how to force mounting an entry in fstab on boot?

[hw]

Hi,

I have an entry in the fstab to mount an NFS share via IPv6. For
unknown reasons, the entry is being ignored on boot, so after booting,
I have to log in as root and do a 'mount -a' which mounts the share
without problems.

The entry in the fstab looks like this:


[fd53::11]:/srv/example /home/example/foo nfs _netdev 0 0


I have another case in which machines need to be connected to a
particular VLAN to mount home directories. In case they are not
connected to that VLAN, I don't want the boot process to proceed at
all because the home directories won't be available.


So how do I force it that the entries in fstab are not being silently
ignored? I want these shares either mounted, like through like 3
retries, or booting to stop when they can't be mounted.

[Greg Wooledge]

On Mon, Oct 23, 2023 at 04:17:11PM +0200, hw wrote:
> I have an entry in the fstab to mount an NFS share via IPv6. For
> unknown reasons, the entry is being ignored on boot, so after booting,
> I have to log in as root and do a 'mount -a' which mounts the share
> without problems.

Do your IPv4 NFS mounts have the same behavior?

> [fd53::11]:/srv/example /home/example/foo nfs _netdev 0 0

On my systems, the options field contains "defaults,_netdev" and possibly
a few other things. I don't know whether that matters.

If you add an entry to /etc/hosts for this NFS server, and mount the
share by hostname, does that change anything?

> I have another case in which machines need to be connected to a
> particular VLAN to mount home directories. In case they are not
> connected to that VLAN, I don't want the boot process to proceed at
> all because the home directories won't be available.

Hmm... can you add the "fail" option after _netdev? I've never tried.

> So how do I force it that the entries in fstab are not being silently
> ignored? I want these shares either mounted, like through like 3
> retries, or booting to stop when they can't be mounted.

I do not know how to allow a specific number of retries. Not without
writing your own hacked-up shell scripts, at least.

[Christoph Brinkhaus]

Am Mon, Oct 23, 2023 at 04:17:11PM +0200 schrieb hw:
> Hi,
>
> I have an entry in the fstab to mount an NFS share via IPv6. For
> unknown reasons, the entry is being ignored on boot, so after booting,
> I have to log in as root and do a 'mount -a' which mounts the share
> without problems.
>
> The entry in the fstab looks like this:
>
>
> [fd53::11]:/srv/example /home/example/foo nfs _netdev 0 0
>
>
> I have another case in which machines need to be connected to a
> particular VLAN to mount home directories. In case they are not
> connected to that VLAN, I don't want the boot process to proceed at
> all because the home directories won't be available.

You might need the "late" option of mount. Its purpose is to mount when
prerequisites as the network are available already.

>
> So how do I force it that the entries in fstab are not being silently
> ignored? I want these shares either mounted, like through like 3
> retries, or booting to stop when they can't be mounted.
>

I have never tried to implement things as 3x retries or so.

Kind regards,
Christoph

[hw]

On Mon, 2023-10-23 at 10:30 -0400, Greg Wooledge wrote:
> On Mon, Oct 23, 2023 at 04:17:11PM +0200, hw wrote:
> > I have an entry in the fstab to mount an NFS share via IPv6. For
> > unknown reasons, the entry is being ignored on boot, so after booting,
> > I have to log in as root and do a 'mount -a' which mounts the share
> > without problems.
>
> Do your IPv4 NFS mounts have the same behavior?

No, I can mount the same share with the host name or the IPv4 address
of the same server, and it works as it should. The IPv6 connection is
set to be required at boot.

> > [fd53::11]:/srv/example /home/example/foo nfs _netdev 0 0
>
> On my systems, the options field contains "defaults,_netdev" and possibly
> a few other things. I don't know whether that matters.

I'll try --- I think it uses defaults anywhen when no defaults are
specified. What else would it use other than defaults ...

> If you add an entry to /etc/hosts for this NFS server, and mount the
> share by hostname, does that change anything?

I have a DNS server (on the same machine that serves the share) which
works fine. Making an entry in /etc/hosts is something I want to
avoid. If the addresses of the server ever change, I wont remember
that entry and will have to spend ever so much time to figure out
what's wrong ...

> > I have another case in which machines need to be connected to a
> > particular VLAN to mount home directories. In case they are not
> > connected to that VLAN, I don't want the boot process to proceed at
> > all because the home directories won't be available.
>
> Hmm... can you add the "fail" option after _netdev? I've never tried.

Hm, in man mount, there's only 'nofail' for when the mount is allowed
to fail. That also means that mounts must not fail and the failure
must not be ignored. Same goes man fstab. I doubt there's a 'fail'
option. Who would want a mount to fail?

> > So how do I force it that the entries in fstab are not being silently
> > ignored? I want these shares either mounted, like through like 3
> > retries, or booting to stop when they can't be mounted.
>
> I do not know how to allow a specific number of retries. Not without
> writing your own hacked-up shell scripts, at least.

The retries aren't exactly necessary; I merely thought it can't hurt
to retry, and systemd should do that anyway when there's a failure the
first time.

[hw]

On Mon, 2023-10-23 at 16:53 +0200, Christoph Brinkhaus wrote:
> Am Mon, Oct 23, 2023 at 04:17:11PM +0200 schrieb hw:
> > Hi,
> >
> > I have an entry in the fstab to mount an NFS share via IPv6. For
> > unknown reasons, the entry is being ignored on boot, so after booting,
> > I have to log in as root and do a 'mount -a' which mounts the share
> > without problems.
> >
> > The entry in the fstab looks like this:
> >
> >
> > [fd53::11]:/srv/example /home/example/foo nfs _netdev 0 0
> >
> >
> > I have another case in which machines need to be connected to a
> > particular VLAN to mount home directories. In case they are not
> > connected to that VLAN, I don't want the boot process to proceed at
> > all because the home directories won't be available.
>
> You might need the "late" option of mount. Its purpose is to mount when
> prerequisites as the network are available already.

There doesn't seem to a 'late' option in the man pages. Having
'_netdev' is supposed to make sure that the network is up before
mounting ...

I found this, though:
https://unix.stackexchange.com/questions/349264/fstab-mount-wait-for-network

I'll try that, plus 'defaults'.

> > So how do I force it that the entries in fstab are not being silently
> > ignored? I want these shares either mounted, like through like 3
> > retries, or booting to stop when they can't be mounted.
> >
> I have never tried to implement things as 3x retries or so.

Well, the retries are not so relevant; I'd expect that to happen
anyway. But how can I stop the booting when a mount fails?

Alternatively, how can I prevent booting or have the machine becoming
inaccessible when it's not connected to a particular VLAN? Like the
users can't log in and instead get a message that the computer is
incorrectly connected ...

[hw]

On Mon, 2023-10-23 at 17:40 +0200, hw wrote:
> On Mon, 2023-10-23 at 16:53 +0200, Christoph Brinkhaus wrote:
> > Am Mon, Oct 23, 2023 at 04:17:11PM +0200 schrieb hw:
> > > Hi,
> > >
> > > I have an entry in the fstab to mount an NFS share via IPv6. For
> > > unknown reasons, the entry is being ignored on boot, so after booting,
> > > I have to log in as root and do a 'mount -a' which mounts the share
> > > without problems.
> > >
> > > The entry in the fstab looks like this:
> > >
> > >
> > > [fd53::11]:/srv/example /home/example/foo nfs _netdev 0
0

Ok, it seems to work with:


... nfs defaults,_netdev,x-systemd.after=network-online.target 0 0


So the '_netdev' option is broken. I'll have to see if this reboot
was an exception, but there's no good reason to assume that it won't
work next time, too.

So the next question remains:

> [...]

> > > So how do I force it that the entries in fstab are not being silently
> > > ignored? I want these shares either mounted, like through like 3
> > > retries, or booting to stop when they can't be mounted.
> > >
> > I have never tried to implement things as 3x retries or so.
>
> Well, the retries are not so relevant; I'd expect that to happen
> anyway. But how can I stop the booting when a mount fails?
>
> Alternatively, how can I prevent booting or have the machine becoming
> inaccessible when it's not connected to a particular VLAN? Like the
> users can't log in and instead get a message that the computer is
> incorrectly connected ...

Let me add that the machines are currently unaware that they are
connected to a VLAN because the switch ports are configured untagged.
I could change that to tagged but I don't see how that would solve
anything.

Unless maybe I could intervene before starting gdm by pinging a server
and bringing up a message instead of starting gdm when the server
can't be reached. That should be possible, but how would I bring up a
message instead of gdm? It doesn't even have to be a GUI that's
starting, just a message would suffice. After that, automatically
shut down after a 2 minutes or so ...

[Christoph Brinkhaus]

Am Mon, Oct 23, 2023 at 05:40:54PM +0200 schrieb hw:
> On Mon, 2023-10-23 at 16:53 +0200, Christoph Brinkhaus wrote:
> > Am Mon, Oct 23, 2023 at 04:17:11PM +0200 schrieb hw:
> > > Hi,
> > >
> > > I have an entry in the fstab to mount an NFS share via IPv6. For
> > > unknown reasons, the entry is being ignored on boot, so after booting,
> > > I have to log in as root and do a 'mount -a' which mounts the share
> > > without problems.
> > >
> > > The entry in the fstab looks like this:
> > >
> > >
> > > [fd53::11]:/srv/example /home/example/foo nfs _netdev 0 0
> > >
> > >
> > > I have another case in which machines need to be connected to a
> > > particular VLAN to mount home directories. In case they are not
> > > connected to that VLAN, I don't want the boot process to proceed at
> > > all because the home directories won't be available.
> >
> > You might need the "late" option of mount. Its purpose is to mount when
> > prerequisites as the network are available already.
>
> There doesn't seem to a 'late' option in the man pages. Having
> '_netdev' is supposed to make sure that the network is up before
> mounting ...

Ups, that has been in my mind. It exists in FreeBSD but not in Debian.

>
> I found this, though:
> https://unix.stackexchange.com/questions/349264/fstab-mount-wait-for-network
>
> I'll try that, plus 'defaults'.

>
> > > So how do I force it that the entries in fstab are not being silently
> > > ignored? I want these shares either mounted, like through like 3
> > > retries, or booting to stop when they can't be mounted.
> > >
> > I have never tried to implement things as 3x retries or so.
>
> Well, the retries are not so relevant; I'd expect that to happen
> anyway. But how can I stop the booting when a mount fails?
>
> Alternatively, how can I prevent booting or have the machine becoming
> inaccessible when it's not connected to a particular VLAN? Like the
> users can't log in and instead get a message that the computer is
> incorrectly connected ...
>

You could start a crontab job to check the status some time after boot
or create a systemd unit after almost everything has been finished.

Kind regards,
Christoph

[Christoph Brinkhaus]

I have digged a little bit because this is an interesting task. I have
tried to use the crontab of root but the messages are not printed to the
console but send by mail. For that test I have not been logged in which
seems to be your use case.

Then I have had a look at gdm. I think one option to display stuff is to
use gdm itself. The message of the greeting screen can be configured. A
restart of gdm should be enough to update the content of the screen. I
do not use gdm to try that. But I think that is at least an option.

Kind regards,
Christoph

[David Wright]

You've read man mount, but have you read man systemd.mount?
Specifically the second paragraph of FSTAB.

Cheers,
David.

[hw]

Thank you very much, it sounds like a good option. I'll look into it
and see if I can get it to work.