I tried to get control over a guest session in another linux system from also a linux system via ssh.
I have experienced the following :

1) can get control over any sudo session remotely via ssh

But

2) cannot get control over any guest session of a linux system remotely via ssh

output is :
" ssh: connect to host 192.xxx.x.x port 22: Connection timed out "


How can I make it happen ? thanks in advance.

SSH is Secure Shell; i.e., you are on machine A and you want to connect to machine B and do some work (in a terminal session).

You open a terminal on machine A and log in as a non-root user (we'll talk about root access later).

You execute ssh-keygen which will create a directory, ~/.ssh in the home directory of the user you are logged in as. What ssh-keygen does is create encrypted key files, one named id_rsa and the other id_rsa.pub that are owned by the userid that created them with appropriate permissions; id_rsa is readable only by the ower, id_rsa.pub is readable by any user, both files are write enabled only for the owner.

The resulting directory looks like this:
The same thing has to happen on machine B -- by that user -- and on any other machines you want to connect to also by those users.

When that's all done and you're ready to connect to machine B (and you know the user account name and the password that you entered when running ssh-keygen), you can connect to the remote machine with this command:
You would type the word "yes" when you see that, and you will be prompted for the password and you'll get connected.

That is, I've connected the user joeytest to the user trona on fubar.lan.

That's how you do it. Note that none of that gobbledygook in that authenticity above is usable on anything else, it's what happen on my system, yours will look similar.

Now, by default, you will not be able to connect as root with ssh from one machine to another even if you know the root passwords on other machines. That's not a bad thing as you can do tremendous damage with root access. It's better to connect remotely and then use either sudo or su - on that machine if you absolutely need to do work as root (there is a way and if you want to know ask and I'll tell you but I do discourage it).

Hopefully, your machines have names and fixed-IP addresses or DHCP configured with a name and address. The reason I can connect with a simple "fubar.lan" is that fubar.lan has a fixed IP address and an entry in the file /etc/hosts that looks like this:
that allows me to connect to any system in my network with ssh systemname rather that entering the complete machine address. Otherwise you must use the complete address of the machine on the remote server. You can also have external addresses in /etc/hosts, for example 75.126.162.205 www.linuxquestions.org linuxquestions.org
which avoids going through a DNS lookup.

Hope this helps some.

I'm wondering if the OP is looking more at attempting VNC-like remote-control instead of a standard ssh session (hence his mention of an existing guest session on the remote machine). If this is the case, there are X11-VNC tools available to enable this. I won't go any further until the OP's intentions become clearer.

Cheers,

Unless the OP is looking for an alternative to the ssh protocol (which I'm not getting from his post) he specifically asked how to perform an action via ssh.

... quite possible I'm reading more into his post than necessary ;-)

... it's the part where he says he wants to remotely access a "guest session " on an Ubuntu computer from another Ubuntu computer ... Made me think of when one wants to remotely control an existing live user session, for remote assistance, for example .... I figured he may have specifically referred to ssh simply because he didn't know of any other remote access tools.

If I'm wrong, then the previous poster's detailed ssh explanation should do the trick.

Cheers :-)

You could be right, Rick. I guess we'll wait to see what OP says. =)