The shared apt download cache is bind-mounted from outside the
chroot, so when an apt of ANOTHER build holds the archives lock from
its own pid namespace, a concurrent build's apt sees the holder as
"process 0", cannot wait for it, and fails the build immediately
(observed as an e2e samba essentials install racing a kernel build's
build-deps transaction on the stonking-amd64 cache).
Set DPkg::Lock::Timeout to ten minutes in the shared-cache apt conf:
apt then waits for the holder instead of erroring. pkh itself
already serializes builds per cache with a host-side flock; the
timeout covers the window where a killed run's orphaned apt is still
winding down.
vhaudiquet
1cc64a37da