On Aug 27, 2014 10:03 PM, "Dale R. Worley" <wor...@alum.mit.edu> wrote: > > > From: Thomas Suckow <thomas.suc...@pnnl.gov> > > > > >> From: Lennart Poettering <lenn...@poettering.net> > > > > > >> Note that a concept of "mount at boot if it is there, otherwise don't" > > >> cannot work. > > > > > > It worked until a week or two ago. I want it back. > > > > > > I'm sure you're right that in the abstract, it cannot be made to > > > work. But that isn't the problem I'm facing. > > > > It seems that a workaround could be to not put the volume in fstab > > and add a unit to the startup that would mount it if present. If you > > wanted to mount it later, you could manually start the unit again. > > I'd rather adjust systemd and leave fstab stable than vice-versa. > > Here's an interesting fact: What systemd does (in this situation) > isn't true automounting; rather it waits for the *first* time the > device/volume becomes available, and then mounts it. Any later > attachments of the volume do not cause mounting (until the next > reboot). > > But at this point, I only need to investigate the issue. The > documentation I've managed to find about systemd is rather abstract, > there's no map between specific bits of functionality and the files > that control them. > > My understanding is that everything systemd does is controlled by > "units". In this case, entries in fstab cause the creation of units > based on a "template". If you could point me to the template file in > question, it would probably point me to all of the things I need to > investigate.
For fstab, the units are created by a 'generator' (systemd-fstab-generator), which writes them under /run/systemd/generator every time the configuration is reloaded. I'm not at my PC right now so I cannot check, but I /do/ remember someone mentioning that if a fstab entry has the 'auto' option, then the generator also symlinks the corresponding .mount unit under <devpath>.device.wants/ (e.g. dev-sda3.device.wants/mnt-backup.mount), causing the .mount unit to be triggered *every* time that device appears on the system. That is, in addition to local-fs.target triggering foo.mount and waiting for bar.device one time only (as you describe), it makes bar.device itself trigger foo.mount every time as well. -- Mantas Mikulėnas <graw...@gmail.com> // sent from phone
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