[CentOS] Determine next UID number

Paul Heinlein heinlein at madboa.com
Wed Oct 13 17:33:44 EDT 2010


On Wed, 13 Oct 2010, James A. Peltier wrote:

> | > > That assumes the highest UID number has a login shell...
> |
> | > which is generally the case...
> | >
> |
> | Exactly, without excluding those who have a shell of nologin the 
> | last uid on my machine is nfsnobody(65534), I don't believe that a 
> | UID can be greater than that.
> |
> Only if authenticating against /etc/passwd.  If authenticating 
> against Kerberos, LDAP, or some other method this is not the case.

Here's the code I use to figure out next-available [GU]IDs:

# ----- %< -----
# figure out the highest UID and GID currently in production, but
# rule out really high numbers (greater than 8000) which are typically
# assigned to pseudo accounts like "nobody."
#
AWKTEST='END { print HUID } { if (($3 > HUID) && ($3 < 8000)) HUID = $3}'
HUID=$(/usr/bin/getent passwd | /bin/gawk -F: "$AWKTEST")
HGID=$(/usr/bin/getent group  | /bin/gawk -F: "$AWKTEST")
#
# increment those UID and GID numbers by 1 for use with the
# new account
#
let HUID=$HUID+1
let HGID=$HGID+1
# ----- %< -----

The 8000 high-end number is arbitrary; it works in our environment...

-- 
Paul Heinlein <> heinlein at madboa.com <> http://www.madboa.com/


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