[ALUG] "!!" in /etc/passwd

[(Ted Harding)]

Hi Folks,

Can anyone interpret the following for me?
I can't find it referred to in 'man' documentation.

Some "user" entries in /etc/passwd have "!!" in the encrypted
password field, e.g.

sshd:!!:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
rpc:!!:32:32:Portmapper RPC user:/:/sbin/nologin

mysql:!!:27:27:MySQL Server:/var/lib/mysql:/bin/bash
postgres:!!:26:26:PostgreSQL Server:/var/lib/pgsql:/bin/bash

For the acounts which have /sbin/nologin as "shell" I cannot
of course gain entry, even from root.

On the other hand, for the accounts (mysql, postgres) which
have a normal shell, I can 'su' from root without entering a
password; while if I try to 'su' from any other user I'm prompted
for a password (which of course does not exist).

I'm wondering what the full interpretation of the "!!" is.
I know about "*" in the encrypted password field: there is
no possible password which encrypts fo "*", so such accounts
cannot be logged into.

I've already found out something (see above) about "!!" accounts,
but is there more that I should know?

In particular, if I were (as root) to use the 'passwd' command
to give a "!!" account a real password, would I be treading on
any toes in the system?

With thanks,
Ted.

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E-Mail: (Ted Harding) <ted.harding at nessie.mcc.ac.uk>
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Date: 06-Jun-07                                       Time: 11:53:29
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