Docker Systemd Unit File

postgres.service

[Unit]                                                                                       
Description=PostgreSQL container                                                             
Requires=docker.service                                                                      
After=docker.service         

[Service]                                                                                    
Restart=on-failure                                                                           
RestartSec=10                                                                                
ExecStartPre=-/usr/bin/docker stop postgres                                                  
ExecStartPre=-/usr/bin/docker rm postgres                                                    
ExecStart=/usr/bin/docker run --name postgres \                                               
 --volume /srv/db/postgres:/var/lib/pgsql/data \                                             
 kiasaki/alpine-postgres                                                                     
ExecStop=/usr/bin/docker stop postgres         

[Install]                                                                                    
WantedBy=multi-user.target    

@f4th4n, the output you show says Started PostgreSQL container, so I think you're fine. The ExecStartPre lines start with -, which means to ignore errors. Apparently it's still printing those errors out. But those ExecStartPre lines are just stopping any existing Docker instances, to ensure that the Docker instance will start up correctly. You should be able to ignore the error messages in the logs.

I don't think you can add redirection to any of the Exec parameters. Otherwise I'd suggest adding >/dev/null 2>&1 to the ExecStartPre lines. Not sure if it's worth adding that; if so, it'd look like this:

ExecStartPre=-/bin/bash -c '/usr/bin/docker stop postgres >/dev/null 2>&1'
ExecStartPre=-/bin/bash -c '/usr/bin/docker rm postgres >/dev/null 2>&1'

But I'm honestly not even sure it's necessary to have those lines in there at all.