Reconnecting to a disconnected ssh session?

berndbausch · 10-09-2019, 07:48 PM

I run Xubuntu in a VirtualBox VM on my Windows PC. Last night I saved the VM before shutting down the PC.

This morning, after restarting the VM, I find three ssh sessions from yesterday. For example this one:

Code:

$ ps -ftpts/2
UID        PID  PPID  C STIME TTY          TIME CMD
bbausch   5003  5002  0 10月06 pts/2  00:00:01 -bash
bbausch  27965  5003  0 10月09 pts/2  00:00:06 vi what-i-learned

bash's parent, sshd, is sitting there waiting for the ssh client to talk to it, but the client doesn't exist anymore. This particular session has been up for almost a week, it seems:

Code:

$ who
bbausch  pts/2        2019-10-04 10:42 (10.0.2.2)
...

I have no real problem killing that Bash process, but I wonder if there is a way to reconnect to such an orphaned session in order to recover whatever can be recovered.

Yes I know about tools like screen and tmux. Unfortunately they only help if you use them before the connection is severed.

evo2 · 10-09-2019, 08:29 PM

Hi,

there used be a program called retty that could do this. Seems not to be in current distros though. See for example https://packages.debian.org/jessie/retty

I stopped using retty after I discovered screen, which I stopped using after I discovered tmux :-)
Now I'm in the habit of using tmux on basically *all* remote sessions.

Evo2.

berndbausch · 10-09-2019, 09:05 PM

Quote:

Originally Posted by evo2

I stopped using retty after I discovered screen, which I stopped using after I discovered tmux :-)
Now I'm in the habit of using tmux on basically *all* remote sessions.

Evo2.

I like your evolution. Fits the user name. Thanks.

EDIT: retty is not in the Ubuntu repos. Some more work required to try it out.

evo2 · 10-09-2019, 10:16 PM

Hi,

Quote:

Originally Posted by berndbausch

EDIT: retty is not in the Ubuntu repos. Some more work required to try it out.

Yes, that's because Debian dropped it because it was not maintained.
See https://tracker.debian.org/pkg/retty
I'd be a little careful about using it: who knows what bugs it has.

Evo2.

berndbausch · 10-09-2019, 11:04 PM

Quote:

Originally Posted by evo2

I'd be a little careful about using it: who knows what bugs it has.

For one thing, its build includes assembler files. I don't understand why that is necessary. What's more, they seem to work on 32 bit kernels or CPUs only.