What's changed: Initial version (topic 2.04, subtopics 2.04.1–2.04.6)
4.3Notifying Users
Learn how to communicate system maintenance status to users: pre-login messages via /etc/issue and /etc/issue.net, the post-login /etc/motd, immediate broadcast to all logged-in users with wall, the shutdown-warning behavior of shutdown, and combining notification with service control via systemctl.
Stopping a system without warning can cost users their in-progress work. Notifying users may look mundane, but it is a basic practice that underpins operational trust—the file or command you use depends on when, where, and to whom the message is shown.
4.3.1Static messages before and after login
- /etc/issue is shown before the local console login prompt. /etc/issue.net is shown before a network login such as telnet (many SSH implementations do not use it by default).
- /etc/motd (message of the day) is displayed after a successful login—used for scheduled maintenance notices or policy announcements.
4.3.2Immediate notification and shutdown
- wall broadcasts a message immediately to every currently logged-in user's terminal (e.g.,
wall "Rebooting in 10 minutes"). - shutdown schedules a stop or reboot at a given time and automatically broadcasts a warning message to users before executing (e.g.,
shutdown -r +10 "Rebooting for maintenance"). - systemctl performs service-level stop/restart operations (e.g.,
systemctl restart); operational practice is to announce with wall or similar before acting.
Standard contrasts: issue = before login, local; issue.net = before login, network; motd = after login; wall = immediate broadcast to all active users; shutdown automatically warns before executing.
The four mechanisms sort cleanly along one axis: when they become visible. /etc/issue and /etc/issue.net are visible even to users who have not yet logged in, so they hold information appropriate before login—system name, policy, or legal warnings (issue for the local console, issue.net for network login prompts). /etc/motd only becomes visible after a successful login, making it suited to information for that logged-in audience—today's maintenance window, password expiry, and so on. When an urgent announcement is needed while the system is running, wall delivers it immediately to every terminal. For a planned outage, shutdown alone is often sufficient: running shutdown -h +30 "System will halt in 30 minutes" automatically broadcasts periodic warnings to all users until the scheduled time, sparing you from issuing wall manually. Restarting a single service (e.g., systemctl restart <service>) is not a full system shutdown, so it falls outside shutdown's automatic warnings—operators must notify affected users separately, typically with wall.
| Mechanism | When shown | Use |
|---|---|---|
| /etc/issue | Before login (local) | System name, warnings |
| /etc/issue.net | Before login (network) | Same, over network |
| /etc/motd | After successful login | Maintenance notices |
| wall | Immediate, while active | Broadcast to all logged-in users |
Trap: "/etc/motd is shown before login" is wrong—motd appears after a successful login; pre-login display is the job of issue/issue.net. Also, "restarting a service with systemctl auto-warns all users like shutdown" is wrong—automatic warnings are a feature of full-system shutdown, not individual service restarts.
4.3.3Section summary
- issue = before login (local) / issue.net = before login (network) / motd = after login
- Urgent notice via wall; planned outage via shutdown (auto-warns before executing); individual service restarts (systemctl) need separate notification
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Quick check
(just a quick review)Q1. You want to immediately notify all currently logged-in users that a service will be stopped for maintenance in 5 minutes. Which command is appropriate?
Q2. You want to display a warning message before the login prompt for users attempting to log in over the network. Which file should you edit?
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