If some Enhance backups intermittently fail with errors like:
Identity file /dev/shm/<uuid> not accessible: No such file or directory
Permission denied (publickey) to <backup server IP>
or mysqldump: Got errno 32 on write, this may be the cause.
appcd keeps the backup's temporary SSH key in /dev/shm, owned by the site user. Ubuntu's default RemoveIPC=yes makes systemd-logind delete that user's /dev/shm files when their last session ends, so any login as the site user that ends mid-backup breaks the transfer. For us it was cPGuard's nightly CMS check, which runs wp-cli via su as each site user.
The fix for us was to set "RemoveIPC=no" on each app server.
Run at your own risk:
sudo mkdir -p /etc/systemd/logind.conf.d
printf '[Login]\nRemoveIPC=no\n' | sudo tee /etc/systemd/logind.conf.d/10-removeipc.conf
sudo systemctl restart systemd-logind
To undo, delete the file and restart systemd-logind.
We had 12 failures in the two weeks before making this change. Since making this change we've seen none over the past 3 days.
