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I'm trying to make a simple message that says something to the effect of
Server will be going down at 11:00pm UTC, March 1st, for updates.
to all users who ssh into my Raspberry Pi server (running Raspbian).
I'm not looking to add a banner, but is there a way to make a simple message appear for all users upon login until a set time or reboot? If so can I make the server run a shell script automatically at that set time?
The way to display messages to users who log onto your server is precisely via ssh banners. These are usually stored in /etc/motd. So, since you want to automate it, you can do the following:
Make a copy of the existing file
sudo cp /etc/motd /etc/motd.orig
Manually edit the file and add your banner or, if you want this automated as well, do something like this:
echo "Server will be going down at 11:00pm UTC, March 1st, for updates." |
sudo tee -a /etc/motd
That will append your message to whatever is currently in the file.
Set up a cronjob that will restore the original file on reboot.
echo '@reboot root cp /etc/motd.orig /etc/motd' | sudo tee -a /etc/crontab
That's it. Anyone who logs in via ssh will now see your message and the message will go away on reboot.
BUT: this isn't a very good idea. For one thing, you will need to remember to remove the @reboot crontjob after you've rebooted because otherwise, it will run on every reboot from now on. Also, the whole thing doesn't make much sense. The banner system is designed to be manually edited since it's a way for the sysadmin to pass messages to users. Since you will be taking the server down manually, applying your updates or whatever maintenance you need manually and rebooting manually, I don't understand why you would bother automating the removal of the banner. Just add it, do your thing and remove it when it is no longer relevant.
apt update and list the number of available packages updates on ssh login, how would you do that?
Feb 22, 2020 at 19:44
/etc/motd but I'm pretty sure there are other ways. Some systems do this automatically, Ubuntu for example, so have a look at how it does it or just ask a new question.
This is exactly what the Message Of The Day system has always been for. Indeed, a "machine will be down on Saturday" warning to users is even the example in the NetBSD and OpenBSD manuals.
Place the warning in your motd file, conventionally /etc/motd. Remove it when you restart for maintenance. Some operating systems over-egg this pudding somewhat, providing complex ways of auto-generating messages that are in some cases more properly parts of the login banner, but even with them the /etc/motd file is a simple hand-edited file.
In general, the motd is the daily message from you the administrator to users as they log on.
motd. FreeBSD File Formats Manual. 1997-02-13.motd. NetBSD File Formats Manual. 1994-12-28.motd. OpenBSD File Formats Manual. 2009-05-06.
/etc/motd. Alternatively, sure, you can set up a@rebootcron job to do it for you. This is exactly why banners exist. The details, however, will depend on your operating system, which you haven't mentioned.at). Seeman atfor details. Unixes power comes form many small tools working together. Don't expectsshto do this for you.@rebootcron job?