Linux cloud computing cluster Architecture Study Notes: user management and root User Password Reset, Study Notes root
RHEL7User Management
Content of this section:
- Configuration files of users and groups
- Manage users and groups
- RHEL7Crack the root password
Compared with windows, users and accounts in LINUX serve the same purpose.
It is based on the user's control over the accessed resources, but there are differences in the presentation details.
User Account:
Super User: root is supreme
Local User: created by the Administrator. The permissions are limited and the permissions are complete in the home directory.
System users: Generally, they do not log on to the system and are used to maintain the normal operation of a service program.
User category:
Based on the account location: Local Account, remote (domain) account. Ldap
Based on account functions: Super User (root) UID: 0
Common User
System User UID: 1-999
Local user UID: 1000 + rhel6 500
UID: ID of each user, similar to the ID number of each user.
Configuration files related to system users and groups:
Account Information and password information
User:/etc/passwd/etc/shadow
Group:/etc/group/etc/gshadow
Command for adding a user account:
Syntax: useradd User Name
Common parameters:
-U UID
-D main directory
-G start group # Only one
-G additional group # There can be multiple
-S logon shell
[root@xuegod60 ~]# useradd SAN[root@xuegod60 ~]# ls /home/San[root@xuegod60 ~]# tail -1 /etc/passwdsan:x:1002:1002::/home/san:/bin/bash
All user account information is saved in the/etc/passwd file. This file stores all the information of each system account in the following format:
(Fields are separated)
The function of each field in/etc/passwd is as follows:
Root: x: 0: 0: root:/bin/bash
Username: Password placeholder: UID: GID: User Description: User main directory (bash "~ "Indicates which): shell used after Logon
Pseudo-user-for security
In linux, any command operation must have a user identity.
Pseudo-users are generally related to systems or program services.
Bin, daemon, shutdown, and halt linux all have these pseudo users by default.
Pseudo users generally do not need or cannot log on to the system
You can have no home directory
Common pseudo users in/etc/passwd files
Install nginx in the source code. By default, the nobody user is used to run the nginx web server.
User UID
Specify the user's home directory
Start Group of the specified user
User additional group
Specify the user's logon shell
Create another USER command
Useradd or adduser
[Root @ xuegod60 ~] # Adduser honghaier
Delete A User:
Userdel
-R CC together with the Home Directory
Password File
/Etc/shadow
Root: $6 $. btynb8q1_zr. KY $412 ...... M8ZHWiidd/: 16274: 0: 99999: 7 :::
Modify user information:
Syntax:
# UsermodUser Name
Common parameters:
-U UID
-DHome Directory
-GStart Group # Only one
-GAdditional group # There can be multiple
-SLog on to shell
Modify UID
Modify shell
Modify additional group
Group category:
Based on the account location: Local Group, remote (domain) group.
Based on account functions: Super User Group (root) GID: 0
Common User Group
System User Group GID: 1-999
Local user group GID: 1000 +
* ** Each user has a group with the same name ***
/Etc/groupConfiguration file structure:
[Root @ xuegod60 ~] # Grep rm/etc/group
Rm: x: 1000: rm
Control the file for adding user rules
When a new user account is added, the following operations are performed by default.
- Its home directory will be created(Generally"/Home/User Name"Unless you set)
- Some Hidden FilesFor example
.bash_logout
,.bash_profile
And.bashrc
Will be copied to the user's home directory.
- A group with the same username will be created unless you specify a group for the new user ).
Solved the problem of abnormal display after the template file is deleted.
[Root @ xuegod60 ~] # Useradd aaa
[Root @ xuegod60 ~] # Echo 123456 | passwd -- stdin aaa
[Root @ xuegod60 ~] # Ls-a/home/aaa/
... Bash_logout. bash_profile. bashrc. mozilla. zshrc
[Root @ xuegod60 ~] # Rm-rf! $. Bash *
Rm-rf/home/aaa/. bash *
[Root @ xuegod60 ~] # Su-aaa
-Bash-4.2 $
Recovery:
[Root @ xuegod60 ~] # Cp/etc/skel/. bash */home/aaa/
[Root @ xuegod60 ~] # Chown aaa: aaa/home/aaa/. bash *
Switch users:
[Root @ xuegod60 ~] # Su-aaa
In addition, the environment variables will be switched together during the switchover.
If this parameter is not added, the original environment variables are retained.
Command for viewing user information:
Id
W
Who
Whoami
Finger
Practice: RHEL7 restore the root password
First restart, press the restart keys to enter the following interface, select the first item, and press e to edit
Find the ro item on this interface and modify it to rw init =/sysroot/bin/sh.
After the change, press Ctrl + X to enter the emergency mode.
Principle: Start a shell environment, and the system does not actually start
Root change and Password Change
/Default
ChrootCommand to run commands in the specified root directory
.Chroot, That isChange root directory(ChangeRootDirectory ). InLinuxIn the system, the default directory structure is/Is the root(Root). In useChrootThen, the system directory structure will take the specified location/Location
AfterChrootAfter the command, the directory and file read by the system will not be under the old system root, but under the new root (that is, the specified new location) directory structure and file,
Note: selinux is disabled when the password is restored.
Restart the system
First exit the current root and execute/bin/sh shutdown-r now