1. Manage user accounts
1. Overview of user accounts
Linux controls access to resources based on user identity.
2. User Account Management
1) User Account
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Super user (root);
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Ordinary users;
-
Program user;
- UID (User IDentify) user identification number;
(1) User account file/etc/passwd
The /etc/passwd file is used to hold basic information such as user name, host directory, login Shell, and so on; each line corresponds to a user's account record.As follows:
(2) User account file/etc/shadow
The /etc/shadow file is used to store the user's password, account validity, etc. Each line corresponds to a user's password record.As follows:
3. Add user accounts
The format of commands and common options for adding user accounts is as follows:
Examples of applications:
<!--Establish bob User, management group is root，Additional groups are root，Specify the host directory as/bob--> [root@centos01 ~]# useradd -d /bob -g root -G root bob [root@centos01 ~]# tail -2 /etc/passwd dhcpd:x:177:177:DHCP server:/:/sbin/nologin bob:x:1001:0::/bob:/bin/bash <!--Establish tom User, no need to create host directory, account can not log on to system--> [root@centos01 ~]# useradd -M -s /sbin/nologin tom [root@centos01 ~]# tail -2 /etc/passwd bob:x:1001:0::/bob:/bin/bash tom:x:1002:1002::/home/tom:/sbin/nologin
4. Set/change user password passwd
The basic command format syntax and common options for setting/changing user passwords are as follows:
Examples of applications:
[root@centos01 ~]# passwd Bob <!--Account Setting Password--> Change the password of the user bob. New password: <!--Enter password--> Invalid password: Password did not pass dictionary check - oversimplification/systematization Re-enter the new password: <!--Determine the password--> passwd: All authentication tokens have been successfully updated. [root@centos01 ~]# passwd-l Bob <!--Lock User--> Lock the password of the user bob. passwd: Operation successful [root@centos01 ~]# passwd-S Bob <!--Check if the user is locked--> Bob LK 2020-01-11 0 99999 7-1 (password locked).) [root@centos01 ~]# passwd-u Bob <!--Unlock User--> Unlock the password of the user bob. passwd: Operation successful [root@centos01 ~]# passwd-S Bob <!--Check if user status is unlocked--> Bob PS 2020-01-11 0 99999 7-1 (Password set, using SHA512 algorithm).) [root@centos01 ~]# passwd-d Bob <!--Empty account password--> Clear the user's password bob. passwd: Operation successful [root@centos01 ~]# userdel-r Bob <!--Delete account and host directory--> [root@centos01 ~]# tail -2 /etc/passwd dhcpd:x:177:177:DHCP server:/:/sbin/nologin tom:x:1002:1002::/home/tom:/sbin/nologin
5. Initial profile of user account
The file is copied from the / etc/skel directory when you create a new user account; the primary user initial profile is as follows:
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~/.bash_profile: Executes at every login.
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~/.bashrc: executed each time a new Bash environment is entered.
- ~/.bash_logout: Executes every time you log out.
2. Management Group Accounts
1. Overview of group accounts
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Basic group (private group);
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Additional groups (public groups);
- GID: Group ID
1) Group Account Document/etc/group
The /etc/group file is used to save basic group account information; as follows:
[root@centos01 ~]# cat /etc/group root:x:0: bin:x:1: daemon:x:2: sys:x:3: adm:x:4: tty:x:5: ............ <!--Omit some content here-->
2) Group Account Document/etc/gshadow
The /etc/gshadow file is used to save password information for group accounts; as follows:
[root@centos01 ~]# cat /etc/gshadow root::: bin::: daemon::: sys::: adm::: tty::: ............ <!--Omit some content here-->
2. Add group account groupadd
The basic format of the Add Group Account command is as follows:
Examples of applications:
[root@centos01 ~]# groupadd -g 200 accp [root@centos01 ~]# tail -3 /etc/group tcpdump:x:72: test:x:1000: accp:x:200: [root@centos01 ~]# groupadd benet [root@centos01 ~]# tail -3 /etc/group dhcpd:x:177: tom:x:1002: benet:x:1003:
3. Add and remove group members gpasswd
Set group account password and add/remove group members; basic format and common options for commands are as follows:
Examples of applications:
[root@centos01 ~]# Gpasswd-a bob benet<!--Join users to a group (create bob users yourself)--> //Adding user'bob'to the'benet' group [root@centos01 ~]# tail -2 /etc/group tom:x:1002: benet:x:1003:bob [root@centos01 ~]# Gpasswd-M tom, Lisi benet <!--Bulk add users to benet group--> [root@centos01 ~]# tail -2 /etc/group benet:x:1003:tom,lisi lisi:x:1004: [root@centos01 ~]# Gpasswd-d tom benet <!--Exit tom user from benet group--> //Removing user "tom" from the "benet" group [root@centos01 ~]# tail -2 /etc/group benet:x:1003:lisi lisi:x:1004:
4. Delete group account groupdel
The basic format of the delete group account command is as follows:
Examples of applications:
[root@centos01 ~]# Groupdel benet <!--Delete benet group-->
5. Specify groups when adding user accounts
The'-g'option in the useradd command specifies the user's base group name (or GID number); the'-G' option specifies the user's additional group name (or GID number).
Examples of applications:
<!--Establish bob User, management group is root，Additional groups are root，Specify the host directory as/bob--> [root@centos01 ~]# useradd -d /bob -g root -G root bob [root@centos01 ~]# tail -2 /etc/passwd dhcpd:x:177:177:DHCP server:/:/sbin/nologin bob:x:1001:0::/bob:/bin/bash
6. Query account information
1) id command
id is used to query user identity; the basic syntax format of the command is as follows:
Examples of applications:
[root@centos01 ~]# ID Bob <!--View user details--> uid=1003(bob) gid=0(root) group=0(root),1005(benet)
2) groups command
The groups command is used to query the groups to which the user belongs; the basic syntax of the command is as follows:
Examples of applications:
[root@centos01 ~]# Groups Bob <!--Query the group the user belongs to--> bob : root benet
3) finger command
The finger command is used to query the details of a user's account; the basic syntax of the command is as follows:
4) users, w, and who commands
users, w, and who commands are used to query user information that is logged on to the host.Examples of applications are as follows:
[root@centos01 ~]# users root [root@centos01 ~]# w 01:57:23 up 53 min, 1 user, load average: 0.00, 0.01, 0.01 USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT root pts/0 192.168.100.254 01:04 3.00s 0.05s 0.00s w [root@centos01 ~]# [root@centos01 ~]# who root pts/0 2020-01-17 01:04 (192.168.100.254)
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