On 22/05/2021 16:48, ghe2001 wrote:
> Buster everywhere, latest update.
>
> I update/upgrade using apt on 3 different computers (SuperMicro
> desktop, Dell laptop, Raspberry Pi cute thing). Sample from a few
> minutes ago, on the desktop:
>
> root@sbox:~# apt update
> Hit:1 http://security.debian.org/debian-security buster/updates InRelease
> Hit:2 http://deb.debian.org/debian buster InRelease
> Get:3 http://deb.debian.org/debian buster-updates InRelease [51.9 kB]
> Get:4 http://deb.debian.org/debian buster-backports InRelease [46.7 kB]
> Fetched 98.6 kB in 2s (52.2 kB/s)
> ...
> Error: GDBus.Error:org.freedesktop.systemd1.UnitMasked: Unit -.mount
> is masked.

*.mount files are systemd representations of mount points. Sometimes
they're autogenerated from /etc/fstab (that is, fstab is still a
first-class place to configure mount points), but they might also be in
the usual systemd locations such as /etc/systemd/system

Now you can't name the mount files exactly after the mount points
(mostly because / isn't valid in file names), so systemd uses an
escaping mechanism

$ systemd-escape --unescape - /

So, this is a mount file for the root directory.

Now, what does it mean that the unit is masked? Here, you need to look
at the man page for "systemctl", in the description for the "is-enabled"
subcommand. "Masked" means "Completely disabled, so that any start
operation on it fails". Masking may be done either by the system, or the
administrator, but it basically means that systemd won't be able to
mount your root directory (however, that's a moot point as userspace
never mounts the root directory; that's the kernel's job :)

In summary, I'd say it's a strange error, but harmless.


> ...
> Reading package lists... Done
> Building dependency tree
> Reading state information... Done
> All packages are up to date.
>
> And all seems to have worked -- when update says there are upgrades
> available, it asks if I want them, then downloads and installs
> properly, but the same error message is displayed.  I've been a Debian
> user for some 15 years, and I've never seen an error from dpkg, apt,
> apt-get, synaptic, or aptitude.  Until a few weeks ago.  On all my
> computers, except the 'Pi (also systemd).  I don't know what makes
> this happen or even what it means (a bent apt update?  a bent systemd
> update?).
>
> Thoughts?  Howtos?
>
>

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