Bug#1053457: live-build: Building live image fails when unmounting /sys: 'target is busy'

[Witold Baryluk <witold.baryluk@gmail.com>]

Package: live-build
Version: 1:20230502
Followup-For: Bug #1053457
X-Debbugs-Cc: witold.baryluk@gmail.com

Also had this issue for some time (maybe 2-3 months) on my amd64
machine.

But I am not so sure it is due to efivars, at least not only.


Instrumented chroot_sysfs with mount | grep chroot, and got this

devpts-live on /home/user/tmp-live-build/20231205T051432Z/chroot/dev/pts type devpts (rw,relatime,gid=5,mode=620,ptmxmode=000,x-gvfs-hide)
proc-live on /home/user/tmp-live-build/20231205T051432Z/chroot/proc type proc (rw,relatime,x-gvfs-hide)
sysfs-live on /home/user/tmp-live-build/20231205T051432Z/chroot/sys type sysfs (rw,relatime,x-gvfs-hide)


Outside of chroot efivars is indeed mounted tho:

efivarfs on /sys/firmware/efi/efivars type efivarfs (rw,nosuid,nodev,noexec,relatime)


I think it is a bit racy, because sometimes I do see efivars being mounted under chroot.

2-3 months ago my workaround was to just add a bit of extra sleep (just
few seconds were enough) before attempting to unmount chroot/sys.

Now, this workaround does not look to be really working, so I made
another workaround - try to unmount efivars, then try to unmount sys in
a loop with a bit of sleep, until it finally succeds.

Cheers