Autossh – automatically restart SSH sessions and tunnels • Hacker News Board

Re: Autossh – automatically restart SSH sessions and tunnels

#11

Post by nine_k » Sat, Sep 28, 2024, 6:41 PM UTC

xk3 wrote: post #6

If you have systemd, you could do this: [Unit] Description=look ma, no autossh After=network.target [Service] Type=exec ExecStart=/usr/bin/ssh -o ServerAliveInterval=60 -o ExitOnForwardFailure=yes -Nn -R 7070:localhost:22 pc 'sleep 20m' Restart=always RestartSec=20 RuntimeMaxSec=30m [Install] WantedBy=default.target

[flagged]

Re: Autossh – automatically restart SSH sessions and tunnels

#12

Post by amlib » Sat, Sep 28, 2024, 6:45 PM UTC

isoprophlex wrote: post #8

Not 100% the same use case as autossh was built for maybe, but I'm now simply throwing tailscale on every box i need to interact with. Does away with all the port forwarding stuff, it's absolutely delightful.

How much reliance on third party am I subjecting myself by using Tailscale? What happens if I make a local connection to a machine/service running on Tailscale, does it still go out of the local network? If so, is the bulk of the payload transferred locally? Is there any advantage on using it if the machine/service is easily accessible over ipv6?

Re: Autossh – automatically restart SSH sessions and tunnels

#13

Post by ChoHag » Sat, Sep 28, 2024, 6:54 PM UTC

xk3 wrote: post #6

If you have systemd, you could do this: [Unit] Description=look ma, no autossh After=network.target [Service] Type=exec ExecStart=/usr/bin/ssh -o ServerAliveInterval=60 -o ExitOnForwardFailure=yes -Nn -R 7070:localhost:22 pc 'sleep 20m' Restart=always RestartSec=20 RuntimeMaxSec=30m [Install] WantedBy=default.target

That's so much better than bourne/bash, which requires this monstrous wart of a code blob:

autossh() {

        # Tiny delay after failure in case of connection errors

        while ! ssh "$@"; do echo Restarting ssh "$@"...; sleep 1; done

}

Re: Autossh – automatically restart SSH sessions and tunnels

#14

Post by frizlab » Sat, Sep 28, 2024, 6:54 PM UTC

How is this different from this

    ssha () {
     while true
     do
      ssh "$@"
      sleep 1
     done
     true
    }

EDIT: Oh I think I know, autossh must be detecting when the connexion is closed but ssh does not automatically…

Re: Autossh – automatically restart SSH sessions and tunnels

#15

Post by botto » Sat, Sep 28, 2024, 6:59 PM UTC

amlib wrote: post #12

isoprophlex wrote: post #8

Not 100% the same use case as autossh was built for maybe, but I'm now simply throwing tailscale on every box i need to interact with. Does away with all the port forwarding stuff, it's absolutely delightful.

How much reliance on third party am I subjecting myself by using Tailscale? What happens if I make a local connection to a machine/service running on Tailscale, does it still go out of the local network? If so, is the bulk of the payload transferred locally? Is there any advantage on using it if the machine/service is easily accessible over ipv6?

That's what Tailscale is built for, when it can it sets up a P2P connection, it only ever sends data through Tailscales servers if you are in a restrictive network environment (i.e. corp network that controls all inbound and outbound traffic)

Re: Autossh – automatically restart SSH sessions and tunnels

#16

Post by botto » Sat, Sep 28, 2024, 7:01 PM UTC

I've used autossh to have a reverse tunnel open connection back to my work desktop, IT never found it and I had that in place for year

Re: Autossh – automatically restart SSH sessions and tunnels

#17

Post by botto » Sat, Sep 28, 2024, 7:02 PM UTC

xk3 wrote: post #6

If you have systemd, you could do this: [Unit] Description=look ma, no autossh After=network.target [Service] Type=exec ExecStart=/usr/bin/ssh -o ServerAliveInterval=60 -o ExitOnForwardFailure=yes -Nn -R 7070:localhost:22 pc 'sleep 20m' Restart=always RestartSec=20 RuntimeMaxSec=30m [Install] WantedBy=default.target

This is quite clean and tidy

Re: Autossh – automatically restart SSH sessions and tunnels

#18

Post by sevg » Sat, Sep 28, 2024, 7:03 PM UTC

nine_k wrote: post #11

xk3 wrote: post #6

If you have systemd, you could do this: [Unit] Description=look ma, no autossh After=network.target [Service] Type=exec ExecStart=/usr/bin/ssh -o ServerAliveInterval=60 -o ExitOnForwardFailure=yes -Nn -R 7070:localhost:22 pc 'sleep 20m' Restart=always RestartSec=20 RuntimeMaxSec=30m [Install] WantedBy=default.target

[flagged]

Do we really still have to turn every conversation into systemd friction?

Re: Autossh – automatically restart SSH sessions and tunnels

#19

Post by hi-v-rocknroll » Sat, Sep 28, 2024, 7:03 PM UTC

The last time I used autossh it was on a client site to keep 2 layers of ssh tunnels open to jump through their network isolation hoops.

In general, when flexibility is possible, such a use-case nowadays would often be better served by deploying WireGuard. Grouchy, out-of-touch corporate net admins probably don't even know what it is and insist on their antiquated Cisco VPNs.

Re: Autossh – automatically restart SSH sessions and tunnels

#20

Post by beagle3 » Sat, Sep 28, 2024, 7:04 PM UTC

14 years ago, i was using auto ash to keep SSH tunnels up; but at some point (quite far back - perhaps 2016?) ssh gained everything needed to do this internally except the restart.

At this point I configure all of the keep alive and retry options in ssh_config and sshd_config, and use

    While true; do ssh user@host ; sleep 10; done

To get the same effect, but with much more flexibility - e.g. alternating connection addresses on a multihomed host, add logging, run from daemontools or systemd unit instead of a loop and let them track the process and restart, etc.