postgres was not the same version as pg_ctl in PostgreSQL 12

Question

As per the log files, I am getting the below errors.

The program "postgres" was found by "/usr/lib/postgresql/12/bin/pg_ctl" but was not the same version as pg_ctl. Check your installation.

I am running Ubuntu 20.04.

I executed the following commands to determine which versions are running:

# /usr/lib/postgresql/12/bin/postgres --version

postgres (PostgreSQL) 12.16 (Ubuntu 12.16-0ubuntu0.20.04.1)

# /usr/lib/postgresql/12/bin/pg_ctl --version

pg_ctl (PostgreSQL) 12.15 (Ubuntu 12.15-0ubuntu0.20.04.1)

Do I need to update or perform some tasks as the current situation has rendered my DB Server useless and I have some databases which I am not able to access?

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Also, now when I run the command, I get this error:

postgres@tvsr-strapi:~$ psql
psql: error: could not connect to server: No such file or directory
 Is the server running locally and accepting
 connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?
postgres@tvsr-strapi:~$

I have tried recreating the symbolic link, it still doesn't work.

• Anubhav Ranjan: Everything was working perfectly fine but then all of a sudden I am seeing this error.

Answer 1

Since I was not able to restart my PostgreSQL Server, I decided to copy the data files located in /etc/postgresql/12/main to another server and check if it works.

While trying to test this on a new Server, I installed the same version of PostgreSQL 12 and then tried checking the version info of the pg_ctl and postgres.

postgres (PostgreSQL) 12.16 (Ubuntu 12.16-0ubuntu0.20.04.1)
pg_ctl (PostgreSQL) 12.16 (Ubuntu 12.16-0ubuntu0.20.04.1)

I was surprised to see that the versions were same unlike in my present server. So, I decided to simply copy the binary files from my new server to my old one from the location /var/lib/postgresql/12.

Once this was done, my PostgreSQL started without any issues or complaints. I know this may not be the best approach, but it worked and allowed me to take a dump of the data.

Although the question still remains as to how the version changed for the old server?