User Administration
Only root (i.e. system administrator) can use adduser command to
create new users. It is not allow to other users.
Adduser is symlink of Useradd which is binary in /usr/sbin. We (root) can customize adduser by
using another word (rocky) & make it
symlink of useradd. Let's see
Main File of useradd
[root@localhost Desktop]# ls
-l /usr/sbin/adduser
lrwxrwxrwx. 1 root root 7 Jun 20
2015 /usr/sbin/adduser -> useradd
[root@localhost Desktop]# which useradd -to check file location
/usr/sbin/useradd ----------------------main file of useradd
command
#useradd ---main file (/usr/sbin/useradd)
#ln –s
/usr/sbin/useradd /user/sbin/u ---create links or short cut file
Now “ u” is symlink of useradd.
#u rocky --- create user
[root@localhost Desktop]# ln -s /usr/sbin/useradd /usr/sbin/T
Now “T” is symlink of useradd.
[root@localhost Desktop]# T mouse
[root@localhost Desktop]# ls /home
rocky lalit
mouse olx rajesh paytm test
--------------------------------------------------------------------------------------------------------------------
There are 3 types of users
________________________|________________________
| | |
Super user System user Normal user
<1> Superuser : At the time of linux
installation it is create. He has right
to make other users & his`userid' & `groupid' is zero in `/etc/Passwd'
file.
<2> Systemuser: These users create by System. They can't
login becoz their shell `sbin/noloin' is
default in seventh field in
`/etc/passwd' file.
<3> Normaluser: These users create by
superuser.(root user)
--------------------------------------------------------------------------------------------------------------------
Let's
see how superuser make normaluser :
[root@localhost root]$ adduser john
[root@localhost root]$ passwd john
New password :( user
password)
Retype new password:(user
password)
Passwd: all authentication
tokens updated successfully.
--------------------------------------------------------------------------------------------------------------------
[root@localhost root]$ userdel john ---> `userdel' command
delete only name of the user from /home directory but it's data remain there.
It's /usr/sbin/userdel
--------------------------------------------------------------------------------------------------------------------
[root@localhost root]$ userdel -r john ---->userdel -r delete name of user as
well as data.
--------------------------------------------------------------------------------------------------------------------
[root@localhost root]$
usermod -G groupname username
i.e. [root@localhost root]$ usermod -G sales vikas
--------------------------------------------------------------------------------------------------------------------
usermod –G ----
Secondary Group
usermod –g ------Primary Group
--------------------------------------------------------------------------------------------------------------------
---->`usermod
-G' command makes the user vikas member of the group sales.
/usr/sbin/usermod.
--------------------------------------------------------------------------------------------------------------------
su
----> with the help of this command root can work as substitute user.
su -r
---->with the help of this command root come out from substitute user.
--------------------------------------------------------------------------------------------------------------------
[root@localhost root]$ adduser
john
# useradd mouse --- after create user, created the below
details
i)
UID -----------------------------------------User
ID
ii)
GID -----------------------------------------Group
ID
iii)
cd /home/mouse/ ---------------------------Create Home Directory
iv)
Owner Group Permission 700 --------- Set Default permission to group
v)
Owner Group (John) ----------------------create owner group same as user name.
vi)
/etc/skel ----------------------Copied all file from /etc/skel to user home
directory.
--------------------------------------------------------------------------------------------------------------------
[root@localhost Desktop]# id---------------------- with the help
of this command to check user id
uid=0(root) gid=0(root) groups=0(root)
[root@localhost ~]# id john
--------------------------- with the help of this command to check user
id
uid=514(john) gid=514(john)
groups=514(john)
[root@localhost ~]# id tushar ---------------------------
with the help of this command to check user id
uid=515(tushar)
gid=515(tushar) groups=515(tushar)
--------------------------------------------------------------------------------------------------------------------
[root@tushar ~]# T -G sales lalit -----user
create and group added as a secondary
[root@tushar ~]# id lalit
uid=3003(lalit)
gid=3005(lalit) groups=3005(lalit),3003(sales)
--------------------------------------------------------------------------------------------------------------------
[root@tushar ~]# T -g maket sohel ---user create and group added as a primary
[root@tushar ~]# id sohel
uid=3004(sohel)
gid=3004(maket) groups=3004(maket)
--------------------------------------------------------------------------------------------------------------------
#
useradd file ---- Refers 2 files
& update
4 files
The information of adduser refers 2 files & updates 4
files.
Refers 2 Files
|----ls /etc/login.defs
|
|----ls /etc/default/useradd
Updates 4 files ------user all information updated in below
files.
IT’S CALL THE LINUX USER DATABASE
|----/etc/passwd
|
|----/etc/group
|
|----/etc/shadow
|
|----/etc/gshadow
l. ----------------------------to see hidden
file
ls –a
------------------------- to see hidden file
---------------------------------------------------------------------------------------------------
[root@localhost
~]# vi
/etc/login.defs -
(.defs –Defaults )
#
Min/max values for automatic uid selection in useradd
#
UID_MIN 500 ------------------ TAG---------500 -----create only 100 user
UID_MAX 60000-----------------TAG---------600 u can change this value
#
#
Min/max values for automatic gid selection in groupadd
#
UID_MIN 500 -------------------- TAG-------500
-- create only 200 groups
UID_MAX
60000-----------------TAG---------700
u can change this value
#
#
If useradd should create home directories for users by default
#
On RH systems, we do. This option is overridden with the -m flag on
#
useradd command line.
#
CREATE_HOME yes ------if should be not create home DIR so u can just type no
You
can manage and change home directory name.
How money user create
in Linux
User and group = 59500 -
by default user created
Answer: its depends on the /etc/login.defs file
--------------------------------------------------------------------------------------------------------------------
# passwd
------to change current user password
--------------------------------------------------------------------------------------------------------------------
/etc/login.defs
<1> /etc/login.defs : It keep the information of directory where mailboxes reside or name of file relative to the home
directory, Password duration & how
many users can login.
"Passwd
file" & "Group file"
get the information of userid & groupid from this file.
"shadow
file" & "Gshadow file" get the information of user login & password
duration of user from this file.
Min/max
values for automatic uid selection in useradd.
UID-MIN 500
UID-MAX
60000
The id of user
start from 500 & max it is 60000 which is default according to REDHAT but
we can customize it.
If there are two
department ACCOUNTANT & MARKETING in one office then I can start userid to
ACCOUNTANT from 1000 & to MARKETING from 2000 which is reliable.
Similar
way to Groupid
GID-MIN 500
GID-MAX 60000
--------------------------------------------------------------------------------------------------------------------
Umask
Default value of
umask is:
For
root 022
For
user 002
777 777
022 002
------ ------
755 775
Umask 077 is
default permissions
MAIL_DIR /var/spool/mail -------------------- TAG -
user mails server indox in /var/spool/mail
_______________________________________________________________________________
/etc/default/useradd
<2> /etc/default/useradd : It has
information of no. of groups, directory of users & user using which shell
in following way.
1. Group=100 ----> It's default no. of
groups according to Redhat which can customise.
2. Home=/home ----> It's default dir of
user as Redhat say to which we can give any name i.e. we can make `ghar'instead of `home' by making
directory under /
3. Inactive ----> It's number of days
after account expire of user.
4. Expire ----> It's number of days for
the password of user will expire.
5. Shell=/bin/bash --> It's path of
user shell.
6. Skel=/etc/skel ---> When user create
there is zero dir or file but when give command `l.' it shows some hidden files
which comes from /etc/skel.
[root@localhost
~]# vi /etc/default/useradd
#
useradd defaults file
GROUP=100 ------------------------------------------------------------------query
HOME=/home
(wallet)----------------------u can
manage home dir and u can change the /home sir name
INACTIVE=-1 ------------------------------------10
account expire day select (-1 ----no value or its depends of
the other files)
EXPIRE= ---------------------------------------------IF
you set 7 days the password will be expire after 7 days
SHELL=/bin/bash -----------------------------------if you
want to change folder eg . /bin/sh ---The shell of the user will be /bin/sh for
feture
SKEL=/etc/skel --------------------------------------If you
want to change this pasth /etc/opt u can
manage that , Then opt folder all file
copied to home dir
IF you want to
share common file to every new joiner get this file so u can copy file in
/etc/skel folder
CREATE_MAIL_SPOOL=yes
--------------------------------------------------------------------------------------------------------------------
[root@localhost
/]# mkdir wallet ---------------wallet dir create in / locaton
[root@localhost
/]# T paresh ------------------------create user
[root@localhost jacky]# cd /wallet/paresh/ --------change
home dir name
[root@localhost
paresh]# l. or ls -a
. ..
.bash_logout .bash_profile .bashrc .gnome2
.mozilla
--------------------------------------------------------------------------------------------------------------------
[root@localhost
~]# cd /home/jacky/
[root@localhost
jacky]# l.
. ..
.bash_logout .bash_profile .bashrc
.gnome2 .mozilla
-------------------------------------------------------------------------------------
LINUX USER DATABASE
Update 4 files
i)
/etc/passwd
ii)
/etc/shadow
iii)
/etc/group
iv)
/etc/gshadow
--------------------------------------------------------------------------------------------------------------------
1)
/etc/passwd
<3> /etc/passwd : * It keeps
the record of new user when create by superuser. Each line is entry of new
user. It is text file & has details of all system users.
* It has 7
fields for each user in each line so
it is called
`system passwd database' & each
field is separated : (colon) also called "Internal field Separator".
--------------------------------------------------------------------------------------------------------------------
[root@localhost
paresh]# vi /etc/passwd
: (colon) is
separated by filed
How many filed
in passwd file = 7
Paresh :x :517 : 517
:
:/wallet/paresh :/bin/bash
\_____/\__/\____/\____/|__|\______________/\__________/
| | | | | | |
1 2 3 4 5 6
7
--------------------------------------------------------------------------------------------------------------------
Champu
:x :500 :500 : :/home/champu :/bin/bash
\_____/\__/\___/\___/|_|\______________/\________/
| | | |
|
| |
1 2 3 4 5 6
7
--------------------------------------------------------------------------------------------------------------------
1 --- It is username
2 ---- X means
your password reside in shadow files
It contain user password which is somewhere
else if exist.
If
we put * in place of x then user can't login.
If we keep
second field blank then user can login without password.
i.e. (x) ---
password somewhere else or its store in shadow file
(*)
--- user can't login.
( ) --- user can
login without passwd.
3 ----
UID ------User id
4 ------ GID-------Group
id
It contains
groupid which is always same as userid. It's
group of users.
5 ------It is comment field or GECOS(General electric compressive
operating
system)
Finger Information’s ( blank filed )
user can keep
his information by using command
Name []: office []:
office phone []: Home phone []:
6 ------- field (/home/champu) : It's home of champu. /home is directory where
all
users store. ( Home directory of the
user )
7 ----- field
(/bin/bash) : shell of the user
It contain the
full path of shell used by user.
Through shell we
can convert shell script into binary format &
Whatever
get from kernel convert into text format.
--------------------------------------------------------------------------------------------------------------------
2)
/etc/shadow ---passwd
policy
: (colon) is
separated by filed: How many filed in passwd file = 9
John : $1$eEfpbdwf$PyPoi0 :16792 : 0 : 99999 : 7
: : :
\___/\_____________________/\______/\_/\_______/\_/|_|_|_|__|
1 2 3
4 5 6
7 8 9
man shadow -------all the detain get in man shadow files.
The meanings of
each field are:
1 ---------User Name (sp_namp
- pointer to null-terminated user name)
2 ------- Password is in MD5 clear text
encryption ( IMP ) (sp_pwdp-password)
3 ------- sp_lstchg - days since Jan1,1970 password was last changed Unix Time is called
epoch time (u can used time conversion) Last password change record
4 --------- sp_min – 10 days before which password may not be changed
User may not change before 10
day his passwd
5 --------- sp_max – 65 days after which password must be changed
User
must be change password after 65 days (forcefully change)
6
---------- sp_warn – 30 days before
password is to expire that user
is warned of pending password expiration
7 ----------- sp_inact – 55 days after password expires that account is
considered inactive and
disabled
8 ------------ sp_expire – 4 days since Jan 1,1970 when account will be disabled
9 -------------- sp_flag - reserved for future use
root:$1$Z.8vsNYS$/cSeo0Sx/5aQlQdR4oF6M.:16793:0:99999:7:::
--------------------------------------------------------------------------------------------------------------------
3)
/etc/group
Group
contain 4 fields
line in this
field like follow
groupadd
maket
tushar:x:3001:
maket:x:3004:
--------------------------------------------------------------------------------------------------------------------
vi
/etc/group
tushar :x :3001
: --------user own group
maket :x :3004 : ---------create
group
\_____/\___/\_____/\_/
1 2 3 4
1 ---- Group Name
2 ---- Group Password
3 ---- group ID
4 ---- Members of the group
--------------------------------------------------------------------------------------------------------------------
$ usermod -G groupname username
[root@localhost
~]# usermod
-G sales
lalit -----add users to in
group
sales:x:3003:lalit - add lalit
to sales group as secondary
[root@tushar
rajeshj]# id lalit
uid=3003(lalit) gid=3005(lalit)
groups=3005(lalit),3003(sales)
--------------------------------------------------------------------------------------------------------------------
[root@localhost
~]# usermod -g maket sohel
[root@tushar ~]#
id sohel
uid=3004(sohel) gid=3004(maket)
groups=3004(maket) ---add as primary
--------------------------------------------------------------------------------------------------------------------
Diferance
between primary and secondary group
usermod
–G ----
Secondary Group
usermod
–g ------Primary Group
--------------------------------------------------------------------------------------------------------------------
Group
Password Set
#gpasswd sales– set group passwd
User can change
this own primary group
[root@localhost
~]# su vikas
[vikas@localhost
root]$ newgrp PUR
Password:
[vikas@localhost
root]$ id
uid=513(vikas)
gid=519(PUR) groups=513(vikas),505(sales),519(PUR)
context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
--------------------------------------------------------------------------------------------------------------------
[root@tushar ~]# su - rajeshj
[rajeshj@tushar ~]$ id
uid=3007(rajeshj) gid=3008(rajeshj) groups=3008(rajeshj)
context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
[rajeshj@tushar ~]$ newgrp sales ---user self-change
group
Password:
[rajeshj@tushar ~]$ id
uid=3007(rajeshj) gid=3003(sales) groups=3008(rajeshj),3003(sales)
context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
--------------------------------------------------------------------------------------------------------------------
<4> /etc/group : This file keep
the information of group. It has four field of each group of each line so it is
called `system group database'.
Member of group
has right to enter other member's of system who is member of same group.
line in this
field like follow
Accounts:x:500:
| | | |
1 2 3 4
1. field
(accounts) : It contain name of group which is always same as the first member
username.
2. field (x) :
It contain group password which is somewhere else if exist & it's password
is same of first member of group.
3. field (500) :
It contain group id which is same of first member's id of group.
4. field : It
contains list of members of group. By default Redhat it is blank but user can
fill it by put the name of members of group.
One user can
makes members of his group by using command
`usermod -G' which
is run by only
root.
$usermod -G
groupname username
when system
admin first time creates users he can send message like
`Thanku for
using redhat linux' through this & user get this mail whenever
he login.
[root@tushar
~]# T -G sales lalit
[root@tushar
~]# id lalit
uid=3003(lalit)
gid=3005(lalit) groups=3005(lalit),3003(sales)
[root@tushar
~]# T -g maket sohel
[root@tushar
~]# id sohel
uid=3004(sohel)
gid=3004(maket) groups=3004(maket)
[root@tushar ~]#
ls -l /home/
-rw-r--r--.
2 root root 47 Dec 18 22:44 harry.txt
drwx------. 4
lalit lalit 4096 Dec 28 02:07 lalit
drwx------.
4 ls ls 4096 Dec 15 23:13 ls
drwx------.
4 rakesh rakesh 4096 Dec 28 02:03 rakesh
drwx------. 4
sohel maket 4096 Dec 28 02:07 sohel
-rw-r--r--.
1 root root 32 Dec 18 20:23 test1.txt
drwx------.
4 tushar tushar 4096 Dec 28 02:03 tushar
---------------------------------------------------------------------------------------------------------
CREATE ANY USER WITHOUT EXECUTE ANY COMMADS
Fist refers 2 files and updates 4 files
1) /etc/login.defs
2) /etc/default/useradd
3) /etc/passwd
4) /etc/shadow/
5) /etc/group
6) /etc/gshadow
Create user home DIR as same user name
chmod 700 /home/samy/
su – samy
copy skel form home dir
cp /etc/skel/.bash* /home/samy/
chown –Rv samy : samy /home/samy
[root@localhost ~]# mkdir /hiome/samy
[root@localhost home]# chmod 700 /home/samy/
[root@localhost home]# ls -l
drwx------. 2 root root 4096 Dec 24 00:13 samy
---------------------------------------------------------------------------------------------------------
drwx------. 2 root root 4096 Dec 24 00:13 samy
---------------------------------------------------------------------------------------------------------
3 # vi /etc/shadow
Ms5-crypt -------you can set encrypted passed to user
Ms5-crypt -------you can set encrypted passed to user
---------------------------------------------------------------------------------------------------------
PASSWORD
AGING CONTROLS:
1. PASS-MAX-DAYS 99999 : The maximum number of days
a password can be used.
i.e max 99999 days.
2. PASS-MIN-DAYS 0 : The minimum number of days
allowed between password
can change.
3. PASS-MIN-LEN 5 : The minimum length of the
password. i.e. 5 character.
4. PASS-WARN-AGE 7 : Specifies the number of days
warning given to user
before the password expire. ie 7 days.
The above PASSWORD AGING information is default
according to REDHAT which we can customize it.
--------------------------------------------------------------------------------------
#
/etc/passwd ------User details for UID
and GID
Whenever
we create second user then system can refer /etc/passwd file
How to delete user account
# userdel champu
------User can delete but user home DIR not delete.
Advantage of
userdel command ----Database delete only but home DIR not delete.
# userdel -r champu
( -r -----recursive) delete USER as well as HOME DIR
----------------------------------------------------------------------------------------------------
How
to check user is created or not
You can check
user name or to search in below files
[root@localhost
home]# less /etc/passwd
OR
[root@localhost
home]# grep tushar /etc/passwd
tushar:x:515:515::/home/tushar:/bin/bash
paresh :x :517
:517 :
:/wallet/paresh :/bin/bash
\______/\_/\___/\____/|_|\_____________/\__________/
| | | | | | |
1 2 3 4 5 6
7
1 ---
It is username
2 ---- X means
your password reside in shadow files
If
we put * in place of x then user can't login.
If we keep
second field blank then user can login without password.
i.e. (x) ---
password somewhere else or its store in shadow file
(*)
--- user can't login.
( ) --- user can
login without passwd.
3 ----
UID ------User id
4 ------ GID-------Group
id It contains groupid which is always same as userid.
5 ------It is comment field or GECOS(General electric compressive
operating
system)
Finger Information’s ( blank filed )
user can keep
his information by using command
Name []: office []:
office phone []: Home phone []:
6 ------- field (/home/champu) : It's home of champu. /home is directory where
all
users store. ( Home directory of the
user )
7 ----- field
(/bin/bash) : shell of the user
--------------------------------------------------------------------------------------------------------------
How to user
modification
Usermod ---------to
modify user
How
to change UID
-u ---------- UID ------- to change UID
-s
------------ Shell ------- to change Shell
-c
------------- add comment ----------to
add comments eg . Thane mob no , add , location off add
-d
--------------home DIR
------------------ to change home DIR name.
-g
--------------GID ----------first check group and decide to set GID value to
user or
---------------------------------------------------------------------------------------------------------------
Add
user to group
Usermod
–u 10 -s /bin/sh
-c “ Thane Dombivali 989283938 98293898 “ –d /opt champu
Practice
and example
[root@localhost
home]# grep john /etc/passwd
john:x:514:514::/home/john:/bin/bash --------------------------before modification
user details
--------------------------After modification john user details in below--------------------
[root@localhost
home]# usermod -u 1000 -s /bin/sh -c " Tushar Jadhav 9892562869 dombivali
thane" -d /GHAR/ john
[root@localhost
home]# grep john /etc/passwd
john:x:1000:514:
Tushar Jadhav 9892562869 dombivali thane:/GHAR/:/bin/sh
----------------------------------------------------------------------------------------------------------------
[root@tushar
~]# useradd jockey
[root@tushar
~]# usermod -u 1000 -s /bin/sh -c " Tushar Jadhav 9892562869 dombivali
thane" -d /GHAR/ jockey
[root@tushar
~]# id jockey
uid=1000(jockey)
gid=3009(jockey) groups=3009(jockey)
[root@tushar
~]# grep jockey /etc/passwd
jockey:x:1000:3009:
Tushar Jadhav 9892562869 dombivali thane:/GHAR/:/bin/sh
---------------------------Change user GID
& user add in group ----------------
[root@localhost
home]# usermod -u
2000 -s /bin/bash -g 519 -c " Tushar
Jadhav 9892562869 dombivali thane" -d
/home/ john
[root@localhost
home]# grep john /etc/passwd
john:x:2000:519: Tushar Jadhav 9892562869 dombivali thane:/home/:
/bin/bash
[root@localhost
home]# id john
uid=2000(john) gid=519(PUR) groups=519(PUR) ----after change GID user add in this group
----------------------------------------------------------------------------------------------------------------
While creating
user we can give specific home DIR shell,
(Create user and
set permission and specific flags,)
Useradd jary
-----set default value
Useradd –d –u –s -- if you used this fags then skip home ,
uid , shell tags
Practice
and example
[root@Tusharjahdav
~]# Useradd
–d /mnt –u 3000 –s
/bin/ksh jokey
[root@Tusharjahdav
~]# grep jary /etc/passwd
Jokey :x: 3000: 3000 : : /mnt: /bin/sh
----------------------------------------------------------------------------------------------------
[root@Tusharjahdav
~]# useradd -u 1002 -s /bin/sh jary
[root@Tusharjahdav
~]# grep jary /etc/passwd
jary:x:1002:1002::/home/jary:/bin/sh
----------------------------------------------------------------------------------------------------
[root@localhost
/]# useradd -u 3001 -m -c "Mr.harry power is back" pintu
useradd:
cannot create directory /home:/pintu
---------------------------------------------------------------------------------------------------- [root@Tusharjahdav
~]# useradd vikey
useradd:
cannot create directory /home:/vikey
Ans : if facing above error then go to /etc/default/useradd file
and check home path.
----------------------------------------------------------------------------------------------------
How
to create 10 users in one command
#
Fist create user file and run for a look
Practice
and example
[root@]
~]# vi /opt/tuss ----- add
user list in this file
[root@tushar
/]# for i in "cat /opt/users" ; do useradd $i ;
done
----------------------------------------------------------------------------------------------------
How to disable user
----there are multiple way to disable user
root@tushar /]# vi /etc/passwd
jary: x : 1002:1002::/home/jary:/bin/sh ----(user will be login)original user passwd
jary: : 1002:1002::/home/jary:/bin/sh -----------------black (disable)
jary:* : 1002:1002::/home/jary:/bin/sh -------------------- * (disable)
jary: x : 1002:1002::/home/jary:/sbin/false --- ---/sbin/false (disable)
jary: x : 1002:1002::/home/jary:/sbin/nolgin --------- /
sbin/nolgin (disable)
root@tushar /]# vi /etc/shadow
paresh:!!:16792:0:99999:7:::9 ------ Put any value of last filed, user will be disable
--------------------------------------------------------------------------------------------------------------
How to Lock user
Passwd
–l john ----------------lock the user
[root@tushar ~]#
passwd -l paresh
Locking password for user paresh.
passwd: Success
Passwd
–u john --------------unlock the user
[root@tushar ~]#
passwd -u paresh
Unlocking
password for user paresh.
passwd: Warning:
unlocked password would be empty.
passwd: Unsafe
operation (use -f to force)
---------------------------------------------------------------------------------------------------------------
All
users will be disable if /etc/login this
file is exist
Touch
/etc/nologin ----just create this file then all users will
be disable
-------------------------------------------------------------------------------------------------------------
How to Add
group ---groupadd Group Name
How to Delete
group -----groupdel Group Name
How
to modify group ------groupmod
How to change shell
Usermode
–s --------------to change shell
[root@tushar /]#
chsh paresh -----------updated in passwd
Changing shell
for paresh.
New shell
[/bin/bash]: /bin/sh
Shell changed.
-----------------------------------------------------------------------------------------
[root@tushar
/]# chfn paresh ----- Finger information --change in gicos filed
Changing
finger information for paresh.
Name
[]: paresh moon
983333883 dombivali current bangalore
Office
[]: ajsdadada
Office
Phone []: asdasda
Home
Phone []: asda
Finger
information changed.
Practice
and example
[root@tushar /]#
grep paresh /etc/passwd
paresh:x:517:517:paresh moon 983333883 dombivali current bangalore,ajsdadada,asdasda,asda:/wallet/paresh:/bin/sh
-----------------------------------------------------------------------------------------
[root@tushar
/]# finger paresh -------all user details
-----------------------------------------------------------------------------------------
To
change the AGING ( to change the
password policy in shadow file)
[root@tushar /]#
chage paresh
Changing
the aging information for paresh
Enter
the new value, or press ENTER for the default
3 Minimum Password Age [0]:
4 Maximum Password Age [99999]:
5 Last Password Change (YYYY-MM-DD)
[2015-12-23]:
6 Password Expiration Warning [7]:
7 Password Inactive [-1]:
8 Account Expiration Date (YYYY-MM-DD)
[1969-12-31]:
John :
$1$eEfpbdwf$PyPoi0 :16792 : 0 :
99999 : 7 : : :
\___/\_____________________/\______/\__/\______/\__/|__|__|__|
1 2 3 4
5 6 7 8 9
1
filed -user name , 2 filed password and last is reserved is skip
Create user and set
password & user will be change password is first login.
[root@tushar /]#
useradd pranay
------------------create user
[root@tushar /]#
passwd pranay
----------------------set password
Changing
password for user pranay.
New password:
BAD PASSWORD: it
is based on a dictionary word
BAD PASSWORD: is
too simple
Retype new
password:
passwd: all
authentication tokens updated successfully.
----------------------------------------------------------------------------------------------------
Before
chage command /etc/shadow entry
pranay:$1$EmTX7J96$7Van4j3TJM.lIjFBwmryZ1:16792:0:99999:7:::
root@tushar /]#
chage -d 0 pranay ---------------------user will be prompt to
change password for 1st login
[root@tushar /]#
su - pranay
----------------------------------------switch user
[pranay@tushar
root]$ su pranay
Password:
You are required
to change your password immediately (root enforced)
Changing
password for pranay.
(current) UNIX
password:
New password:
Retype new
password:
Grep prnay
/etc/shadow
After chage
command 3 filed value will be change
pranay:$1$EmTX7J96$7Van4j3TJM.lIjFBwmryZ1:0:0:99999:7:::
This entry goes
to ( 1 jan, 1970 ) Value will be change 0
----------------------------------------------------------------------------------------------------
All created
users call Valid Linux Users
[root@tushar
~]# Vi /etc/passwd
[root@tushar ~]#
vipw------------------short cut file of vi
/etc/passwd
[root@tushar
~]# vi /etc/grouphu
[root@tushar ~]#
vigr -------------shart cut file of vi
/etc/group
---------------------------------------------------------------------------------------------------
How to disable
shadow file
[root@tushar
etc]# cd /etc/shadow
----------------- shadow file
[root@tushar
etc]# pwunconv ----Disable command ---After this command
shadow file will be disable and password will show in passwd file ..
[root@localhost
Desktop]# less /etc/shadow- disable file
passwd file user
entry qiukr:$1$ml1iS2Ke$TL0UYLWoGTbIfczYwy7tL.:500:500:Centos:/home/qiukr:/bin/bash
[root@tushar
etc]# less /etc/shadow ---------------------- shadow- its menas disable
[root@tushar
etc]# pwconv ---------- Enable
command-----------------shadow file will be enbale
[root@tushar
etc]# less /etc/shadow
-------------------enable file
---------------------------------------------------------------------------------------------------------------------
Permission
of shadow files 400
[root@tushar
etc]# ls -l /etc/shadow
-r--------.
1 root root 1236 Dec 24 05:29 /etc/shadow
passwd
file will be deleted by mistake
there
is already backup file is system so just copy this file passwd
passwd- ---------------------backup files
passwd.OLD -------------------- old backup files
[root@localhost etc]# cp
/etc/passwd- /etc/passwd
