How change what’s displayed before login to shell or after

Before login
The text displayed before the login prompt is stored in /etc/issue 

After login
The text displayed after login is stored in /etc/motd, 

It's just a normal text file, but it accepts many of escape sequences:

\b -- Baudrate of the current line.
\d -- Current date.
\s -- System name, the name of the operating system.
\l -- Name of the current tty line.
\m -- Architecture identifier of the machine, eg. i486
\n -- Nodename of the machine, also known as the hostname.
\o -- Domainname of the machine.
\r -- Release number of the OS, eg. 1.1.9.
\t -- Current time.
\u -- Number of current users logged in.
\U -- The string "1 user" or " users" where is the number of current users logged in.
\v -- Version of the OS, eg. the build-date etc.

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