Whenever user is added to system, information regarding the same is stored in
three main files which are
/etc/passwd :- Account information Lets get practical and get started with basi command for adding user
useradd : adds user to the system, entry of the account is made in the
/etc/passwd file and password for the account is stored in password /etc/shadow Example :
Lets look how the entry is stored in /etc/passwd file
bash# cat /etc/passwd
root:x:0:1:Super-User:/:/sbin/sh
daemon:x:1:1::/: bin:x:2:2::/usr/bin: sys:x:3:3::/: adm:x:4:4:Admin:/var/adm: lp:x:71:8:Line Printer Admin:/usr/spool/lp: uucp:x:5:5:uucp Admin:/usr/lib/uucp: nuucp:x:9:9:uucp Admin:/var/spool/uucppublic:/usr/lib/uucp/uucico smmsp:x:25:25:SendMail Message Submission Program:/: listen:x:37:4:Network Admin:/usr/net/nls: nobody:x:60001:60001:Nobody:/: noaccess:x:60002:60002:No Access User:/: nobody4:x:65534:65534:SunOS 4.x Nobody:/: Each of those file are
loginname:x:UID:GID:comment:home_directory:login_shell
where x specfied the password is encrypted and stored in /etc/shadow file
UID is the user-id of the user, GID is the group id
Note :
account file i.e /etc/passwd file can be read by anyone however /etc/shadow can be read by only root Now the user has been created you could create password for it by using 'passwd command
bash# passwd user1
after that it prompts for password, which is then encrypted and stored in /etc/shadow
If we were to modify setting for existing users, we have following commands
useradd : Adds a new user account to the local system
usermod : Modifies a user’s account on the local system userdel : Deletes a user’s account from the local system Groups
/etc/group : Stores the information regarding the groups configured on the system.
# cat /etc/group Lets look at each field <group name>:<optional password>:<GID>:<comma delimited members >
Commands
groupadd : Adds (creates) a new group account on the system
groupmod : Modifies a group account on the system groupdel : Deletes a group account from the system |
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