在ssh会话中继承环境变量？

Question

I need to deal with a lot of remote machines, and each machine shares a global environment variable ( like CONTROLLER_IP). When I try to ssh to the remote machine, I would like to set the CONTROLLER_IP according to current localhost setting. is there any way to make it happen?

Example:

In localhost host, I set ofc1=192.168.0.1, and ofc2=192.168.1.1 and I need to ssh to ofs1, ofs2. I would like to do something like:

CONTROLLER_IP=$ofc1 ssh root@ofs1; CONTROLLER_IP=$ofc2 ssh root@ofs2

then I will get the CONTROLLER_IP setting in each ssh session. (the code shown above does not work...)

Answer 1

In /etc/sshd_config on the server you can define the list of accepted environment variables using the AcceptEnv setting, and then you can send environment variables like this:

CONTROLLER_IP=$ofc1 ssh -o SendEnv=CONTROLLER_IP root@ofs1

But this seems a bit overkill for your purposes.

The alternative is to pass the variables in the remote command, like this:

ssh root@ofs1 "CONTROLLER_IP=$ofc1 somecmd"

Or if you run multiple remote commands then like this:

ssh root@ofs1 "export CONTROLLER_IP=$ofc1; cmd1; cmd2; cmd3; ..."

If you need to quote the value of the variable, you can do like this:

ssh root@ofs1 "CONTROLLER_IP='$ofc1' somecmd"

Answer 2

Try

 ssh root@ofs1 "env CONTROLLER_IP=$ofc1 somescript"

(assuming $ofc1 is evaluated to some IP address like 12.234.56.178 without spaces or naughty characters)

or perhaps

 ssh root@ofs1 "env CONTROLLER_IP='$ofc1' somescript"

if $ofc1 could contain spaces or naughty characters

where somescript is a script on the remote machine ofs1 ; if you want an interactive shell try

 ssh root@ofs1 "env CONTROLLER_IP='$ofc1' /bin/bash"

At last, ssh is usually setting some environment variables (on the remote machine), notably the SSH_CONNECTION one. You could use it on the remote machine. Its third field is the IP address of the origin host (the one on which you do the ssh ...). So perhaps the .bashrc on the remote host might contain

 if [ -n "$SSH_CONNECTION" ]; then
   export CONTROLLER_IP=$(echo $SSH_CONNECTION|cut -f3 -d' ')
 fi

better yet, replace the CONTROLLER_IP occurrences in your remote scripts with something using SSH_CONNECTION