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SSH

Reverse SSH Tunneling

Tunneling from you work computer out to your home computer.
    On work computer: 
    ssh -4Nnfg -R 2222:127.0.0.1:22  -lroot tunnelMachine -o keepalive=yes
    On stepping machine: 
    ssh -gf -L 2223:tunnelMachine:2222 localhost sleep 60
    On home computer: 
    ssh root@tunnelMachine -p 2223

Updating SSH on a running System

First get the sources, configure and do a make. Do not go for the make install yet!
    mkdir /tmp/ssh
    cd /tmp/ssh
    cp /usr/local/bin/sshd .
    cp /usr/local/etc/sshd_config .
    ./sshd -f ./sshd_config -p 1022
Connect with a new session to port 1022. Go on from there and do the make install. Then restart the sshd daemon which was running no the port 22 (usually via /etc/rc.d/sshd restart).

Updating SSH on a running System II

Here is another variant:
    echo "rcsshd stop; rcsshd start"|at now + 3 minutes

FanOUT

In some environments you want to execute the same command on multiple hosts at once. For example to patch systems. A utily which helps you doing this is FanOUT.

Restricting Access

You can make SSH only allow the execution of certain sepecific commands. To do so, generate a key for the client and deposit the public key on the server, where the key can be generated as follows: 
    printf 'from="host.name.com",command="/usr/local/bin/command" \
%s\n' "'cat ~/.ssh/key.pub'" | ssh server 'cat >> ~/.ssh/authorized_keys2'
This client with this key can now only execute one command.

Passing vairous Parameters

You can pass some specific parameters to an SSH server as follows: 
    ssh -T -o "IdentityFile2 /root/.ssh/key" server
This will for example choose another identity to connect to the server.

Passing Binary Data to a Remote Shell

    cat myfile | ssh user@desktop lpr
     running a file into the lpr spooler on desktop
    tar -cf - source_dir | ssh user@desktop 'cat > dest.tar'
     piping file over the network.
    OR: 
    dd if=t41.home.ram.tar.gz | ssh ram@192.168.0.13 'tar --exclude=ram/software/ -C /mnt/backup -xzf -'



CopyLeft (l) 2003 by Raffael Marty