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Re: pruning cruft in /etc/passwd and /etc/group



Andrew Schulman wrote:
> backup bin daemon games irc list lp mail man messagebus operator 
> proxy sync sys uucp
backup: historical, probably safe to remove
bin: historical, and possibly used
daemon: historical, commonly used by daemons that need to own files, but can't
 have their own user for some reason
games: placeholder for group games, don't remove it
irc: used for irc daemon(s), probably not necessary
list: I don't know
lp: used for printing daemon(s) and as a placeholder for group lp, don't remove
 unless you don't have a printer and have no printing software installed
mail: placeholder for group mail, sometimes used by mail daemon(s), don't remove
man: placeholder for group man, don't remove unless you don't use the man
 command
messagebus: I don't know
operator: historical, probably safe to remove
proxy: almost definately safe to remove unless you run any proxy server(s) that
 use it
sync: I don't know
sys: I don't know
uucp: if you've never heard of it, you probably don't need it

> adm audio backup bin daemon dialout dip disk fax floppy games irc kmem 
> list logcheck lp lpadmin mail man messagebus nogroup ntop operator proxy 
> sasl scanner shadow src ssh staff sudo sword sys tape tty utmp uucp 
> video voice
adm: used for logs, do not remove
audio: used for sound devices, only remove if you have no sound devices and
 don't plan on ever having any
backup: see above
bin: see above
daemon: see above
dialout: used by suid ppp programs and possible ppp devices, if you are sure
 you'll never use a modem (including dsl and some other high speed ones) it may
 be safe to remove
dip: I don't know
disk: DO NOT REMOVE, it's used for hard drives
fax: self explanitory, can probably be safely removed if you don't use it
floppy: don't remove unless you will never have a floppy drive
games: used to control which users can play games, including things like fortune
 and sl. probably shouldn't be removed
irc: see above
kmem: I don't know, but k* (in system stuff) usually has to do with the kernel,
 so it probably shouldn't be removed
list: see above
logcheck: I don't know
lp: controls who can use a printer, only remove if you don't and never will
 print
lpadmin: controls who can add/change/remove printers, see above for removal
 conditions
mail: used for mail boxes in shared directories and for controlling various mail
 related ACLs
man: see above
messagebus: see above
nogroup: DO NOT REMOVE, it's used for minimal access rights
ntop: I don't know
operator: see above, also commonly used by sudo to grant rights
proxy: see above
sasl: commonly used for smtp and/or pop/imap authentication, can be removed if
 not in use and the sasl programs aren't installed
scanner: simillar to lp, but for scanners
shadow: DO NOT REMOVE, used to conrol read access to /etc/shadow and
 /var/backup/shadow*
src: used to control write access to /usr/src, don't remove
ssh: I don't know exactly what it's for, but obviously is related to ssh and/or
 sshd
staff: historical, used in /home, don't remove without cleaning up /home first
sudo: I don't know, but related to sudo
sword: I don't know
sys: see above
tape: used for tape devices, don't remove if you have/will have one
tty: DO NOT REMOVE, used for virtual consoles, serial, ports, etc.
utmp: DO NOT REMOVE, used for logs
uucp: see above
video: like audio, but for video devices
voice: I don't know

> As a general security measure, I want to prune the useless entries from 
> these files (and /etc/shadow too, of course).  The problem is to be sure 
> that before I remove an entry, it's not going to make bad things happen.
That doesn't affect security very much (if at all), and if done incorrectly can
make your system unusable.



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David Mandelberg
mandelbergd@eth0.is-a-geek.org

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