Stop ssh login from printing motd from the client?

Solution 1:

I'm not sure why you have an aversion to doing this correctly - either on the server a la

PrintMotd no
PrintLastLog no

and

#/etc/pam.d/ssh
# Print the message of the day upon successful login.
# session    optional     pam_motd.so

Or adding ~/.hushlogin for each user.

Hint, for ~/.hushlogin, add it to /etc/skel so new user home directories are created with the file.

Update:

Without more information about your backup cron job, my only other suggestion is to redirect the output of the command to a file (or let cron capture it in email) and the output of the ssh session to /dev/null. Something like:

0 0 * * * ssh backuphost "backup_script_that_writes_to_a_log" >/dev/null

Or

0 0 * * * ssh backuphost "backup_command 2>&1" >/dev/null

I'd have to play around with the commands a bit, but that should get you started.

Solution 2:

If you want this on a per-user basis, just do a touch ~/.hushlogin and you're all set with OpenSSH.

Update: As pointed out elsewhere, pam_motd may be configured to not use a per-user .hushlogin; check /etc/login.defs for HUSHLOGIN_FILE. It may be configured to have all users listed in /etc/hushlogins or similar.

Solution 3:

@note All examples assume you've set a variable connectionString with something like connectionString=user@server.

How I got to the solution

Using ssh -T should work for simple commands. For example this doesn't print any extra information:

ssh -T $connectionString "echo 'blah'"

The problem is when you try to use here-doc to run many commands. For example - bellow will NOT work - it will echo message of the day (MoTD) and also might show you "stdin: is not a tty".

somethingLocal='something local'
ssh -T $connectionString <<EOC
    echo 'blah'
    echo "blah $somethingLocal"
EOC

To workaround the issue you need first save commands to local variable and the send them to remote server.

somethingLocal='something local'
read -r -d '' commands <<EOC
    echo 'blah'
    echo "blah $somethingLocal"
EOC
ssh -T $connectionString "$commands"

But that's messy...

Final solution

Make a universal function (note that it can take a string or HEREDOC as commands).

function silentSsh {
    local connectionString="$1"
    local commands="$2"
    if [ -z "$commands" ]; then
        commands=`cat`
    fi
    ssh -T $connectionString "$commands"
}

Examples

Use this like so:

somethingLocal='something local'
silentSsh $connectionString <<EOC
    echo 'blah'
    echo "blah $somethingLocal"
EOC

Or like so:

silentSsh $connectionString "echo 'blah'"

Or like so:

silentSsh $connectionString <<'EOC'
    echo 'blah'
    somethingRemote=`echo 'whatever'`
    echo "blah $somethingRemote"
EOC

Or even like so:

silentSsh $connectionString < getlines.sh

Solution 4:

How about this hack? ;-P

ssh -t user@machineName '/bin/bash'

The following is not valid:

Passing -T to ssh to disable tty allocation:

ssh -T machineName 'echo foo'

Solution 5:

What operating system is this? On some systems (like ubuntu) the motd isn't printed by the ssh server (PrintMotd in /etc/ssh/sshd_config), but by pam with pam_motd. If this is the case then you probably can't control it from the client.

Tags:

Linux

Bash

Ssh

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