While docker run: docker: failed to register layer: Error processing tar file(exit status 1): no space left on device

my Docker Runtime crashed while cleaning up the linux engine. So I reinstalled Docker by unsing zypper. When I run

docker run --detach --hostname psmonster  
 --env GITLAB_OMNIBUS_CONFIG="external_url 'http://psmonster:20080/'; gitlab_rails['lfs_enabled'] = true;"  
 --publish 20443:443
 --publish 20080:80 
 --publish 20022:22 
 --name gitlab_2
 --restart always   
 --volume /srv/gitlab/config:/etc/gitlab
 --volume /srv/gitlab/logs:/var/log/gitlab
 --volume /srv/gitlab/data:/var/opt/gitlab 
 gitlab/gitlab-ce:12.4.6-ce.0  

The result I get is

docker: failed to register layer: Error processing tar file(exit status 1): write
/opt/gitlab/embedded/service/gitlab-shell/bin/gitlab-shell-authorized-keys-check: 
no space left on device.

This is confusing because

root@psmonster:/opt> df
Filesystem     1K-blocks     Used Available Use% Mounted on
devtmpfs         8201716        8   8201708   1% /dev
tmpfs            8209452        8   8209444   1% /dev/shm
 ...
/dev/sda5        6654108  4257644   2038732  68% /var
/dev/sde1       51342816 31499924  17205120  65% /opt
/dev/sdh1      102686648 51480544  45946892  53% /srv

That should be enough space. So what happens here? Thanks for your support in advanced. Kind regards Markus

I just extended the space in the var folder. The error message mislead me to extend the opt folder.