Ok, I double checked and my problem was caused by using the wrong path in the LXC settings (/mnt/user/...).
I changed that and everything works fine. Thanks for your help.
Hi there,
I have a problem with docker inside LXC containers - all extractions are very slow and it takes about 30 minutes to run docker container for the first time when it installs all dependencies. I didnt have this problem on regular VM using the same disk for system.