The official way to send environment variables from client to server is through
AcceptEnv. The problem is that you need root access on the server to configure
AcceptEnv. Most servers are configured to accept no or only a few predetermined variables.
I found two tricks to send environment variables from client to server, both work without needing root access on the server.
ssh -t server SSH_ORIGIN=$USERNAME@$HOSTNAME bash
this will connect to server and then execute the command
SSH_ORIGIN=$USERNAME@$HOSTNAME bash, with
$HOSTNAME already replaced on the client side. then, on the server side, you can further process the information contained in the variable
-t is needed otherwise bash will be started on the server without a tty (try it, you will see).
a slight modification will allow to pass the information transitively down a longer ssh chain.
ssh -t server SSH_ORIGIN=$USERNAME@$HOSTNAME:$SSH_ORIGIN bash
- bash is started as an interactive non-login shell (
.profile is not read).
- bash is run twice (
.bashrc is read twice). once by sshd and once by the user command.
- it will always start bash, ignoring your default shell on the server.
first you must generate a ssh key and transfer that to
~/.ssh/authorized_keys on the server. then prepend the line with
command="$SHELL". see the sshd manpage for more information on this.
connect to ssh server using the command:
ssh -t server SSH_ORIGIN=$USERNAME@$HOSTNAME
this will connect to the server but this time the variable assignment is not executed. instead, the string is stored in the environment variable
$SSH_ORIGINAL_COMMAND. then the command provided in
~/.ssh/authorized_keys is executed. once you are in the shell you can process the information contained in
as above, you can make this transitive:
ssh -t server SSH_ORIGIN=$USERNAME@$HOSTNAME:$SSH_ORIGIN
- it will start the default shell on the server.
- it will always start the default shell on the server. any command you give to the ssh command will be ignored and stored in
$SSH_ORIGINAL_COMMAND. if you want to execute a command over ssh you can use a different ssh key or have your shell init file to detect and execute