Re: Multiple instances of Unison with same profile

Michael von Glasow <[email protected]> writes:

>>> Where does Unison place lock files, and what do they refer to (a root, a
>>> single file or something else)?
>> I see them in ~/.unison and they appear to be named for a pair of roots
>> just like ar/fp.

> I currently have a longish sync job running between two systems. Either
> system has one lk file, however it is 9 months old and its hash does not
> match any ar/fp files. That file has not prevented that sync job from
> running over the past couple of months. Looks like it has nothing to do
> with the sync job in progress, which would mean no .unison/lk* file has
> been created for that job.

Interesting.  You might as well clean up the old lk file.

What is the longish job doing?  I wonder if while transfering a big
file, the archives are not locked, and there is a lock/modify/unlock,
esentially a database transaction.

I just ran a sync of a big new file and found that during transfer there
was no lock, and a while true; ls -l; sleep 1; done did not catch any
lockfiles at end.  Not a surprise.

>> It looks like finding a lock file is fatal, rather than waiting.
>
> https://urldefense.com/v3/__https://unix.stackexchange.com/a/776555/91283__;!!IBzWLUs!SnKU0t2hgFKQvLie5Z-Ev3kKlCgpPbVme3qhXRb7B7A44dEKjrBc-xc4BXGcoXfBep34-miF7SPg1beaoQ$  suggests that the fatal
> error occurs only when Unison tries to update the archives, which is
> after it attempts to sync files that have changed.

Makes sense, but maybe it should check/error at the beginning.

> Also, another answer to my question there suggested an elegant way to
> tun Unison periodically while preventing multiple instances of the same
> sync job: run it as a systemd service that is started by a timer. The
> service is disabled so it will never run until explicitly started (e.g.
> by the timer), and will be considered running until sync finishes. Since
> starting an already-started service is a no-op, the timer will never
> launch a second Unison instance if one is already running. An added
> benefit is being able to start sync from a console at any time (by
> starting the service manually) and being able to log out while sync is
> still running, without interrupting anything.

You should get some kind of award for using elegant and systemd in the
same sentence, without sarcasm!

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