Hi,
if you do not always want to enter your private key password/passphrase when using certificate based ssh or scp connections then ssh-agent is your friend 
.
When ssh-agent starts it creates a UNIX socket to which ssh or scp connects to.
1 2 3 | michael@debdev:~# ssh-agentSSH_AUTH_SOCK=/tmp/ssh-xpu8YEvBmBKf/agent.537; export SSH_AUTH_SOCK;SSH_AGENT_PID=538; export SSH_AGENT_PID; |
ssh-agent writes two lines with environment variables which must be set so that ssh or scp can use it. ssh-agent cannot set the environment variables directly because it cannot set variables in its parent process (bash).
1 2 3 4 | michael@debdev:~# SSH_AUTH_SOCK=/tmp/ssh-xpu8YEvBmBKf/agent.537michael@debdev:~# export SSH_AUTH_SOCKmichael@debdev:~# SSH_AGENT_PID=538michael@debdev:~# export SSH_AGENT_PID |
But there is also a shorter way. eval executes its 1st argument in the shells context. The command executed inside of the backticks `ssh-agent` tells the shell to take the output of the command an use it as a command line(s).
1 2 3 4 5 | michael@debdev:~# eval `ssh-agent`Agent pid 538michael@debdev:~# set | grep SSHSSH_AGENT_PID=538SSH_AUTH_SOCK=/tmp/ssh-xpu8YEvBmBKf/agent.537 |
Ok ssh-agent is running now. Now you have to add a ssh private key.
1 2 3 | michael@debdev:~# ssh-add .ssh/id_rsaEnter passphrase for .ssh/id_rsa:Identity added: .ssh/id_rsa (rsa-key-Michael-20180820) |
If your key uses the default name id_rsa you can omit the parameter
1 2 3 | michael@debdev:~# ssh-addEnter passphrase for /home/michael/.ssh/id_rsa:Identity added: /home/michael/.ssh/id_rsa (rsa-key-Michael-20180820) |
Check it
1 2 3 | michael@debdev:~# ssh debdev2 Linux debdev 4.9.0-7-686 #1 SMP Debian 4.9.110-3+deb9u2 (2018-08-13) i686... |
Your ssh-agent can also forwarded through a ssh connection to the connected machine and you can use it there too. Start the ssh session with -A
1 2 3 4 5 | michael@debdev:~# ssh -A debdev2 Linux debdev 4.9.0-7-686 #1 SMP Debian 4.9.110-3+deb9u2 (2018-08-13) i686...michael@debdev2:~# ssh debdev3.... |
Michael