If you are trying to run azure devops and run a container. Maybe you can find this issue:
permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock
This is an error based on the user that is running the agent service. For this reason, you should check which user is running the service.
$ ps aux |grep agent
admin 2736 0.0 0.0 7340 2048 ? Ss Jan06 0:00 /bin/bash /home/admin/azagent/runsvc.sh
admin 2747 0.0 3.9 274117020 81476 ? Sl Jan06 0:16 /home/admin/azagent/bin/Agent.Listener run --startuptype service
admin 8840 0.0 0.0 6544 2048 pts/0 S+ 17:03 0:00 grep --color=auto agent
Check the user of that pid
$ ps -u -p 2736
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND admin 2736 0.0 0.0 7340 2048 ? Ss Jan06 0:00 /bin/bash /home/admin/azagent/runsvc.sh
Add the group docker, just in case.
$ sudo groupadd docker
groupadd: group 'docker' already exists
Add the user to that group
$ sudo usermod -aG docker admin
$ reboot
Try again after the reboot.