[Pan-users] Re: Permissions Re: Aaarrrgghhh! Whahoppena Terminal??

[Duncan]

Beartooth <address@hidden> posted
address@hidden, excerpted below, on  Sat, 07 Mar 2009
17:16:39 +0000:

> Well, starting just on this machine, the entry for btth in /etc/ shadow
> is some great 1 1/2 line string of gibberish, presumably encrypted; no
> indication even of UID, unless there's some easy way to decrypt it.
> /etc/passwd and system-config-users both show UID 500, if that means
> anything.

Yes, the main reason for /etc/shadow is encrypted passwords.  /etc/passwd 
needs to remain readable by all so shell and UID etc info can be seen by 
the applications that need it, and even if the passwords are encrypted 
(actually hashed), it's a bit easier to brute-force them if the hashed 
form is available, so having them in /etc/passwd isn't ideal.  Thus the 
origin of /etc/shadow, which can be read only by root.

Rinaldi's suggestion on the tarball and restore backups permissions 
problems was that the UIDs/GIDs may differ between machines.  You may 
have the same usernames/groupnames on each, but with different UIDs/
GIDs.  Since what's actually saved for file permissions is the UID/GID, 
if you tarball your home dir up on one machine that's using one set of 
UIDs/GIDs and try to use it on a different machine with different 
numbers, the result would be issues such as you mentioned.

So, you now know that your current machine is using UID 500 for your user 
(btth).  What about your other machines?  If one or more of them have a 
different UID for user btth, you'll see the padlock and have to do a 
chown on anything tarballed up and copied between the machines with 
different UIDs.

Putting it a different way, the username (and groupname) are simply for 
the benefit of the human.  What really counts for the computer is the UID/
GID, the numbers.  So if those numbers are different, it'll see it as a 
different user/group, regardless of what the username/groupname says, 
until you change it.

Thus, if you do indeed have different UIDs for your btth user on 
different machines, you may want to figure out which UID number is used 
for btth on the most machines, and change the UID of the btth user on the 
others so everything matches.  Of course, once you do, you'll have to do 
a chown -R to change all the files on the affected machines too, but once 
that's done and all your UIDs/GIDs match between all your machines, you 
should be fine.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman