Group Administration:
The groupadd command creates a new group account using the values specified on the command
line and the default values from the system. The new group will be entered into the system files as
needed.
There are two types of group:
1. Primary groups: Primary groups are automatically created at the time of user creation. Name of
primary group is same as the user name.
2. Secondary groups : Secondary groups are user define and group id will be unique
it edits on file /etc/group and /etc/gshadow
syntax:
# groupadd <groupname>
eg:
[root@localhost ~]# groupadd redhat
[root@localhost ~]# tail -1 /etc/group
redhat:x:1001:
redhat :x : 1001:
1 2 3 4
➢ field 1: Group name.
➢ field 2: Redirected Password. (link of the /etc/gshadow file)
➢ field 3: Group ID
➢ field 4: User list (group members
[root@localhost ~]# tail -1 /etc/gshadow
redhat:!::
# group customize
# syntax:
#groupadd <option> <argument> <groupname>
eg:
[root@localhost ~]# groupadd -g 5050 admin
[root@localhost ~]# tail -1 /etc/group
admin:x:5050:
GROUP MODIFICATION
cmd: groupmod
this command is use to modify the attributes of group
synatx:
# groupmod <option> <argument> <existing groupname>
options:
-g groupid
-n group name
-o non-unique
eg:
[root@localhost ~]# groupadd testing
[root@localhost ~]# tail -1 /etc/group
testing:x:5051:
[root@localhost ~]# groupmod -g 3030 testing
[root@localhost ~]# tail -1 /etc/group
testing:x:3030:
[root@localhost ~]# groupmod -n sales testing
[root@localhost ~]# tail -1 /etc/group
sales:x:3030:
[root@localhost ~]# tail -2 /etc/group
admin:x:5050:
sales:x:3030:
[root@localhost ~]# groupmod -o -g 5050 sales
[root@localhost ~]# tail -2 /etc/group
admin:x:5050:
sales:x:5050:
GROUP PASSWORD MANAGEMENT
cmd: gpasswd
/etc/group, /etc/gshadow
syntax:
#gpasswd <groupname> use to set group password
#gpasswd <option> <argument> <group>
# options:
-a --> add members in group
-A --> create group administration
-M --> add multiple users in group
-r --> remove group password
-d -> delete user from group
eg:
[root@localhost ~]# groupadd rhcsagroup
[root@localhost ~]# tail -1 /etc/group
rhcsagroup:x:5051:
[root@localhost ~]# tail -1 /etc/gshadow
rhcsagroup:!::
[root@localhost ~]# gpasswd rhcsagroup
Changing the password for group rhcsagroup
New Password: redhat
Re-enter new password: redhat
[root@localhost ~]# tail -1 /etc/gshadow
rhcsagroup:$6$4rt7XFvfh4Z$jLwzAMiXsWqoHXHgz1ayuU7OBA2enOTY9oSDMaVmSkeBmLuKCjVcUf
mwhN5LJsfQss.tutHqlonFz/0pvAUOg1::
rhcsagroup :$qlonFz/0pvAUOg1 : :
1 2 3 4
field1: groupname
field2: encrypted password
field3: group admin
field4: grouo members list
[root@localhost ~]# useradd jack; useradd jerry; useradd john
[root@localhost ~]# tail -3 /etc/group
jack:x:5052:
jerry:x:1002:
john:x:1003:
[root@localhost ~]# groupadd rhce
[root@localhost ~]# tail -1 /etc/group
rhce:x:5053:
[root@localhost ~]# gpasswd rhce
Changing the password for group rhce
New Password:
Re-enter new password:
[root@localhost ~]# tail -1 /etc/gshadow
rhce:$6$0ta9X6kMQR/q$HiliFlUFwwwXPtCRzyuhhVu6XxUtcvoPjFb2lBsOIQiINv4VjB/qg9VcN7Kwy4Q
nla3UguPnhpgB12c2ffi6b1::
[root@localhost ~]#
[root@localhost ~]# # -r --> remove group password
[root@localhost ~]# gpasswd -r rhce
[root@localhost ~]# tail -1 /etc/gshadow
rhce:::
[root@localhost ~]# # -a --> add user in group
[root@localhost ~]#
[root@localhost ~]# gpasswd -a jack rhce
Adding user jack to group rhce
[root@localhost ~]# tail -1 /etc/group
rhce:x:5053:jack
[root@localhost ~]# tail -1 /etc/gshadow
rhce:::jack
[root@localhost ~]# gpasswd -a jerry rhce
Adding user jerry to group rhce
[root@localhost ~]# tail -1 /etc/group
rhce:x:5053:jack,jerry
[root@localhost ~]# useradd harry
[root@localhost ~]# gpasswd -M john,harry rhce
[root@localhost ~]# tail -2 /etc/group
rhce:x:5053:john,harry
harry:x:1004:
[root@localhost ~]# gpasswd -M john,harry,jerry,jack rhce
[root@localhost ~]# tail -2 /etc/group
rhce:x:5053:john,harry,jerry,jack
harry:x:1004:
[root@localhost ~]# tail -2 /etc/group
rhce:x:5053:john,harry,jerry,jack
harry:x:1004:
-A --> group admin
[root@localhost ~]# gpasswd -A john rhce
[root@localhost ~]# tail -2 /etc/gshadow
rhce::john:john,harry,jerry,jack
harry:!::
[root@localhost ~]# gpasswd -A jerry rhce
[root@localhost ~]# tail -2 /etc/gshadow
rhce::jerry:john,harry,jerry,jack
harry:!::
[root@localhost ~]# gpasswd -A jerry,john rhce
[root@localhost ~]# tail -2 /etc/gshadow
rhce::jerry,john:john,harry,jerry,jack
harry:!::
# -d --> delete user from group
[root@localhost ~]# gpasswd -d jack rhce
Removing user jack from group rhce
[root@localhost ~]# tail -2 /etc/gshadow
rhce::jerry,john:john,harry,jerry
harry:!::
[root@localhost ~]# gpasswd -d harry,jerry rhce
Removing user harry,jerry from group rhce
gpasswd: user 'harry,jerry' is not a member of 'rhce'
to check users in group
cmd:groups
[root@localhost ~]# tail /etc/group
student:x:1000:
redhat:x:1001:
admin:x:5050:
sales:x:5050:
rhcsagroup:x:5051:
jack:x:5052:
jerry:x:1002:
john:x:1003:
rhce:x:5053:john,harry,jerry
harry:x:1004:
[root@localhost ~]# gpasswd -a john rhcsagroup
Adding user john to group rhcsagroup
[root@localhost ~]# gpasswd -a john admin
Adding user john to group admin
[root@localhost ~]# gpasswd -a john sales
Adding user john to group sales
[root@localhost ~]# groups john
john : john sales rhcsagroup rhce
[root@localhost ~]# tail /etc/group
student:x:1000:
redhat:x:1001:
admin:x:5050:john
sales:x:5050:john
rhcsagroup:x:5051:john
jack:x:5052:
jerry:x:1002:
john:x:1003:
rhce:x:5053:john,harry,jerry
harry:x:1004:
[root@localhost ~]# id john
uid=1003(john) gid=1003(john) groups=1003(john),5050(sales),5051(rhcsagroup),5053(rhce)
#group deletion
#cmd: groupdel
#syntax:
#groupdel <groupname>
#eg:
[root@localhost ~]# groupadd linux
[root@localhost ~]# gpasswd linux
Changing the password for group linux
New Password: redhat
Re-enter new password: redhat
[root@localhost ~]# tail -1 /etc/group
linux:x:5054:
[root@localhost ~]# tail -1 /etc/gshadow
linux:$6$zFPDwevpHA/VLd$PoCWtvQ7JcRGfLaqRaCc3AgSkGuSH7A89R3VBcUmP6oxAorr/c9SmwRo
mVnJYZODccTUSJXy4fYjll12Km4WA/::
[root@localhost ~]# gpasswd -a jack linux
Adding user jack to group linux
[root@localhost ~]# tail -1 /etc/group
linux:x:5054:jack
[root@localhost ~]# groupdel linux
[root@localhost ~]# tail /etc/group
student:x:1000:
redhat:x:1001:
admin:x:5050:john
sales:x:5050:john
rhcsagroup:x:5051:john
jack:x:5052:
jerry:x:1002:
john:x:1003:
rhce:x:5053:john,harry,jerry
harry:x:1004:
# -f --> delete group forcefully
[root@localhost ~]# #groupdel -f <group name>
[root@localhost ~]# groupdel admin
[root@localhost ~]# tail /etc/group
tcpdump:x:72:
student:x:1000:
redhat:x:1001:
sales:x:5050:john
rhcsagroup:x:5051:john
jack:x:5052:
jerry:x:1002:
john:x:1003:
rhce:x:5053:john,harry,jerry
harry:x:1004:
[root@localhost ~]# useradd sam
[root@localhost ~]# tail -1 /etc/passwd
sam:x:1005:1005::/home/sam:/bin/bash
[root@localhost ~]# tail -1 /etc/group
sam:x:1005:
[root@localhost ~]#
[root@localhost ~]# gpasswd -a john sam
Adding user john to group sam
[root@localhost ~]# tail -1 /etc/group
sam:x:1005:john
[root@localhost ~]# userdel sam
userdel: group sam not removed because it has other members.
[root@localhost ~]#
[root@localhost ~]# tail -1 /etc/passwd
harry:x:1004:1004::/home/harry:/bin/bash
[root@localhost ~]#
[root@localhost ~]# tail -1 /etc/shadow
harry:!!:19032:0:99999:7:::
[root@localhost ~]#
[root@localhost ~]# tail -1 /etc/group
sam:x:1005:john
[root@localhost ~]# tail -1 /etc/gshadow
sam:!::john
[root@localhost ~]# groupdel sam
[root@localhost ~]# tail -1 /etc/group
harry:x:1004:
[root@localhost ~]# tail -1 /etc/gshadow
harry:!::
[root@localhost ~]#
[root@localhost ~]#
