ssh login problem on ubuntu VM

[himself]

Hi all,

i have some weired behaviour from a ubuntu VM (20.04). I can randomly ssh into the VM, then it stopps working.
I do not see any hint in the logs what is going wrong.

i set up ssh had some issues and changed the port to 222. If i restart the VM it randomly starts working on that port. Then it stops working. I can not even enter the password if i try to reconnect.
Output of ssh -vvv on the correct port 222 if i try to connect:

ssh user@192.168.178.29 -p 222 -vvv
OpenSSH_8.4p1 Debian-5, OpenSSL 1.1.1n  15 Mar 2022
debug1: Reading configuration data /root/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: include /etc/ssh/ssh_config.d/*.conf matched no files
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug2: resolve_canonicalize: hostname 192.168.178.29 is address
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts' -> '/root/.ssh/known_hosts'
debug3: expanded UserKnownHostsFile '~/.ssh/known_hosts2' -> '/root/.ssh/known_hosts2'
debug2: ssh_connect_direct
debug1: Connecting to 192.168.178.29 [192.168.178.29] port 222.
debug1: connect to address 192.168.178.29 port 222: Connection refused
ssh: connect to host 192.168.178.29 port 222: Connection refused

if i try from within the proxmox it works sometimes.

If i wouldn't experience the diffrence between working within the proxmoxx setup and from outside (Same network by the way) i would guess on 2 instances of ssh being active.

The auth.log doesn't hold any infomation about the ssh attempts.

For any help i would be really gratefull.

BTW it shows the behaviour with all install i tried.

 

[shrdlicka]

Hi,
can you access the port telnet 192.168.178.29 222 or does it run into a timeout? Do you have the firewall enabled?

 

[E_Mouws]

What do you mean with "If i try from within proxmox it works sometimes" ? Is that login into the vm using the proxmox-console?

If it's the console it does not use SSH

 

[D0K]

if your on the host machine which hosts the VM you can do the command "qm enter $VMID " in the CLI

have you tried connecting to port 22 again after not being able on port 222 ? to see if the configuration changes ?

there's also a possibility that is the ssh service that stops because of some error ?

also make sure to edit the /etc/ssh/sshd_config* and NOT /etc/ssh/ssh_config for this purpose.

 

[himself]

Hi

@shrdlicka: do not know if this is a timeout guess its more not allowed?

telnet 192.168.178.29 222
Trying 192.168.178.29...
telnet: Unable to connect to remote host: Connection refused

Firewall is disabled.

@E_Mouws: What i wanted to say is that if i ssh from on virtual machine on the proxmoxx Node into the specific VM it works. I only see this issue from outside. That is why i changed the port because i thoughth all the port 22 causes the confusion ... not the case obviously.

@D0K:
i checked this already.
ssh is running and working from inside the node.

All machines are in the same network 192.168.178.xxx.

I think the issue is related to proxmox, not the VM as it works within the node.

Thanks for your replies

 

[E_Mouws]

Since it works from within Proxmox but not from outside.
Has your VM the right settings for the gateway ? Can it ping to the outside ?

 

[himself]

Yes, connectivity of the VM is ok. Local as well as Internet. So i do not think it is related to th enetwork settings i used. Anyway i will post them so you can have a look at it. I can also ping the VM from any machine in the network.

# This is the network config written by 'subiquity'
network:
  ethernets:
    ens18:
      addresses:
      - 192.168.178.29/24
      gateway4: 192.168.178.1
      nameservers:
        addresses:
        - 8.8.8.8
        - 8.8.4.4
        search: []
  version: 2

What i noticed while checking for the configuration is a file networks, holding this info:

# symbolic names for networks, see networks(5) for more information
link-local 169.254.0.0

I have no clue where this is comming from and what it is needed for.

Besides there are some other network related folders (networkd-dispatcher) network and of course netplan where i took the config from.

I am not sure if this might have an impact on the ssh-server behaviour.


SSH from the VM to any other machine in the network works. Issue seems to be one directional.

 

[E_Mouws]

Is a firewall active? If so; can you post the configuration?
Also please configuration from "netstat -tulpn"

 

[himself]

No. Firewall in Proxmox is not active:

netstat says:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      650/systemd-resolve
tcp        0      0 0.0.0.0:222             0.0.0.0:*               LISTEN      1072/sshd: /usr/sbi
tcp6       0      0 :::222                  :::*                    LISTEN      1072/sshd: /usr/sbi
tcp6       0      0 :::6720                 :::*                    LISTEN      1/init
udp        0      0 127.0.0.53:53           0.0.0.0:*                           650/systemd-resolve
udp        0      0 0.0.0.0:3671            0.0.0.0:*                           671/knxd

 

[himself]

After completly rebooting the system (host, not only VM) it suddenly seems to work.
Thanks for your help anyway