FreeBSD >Sending a Message to All Users on a Remote UNIX/Linux/FreeBSD System

Posted on in Categories News last updated February 23, 2005

Traditionally we used rwall command to send a message to every user on a network. Rwall works over insecure network. Instead of that, we can use wall command over ssh as follows, which is more secure and works with almost all UNIX variant.

1) ssh with wall syntax is as follows, after EOF press enter/return key and type message. When the message is complete, type EOF:
$ ssh [email protected] wall<&ltEOF
message1
message2
…
…
EOF

2) To display message “Kernel is upgraded on this server. System is schedule to reboot in 45-minute time. Please logout and save your work” to ever user on remote FreeBSD system pweb.test.com

$ ssh [email protected] wall <&ltEOF
Kernel is upgraded on this server $(hostname).
System is schedule to reboot in 45-minute time.
Please logout and save your work.
Current local data and time is $(date)
EOF

Please note it might prompt for password if ssh-keys not used. Once password supplied it will execute wall command on remote server pweb.test.com. In order to work this remote UNIX/BSD/Linux must have sshd (ssh server) running. Also, notice that we have executed hostname and date command using command substitution feature of shell. This tips also works with Linux and other UNIX like operating system.

Posted by: Vivek Gite

The author is the creator of nixCraft and a seasoned sysadmin and a trainer for the Linux operating system/Unix shell scripting. He has worked with global clients and in various industries, including IT, education, defense and space research, and the nonprofit sector. Follow him on Twitter, Facebook, Google+.

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