motd

displayed to users upon login

TLDR

Edit static MOTD

$ sudo nano /etc/motd

View MOTD

$ cat /etc/motd

Add dynamic MOTD script

$ sudo nano /etc/update-motd.d/[99-custom]

Make dynamic script executable

$ sudo chmod +x /etc/update-motd.d/[99-custom]

Regenerate dynamic MOTD

$ run-parts /etc/update-motd.d/

motd (Message of the Day) is displayed to users upon login. It can be a static text file or dynamically generated from scripts.The contents of /etc/motd are displayed by login(1) after a successful login but just before executing the login shell. On systems with PAM, the pam_motd module handles display and can show files from multiple locations. Dynamic MOTD systems run scripts from /etc/update-motd.d/.

STATIC MOTD

$ # /etc/motd
Welcome to myserver
Authorized users only

DYNAMIC MOTD

$ #!/bin/bash
# /etc/update-motd.d/10-sysinfo
echo "System: $(uname -n)"
echo "Uptime:$(uptime -p)"
echo "Users: $(who | wc -l)"

FILE LOCATIONS

$ /etc/motd              - Static message
/etc/motd.d/           - Static message directory
/run/motd              - Runtime generated message
/run/motd.d/           - Runtime message directory
/usr/lib/motd          - Distribution-provided message
/usr/lib/motd.d/       - Distribution-provided message directory
/etc/update-motd.d/    - Dynamic scripts (Ubuntu/Debian)
/run/motd.dynamic      - Generated output (Ubuntu/Debian)

CAVEATS

Dynamic MOTD requires update-motd package on Ubuntu/Debian. Scripts must be executable. SSH may have a separate banner configured via the Banner directive in sshd_config. PAM configuration affects display. Each message file is limited to 64KB.