One more update: I verified that the steps from comment #17 can be used
to reproduce the issue in an Ubuntu Core image started in qemu, and
without using the spread. I verified it with the 20211105 image provided
by Lukas in https://people.ubuntu.com/~slyon/uc18/
To reproduce it, start the image in QEMU:
qemu-system-x86_64 -enable-kvm -smp 2 -m 1500 \
-netdev user,id=mynet0,hostfwd=tcp::8022-:22,hostfwd=tcp::8090-:80 \
-device virtio-net-pci,netdev=mynet0 \
-drive file=~/Downloads/uc18-20211105+systemd+3G.img,format=raw \
-drive
file=/usr/share/OVMF/OVMF_CODE.fd,if=pflash,format=raw,unit=0,readonly=on
configure it as usual, and install a snap. Then:
sudo snap install hello-world
sudo systemctl start 'snap-hello\x2dworld-29.mount'
sudo systemctl daemon-reload
sudo systemctl stop 'snap-hello\x2dworld-29.mount'
sudo systemctl start 'snap-hello\x2dworld-29.mount'
The last command will hang for 90 seconds, after which the logs (`sudo
journalctl -xe`) will say:
```
Nov 15 06:10:20 localhost systemd[1]: dev-loop6.device: Job
dev-loop6.device/start timed out.
Nov 15 06:10:20 localhost systemd[1]: Timed out waiting for device /dev/loop6.
-- Subject: Unit dev-loop6.device has failed
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- Unit dev-loop6.device has failed.
--
-- The result is RESULT.
Nov 15 06:10:20 localhost systemd[1]: Dependency failed for Mount unit for
hello-world, revision 29.
-- Subject: Unit snap-hello\x2dworld-29.mount has failed
-- Defined-By: systemd
-- Support: http://www.ubuntu.com/support
--
-- Unit snap-hello\x2dworld-29.mount has failed.
--
-- The result is RESULT.
Nov 15 06:10:20 localhost systemd[1]: snap-hello\x2dworld-29.mount: Job
snap-hello\x2dworld-29.mount/start failed with result 'dependency'.
Nov 15 06:10:20 localhost systemd[1]: dev-loop6.device: Job
dev-loop6.device/start failed with result 'timeout'.
```
--
You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to systemd in Ubuntu.
https://bugs.launchpad.net/bugs/1949089
Title:
systemd randomly fails to activate mount units in Ubuntu Core 18
Status in systemd package in Ubuntu:
New
Status in systemd source package in Bionic:
New
Bug description:
Since a month or so, we've been seeing random failures in our snapd
spread tests where systemd could not start the mount unit associated
with a snap because of a failed dependency.
The issue is described in the comments to PR
https://github.com/snapcore/snapd/pull/10935, but I'll summarize it
here.
When starting a snap, snapd creates a mount unit to mount the snap's
squashfs (the template is
https://github.com/snapcore/snapd/blob/release/2.53/systemd/systemd.go#L1186-L1205).
The snapd asks systemd to reload the configuration, and starts the
mount unit.
The failure we've observed is that sometimes systemd decides to stop
our mount unit (search for "Unmounting Mount unit for test-snapd-svc-
flip-flop" in the attached log), and then tries to reactivate it
again, and at that point it fails.
When I asked for help, Lukas pointed out that the latest update
contains a patch that is related to reload handling and mount units:
http://launchpadlibrarian.net/555420796/systemd_237-3ubuntu10.51_237-3ubuntu10.52.diff.gz
(the patch itself is better visible at
https://github.com/systemd/systemd/commit/f0831ed2a03fcef582660be1c3b1a9f3e267e656).
When looking at the systemd git log, though, I noticed another patch
that was applied shortly after this one, which also seems related but
was not backported:
https://github.com/systemd/systemd/commit/04eb582acc203eab0bc5c2cc5e13986f16e09df0
Since the stopping of our mount unit happens immediately after a
systemd reload, it actually seems very likely that the inclusion of
f0831ed2a03fcef582660be1c3b1a9f3e267e656 in the systemd update is what
causes our woes (though, indeed, the issue is not reliably
reproducible, so we cannot be sure).
To manage notifications about this bug go to:
https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1949089/+subscriptions
--
Mailing list: https://launchpad.net/~touch-packages
Post to : touch-packages@lists.launchpad.net
Unsubscribe : https://launchpad.net/~touch-packages
More help : https://help.launchpad.net/ListHelp
