[TUHS] Origin of the MOTD file?

Doug McIlroy doug at cs.dartmouth.edu
Fri Mar 16 06:00:10 AEST 2018

> So what are its origins? Where did it first appear?

It was a direct copy from CTSS, which already had it
n 1965 when we BTL folk began to use it.

The greatest MOTD story of all time happened at CTSS.

To set the stage, the CTSS editor made a temp file,
always of the same name, in one's home directory.
The MOTD was posted by the administrator account.

The password file was plain text, maintained by
editing it.

And multiple people had access to the administrator

It happened one day that one administrator was
working on the password file at the same time
another was posting MOTD. The result: the password
file (probably the most secret file on the system)
got posted as the MOTD (the most public).

Upon seeing the password file type out before him,
an alert user shut the machine down by writing
and running one line of assembly code:


(The star is for indirect addressing, and indirection
was transitive.)


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