[SOLVED] SSH issue

variable-root · 2022-07-31 07:15:48

Hello,

I have two arch devices (client and server) which I am attempting to connect to via SSH. The issue is however that I can only connect to the server if a local login is already established.

ssh -V
OpenSSH_9.0p1, OpenSSL 1.1.1q  5 Jul 2022

The versions are the same for both client and server. The SSH connection works if I am already
logged in at the server, however if I do not:

$PS1:[41]~ $ ssh -v SERVER                                                          
OpenSSH_9.0p1, OpenSSL 1.1.1q  5 Jul 2022                                                             
debug1: Reading configuration data /home/USER/.ssh/config                                          
debug1: /home/USER/.ssh/config line 4: Applying options for SERVER
debug1: Reading configuration data /etc/ssh/ssh_config                                                
debug1: Connecting to 192.168.0.20 [192.168.0.20] port 22.                                           
debug1: connect to address 192.168.0.20 port 22: No route to host                                    
ssh: connect to host 192.168.0.20 port 22: No route to host

There was no journalctl output. Any help is appreciated.

Last edited by variable-root (2022-08-03 00:58:32)

Grigorios · 2022-07-31 08:06:27

Hello,

I have never heard of the problem that you cannot connect to a system via ssh if no user is locally logged in.

Based on your ssh -V Server output, we can see that your system has no route to the SERVER.
Check if both machines are in the same subnet and maybe post the output from

$ip route

and

$ip a

Greetings

Grigorios

Last edited by Grigorios (2022-07-31 08:07:46)

ewaller · 2022-07-31 15:09:43

My SWAG (Scientific Wild Ass Guess): The server is using a WiFi connection? You are using something on the server to control the Network connection that is based not on system level credentials, but rather user level credentials: Like i3wm with NetworkManager? If this is the case, the Network connection will not associate until the user logs in. You can check that by checking the journal.

PerfMonk · 2022-07-31 17:34:45

Is the server and/or client are virtual machines on same host ?
Normally a VM has no route to reach its host, it just gives you a gateway access to internet.

variable-root · 2022-08-01 03:45:32

@ewaller & @Perfmonk

The server is a ethernet wired seperate station. It is also not a VM but bootable archlinux on the disk.

@Grigorios

For client (with MAC addresses REDACTED for security):

ip route
default via 192.168.0.1 dev wlp2s0 proto dhcp src 192.168.0.50 metric 600 
192.168.0.0/24 dev wlp2s0 proto kernel scope link src 192.168.0.50 metric 600

ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: enp3s0f1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000
    link/ether REDACTED
3: wlp2s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether REDACTED permaddr REDACTED
    inet 192.168.0.50/24 brd 192.168.0.255 scope global dynamic noprefixroute wlp2s0
       valid_lft 604730sec preferred_lft 604730sec
    inet6 REDACTED scope global dynamic noprefixroute 
       valid_lft 3532sec preferred_lft 3532sec
    inet6 REDACTED scope global dynamic noprefixroute 
       valid_lft 172799sec preferred_lft 172799sec
    inet6 REDACTED scope link noprefixroute 
       valid_lft forever preferred_lft forever

For server:

ip route
default via 192.168.0.1 dev enp33s0 proto dhcp src 192.168.0.20 metric 100 
192.168.0.0/24 dev enp33s0 proto kernel scope link src 192.168.0.20 metric 100

ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: enp33s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
    link/ether REDACTED permaddr REDACTED
    inet 192.168.0.20/24 brd 192.168.0.255 scope global dynamic noprefixroute enp33s0
       valid_lft 534074sec preferred_lft 534074sec

It is a strange issue, and unfortunately the few posts made by other users various forums are all dead ends as well.

seth · 2022-08-01 06:42:37

ssh: connect to host 192.168.0.20 port 22: No route to host

is either a really weird bug in the ssh client or obvious.
W/o being logged into the server (what I understand is the problematic condition, it's NOT that you first need to locally log into the client, right?)

ip r 192.168.0.20
ping -c 192.168.0.20
nmap -p 192.168.0.20

Do you configure a static IP on the server?
How is the NIC configured to begin with (you could still eg. be activating w/ a user service - wifi or not)?

It's *only* about being logged into the server, you're positive (not "I think", *know*) that it's up, running and not in S3?
=> Try to disable the NICs power saving, set /sys/class/net/enp33s0/power/control to "on", https://wiki.archlinux.org/title/Power_ … Management
or disable aspm altogether (for a quick test), "pcie_aspm=off", https://wiki.archlinux.org/title/Kernel_parameters

variable-root · 2022-08-02 07:51:40

@seth

The current server behavior is to only allow a valid remote ssh connection from the client if the client is already logged in locally.
The desired server behavior is to allow a valid remote ssh connection from the client after the server completes booting (multi-user.target).

I have reinstalled open-ssh on both the client and server. I have moved the authorized_keys file outside the user home directory. As you suggested I also:
Disabled the NICs power-saving by setting set /sys/class/net/enp33s0/power/control to "on" from "auto".
Set pcie_aspm=off during boot. Unfortunately, none of these steps resolved the issue.

Using the ping command, and root login I was able to determine - as you suspected - that NIC configuration seems to only be happening when the user
is logged in. As soon as the user logs out the NIC releases the static IP and goes down. I am not certain as to why since NIC configuration is handled by NetworkManager.service which
is a target.wants of multi-user.

After boot without local user login:
http://ix.io/46q7
http://ix.io/46q8

Raynman · 2022-08-02 09:09:31

But how is the connection configured in NM? I remember that nm-connection-editor has a checkbox with something like "allow all users to connect". If that is unchecked, I think it would explain this behavior.

seth · 2022-08-02 11:54:59

Aug 02 03:25:51 HOSTNAME_REDACTED NetworkManager[520]: <info> [1659410751.4985] device (enp33s0): state change: unmanaged -> unavailable (reason 'managed', sys-iface-state: 'external')

find /etc/systemd -type l -exec test -f {} \; -print | awk -F'/' '{ printf ("%-40s | %s\n", $(NF-0), $(NF-1)) }' | sort -f

Otherwise see https://wiki.archlinux.org/title/Networ … ic_devices

variable-root · 2022-08-03 00:57:30

@Raynman

This turned out to be exactly the issue. After setting the option I was able to ssh into the server without login as desired.

Thank you all for the help.

seth · 2022-08-03 05:37:29

enp33s0 is an ethernet NIC and afaiu NM this doesn't require sharing.
There might be a conflicting service or you blocked the NIC from autoconnection.
=> see #9

Also, ftr. w/ only one wired NIC being autoconnected and on a server, you don't need NM at all - just dhcpcd will do.

Arch Linux

#1 2022-07-31 07:15:48

[SOLVED] SSH issue

#2 2022-07-31 08:06:27

Re: [SOLVED] SSH issue

#3 2022-07-31 15:09:43

Re: [SOLVED] SSH issue

#4 2022-07-31 17:34:45

Re: [SOLVED] SSH issue

#5 2022-08-01 03:45:32

Re: [SOLVED] SSH issue

#6 2022-08-01 06:42:37

Re: [SOLVED] SSH issue

#7 2022-08-02 07:51:40

Re: [SOLVED] SSH issue

#8 2022-08-02 09:09:31

Re: [SOLVED] SSH issue

#9 2022-08-02 11:54:59

Re: [SOLVED] SSH issue

#10 2022-08-03 00:57:30

Re: [SOLVED] SSH issue

#11 2022-08-03 05:37:29

Re: [SOLVED] SSH issue

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