository.

But first we are installing EPEL (Extra Packages for Enterprise Linux) yum repository, because pgAdmin 4 requires some packages that are available in EPEL yum repository.

# yum install -y epel-release

Build yum cache for EPEL repository.

# yum makecache fast

Install pgAdmin 4 using yum command.

# yum install -y pgadmin4

pgAdmin 4 is a python based web application, therefore it requires a web server with python language support for deployment. Luckily, pgAdmin 4 automatically installs Apache HTTP server and Python language support during installation.

Enable and start Apache Service.

# systemctl enable httpd.service
Created symlink from /etc/systemd/system/multi-user.target.wants/httpd.service to /usr/lib/systemd/system/httpd.service.
# systemctl start httpd.service

Allow HTTP service in Linux firewall.

# firewall-cmd --permanent --add-service=http
# firewall-cmd --reload

pgAdmin 4 also installed a configuration file in Apache configuration directory. Therefore, to enable pgAdmin web application, we have to rename this file to make is readable by the httpd.service.

# mv /etc/httpd/conf.d/pgadmin4.conf.sample /etc/httpd/conf.d/pgadmin4.conf

Edit /etc/httpd/conf.d/pgadmin4.conf file and the file contents after editing should be look like as follows. (The lines in yellow has been added here).

<VirtualHost *:80>
LoadModule wsgi_module modules/mod_wsgi.so
WSGIDaemonProcess pgadmin processes=1 threads=25
WSGIScriptAlias /pgadmin4 /usr/lib/python2.7/site-packages/pgadmin4-web/pgAdmin4.wsgi

<Directory /usr/lib/python2.7/site-packages/pgadmin4-web/>
        WSGIProcessGroup pgadmin
        WSGIApplicationGroup %{GLOBAL}
        <IfModule mod_authz_core.c>
                # Apache 2.4
                Require all granted
        <IfModule !mod_authz_core.c>
                # Apache 2.2
                Order Deny,Allow
                Deny from All
                Allow from
                Allow from ::1

Define path variables in following file.

# vi /usr/lib/python2.7/site-packages/pgadmin4-web/config_distro.py

Add following settings therein.

SQLITE_PATH = '/var/lib/pgadmin/pgadmin.db'
SESSION_DB_PATH = '/var/lib/pgadmin/sessions'
STORAGE_DIR = '/var/lib/pgadmin/storage'
LOG_FILE = '/var/log/pgadmin/pgadmin.log'

Adjust file permissions.

# chown -R apache:apache /var/log/pgadmin/
# chown -R apache:apache /var/lib/pgadmin/

Set SELinux file contexts.

# semanage fcontext -a -t httpd_sys_rw_content_t "/var/lib/pgadmin(/.*)?"
# restorecon -R /var/lib/pgadmin/
# semanage fcontext -a -t httpd_sys_rw_content_t "/var/log/pgadmin(/.*)?"
# restorecon -R /var/log/pgadmin/

Set SELinux boolean, so that Apache can access PostgreSQL service port.

# setsebool -P httpd_can_network_connect_db 1

Restart Apache service to apply changes.

# systemctl restart httpd.service

Initialize pgAdmin 4 application as follows.

# python /usr/lib/python2.7/site-packages/pgadmin4-web/setup.py
NOTE: Configuring authentication for SERVER mode.

Enter the email address and password to use for the initial pgAdmin user account:

Email address: ahmer@postgresql-01.example.com
Retype password:
pgAdmin 4 - Application Initialisation

Browse URL http://postgresql-01.example.com/pgadmin4/ in client's browser.


Login with Email and Password that we have defined in previous step.


Click on Add New Server to add our PostgreSQL database server to pgAdmin 4 web interface.


Provide the necessary information as per above screenshot.

Click on Connection Tab and provide connection information as per following screenshot.


Click on Save.


Our PostgreSQL database has been added in pgAdmin 4 SQL web interface.

We have successfully installed PostgreSQL 11 and pgAdmin 4 on CentOS 7 server.

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  1. Please help me,
    i have a problen when I try to install pgadmin 4 on Oracle Linux Server release 7.7
    I have epel/x86_64 repo allredy installed, but when i start yum -y install pgadmin4, the next error appears:

    Error: Package: pgadmin4-python-flask-principal-0.4.0-14.rhel7.1.noarch (pgdg11)
    Requires: python-flask
    and I don't know how to install it

    1. Install Flask using pip command.

      # yum install -y pip
      # pip install Flask

  2. FATAL : ident authentication failed for user "postgres" , anyone can help ??

    1. Please share screenshot of the error at our Facebook Page.

  3. Please Help I am having the following errors:

    ~]# chown -R apache:apache /var/log/pgadmin/
    chown: cannot access ‘/var/log/pgadmin/’: No such file or directory

    ~]# chown -R apache:apache /var/lib/pgadmin/
    chown: cannot access ‘/var/lib/pgadmin/’: No such file or directory

  4. another error related to the first error I posted, please I need help

    ~]# restorecon -R /var/lib/pgadmin/
    restorecon: lstat(/var/lib/pgadmin) failed: No such file or directory

    ~]# restorecon -R /var/log/pgadmin/
    restorecon: lstat(/var/log/pgadmin) failed: No such file or directory

    ~]# python /usr/lib/python2.7/site-packages/pgadmin4-web/setup.py
    NOTE: Configuring authentication for SERVER mode.

    Enter the email address and password to use for the initial pgAdmin user account:

    Email address: trainee@sqlserv.example.com
    Retype password:
    Password must be at least 6 characters. Please try again.
    Retype password:
    Traceback (most recent call last):
    File "/usr/lib/python2.7/site-packages/pgadmin4-web/setup.py", line 413, in
    File "/usr/lib/python2.7/site-packages/pgadmin4-web/setup.py", line 347, in setup_db
    app = create_app()
    File "/usr/lib/python2.7/site-packages/pgadmin4-web/pgadmin/__init__.py", line 400, in create_app
    File "/usr/lib/python2.7/site-packages/pgadmin4-web/pgadmin/utils/driver/__init__.py", line 40, in init_app
    File "/usr/lib/python2.7/site-packages/pgadmin4-web/pgadmin/utils/driver/registry.py", line 88, in load_drivers
    module = import_module(module_name)
    File "/usr/lib64/python2.7/importlib/__init__.py", line 37, in import_module
    File "/usr/lib/python2.7/site-packages/pgadmin4-web/pgadmin/utils/driver/psycopg2/__init__.py", line 28, in
    from .server_manager import ServerManager
    File "/usr/lib/python2.7/site-packages/pgadmin4-web/pgadmin/utils/driver/psycopg2/server_manager.py", line 30, in
    from sshtunnel import SSHTunnelForwarder, BaseSSHTunnelForwarderError
    File "/usr/lib/python2.7/site-packages/pgadmin4-web/sshtunnel.py", line 25, in
    import paramiko
    File "/usr/lib/python2.7/site-packages/paramiko/__init__.py", line 30, in
    from paramiko.transport import SecurityOptions, Transport
    File "/usr/lib/python2.7/site-packages/paramiko/transport.py", line 55, in
    from paramiko.dsskey import DSSKey
    File "/usr/lib/python2.7/site-packages/paramiko/dsskey.py", line 27, in
    from cryptography.hazmat.primitives.asymmetric.utils import (
    ImportError: cannot import name decode_dss_signature

    1. Hi,

      It looks like pgadmin is installed at some other location on your server.
      Locate the directory and then replace with the actual paths in the commands.

  5. i am getting 500 Internal Server Error when accessing the URL

    1. Hi, 500 is a generic error and caused by the server configuration. Please double check the steps provided in this article.

    2. I double check the steps on the server configuration and everything was according to your guide, but still have the 500 Internal Server Error and cannot open the URL, I try with localhost/pgadmin4 or IP_Computer/pgadmin4
      any idea of why I'm having this issue

    3. I review and double check all the postgresql installation and I can confirm is well installed, but still receiving the 500 error

    4. Hi, "500 Internal Server Error" is a generic error. You may find the actual cause of this error in /var/log/httpd/error.log file.

      Please contact us at our Facebook page.

  6. Hi friend, I did everything as you did but, when I execute "[root@soft4you pgadmin4-web]# python /usr/lib/python2.7/site-packages/pgadmin4-web/setup.py" I received the following error:
    "python: can't open file '/usr/lib/python2.7/site-packages/pgadmin4-web/setup.py': [Errno 2] No such file or directory" and I can´t find a solution. Please help.

    1. Use following command to locate the location of pgadmin4 and then replace the path in your command with actual path.

      # rpm -ql pgadmin4

  7. I tried to locate pgadmin4 but it seems it's not here. I reapeat the process completly.
    [root@soft4you bin]# find / -name pgadmin4
    [root@soft4you pgadmin4]# ls -l
    total 4
    drwxr-xr-x 2 root root 4096 Jun 23 22:55 bin
    [root@soft4you pgadmin4]# cd bin
    [root@soft4you bin]# ls

    (this folder is empty)

    1. The command in my previous comment will provide you the location of the pgadmin4. Please discuss it on our Facebook page if problem persists.


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