Linux command of the day, 12 of 31 - wall

By Gavin Davies on 11 August 2020

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I’m looking briefly at a Linux command every day for a month. Today: wall

I’m looking briefly at a Linux command every day for a month

Yesterday, I explored the mesg command for turning on and off “yes I want people to be able to message me in this shell session”.

Today, I’ll look at ‘wall’. ‘wall’ means “Write to ALL” (nothing to do with wall time) and it broadcasts a message regardless of user mesg setting.

$ wall -g pi "hello pi people"

Then, on every terminal session for every user in the group pi, I see “hello pi people” pop rudely into the terminal!

Root is able to add --nobanner which removes the Broadcast message from gavin@hostname (pts/0) (Wed Aug 12 06:57:56 2020): but obviously that could be confusing to users.

This command is useful for saying ‘hey everybody get off the server it’s about to blow’. Although, in this age of containers, it’s rare to see multiuser terminal access, but still, in an incident response scenario, running who is a very good idea to make sure J Random Colleague isn’t also hacking on the box. If he is, message him with write, and if he has msg disabled, or there’s multiple people on the box, you can use wall to say “get off the box, or we’re going to end up mutating the same state!”