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2025-04-04 Update From: SLTechnology News&Howtos shulou NAV: SLTechnology News&Howtos > Servers >
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Shulou(Shulou.com)06/02 Report--
I. Management of users and groups
-types of users in Linux:
Root: administrator, with supreme authority, unrestricted, UID of 0
Ordinary user: a user created by an administrator. Subject to permission restrictions, the UID is generally 5000060000 and can log in to the system.
Program users: install the application, created by the system, UID is generally 1x500, generally can not log in to the system, shell is generally / sbin/nologin
-types of groups in Linux:
Basic group (private group) A user has only one private group. When a user creates directories and files, the default subordinate group for directories and files is the basic group.
Additional groups (public groups) users can have multiple additional groups
-user management:
/ etc/passwd # stores the user's information
Root: user account
X: password placeholder
0:uid
0:gid
Root: descriptive information
Root: home directory
/ bin/bash: log in to shell
/ etc/shadow # stores the user's password information, etc. (corresponds to each line of / etc/passwd user information)
The red part after root: ciphertext, usually generated by HASH algorithm
14374: time from January 1, 1970 to the present (in days)
0: minimum password life
99999: the longest valid period of password
7: password expiration reminder 7 days in advance
... How long will the account expire and the items will be retained
-add user account
Useradd command
Useradd [options]... User name
-u: specify the UID tag number
-d: specify the host directory, default to / home/ user name (the specified directory will be created on its own, and the initial configuration file will not be copied when the specified directory exists)
-e: specify the expiration time of the account
-g: specify the basic group name (or UID number) of the user
-G: specify the additional group name (or GID number) of the user (cannot create the user when the specified additional group does not exist)
-M: do not create and initialize host directories for users
-s: specifies the login Shell of the user
-set / change user password
Passwd command
Passwd [options]... User name
-d: clear the user's password so that it can log in without a password
-l: lock the user account
-S: check the status of the user account (whether it is locked)
-u: unlock user account
Supplement: standard input:
Echo "123456" | passwd-- stdin test02
Set the password 123456 to the test02 account
-exit
You can return the account from the last time you switched it.
-modify the attributes of a user's account
Usermod command
Usermod [options]... User name
-l: change the login name of the user account
-L: lock user account
-U: unlock user account
-u: specify the UID tag number
-d: specify the host directory, default to / home/ user name
-e: specify the expiration time of the account
-g: specify the basic group name (or UID number) of the user
-G: specify the user's additional group name (or GID number)
-M: do not create and initialize host directories for users
-s: specifies the login Shell of the user
-Delete user account
Userdel command
Userdel [- r] username (when the-r option is added, the user's host directory is deleted)
-initial configuration file of user account:
File source: copied from / etc/skel directory
Main user initial profile:
Execute each time the user logs in
Execute each time you enter a new bash environment
Execute each time the user logs out
Group account file
-add a group account
Groupadd command
Groupadd [- g GID] group account name
Both basic groups and additional groups are in / etc/group
-add / remove group members
Gpasswd command
Purpose: set group account password (rarely used), add / remove group members
Gpasswd [options]... Group account name
-a: add a user to the group
-d: removes a user member from the group
-M: define a list of group members separated by commas (will overwrite the original group members)
-Delete a group account
Groupdel command
Groupdel group account name
-query account information:
Id command
Purpose: query user identity
Format: id [user name]
Groups command
Purpose: query the group to which the user belongs
Format: groups [user name]
Finger command
Purpose: to query the details of user accounts
Format: finger [user name]
Users, w, who commands
Purpose: query user information that has logged in to the host
Two. attributes of files and directories: owners, groups, permissions
-permissions and attribution of files / directories
a. Access permission
Read r: allows you to view file contents and display directory lists
Write w: allows file contents to be modified, new files or subdirectories to be created, moved, or deleted in the directory
Executable x: allows you to run programs and change directories
b. Ownership (ownership)
Owner: the user account that owns the file or directory
Group: the group account that owns the file or directory
Ls-l gets the result analysis after executing the command
Example:
The first character: indicates the type of file or directory:
D (table of contents)
B (block device file)
C (character device file)
"-" (ordinary document)
"l" (linked file)
2-4 characters: indicates the authority of the owner
5-7 characters: indicates permissions that belong to a group
8-10 characters: indicates the permissions of others
34298: file size in bytes
04-02 00:23: file creation time
Install.log: file name
The basic permissions in Linux are divided into r (4), w (2), x (1).
View permissions and attribution of files / directories
-set permissions for files and directories
Chmod command
Format 1:chmod [ugoa] [+-=] [rwx] file or directory.
Format 2:chmod nnn file or directory. (recommended)
Common command options
-R: recursively modify the brand new of all subitems under the specified directory
-set the attribution of files and directories
Chown command
Format: chown master file or directory
Chown: a group file or directory
Chown owner: group file or directory
Common command options
-R: recursively modify the attribution of all files and subdirectories under the specified directory
-setting of the file permission mask
Umask can set the default permissions when creating new files and directories (default permissions = existing default permissions-permission mask)
Umask to view the current permission mask
Umask [permission mask]
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