I am going to review basic user group management tasks such as user creation, group creation, group membership changes, the files where user,group objects are stored. I have a CentOS7 basic installation. Before jumping into hands-on’s, it should be good to remind you about /etc/passwd and /etc/group files.
/etc/passwd file stores user informations created in your linux OS and a sample view of /etc/passwd file is shown below.
Let’s scrutinize the meaning of fields at first.
1st field > baris : This field represents the user logon name
2nd field > x : This one represents the encrypted password which is stored in /etc/shadow file.
3rd field > 1003 : A unique user identifier. (UID)
PS: UID 0(zero) is reserved for “root” , 1-99 are for pre-defined accounts , 100-999 are reserved by system for several purposes.
4th field > 1008 : ID of primary group that the user belongs to. The group information is stored in /etc/group file.
5th field > this field has not set yet: This is comment field that can be used for user’s full name etc. A sample view is shown below.
6th field > /home/baris : The home directory of the user.
7th field > /bin/bash : User’s login shell. If this field is not set explicitly, the parameters which are defined in /etc/default/useradd file are used when creating user account.
/etc/group file stores group information like below.
Let’s scrutinize fields in the line “SaleTeam:x:1009:billy,cibil,milly”
1st field > SaleTeam : The name of the field.
2nd field > x : The password stored in /etc/gshadow file. I have not examine the usage of password on group objects. You can gain extra permission by entering the group password if it set. Google ftw :)
3rd field > 1009 : Unique ID like user objects have.
4th field > billy,cibil,milly : Members of the group.
To make it short I’ll give a break.
I wish you have a nice day.