Mylinux Note---6th day

First, view the user

/etc/passwd

[Email protected] ~]# Cat/etc/passwd|head-5root:x:0:0:root:/root:/bin/bashbin:x:1:1:bin:/bin:/sbin/nologindaemon : x:2:2:daemon:/sbin:/sbin/nologinadm:x:3:4:adm:/var/adm:/sbin/nologinlp:x:4:7:lp:/var/spool/lpd:/sbin/nologin[ [Email protected] ~]#

Each line of the file represents a user,

Each line is separated by a colon ":" Into 7 fields,

Structure is the same, the structure is as follows:

User name: Password: uid:gid: User tag: Home directory: Shell

① User name: uppercase and lowercase letters, numbers, minus signs (not appearing in the first place), dots, and underscores, other characters are illegal.

② Password: the "x" letter placeholder, in fact the password is stored in "/etc/shadow".

[Email protected] ~]# head-5/etc/shadow root:$6$zj4ryp1lfptznzdm$ jzbdsgce0pnze6pev9l8ncoxmohr90cfzubxikl2ookjhveeup/uydg6unninkvqmizd6dsan5pwudnxng.qe0:16496:0:99999:7:::bin:* : 15980:0:99999:7:::d aemon:*:15980:0:99999:7:::adm:*:15980:0:99999:7:::lp:*:15980:0:99999:7:::[[email protected] ~]#

③uid:user ID User Identification Code, the special value "0" is saved to "root", 1~499 belongs to the system user, 500~4294967294 (2^32-2) is assigned to the ordinary user.

④gid:group ID User Group identification code, from "/etc/group".

[Email protected] ~]# head-5/etc/group root:x:0:bin:x:1:bin,daemondaemon:x:2:bin,daemonsys:x:3:bin,admadm:x:4:adm , Daemon[[email protected] ~]#

⑤ User Tags: This field does not make any sense, usually records some of the user's properties, such as name, phone, address, etc., with CHFN change

[[email protected] ~]# grep  "Mylinux"  /etc/passwdmylinux:x:1000:1000::/home/mylinux:/ bin/bash             #  User Mylinux Fifth paragraph is empty; [[ email protected] ~]# chfn -f mylinux -p 13800138000 mylinux #   Add description-f full-name;changing finger information for mylinux.   with CHFN                  -p  Office-phone;finger information changed. [[email protected] ~]# !grep                               The      #  fifth paragraph has been added to the information just now grep  "Mylinux"  /etc/passwdmylinux:x:1000:1000: mylinux,,13800138000:/home/mylinux:/bin/bash[[email protected] ~]#

⑥home Directory: User home directory Location

⑦shell: Identify user shell type:/bin/bash;/sbin/nologin;/sbin/shutdown, etc.

Second, the user password

/etc/shadow

[Email protected] ~]# head-5/etc/shadowroot:$6$zj4ryp1lfptznzdm$ jzbdsgce0pnze6pev9l8ncoxmohr90cfzubxikl2ookjhveeup/uydg6unninkvqmizd6dsan5pwudnxng.qe0:16496:0:99999:7:::bin:* : 15980:0:99999:7:::d aemon:*:15980:0:99999:7:::adm:*:15980:0:99999:7:::lp:*:15980:0:99999:7:::[[email protected] ~]#

Each line of the file represents a user,

Each line is separated by a colon ":" Into 9 fields,

User name:

Password: MD5 encrypted, non-encrypted

Change password time: The last time you changed your password

Change Password Age: How many geniuses can be changed password, default value "0", unlimited

Password expiry time: the number of days after the password expires, the default value of "99999"

password Age: Password expiration reminder, default value "7" is the first 7 days before password expires reminder

Lockout period: after the password expires, the account number days after the lock, the default value is empty

life cycle: account life cycle, default value NULL

Reserved bits

Iii. Users and Groups

① user's creation/deletion

User-Created

format : useradd [options] [user name]

[Email protected] ~]# useradd linux[[email protected] ~]# tail-1/etc/passwdlinux:x:1002:1003::/home/linux:/bin/bash[ [Email protected] ~]#

option :-u Specify user uid

-U Specify user group

-g Specifies the user gid (to contain this ID in passwd)

-G Specify user group GID

-M Create user home directory

-M do not create user home directory

-D User Home directory

-D print or change useradd default configuration

-s Specifies the shell type

User Delete

format : Userdel [options] [user name]

[[email protected] ~]# tail-5/etc/passwdnfsnobody:x:65534:65534:anonymous NFS user:/var/lib/nfs:/sbin/nologinanon:x : 600:600:anonymous,,13800138000:/home/anon:/bin/bashwww:x:1001:1001::/home/www:/bin/bashanonymous:x:501:501::/ Home/anonymous:/bin/bashlinux:x:1002:1003::/home/linux:/bin/bash[[email protected] ~]# Userdel Linux[roo[email Protected] ~]#!tailtail-5/etc/passwdrpcuser:x:29:29:rpc Service user:/var/lib/nfs:/sbin/nologinnfsnobody:x : 65534:65534:anonymous NFS user:/var/lib/nfs:/sbin/nologinanon:x:600:600:anonymous,,13800138000:/home/anon:/bin/ Bashwww:x:1001:1001::/home/www:/bin/bashanonymous:x:501:501::/home/anonymous:/bin/bash[[email protected] ~]#

option :-F Force Delete

-R Delete User home directory and mail buffer

Creation and deletion of ② groups

Creation of groups

format : groupadd [Options] [group name]

[Email protected] ~]# groupadd linux[[email protected] ~]# tail-5/etc/groupanon:x:600:www:x:1001:anonymous:x:1002: Test:x:501:linux:x:1003:[[email protected] ~]#

option :-G to specify GID for the group created

-p to create a group encryption

-R Create a system account

Deletion of groups

format : Groupdel [Options] [group name]

[Email protected] ~]# Groupdel linux[[email protected] ~]# tail-5/etc/groupnfsnobody:x:65534:anon:x:600:www:x:1001: Anonymous:x:1002:test:x:501:[[email protected] ~]#

③usermod Modification of user information

Format: usermod [options] [user name]

[[email protected] ~]# tail-5/etc/passwdnfsnobody:x:65534:65534:anonymous NFS user:/var/lib/nfs:/sbin/nologinanon:x : 600:600:anonymous,,13800138000:/home/anon:/bin/bashwww:x:1001:1001::/home/www:/bin/bashanonymous:x:501:501::/ Home/anonymous:/bin/bashlinux:x:1002:1003::/home/linux:/bin/bash[[email protected] ~]# usermod-g 501 Linux # Switch to user GID information [[email protected] ~]#!tailtail-5/etc/passwdnfsnobody:x:65534:65534:anonymous NFS user:/var/lib/nfs:/sbin/ Nologinanon:x:600:600:anonymous,,13800138000:/home/anon:/bin/bashwww:x:1001:1001::/home/www:/bin/bashanonymous : X:501:501::/home/anonymous:/bin/bashlinux:x:1002:501::/home/linux:/bin/bash[[email protected] ~]#

Option:-L change User login name

-C Update user passwd in comment bar information

-D Specify a new user home directory

-g Specifies a new GID

-g Specifies the new group GID

-u Specifies the new user uid

-M mobile home directory to new location

-p Use new encryption password

-S using the new shell type

-L Lock user account

-U Unlock user account

Iv. Creating/modifying user passwords

Create a user password

For the new user, no password is set, the password needs to be created and the command is as follows:

[[email protected] ~]# passwd Linux # format passwd [username] Change the password of the user Linux. New Password: Re-enter the new password: passwd: All authentication tokens have been successfully updated. [Email protected] ~]#

Option:-D Delete the named account password

-k password not in period

--stdin obtaining a password from standard input

[[email protected] ~]# passwd linux--stdin change password for user Linux. 123456789PASSWD: All the authentication tokens have been successfully updated. [Email protected] ~]#

mkpaswd Password Generation command

There is no need for this command to perform Yum install-y expect

Option: The length of the-l password, the default value is "9"

-d password contains several numbers, the default value is "2"

-c password contains several lowercase letters, the default value is "2"

-c password contains several uppercase letters, the default value is "2"

-S password contains several special characters, the default value is "1"

-P Encrypt the program

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Mylinux Note---6th day