[BUG] deploy links: failed to add containerlab ownership altname

[sdargoeuves]

Describe the bug

Since moving to the latest version of containerlab (0.75.0), I am not able to start a lab (on 1 server, not on my other server)
I initially thought it would only affect the mix lab with vagrant boxes AND containers, but I have the same issue with only containers labs.

I also tried to remove the multilab plugin, still the same error happened.

To Reproduce

Any topology file containing containers (as far as I've experienced...)

Lab topology

Simplified topology that works fine on one of my server, but not on the other...

---
plugin: [ multilab ]
defaults:
    multilab.id: 2
    device: eos
    devices.eos.clab.image: ceos:4.34.5M
    links.stub_loopback: false
    provider: clab

module: ospf

nodes:
  r1:
  r2:
  r3:

links:
  - r1-r2
  - r2-r3
  - r3-r1

Output

From the server where it fails

╰─❯ dnetlab up -vvv

┌──────────────────────────────────────────────────────────────────────────────────┐
│ CREATING configuration files                                                     │
└──────────────────────────────────────────────────────────────────────────────────┘
loaded plugin netlab.extra.multilab
Removing unmanaged devices from topology
[INFO]    Rendered normalize template for r1 into r1/normalize
[INFO]    Rendered initial template for r1 into r1/initial
[INFO]    Rendered ospf template for r1 into r1/ospf
[INFO]    Rendered normalize template for r2 into r2/normalize
[INFO]    Rendered initial template for r2 into r2/initial
[INFO]    Rendered ospf template for r2 into r2/ospf
[INFO]    Rendered normalize template for r3 into r3/normalize
[INFO]    Rendered initial template for r3 into r3/initial
[INFO]    Rendered ospf template for r3 into r3/ospf
Removing unmanaged devices from topology
[CREATED] provider configuration file: clab.yml
[CREATED] pickled transformed topology data into netlab.snapshot.pickle
Removing unmanaged devices from topology
[GROUPS]  group_vars for all
[GROUPS]  group_vars for modules
[GROUPS]  group_vars for eos
[HOSTS]   host_vars for r1
[HOSTS]   host_vars for r2
[HOSTS]   host_vars for r3
[CREATED] minimized Ansible inventory hosts.yml
[CREATED] Ansible configuration file: ansible.cfg
Removing unmanaged devices from topology

┌──────────────────────────────────────────────────────────────────────────────────┐
│ CHECKING virtualization provider installation                                    │
└──────────────────────────────────────────────────────────────────────────────────┘
Checking virtualization provider installation
run_command executing: containerlab version
Adding /home/sa/code/quick-netlab-lab/netlab to system PATH
New system path: /home/sa/code/quick-netlab-lab/netlab:/home/sa/code/netsim-main-lab/venv/bin:/home/sa/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin
... run result: CompletedProcess(args=['containerlab', 'version'], returncode=0, stdout='\n ⣴⡾⠛⠛⠖ ⢠⣶⠟⠛⢷⣦ ⢸⣿⣧  ⣿ ⠘⠛⢻⡟⠛⠛  ⣾⣿⡀  ⣿⡇ ⣿⣿⡄ ⢸⡇ ⣿⡟⠛⠛⠃⢸⣿⠛⠛⣷⡄ \x1b[38;2;0;201;255m⣿⡇\x1b[0m      \x1b[38;2;0;201;255m⣿⡇\x1b[0m    \n⢸⣿     ⣿⡇   ⣿⡇⢸⣿⠹⣧⡀⣿   ⢸⡇   ⣸⡏⢹⣧  ⣿⡇ ⣿⡏⢿⣄⢸⡇ ⣿⣧⣤⣤ ⢸⣿⣀⣀⣾⠇ \x1b[38;2;0;201;255m⣿⡇⠐⠟⠛⢿⡆\x1b[0m \x1b[38;2;0;201;255m⣿⡷⠛⢿⣆\x1b[0m \n⠘⣿⣄  ⡀ ⢻⣧⡀ ⣠⣿⠃⢸⣿ ⠘⣷⣿   ⢸⡇  ⢠⣿⠷⠶⢿⡆ ⣿⡇ ⣿⡇ ⢻⣾⡇ ⣿⡇   ⢸⣿⠉⢻⣧⡀ \x1b[38;2;0;201;255m⣿⡇⢰⡟⠛⣻⡇\x1b[0m \x1b[38;2;0;201;255m⣿⡇\x1b[0m \x1b[38;2;0;201;255m⣸⡿\x1b[0m \n ⠈⠙⠛⠛⠉  ⠉⠛⠛⠋⠁ ⠘⠛  ⠈⠛   ⠘⠃  ⠚⠃  ⠘⠛ ⠛⠃ ⠛⠃  ⠙⠃ ⠛⠛⠛⠛⠃⠘⠛  ⠙⠓ \x1b[38;2;0;201;255m⠛⠃⠈⠛⠛⠙⠃\x1b[0m \x1b[38;2;0;201;255m⠛⠛⠛⠛⠁\x1b[0m \n\n    version: 0.75.0\n     commit: 6a686b7d7\n       date: 2026-04-27T09:35:56Z\n     source: https://github.com/srl-labs/containerlab\n rel. notes: https://containerlab.dev/rn/0.75/\n', stderr='')
run_command executing: ['bash', '-c', "[[ `containerlab version|awk '/version/ {print $2}'` > '0.74.99' ]] && echo OK"]
... run result: CompletedProcess(args=BoxList(['bash', '-c', "[[ `containerlab version|awk '/version/ {print $2}'` > '0.74.99' ]] && echo OK"]), returncode=0, stdout='OK\n', stderr='')
[SUCCESS] clab installed and working correctly
clab: validating node r1 image ceos:4.34.5M
run_command executing: ['docker', 'image', 'ls', '--format', 'json', 'ceos:4.34.5M']
... run result: CompletedProcess(args=['docker', 'image', 'ls', '--format', 'json', 'ceos:4.34.5M'], returncode=0, stdout='{"Containers":"N/A","CreatedAt":"2026-03-27 21:27:56 +0000 UTC","CreatedSince":"5 weeks ago","Digest":"\\u003cnone\\u003e","ID":"c60da6ae96b7","Repository":"ceos","SharedSize":"N/A","Size":"2.57GB","Tag":"4.34.5M","UniqueSize":"N/A","VirtualSize":"2.572GB"}\n', stderr='')
clab: validating node r2 image ceos:4.34.5M
clab: validating node r3 image ceos:4.34.5M

┌──────────────────────────────────────────────────────────────────────────────────┐
│ STARTING clab nodes                                                              │
└──────────────────────────────────────────────────────────────────────────────────┘
pre-start hook for Containerlab - create any bridges and load kernel modules
provider clab: executing sudo -E containerlab deploy --reconfigure -t clab.yml
run_command executing: sudo -E containerlab deploy --reconfigure -t clab.yml
08:53:12 INFO Containerlab started version=0.75.0
08:53:12 INFO Parsing & checking topology file=clab.yml
08:53:12 INFO Removing directory path=/home/sa/code/quick-netlab-lab/minitest/clab-ml-2
08:53:12 INFO Creating docker network name=nl_mgmt_2 IPv4 subnet=10.194.57.0/24 IPv6 subnet="" MTU=0
08:53:12 INFO Creating lab directory path=/home/sa/code/quick-netlab-lab/minitest/clab-ml-2
08:53:12 INFO Creating container name=r3
08:53:12 INFO Creating container name=r1
08:53:13 INFO Creating container name=r2
08:53:13 ERRO failed deploy links for node "r3": failed to add containerlab ownership altname: operation not supported
08:53:13 ERRO failed deploy links for node "r2": failed to add containerlab ownership altname: operation not supported
08:53:13 ERRO failed deploy links for node "r1": file exists

   ERROR

  Deployment failed for one or more nodes: node "r3" deploy links: failed to add containerlab ownership altname:
  operation not supported node "r2" deploy links: failed to add containerlab ownership altname: operation not
  supported node "r1" deploy links: file exists.

Error executing sudo -E containerlab deploy --reconfigure -t clab.yml:
  Command '['sudo', '-E', 'containerlab', 'deploy', '--reconfigure', '-t', 'clab.yml']' returned non-zero exit status 1.
[FATAL]   netlab up: sudo -E containerlab deploy --reconfigure -t clab.yml failed, aborting...
╭─   ~/code/quick-netlab-lab/minitest

Version

dev branch of netlab (commit 0ed7eb3ef)

but the same happens on the latest production netlab version, (with the same containerlab 0.75.0)

Other information

Server with issue runs on Ubuntu 20.04.6

╰─❯ dnetlab version
netlab version 26.04
  executable location: /home/sa/code/quick-netlab-lab/netlab/netlab
  package location: ['/home/sa/code/quick-netlab-lab/netlab/netsim']
  user defaults: []

Required packages:
  python-box: 7.2.0
  Jinja2: 3.1.4
  PyYAML: 6.0.2
  netaddr: 1.3.0
  requests: 2.32.5
  filelock: 3.18.0
  rich: 13.8.0

Optional packages:
  ruamel.yaml: 0.19.1

Ansible components:
  ansible: 10.3.0
  ansible-core: 2.17.3
  ansible-pylibssh: 1.2.2

Server OK runs on Ubuntu 24.04.4

╰─ dnetlab version
netlab version 26.04
  executable location: /home/seb/code/netlab/netlab/netlab
  package location: ['/home/seb/code/netlab/netlab/netsim']
  user defaults: []

Required packages:
  python-box: 7.2.0
  Jinja2: 3.1.4
  PyYAML: 6.0.2
  netaddr: 1.3.0
  requests: 2.32.3
  filelock: 3.16.1
  rich: 13.8.1

Optional packages:
  ruamel.yaml: not installed

Ansible components:
  ansible: 10.4.0
  ansible-core: 2.17.4
  ansible-pylibssh: 1.2.2

[sdargoeuves]

hmm I need to do more digging, no issue on a different server with the same containerlab version

[ipspace]

Thanks a million for reporting this. I tried with a fresh install of Docker on Ubuntu 20.04 and got the same error. Containerlab 0.75.0 obviously DOES NOT work with Ubuntu 20.04.

Now we have two options:

• Declare Ubuntu 20.04 no longer supported (26.04 LTS is out) and document this as a breaking change
• Keep containerlab version @ 0.74.latest and maybe test for the actual version when doing stuff discussed in Containerlab 0.75 is out #3342

The one thing we SHOULD NOT be doing is trying to persuade the containerlab team to fix stuff to work on a 6-year-old OS (which still runs Python 3.8).

Thoughts @sdargoeuves @ssasso @a-v-popov @ddutt @ubaumann @steffann? I know @DanPartelly would have no problem with that, and @jbemmel was already pushing me to drop old Python a while ago.

[sdargoeuves]

Oh, I missed that 26.04 LTS is out! I had started creating backups of the Vagrant boxes and Docker images to slowly prepare for the migration away from 20.04, but I haven’t gotten any further than that yet... looks like now is the time!

Someone reported this on containerlab, so maybe they’ll look into that issue. Either way, it’s probably a good time to say goodbye to that good old 20.04. If I remember correctly, you mentioned somewhere that once 26.04 is out, we should ditch 20.04.

which still runs Python 3.8

That’s an absolutely fine version of python 🙊... or at least much better than the one shipped by default on some network virtual boxes. I can’t remember which one I used not that long ago, but I’m not even sure it had python 3 😭

[sdargoeuves]

Fix for old Ubuntu 20.04 -- if you really don't want to update your OS

1. uninstall containerlab if you are running 0.75.0
2. install containerlab 0.74.3
3. stick to netlab 26.04

sudo apt remove containerlab
bash -c "$(curl -sL https://get.containerlab.dev)" -- -v 0.74.3
pip install networkinglab==26.4

[ipspace]

Fix for old Ubuntu 20.04

Not sure I want to go down that path... :(

[sdargoeuves]

Not sure I want to go down that path... :(

Sorry that was more a note on how to keep using that old server, not a suggestion for an actual fix.

[ubaumann]

I think it is okay to drop Python 3.8 and 3.9, and Ubuntu 20.04 support

[ipspace]

I think it is okay to drop Python 3.8 and 3.9, and Ubuntu 20.04 support

Which would automatically make it impossible to install the new version on Ubuntu 20.04. I like the idea, let's wait to hear from everyone else. If there won't be a strong "don't do it" feedback in a week or so, I'll make the change just before pushing out 26.05.

[DanPartelly]

Standard support for Ubuntu 20.04 ended last year. Python 3.9 reached end of life in Oct 2025 and it's ports in distros are in maintenance status or long removed. No one will miss Ubuntu 20.04 and Python 3.8 / 3.9

[ssasso]

Let's consider Ubuntu 20.04 as dead, imho.

[ipspace]

Let's consider Ubuntu 20.04 as dead, imho.

Unless I hear a loud complaint by @sdargoeuves, that's it 🪦

[sdargoeuves]

Unless I hear a loud complaint by @sdargoeuves, that's it 🪦

I won't complain, it makes sense to drop it. And I've got a workaround until that server is migrated. 👋🐧20.04 🐧👋
The only impact, is that I can't test the dev branch, or newer version, with my main lab.
Once I've sorted a few other fires, I'll address that.

[ipspace]

I won't complain, it makes sense to drop it.

Thank you.