Re: why is the same mount point repeatedly mounted in nested manner?

[Goffredo Baroncelli <kreijack@inwind.it>]

On 8/9/21 10:15 PM, Dave T wrote:
> On Mon, Aug 9, 2021 at 3:29 PM Goffredo Baroncelli <kreijack@libero.it> wrote:
>>
[...]

> 
> Also, in recent days I stopped mounting and umounting /mnt/btrtop/root
> and just left it mounted all the time. However, when checking today, I
> still found a nested mount:
> 
> ├─/srv/nfs/var/cache/pacman
> │
> │ └─/srv/nfs/var/cache/pacman
> 
> 

Ok, so it seems that these mounts are triggered not by the mount of /mnt/btrtop/root (see below). What is the output of

$ systemctl --reverse list-dependencies -- srv-nfs-var-cache-pacman.mount



[...]
> 
> As mentioned, I have (temporarily) stopped unmounting these volumes
> and I just leave them mounted all the time. The logs now look like
> this:
> 
> Aug 06 03:00:14 btrbk_run.sh[3022708]: mounting btrbk btrtop volumes...
> Aug 06 03:00:14 btrbk_run.sh[3022708]: INFO: [/mnt/btrtop/root] (1 of
> 3) was already mounted. Nothing to do.
> Aug 06 03:00:14 btrbk_run.sh[3022708]: INFO: [/mnt/btrtop/home] (2 of
> 3) was already mounted. Nothing to do.
> Aug 06 03:00:14 btrbk_run.sh[3022708]: INFO: [/mnt/btrtop/user] (3 of
> 3) was already mounted. Nothing to do.

This told another story. It seems that "btrbk" itself already try to mount the btrfs subvolume. I understood that it was the systemd unit to do that. Could you share the content of btrbk_run.sh ?


> Aug 06 03:00:14 btrbk_run.sh[3022708]: Finished mounting btrbk btrtop volumes.
> Aug 06 04:00:14 btrbk_run.sh[3033520]: mounting btrbk btrtop volumes...
> Aug 06 04:00:14 btrbk_run.sh[3033520]: INFO: [/mnt/btrtop/root] (1 of
> 3) was already mounted. Nothing to do.
> Aug 06 04:00:14 btrbk_run.sh[3033520]: INFO: [/mnt/btrtop/home] (2 of
> 3) was already mounted. Nothing to do.
> Aug 06 04:00:14 btrbk_run.sh[3033520]: INFO: [/mnt/btrtop/user] (3 of
> 3) was already mounted. Nothing to do.
> Aug 06 04:00:14 btrbk_run.sh[3033520]: Finished mounting btrbk btrtop volumes.
> 
>>
>>>
>>> The path /var/cache/pacman is not a subvolume, but it resides on btrfs
>>> subvolume @btrtop/snapshot. @btrtop/snapshot is normally mounted at
>>> "/" but for btrfs tasks, it is also mounted at /mnt/btrtop/root. This
>>> additional mount operation seems to be causing these nested mounts of
>>> my bind mount for  /srv/nfs/var/cache/pacman .
>>>
>>> P.S. I cannot test without using systemd. (I'm not even sure I
>>> remember how to use a non-systemd distro anymore!)
>>>
>>
>>
>> --
>> gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
>> Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5


-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5