Rclone mount w/ systemd when user logs in, unmounts @ logout

#1

For those familiar with systemd: It seems like I could write a systemd config/script which would get invoked upon the 1st instance of a user's login (and not on the 2nd, 3rd, ... nth additional processes) - which would do a mount that would last until any last process of that user logs out or terminates. In between, the user may have other login sessions or even incoming ssh sessions that start, operate and themselves exit/logout. Only upon the last process owned by that user being terminated would the rclone unmount happen. (The system continues to run allowing other users continued access to their ${HOME} and files. Any next time the specific indicated user logs in again, would systemd again start the user UID's session tree's rclone mount.)

If I understand correctly, one could create a systemd control file like user@UID.slice (where UID is my user id, say 7445) acting as the umbrella for all user@UID logins/sessions. With this, a Google Drive mount within the user's ${HOME} dir tree would:

  1. become available the 1st time the user UID logs in or has a session started, or remotes in via ssh, ...
  2. remain available as long as the user UID has at least one process running, and
  3. an rclone unmount (likely via an fuser unmount command) would occur as the last of user UID's processes exits, then
  4. Repeat from 1. the next time user UID starts some processes

Do I have that about right?

#2

I'm afraid I don't know enough about systemd to help here, but I'd love to see the result if you do achieve it!

#3

Yes, of course you can write a oneshot service for systemd. There are plenty of ways to autostart rclone mounts at login and (not so necessary) unmount at shutdown. Don't forget about the rclone --daemon option which, in combination with (slightly more necssary) a mountpoint check is really all you need.

#4

I'm certainly aware of several ways to start rclone from a ~/.bash_login (or similar) script, and the differences in usage instances whether or not the ~/.bashrc script is processed. The reason to ask about a systemd unit is so that no matter:

  1. how I get a process running with my user ID (UID),
  2. regardless of the pattern of further logins - ssh, GUI, su, etc.,
  3. which shell they are running (if any), and
  4. regardless of the pattern/order of logouts/exits of any of these processes

(i.e. there's some process with my UID running, regardless how it got started) the Google Drive mount point should be present in my ${HOME} directory tree, is visible to any of those processes during its lifetime, and any shell or program can traverse that tree.

The only thing I know of to accomplish this would be some careful crafting of running-or-not breadcrumbs & conditional invokes of rclone - except for occasional use of csh, zsh, other command-line shells or bare process creation.

To avoid all kinds of problems or complications, I'd like something running the whole time my systemd user slice is running. The systemd unit tree structure supposedly supports this - I can write a systemd script for systemctl --user usage, but I'm unsure how to "glue it" into the user-7455.slice or user@7445.service unit or other appropriate descendant.

#5

You definitely know more than me about systemd; I've haven't written any complex scripts for it. It definitely is the best use case for something like this -- doesn't the system use it to mount nfs drives? maybe someone else can help but yif you're looking for assistance, but to me it sounds like you have it down

#7

Thanks for pointing out the --daemon option, however the documentation (i.e. man rclone) does not describe very well what that option actually does. Is there a more complete description somewhere else?

Is it simply that rclone sets itself up to be disowned, not use stdout nor stderr, then fork()s* (with parent process exiting) to run as an independent process? (If so, I guess I should use the systemd [Service] unit option Type=forking - right?

*Or whatever equivalent rclone uses on Windows® to do a similar action...

#8

You also referred to "a mountpoint check". Being a newbie to rclone I'm not sure what that means. Is it something I should do in the ExecStop= clause before the fusermount -u (i.e. unmount)? I could understand something that 1st flushes or sync's data to the Cloud.

#9

So looking at the codebase for rclone, I found what I had suspected rclone is doing when it uses daemon:

You can either run mount in foreground mode or background(daemon) mode. Mount runs in
foreground mode by default, use the --daemon flag to specify background mode mode.
Background mode is only supported on Linux and OSX, you can only run mount in
foreground mode on Windows.

This means it is equivalent of starting a mount normally, hitting Ctrl-Z to sleep and typing disown. Basically the rclone process detaches from the shell as being it's parent and attaches to init (I believe is the default for detachment).

What I meant by a mountpoint check, is that I have setup rclone mounts up countless different ways, and one of the quickest is use a script that first calls mountpoint -q /my/mount/point (the q is quiet mode), and if that returns 0 then that location IS already a mountpoint (i.e. it is registered in /etc/mtab I believe), so you don't need to moutn again. Otherwise, if mountpoint returned anything other than 0, you can attempt the mount there.

This script can be called even in an cron job because it takes literally no resources to check if that mount is still alive -- although I only use that method for places like a seedbox where conditions are uncertain compared to your desktop.

Let me know if you have any questions.

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#10

I usually run rclone without --daemon so systemd controls the process directly.

Here is the systemd file I use for serving beta.rclone.org. Note the Type=notify - rclone sends a systemd notification when the mount is ready.

[Unit]
Description=rclone mount
Documentation=http://rclone.org/docs/
After=network-online.target

[Service]
Type=notify
User=www-data
Group=www-data
ExecStart=/usr/bin/rclone mount -v --read-only --config /home/www-data/.rclone.conf --cache-dir /home/www-data/.cache/rclone --dir-cache-time 1m --vfs-cache-mode full --vfs-cache-max-age 168h --allow-non-empty --allow-other --use-mmap=true --vfs-cache-max-size 30G --rc memstore:beta-rclone-org /mnt/beta.rclone.org
ExecStop=/bin/fusermount -uz /mnt/beta.rclone.org
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target
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#11

You mention Type=notify, causing "rclone [to send] a systemd notification when the mount is ready".

While I am aware of the systemd API call sd_notify(), but I don't see any command line option (in your example) or rclone.conf item to cause that signal to be sent from rclone. Am I missing something?

Alternately, does specifying notify in the ….service file mean that systemctl — or whatever is processing that file — is the agent that sends the notification if/when the ExecStart=… clause completes with 0 (OK) status?

#12

Rclone detects whether it is running under systemd and sends the sdnotify automatically when the mount is up.

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