Interview Question | What is UID and GID in Linux | User Identifier | Group Identifier in Linux

What is UID and GID in Linux ?

What is UID and GID in Linux ?

What is UID in Linux ?
How to Default value of UID ?
What is differences of UID and GID ?
What is uid and gid for the root user?

UID : User Identifier

UID (User identifier)is a number that assigned by Linux to every user of the system. UIDs are stored in the /etc/passwd

Value of UID

0 to 99 value = System

100 to 499 = Reserved for dynamic allocation

500 / 1000 = Reserved for new users

How to Check Default UID Value ?

We can check default uid value by the command :

cat /etc/login.defs | grep UID

Output something like this

UID_MIN 1000
UID_MAX 60000
#SYS_UID_MIN 100
#SYS_UID_MAX 999


What is UID and GID of root User ?

root is the first user of the system so uid and gid is 0

GID : Group Identifier

All Groups of Linux are defined by GIDs (group IDs). GIDs are stored in the /etc/groups file. the first 100 GIDs are usually reserved for system use.


Difference UID and GID


UID

UID full form is User Identifier, It Used to assign a Identity Number of User
UID Store in /etc/passwd

GID

GID full form is Group Identifier, It Used to assign a Identity Number of Group
GID Store in /etc/group



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