#755471 ifupdown: fails to bring up network: cannot access '/dev/net/tun': ENOENT

Package:
uml-utilities
Source:
uml-utilities
Description:
User-mode Linux (utility programs)
Submitter:
Thorsten Glaser
Date:
2025-02-26 10:15:03 UTC
Severity:
important
#755471#5
Date:
2014-07-21 08:18:28 UTC
From:
To:
Hi,

after a reboot, my tun* network interfaces are no longer
brought up. In my case, this does not make the entire
system unusable, luckily, but I assume that this may be
the case for others. Nevertheless, conservatively setting
the severity "only" to important, for now.

I have stanzas like this one in /e/n/i:

auto tap0
iface tap0 inet static
	address 192.168.0.1
	pointopoint 192.168.0.2
	netmask 255.255.255.255
	tunctl_user tglase
	up iptables -t nat -A POSTROUTING -s 192.168.0.2 -j MASQUERADE
	up echo 1 > /proc/sys/net/ipv4/ip_forward
	down iptables -t nat -D POSTROUTING -s 192.168.0.2 -j MASQUERADE

This is so I can run ARAnyM (Atari emulators) with network
access as regular (non-root) user.

I'm attaching two bootlogd outputs (with a bit of context
around the lines in question) to show the problem.

Running both 'ip a' and 'ifconfig -a' after boot shows that,
indeed, the tun interfaces are not there, which is a problem.

I am not sure whether ifupdown is the correct package for this
bugreport. Please reassign to whatever is, if it isn't.

Thanks!
#755471#10
Date:
2014-07-21 08:26:09 UTC
From:
To:
Dixi quod…

Hm… in fact, it probably isn’t… my OpenVPN is also not “up”.

bye,
//mirabilos
#755471#15
Date:
2014-07-21 08:42:42 UTC
From:
To:
Interesting. I have been observing this ever since I have been
using tun interfaces in unstable. I always have to manually
start the interfaces with ifup and then add them to the bridge
with brctl.

I never bothered filing a bug report though, so thanks!

Adrian
#755471#20
Date:
2014-07-21 08:26:41 UTC
From:
To:
Hello,

I'm not sure what causes this, but /dev/net/tun is missing, as the logs
say. Could be a kernel problem, or a bug in uml-utilities, I don't know.
#755471#29
Date:
2014-07-21 16:29:22 UTC
From:
To:
Andrew Shadura dixit:

Hrm, weird. Anyway:

ii  uml-utilities         20070815-1.3    i386            User-mode Linux (utility programs)
 -- Jakub Wilk <jwilk@debian.org>  Wed, 02 Nov 2011 22:35:36 +0100

I don’t quite think so…


John Paul Adrian Glaubitz dixit:

Oh? For me, this worked until extremely recently.

Fun fact:

$ sudo modprobe tun
$ sudo /etc/init.d/openvpn start

This seems to work. So I think the module may not be autoloaded
correctly any more. Maybe the kernel? My last boot was on 2nd of
July, therefore almost certainly with linux 3.14.9-1 whereas now
I run:

Linux tglase.lan.tarent.de 3.14-1-amd64 #1 SMP Debian 3.14.12-1 (2014-07-11) i686 GNU/Linux

Adrian, you’re welcome for me filing the bug ☺

bye,
//mirabilos
#755471#34
Date:
2014-07-21 16:38:29 UTC
From:
To:
That sounds like #749021

Cheers,
Julien
#755471#39
Date:
2025-02-26 10:14:01 UTC
From:
To:
Steeg