User and group management

user and group managment:-

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user --> the pernson who is using the perticular machine

group: -> the collection of users  is calles as group

user management:

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-> users have there own UID for the kernel and username is for our referance

-> UID from 1 to 999 is applied  for default users.

-> the users we create are started with UID 1000 + 

-> the complete user details are stored in /etc/passwd  file

-> the password related details are stored under /etc/shadow file

#vim /etc/passwd

<username>:<pointer to password>:<UID>:<primary group ID>:<description>:<home directory>:<shell path>

ex: root:x:0:0:root:/root:/bin/bash

#vim /etc/shadow

<username>: <encrypted password>: <password aging>

root: bcslsdbbvjksd  c dbdjkvjwdnvv d cm: 99999: 7:

creating  a user:

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#useradd <username> --> to create default user

ex: #useradd fed

#vim /etc/passwd  --> go to last line and verify

#cat  /etc/passwd  --> you can the data on screen

#getent passwd <username>  --> to get the user info of perrticular user

eX: #getent passwd fed

setting  a password for user:-

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#passwd <username>   

ex: #passwd fed

new password: ----

confirm password: ----

group management:-

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-> all group details are stored in /etc/group file

-> group have there own GID which are for kernel referance & group name is for our referance

#vim /etc/group

<group name>  :  <pointer to  password> : <group ID>  : <group members>

ex: root : x : 0 : 

# vim /etc/gshadow

<group name> : <encrypted password> : <<group admin> : <group members>

root: ---------: zafar: zaf,pragthi

creating a group:-

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#groupadd <group name> 

ex: #groupadd ka

#vim /etc/group    --> go to last and verify

#cat /etc/group   --> to show the complete details of group file on screen

#getent group <group name>  --> to show the entry of perticular group

ex: #getent group ka

create a group with custom GID:-

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#groupadd -g  <group id>   <group name>  

ex: #groupadd -g 25000  csk

#getent group csk

-> types of groups:

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1) primary group  --> the group created while creating  a perticular user is called as primary.

2) secondary group  --> for one perticcular user groups other than primary group which he is present are called as secondary group

setting a password:-

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#gpasswd <group name> 

ex: #gpasswd ka

new password: -----

confirm password: -----

#vim /etc/gshadow  --> to verify

modifing the groups created:-

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#groupmod -n <new group name>  <old group name>   --> to change the group name

ex: #groupmod -n karnataka ka 

#getent group ka  --> to details

#getent group karnataka  ---> to know the deatails of that perticular group

#groupmod -g <custom group ID>   <group name>   --> to chnage the group ID of existing group

ex: #group -g 22500  karnataka

#getent group karnataka