Hi,
I come by trying to clear old bugs that were dormant for too long either
resolving or reviving them.
First of all I can confirm what you have found (insmod vs modprobe
changes), but I also found why.
I've found that this makes modprobe work like before:
modprobe dummy numdummies=1
So I wondered if only the default config changed.
modprobe uses config files and it picks up defaults from
/lib/modprobe.d/ and /etc/modprobe.d/.
And in there I found:
root@b:~# cat /lib/modprobe.d/systemd.conf
...
# When bonding module is loaded, it creates bond0 by default due to max_bonds
# option default value 1. This interferes with the network configuration
# management / networkd, as it is not possible to detect whether this bond0 was
# intentionally configured by the user, or should be managed by
# networkd/NM/etc. Therefore disable bond0 creation.
options bonding max_bonds=0
# Do the same for dummy0.
options dummy numdummies=0
That is the reason the new default number of dummies is zero when using
modprobe.
You can change via a config file or pass numdummies=1 to modprobe to resolve
that.
The default value was discussed upstream (denied) and the same problem but from
a "where to configure" POV in Ubuntu (see bug 1937953).
Following that bug 1937953 and marking this one invalid as I think it is
explained and not something that will be fixed/changed in the package.
That bug also has some hints on how to overwrite that default config as there
are some intricacies in regard to "which overwrites which" for these conffiles.
** Changed in: net-tools (Ubuntu)
Status: New => Invalid
** Changed in: ifupdown (Ubuntu)
Status: New => Invalid
** Also affects: kmod (Ubuntu)
Importance: Undecided
Status: New
** Also affects: systemd (Ubuntu)
Importance: Undecided
Status: New
** Changed in: kmod (Ubuntu)
Status: New => Invalid
** Changed in: systemd (Ubuntu)
Status: New => Invalid
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You received this bug notification because you are a member of Ubuntu
Touch seeded packages, which is subscribed to ifupdown in Ubuntu.
https://bugs.launchpad.net/bugs/1828749
Title:
ifconfig dummy0 : Device not found
Status in ifupdown package in Ubuntu:
Invalid
Status in kmod package in Ubuntu:
Invalid
Status in net-tools package in Ubuntu:
Invalid
Status in systemd package in Ubuntu:
Invalid
Bug description:
Desired behavior:
The ifconfig command should be able to deal with the
dummy device. This worked fine until recently.
Observed behavior:
:; ifconfig dummy0
dummy0: error fetching interface information: Device not found
This problem appeared when I upgraded to bionic.
Highly informative workaround:
:; ip link add dummy0 type dummy
That command works, and makes the problem go away permanently.
The ifconfig command works fine after that.
The ifup and ifdown commands also work fine after that.
For convenient debugging, you can use the command:
:; ip link del dummy0 type dummy
which makes the problem come back.
You can also experiment with dummy1 et cetera.
Package ownership issues:
Compare: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=909204
That report was filed against ippusbxd, which is almost certainly
not the relevant package.
For that matter, I have no idea whether the root cause is in the
net-tools package or the kernel networking stack. All I know is
the ip command plays nicely with the kernel while the ifconfig
command does not.
Notes:
The kernel module for the dummy interface is preloaded in
all situations described here. That's not the issue.
An apport file is attached, to describe the environment.
Also, since you asked:
:; apt-cache policy net-tools
net-tools:
Installed: 1.60-26ubuntu1
Candidate: 1.60-26ubuntu1
Version table:
*** 1.60-26ubuntu1 500
500 http://ubuntu.cs.utah.edu/ubuntu xenial/main amd64 Packages
100 /var/lib/dpkg/status
:; lsb_release -rd
Description: Ubuntu 16.04.6 LTS
Release: 16.04
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https://bugs.launchpad.net/ubuntu/+source/ifupdown/+bug/1828749/+subscriptions
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