Container slower first boot time compared to VMs

LXD
1

I have noticed that when launching or booting a container for the first time, the startup is significantly longer:

$ time lxc launch ubuntu:20.04 container-test
Creating container-test
Starting container-test
                               
real	0m4,076s
user	0m0,086s
sys	0m0,080s

$ lxc stop container-test
$ time lxc start container-test

real	0m0,417s
user	0m0,035s
sys	0m0,039s

VMs while also taking a bit longer don’t show such a large difference and actually startup faster than containers on the first boot:

$ time lxc launch ubuntu:20.04 vm-test -p vm --vm
Creating vm-test
Starting vm-test

real	0m2,264s
user	0m0,086s
sys	0m0,049s

$ lxc stop vm-test
$ time lxc start vm-test

real	0m1,143s
user	0m0,035s
sys	0m0,119s

I am guessing this has to do with the extra Remapping container filesystem step that is not present on VM instances?

2

This should only occur on first boot, it is required for unprivileged containers to remap the filesystem UID/GIDs to the unprivileged user.