[SOLVED] ifupdown2 install breaks network PVE 7.3-4

[cave]

Hi,

I'm not the first here to raise that kind of thread regarding ifupdown2 issues after install of the package. I was reading the other threads and could not find a solution for my issue.


i was creating a new vlan aware linux bridge, stumbled upon the package ifupdown2 requirement, to get rid of reboots for network changes. sounds like a thing which comes handy.
As it was recommended and ships automatically with PVE 7, i installed it.

bad mistake...

cave@cave:~$ ssh root@proxmox
Linux proxmox 5.15.83-1-pve #1 SMP PVE 5.15.83-1 (2022-12-15T00:00Z) x86_64

The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Last login: Sat Jan 21 09:44:16 2023 from 192.168.100.45


root@proxmox:~# apt install ifupdown2
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
apt autoremove suggestions removed
Suggested packages:
ethtool python3-gvgen python3-mako
The following packages will be REMOVED:
ifupdown
The following NEW packages will be installed:
ifupdown2
0 upgraded, 1 newly installed, 1 to remove and 0 not upgraded.
Need to get 237 kB of archives.
After this operation, 1,464 kB of additional disk space will be used.
Do you want to continue? [Y/n] y
Get:1 http://download.proxmox.com/debian/pve bullseye/pve-no-subscription amd64 ifupdown2 all 3.1.0-1+pmx3 [237 kB]
Fetched 237 kB in 0s (522 kB/s)
dpkg: ifupdown: dependency problems, but removing anyway as you requested:
ifenslave depends on ifupdown.

(Reading database ... 106875 files and directories currently installed.)
Removing ifupdown (0.8.36+pve2) ...
Selecting previously unselected package ifupdown2.
(Reading database ... 106839 files and directories currently installed.)
Preparing to unpack .../ifupdown2_3.1.0-1+pmx3_all.deb ...
Unpacking ifupdown2 (3.1.0-1+pmx3) ...
Setting up ifupdown2 (3.1.0-1+pmx3) ...
Installing new version of config file /etc/default/networking ...

network config changes have been detected for ifupdown2 compatibility.
Saved in /etc/network/interfaces.new for hot-apply or next reboot.

Reloading network config on first install

Progress: [ 71%] [#############################################################################################......................................]

And stuck. I cannot ping, ssh or webinterface my PVE Host anymore. The guests with their veth on the vmbr0 Bridge are still available. But the IP of the vmbr0 Bridge seems to be down. The NIC assigned to vmbr0 (bridge_ports eth1) seems to be working.

root@proxmox:~# pveversion -v

proxmox-ve: 7.3-1 (running kernel: 5.15.83-1-pve)
pve-manager: 7.3-4 (running version: 7.3-4/d69b70d4)
pve-kernel-helper: 7.3-2
pve-kernel-5.15: 7.3-1
pve-kernel-5.4: 6.4-20
pve-kernel-5.0: 6.0-11
pve-kernel-5.15.83-1-pve: 5.15.83-1
pve-kernel-5.4.203-1-pve: 5.4.203-1
pve-kernel-5.4.60-1-pve: 5.4.60-2
pve-kernel-5.0.21-5-pve: 5.0.21-10
ceph-fuse: 14.2.21-1
corosync: 3.1.7-pve1
criu: 3.15-1+pve-1
glusterfs-client: 9.2-1
ifupdown: residual config
ifupdown2: not correctly installed
ksm-control-daemon: 1.4-1
libjs-extjs: 7.0.0-1
libknet1: 1.24-pve2
libproxmox-acme-perl: 1.4.3
libproxmox-backup-qemu0: 1.3.1-1
libpve-access-control: 7.3-1
libpve-apiclient-perl: 3.2-1
libpve-common-perl: 7.3-1
libpve-guest-common-perl: 4.2-3
libpve-http-server-perl: 4.1-5
libpve-storage-perl: 7.3-1
libqb0: 1.0.5-1
libspice-server1: 0.14.3-2.1
lvm2: 2.03.11-2.1
lxc-pve: 5.0.0-3
lxcfs: 4.0.12-pve1
novnc-pve: 1.3.0-3
proxmox-backup-client: 2.3.2-1
proxmox-backup-file-restore: 2.3.2-1
proxmox-mini-journalreader: 1.3-1
proxmox-offline-mirror-helper: 0.5.0-1
proxmox-widget-toolkit: 3.5.3
pve-cluster: 7.3-2
pve-container: 4.4-2
pve-docs: 7.3-1
pve-edk2-firmware: 3.20220526-1
pve-firewall: 4.2-7
pve-firmware: 3.6-2
pve-ha-manager: 3.5.1
pve-i18n: 2.8-1
pve-qemu-kvm: 7.1.0-4
pve-xtermjs: 4.16.0-1
qemu-server: 7.3-2
smartmontools: 7.2-pve3
spiceterm: 3.2-2
swtpm: 0.8.0~bpo11+2
vncterm: 1.7-1
zfsutils-linux: 2.1.7-pve3

ifupdown: residual config
ifupdown2: not correctly installed

??

root@proxmox:~# cat /etc/network/interfaces

# network interface settings; autogenerated
# Please do NOT modify this file directly, unless you know what
# you're doing.
#
# If you want to manage part of the network configuration manually,
# please utilize the 'source' or 'source-directory' directives to do
# so.
# PVE will preserve these directives, but will NOT its network
# configuration from sourced files, so do not attempt to move any of
# the PVE managed interfaces into external files!

source /etc/network/interfaces.d/*

auto lo
iface lo inet loopback

iface eth1 inet manual

iface eth0 inet manual

allow-hotplug eth1

auto vmbr0
iface vmbr0 inet static
address 192.168.100.199
netmask 255.255.255.0
gateway 192.168.100.1
bridge_ports eth1
bridge_stp off
bridge_fd 0

iface vmbr0 inet6 static
address xxxx:xxxx:xxxx:xxxx::1
netmask 64
gateway xxxx:xxxx:xxxx:xxxx::1

auto vmbr1
iface vmbr1 inet static
address 192.168.100.198
netmask 255.255.255.0
bridge_ports eth0
bridge_stp off
bridge_fd 0

eth0 (pcie card) and vmbr1 are at the moment not in use. driver issues with r8168 since debian bullseye upgrade. This card is anyhow to be replaced soon and is not the issue here.

eth1 is the onboard NIC, connected to vmbr0

root@proxmox:~# apt list --installed | grep ifup

ifupdown2/stable,now 3.1.0-1+pmx3 all [installed]

ifupdown2 is now fully installed. at least it seems.
As connectivity to my gateway is broken, i cannot step back easily to ifupdown.


I've removed the various veth, fwpr and fwln parts from the ifconfig output below, to focus on the vmbr0 settings.

root@proxmox:~# ifconfig

eth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
ether e8:39:35:ea:43:ba txqueuelen 1000 (Ethernet)
RX packets 1199734 bytes 477009442 (454.9 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 2824510 bytes 585841125 (558.7 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
device interrupt 18


lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
inet6 ::1 prefixlen 128 scopeid 0x10<host>
loop txqueuelen 1000 (Local Loopback)
RX packets 180532 bytes 58090462 (55.3 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 180532 bytes 58090462 (55.3 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0


vmbr0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.100.199 netmask 255.255.255.0 broadcast 192.168.100.255
inet6 xxxx:xxxx:xxxx:xxxx::1 prefixlen 64 scopeid 0x0<global>
inet6 xxxx::xxxx:xxxx:xxxx:xxxx prefixlen 64 scopeid 0x20<link>
ether e8:39:35:ea:43:ba txqueuelen 1000 (Ethernet)
RX packets 2878940 bytes 261862386 (249.7 MiB)
RX errors 0 dropped 173331 overruns 0 frame 0
TX packets 471180 bytes 336694224 (321.0 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

vmbr1: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
inet 192.168.100.198 netmask 255.255.255.0 broadcast 192.168.100.255
inet6 xxxx::xxxx:xxxx:xxxx:xxxx prefixlen 64 scopeid 0x20<link>
ether 22:22:f8:03:4b:bd txqueuelen 1000 (Ethernet)
RX packets 0 bytes 0 (0.0 B)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 7 bytes 826 (826.0 B)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

My LXC Containers connected via vmbr0 are still up and running. I can ssh & ping them, operational and running. Therefore i hesitate to reboot, do not want to make it possibly worse.

i hope i have provided all the settings & configs, pretty basic though. one eth1 connected to vmbr0, though ifupdown2 broke things.

Any idea how to fix the issue?

 

[cave]

root@proxmox:~# systemctl status networking

● networking.service - LSB: Raise network interfaces.
Loaded: loaded (/etc/init.d/networking; enabled; vendor preset: enabled)
Active: active (exited) since Sun 2023-01-22 13:46:49 CET; 19min ago
Docs: man:systemd-sysv-generator(8)
Process: 2073318 ExecStart=/etc/init.d/networking start (code=exited, status=0/SUCCESS)
CPU: 19ms

Jan 22 13:46:49 proxmox systemd[1]: Starting LSB: Raise network interfaces....
Jan 22 13:46:49 proxmox networking[2073318]: Configuring network interfaces...
Jan 22 13:46:49 proxmox networking[2073322]: /usr/bin/env: ‘python3’: No such file or directory
Jan 22 13:46:49 proxmox networking[2073323]: /usr/bin/env: ‘python3’: No such file or directory
Jan 22 13:46:49 proxmox networking[2073324]: /usr/bin/env: ‘python3’: No such file or directory
Jan 22 13:46:49 proxmox networking[2073318]: failed.
Jan 22 13:46:49 proxmox systemd[1]: Started LSB: Raise network interfaces..

/usr/bin/env: ‘python3’: No such file or directory ??? <= is that a failed/missing dependency of ifupdown2?

python3 was not resolved correctly from apt as a dependency? Is that a bug?

As you can see above, ifupdown2 is from the pve-no-subscription repo, not debian.


my apt sources list, just to have it posted.

root@proxmox:~# cat /etc/apt/sources.list

deb http://ftp.debian.org/debian bullseye main contrib non-free
deb http://ftp.debian.org/debian bullseye-updates main contrib

# PVE pve-no-subscription repository provided by proxmox.com,
# NOT recommended for production use
deb http://download.proxmox.com/debian/pve bullseye pve-no-subscription
#deb http://download.proxmox.com/debian/pve buster pve-no-subscription

# security updates
deb http://security.debian.org/debian-security bullseye-security main contrib

My interfaces with the new bridge vmbr2, where this all began.

root@proxmox:~# /etc/network/interfaces.new

# network interface settings; autogenerated
# Please do NOT modify this file directly, unless you know what
# you're doing.
#
# If you want to manage parts of the network configuration manually,
# please utilize the 'source' or 'source-directory' directives to do
# so.
# PVE will preserve these directives, but will NOT read its network
# configuration from sourced files, so do not attempt to move any of
# the PVE managed interfaces into external files!

source /etc/network/interfaces.d/*

auto lo
iface lo inet loopback

auto eth1
iface eth1 inet manual

iface eth0 inet manual

auto vmbr0
iface vmbr0 inet static
address 192.168.100.199/24
gateway 192.168.100.1
bridge-ports eth1
bridge-stp off
bridge-fd 0

iface vmbr0 inet6 static
address ****:****:****:****::1/64
gateway ****:****:****:****::1

auto vmbr1
iface vmbr1 inet static
address 192.168.100.198/24
bridge-ports eth0
bridge-stp off
bridge-fd 0

auto vmbr2
iface vmbr2 inet manual
bridge-ports none
bridge-stp off
bridge-fd 0
bridge-vlan-aware yes
bridge-vids 2-4094

how to repair this?

step back to the previous binary? install manually per dpkg -i


Removing ifupdown (0.8.36+pve2) ... => so ifupdown was from the pve repository, ifupdown_0.8.36+pve2_amd64.deb

http://download.proxmox.com/debian/...n/binary-amd64/ifupdown_0.8.36+pve2_amd64.deb

Package: ifupdown
Architecture: amd64
Version: 0.8.36+pve2
Multi-Arch: foreign
Priority: important
Section: admin
Maintainer: Josué Ortega <josue@debian.org>
Installed-Size: 216
Depends: libc6 (>= 2.14), lsb-base, adduser, iproute2
Recommends: isc-dhcp-client | dhcp-client
Suggests: ppp, rdnssd
Breaks: systemd (<< 228-3~)
Replaces: systemd (<< 228-3~)
Filename: dists/bullseye/pve-no-subscription/binary-amd64/ifupdown_0.8.36+pve2_amd64.deb
Size: 82336
MD5sum: 9f8e8d97bdadd757db11febada18c8ff
SHA256: 487f81e1f69afc1ab3dcf0da3f23f18c1b2fa6ee78d3a6e09c2c1a4169428283
SHA512: af82d6ef9e092dc876b370fa39c31ff63e5ee8cf1214e81a326d24635f605bd8dfbf07ccc1f8364738e0326ee4a9f3be2221183f65f170f8008f5285cb4364f3
Description: high level tools to configure network interfaces
This package provides the tools ifup and ifdown which may be used to
configure (or, respectively, deconfigure) network interfaces based on
interface definitions in the file /etc/network/interfaces.

and also ifenslave needs to be re-installed i guess.
which i could not locate in the pve repo, so it must have been from debian.
but which version should be used. Which version has been removed?

That one 2.13~deb11u1_all ? from: https://ftp.debian.org/debian/pool/main/i/ifenslave/
https://ftp.debian.org/debian/pool/main/i/ifenslave/ifenslave_2.13~deb11u1_all.deb

Afterwards, when network is back working, which packages are missing? and should be installed for ifupdown2? why in the first place are they missing?

Should i install ifupdown & ifenslave to remove ifupdown2 ?!

This System was a Debian Jessie to Proxmox 4.1 Transformation-Installation, back then with PVE 4.0, as PVE-3.x was using openVZ and i did want to have a fresh install beginning with LXC.
Upgrades 4->5, 5->6 and 6->7 went smooth with apt dist-upgrade, and survived some reboot as well before installing ifupdown2.

root@proxmox:~# apt list --installed | grep python*

Listing...
python-apt-common/stable,now 2.2.1 all [installed,automatic]
python-pkg-resources/stable,now 44.1.1-1 all [installed,auto-removable]
python-setuptools/stable,now 44.1.1-1 all [installed,auto-removable]
python-six/stable,now 1.16.0-2 all [installed,auto-removable]
python2-minimal/stable,now 2.7.18-3 amd64 [installed,auto-removable]
python2.7-minimal/stable,now 2.7.18-8 amd64 [installed,automatic]
python2.7/stable,now 2.7.18-8 amd64 [installed]
python2/stable,now 2.7.18-3 amd64 [installed,auto-removable]
python3-apt/stable,now 2.2.1 amd64 [installed,automatic]
python3-asn1crypto/stable,now 1.4.0-1 all [installed,auto-removable]
python3-ceph-argparse/stable,now 14.2.21-1 amd64 [installed,automatic]
python3-cephfs/stable,now 14.2.21-1 amd64 [installed,automatic]
python3-certifi/stable,now 2020.6.20-1 all [installed,automatic]
python3-cffi-backend/stable,now 1.14.5-1 amd64 [installed,automatic]
python3-chardet/stable,now 4.0.0-1 all [installed,automatic]
python3-cryptography/stable,now 3.3.2-1 amd64 [installed,automatic]
python3-debconf/stable,now 1.5.77 all [installed,automatic]
python3-debian/stable,now 0.1.39 all [installed,automatic]
python3-debianbts/stable,now 3.1.0 all [installed,automatic]
python3-gpg/stable,now 1.14.0-1+b2 amd64 [installed,automatic]
python3-httplib2/stable,now 0.18.1-3 all [installed,automatic]
python3-idna/stable,now 2.10-1 all [installed,automatic]
python3-jwt/stable,now 1.7.1-2 all [installed,automatic]
python3-ldb/stable,stable-security,now 2:2.2.3-2~deb11u2 amd64 [installed,automatic]
python3-minimal/stable,now 3.9.2-3 amd64 [installed,automatic]
python3-pkg-resources/stable,now 52.0.0-4 all [installed,automatic]
python3-prettytable/stable,now 0.7.2-5 all [installed,automatic]
python3-protobuf/stable,now 3.12.4-1 amd64 [installed,automatic]
python3-pycurl/stable,now 7.43.0.6-5 amd64 [installed,automatic]
python3-pysimplesoap/stable,now 1.16.2-3 all [installed,automatic]
python3-rados/stable,now 14.2.21-1 amd64 [installed,automatic]
python3-rbd/stable,now 14.2.21-1 amd64 [installed,automatic]
python3-reportbug/stable,now 7.10.3+deb11u1 all [installed,automatic]
python3-requests/stable,now 2.25.1+dfsg-2 all [installed,automatic]
python3-samba/stable,stable-security,now 2:4.13.13+dfsg-1~deb11u5 amd64 [installed,automatic]
python3-six/stable,now 1.16.0-2 all [installed,automatic]
python3-talloc/stable,now 2.3.1-2+b1 amd64 [installed,automatic]
python3-tdb/stable,now 1.4.3-1+b1 amd64 [installed,automatic]
python3-urllib3/stable,now 1.26.5-1~exp1 all [installed,automatic]
python3.7-minimal/now 3.7.3-2+deb10u4 amd64 [installed,local]
python3.9-minimal/stable,now 3.9.2-1 amd64 [installed,automatic]
python3.9/stable,now 3.9.2-1 amd64 [installed,automatic]
python3/stable,now 3.9.2-3 amd64 [installed,automatic]

looks like, python3 is installed.


hmm=> /usr/bin/env: ‘python3’: No such file or directory

 

[cave]

Time to check my env PATH variables, if there is really no python3.

I hope someone understands a bit more about ifupdown2 and python3 with env PATH settings.

or maybe i am already looking in the complete wrong direction and don't see the obvious.

root@proxmox:~# whereis python

python: /usr/bin/python3.7 /usr/bin/python2.7 /usr/bin/python3.9 /usr/bin/python3.7m /usr/lib/python3.7 /usr/lib/python2.7 /usr/lib/python3.9 /usr/lib/python3.4 /etc/python3.7 /etc/python /etc/python2.7 /etc/python3.5 /etc/python3.9 /etc/python3.4 /usr/local/lib/python3.7 /usr/local/lib/python2.7 /usr/local/lib/python3.9 /usr/share/python

root@proxmox:~# which python3
/usr/bin/python3

PATH variable of env

root@proxmox:~# env | grep PATH
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

PATH from my shell

root@proxmox:~# echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

python is not available

root@proxmox:~# env python --version
env 'python' : No such file or version

root@proxmox:~# /usr/bin/env python
/usr/bin/env python : No such file or directory

python3 is available.

root@proxmox:~# env python3 --version
Python 3.9.2

root@proxmox:~# /usr/bin/env python3
Python 3.9.2 (default, Feb 28 2021, 17:03:44)
[GCC 10.2.1 20210110] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>

Which python versions are available in /usr/bin/

root@proxmox:~# ls /usr/bin/ | grep python

lrwxrwxrwx 1 root root 23 Jul 14 2021 pdb2.7 -> ../lib/python2.7/pdb.py
lrwxrwxrwx 1 root root 23 Feb 28 2021 pdb3.9 -> ../lib/python3.9/pdb.py
lrwxrwxrwx 1 root root 31 Apr 5 2021 py3versions -> ../share/python3/py3versions.py
lrwxrwxrwx 1 root root 9 Jul 28 2021 python2 -> python2.7
-rwxr-xr-x 1 root root 3.5M Jul 14 2021 python2.7
lrwxrwxrwx 1 root root 9 Apr 5 2021 python3 -> python3.9
-rwxr-xr-x 2 root root 4.7M Oct 31 15:04 python3.7
-rwxr-xr-x 2 root root 4.7M Oct 31 15:04 python3.7m
-rwxr-xr-x 1 root root 5.3M Feb 28 2021 python3.9
lrwxrwxrwx 1 root root 29 Jul 28 2021 pyversions -> ../share/python/pyversions.py

python3 is available and points to the latest version of python3.9

I do not understand the errormessage from ifupdown2 "/usr/bin/env: ‘python3’: No such file or directory " from 'systemctl status networking'

 

[fabian]

networking.service should not be provided by the init script, but by a proper systemd unit.. could you post the relevant part of /var/log/apt/term.log ?

 

[cave]

could you post the relevant part of /var/log/apt/term.log ?

root@proxmox:~# tail -n25 /var/log/apt/term.log

Log started: 2023-01-21 15:12:52
[1mdpkg:[0m ifupdown: dependency problems, but removing anyway as you requested:
ifenslave depends on ifupdown.

(Reading database ...
(Reading database ... 5%
...
(Reading database ... 100%
(Reading database ... 106875 files and directories currently installed.)
Removing ifupdown (0.8.36+pve2) ...
Selecting previously unselected package ifupdown2.
(Reading database ...
(Reading database ... 5%
...
(Reading database ... 100%
(Reading database ... 106839 files and directories currently installed.)
Preparing to unpack .../ifupdown2_3.1.0-1+pmx3_all.deb ...
Unpacking ifupdown2 (3.1.0-1+pmx3) ...
Setting up ifupdown2 (3.1.0-1+pmx3) ...
Installing new version of config file /etc/default/networking ...

network config changes have been detected for ifupdown2 compatibility.
Saved in /etc/network/interfaces.new for hot-apply or next reboot.

Reloading network config on first install
error: vmbr1: bridge port eth0 does not exist
[1mdpkg:[0m error processing package ifupdown2 (--configure):
installed ifupdown2 package post-installation script subprocess returned error exit status 1
Processing triggers for man-db (2.9.4-2) ...
Errors were encountered while processing:
ifupdown2
Log ended: 2023-01-21 15:13:03

Similar issues there? https://forum.proxmox.com/threads/w...2-not-installed-correctly.111731/#post-481905

root@proxmox:~# dpkg-query --list ifupdown

Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-============-============-================================================
rc ifupdown 0.8.36+pve2 amd64 high level tools to configure network interfaces

rc <-- leftovers from ifupdown hinder ifupdown2 install?

root@proxmox:~# dpkg-query --list ifupdown2

Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name Version Architecture Description
+++-==============-============-============-=====================================================
iF ifupdown2 3.1.0-1+pmx3 all Network Interface Management tool similar to ifupdown

@fabian Thanks for your replies and help.

 

[fabian]

the error seems quite clear to me:

error: vmbr1: bridge port eth0 does not exist

your eth0 device is lacking the 'auto' line? it seems that error aborted the install of ifupdown2, so you were left with a halfway in-between state.

 

[cave]

so purging eth1, vmbr1 and vmbr2 from /etc/network/interfaces.new
and redo apt install ifupdown2 ?

 

[fabian]

what? no, just make sure your network config is actually complete..

 

[cave]

as eth0 is not active, not working and going to replaced, i removed it comepletely from interfaces and interfaces.new

root@proxmox:/etc/network# apt install ifupdown2
root@proxmox:/etc/network# systemctl restart networking
root@proxmox:/etc/network# ping 192.168.100.1
PING 192.168.100.1 (192.168.100.1) 56(84) bytes of data.
64 bytes from 192.168.100.1: icmp_seq=1 ttl=64 time=0.343 ms

pveversion shows ifupdown2 now as working/installed.

root@proxmox:~# pveversion -v | grep ifup
ifupdown: residual config
ifupdown2: 3.1.0-1+pmx3

vmbr0 is back online.
ifupdown2 is installed, ifupdown is purged, i even created some new bridges with the apply-configuration in the webgui.



Thank You