[systemd-devel] help: unmounting iscsi xfs filesystem without using netdev in /etc/fstab

[Tony Rodriguez]

Interesting that you mentioned the following. I actually added logic to do something like this early yesterday.   Will discuss with my team to see if this is good enough.  I'd rather not bypass _netdev either. Feels like I am re-eventing the wheel. I think the main issue regarding using _netdev is the amount of time it takes to check/mount iscsi devices.  Believe it waits up to 90 seconds to timeout for an iscsi device/filesystem and I am not sure this can be bypassed.  Is it possible to limit the amount of time _netdev will take?  I tried setting x-systemd.device-timeout and x-systemd.mount-timeout with _netdev in /etc/fstab but it didn't seem to work.  It also didn't propagate to /run/systemd/generators/remote-fs-target.requires   I believe the systemd document mentioned such settings are ignored.

"I haven't been following your earlier threads too closely, but if you're
stuck with stupid fstab requirements why not just bypass them with
altogether with drop-in:

     # path-to-mountpoint.mount.d/20-Options.conf
     [Mount]
     Options=_netdev"



On 8/27/19 2:33 AM, Michael Chapman wrote:
> On Tue, 27 Aug 2019, Tony Rodriguez wrote:
>> Managed to detect/mount iscsi devices without using _netdev keyword in
>> /etc/fstab.  Made changes within src/fstab-generator/ftstab-generator.c and it
>> seems to work.  The only problem is during shutdown/reboot, my iscsi xfs
>> filesystem does not unmount cleanly before the network/iscs service/system is
>> shutdown.  When this happens I receive a xfs error/warning.
>>
>> However this doesn't happen when _netdev is specified in /etc/fstab for my
>> iscsi device.  Seems _netdev handles management of mounts/unmounts before
>> killing things off.  How exactly does _netdev manage unmounting filesystems
>> during a shutdown/reboot?
> One of the "default dependencies" for a mount unit that systemd thinks is
> a network filesystem is After=network.target. During shutdown, this
> ensures the filesystem is unmounted before networking is brought down:
>
>      https://github.com/systemd/systemd/blob/fef40ceb5dfbb76d4733e579846a380a224efd55/src/core/mount.c#L455-L482
>
> If you're not using the _netdev keyword, and systemd does not otherwise
> think this is a remote filesystem, you will need to add this dependency
> manually. You'll probably also want:
>
>      Wants=network-online.target
>      After=network-online.target
>
> to match the code linked above.
>
>>    I would like to invoke that same netdev unmount
>> code/logic myself from within systemd source but without using the _netdev
>> keyword. Unfortunately it is a requirement to not use _netdev within
>> /etc/fstab for iscsi.  Seems _netdev takes a long time to timeout and continue
>> when unable to mount.
> I haven't been following your earlier threads too closely, but if you're
> stuck with stupid fstab requirements why not just bypass them with
> altogether with drop-in:
>
>      # path-to-mountpoint.mount.d/20-Options.conf
>      [Mount]
>      Options=_netdev
>
> Plus any other options you may need, of course; this directive is not
> "list-valued", so you can't use it to add just one option.
>
>> Checked src/core/mount.c and src/core/unmount.c but not sure what to do to
>> duplicate how _netdev manages unmounting before the system is shutdown or
>> rebooted.  Do I need a special before and after keyword in /etc/fstab so my
>> xfs filesystems is unmounted before shutting down the iscsi
>> service/network/system?  If so, will such keywords also propagate to
>> /run/systemd/generator/remote-fs-target.requires?
>>
>>
>> Thanks,
>> Tony
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