Mar 12, 2018:
There's now a deep-ssh-like which behaves closer to (open)ssh. It is suitable for wrapping with rsync or sshfs.
EG: In both cases, you can then use bang paths for your ssh hops.
If you've ever worked with an unrouted network, one or more discontinuities (ssh hops, not one-network VPN's) deep, then you may appreciate "deep-ssh".

Basically, deep-ssh just constructs a bunch of ssh's that call other ssh's, until you're at your destination, at which point, a command is run.

Usage is like:
deep-ssh '' host1!host2!host3 'uname -a'
This command will ssh to host1, which in turn will ssh to host2, which in turn will ssh to host3, and then on host3 the command "uname -a" is run.

You can also do something like:
deep-ssh '' host1!someuser@host2!host3 'uname -a'
Note the addition of a username specification.
You may want to consider setting up passwordless, passphraseless ssh, once for each ssh hop. Alternatively, you can just let ssh run a bunch of ssh-askpass/x11-ssh-askpass/gnome-ssh-askpass commands to ask for a password on each host in turn.
deep-ssh will attempt to set up X11 tunneling on each hop. However, if for some reason one or more of the hosts you are connecting through, or the host you are initiating the deep-ssh from, has X11 forwarding problems, then the X11 forwarding will not work. Someday, I may have to revise this to do ssh -Y instead of ssh -X...
I gave in and revised the quoting style to use exponential backslashing, instead of trying to get away with alternating ' and ". This is much more in line with how I really expected things to work.
I've tested deep-ssh as far as:

~/bin/deep-ssh '' host1!root@host2!host3!host4!host5 "uname -a"
Executing: eval ssh -X host1 \" eval ssh -X root@host2 \\\" eval ssh -X host3\\\\\\\" eval ssh -X host4 \\\\\\\\\\\\\\\" eval ssh -X host5 \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\"uname -a\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\" \\\\\\\\\\\\\\\" \\\\\\\" \\\" \"
It asked me for a lot of passwords (via the GUI each time), but it did eventually give me "uname -a" output from host5! :)

Shell metacharacters in your command are now escaped quite well, but here documents aren't attempted. So, for example:
deep-ssh host1!host2 'cat > /tmp/foo' < /tmp/foo
should work fine now.
Note that some shells may require you to escape your !'s. Other shells may or may not require you to escape them, depending on how they're configured. Still others may not allow you to escape the !'s at all. If you're in this latter situation, you might want to use a real shell :), or modify deep-ssh to use a different delimiter.
Download deep-ssh here. It's going to need my bashquote python module.

Another approach can be found here. I must say, it's an interesting way of accomplishing much the same thing, and even has advantages over deep-ssh. I hope to find time to look into this eventually. It'll most likely take longer to set up, but once it's set up, you no longer have a "weak as the weakest link in the chain" situation. Which of course leads one to consider a deep-ssh - like program that configures what's needed for the method at the URL. :)

Also likely relevant: setup-passwordless-ssh

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Timestamp: 2024-04-20 12:04:00 PDT

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