Linux Commands (ii)

Aliase : Defines an alias for a shell command

Aliases Cmdalias=command

unaliase COMMAND is to revoke the command alias

permissions:r,w,x Each class has three permissions

File:

R: Readable , you can view the contents of the file using commands like cat

W: writable , can edit or delete this file

X: executable, can be submitted to the kernel at the command prompt as a command to run

Directory:

R: You can perform LS on this directory to list all internal files

W: You can create files in this directory

x : You can use CD switch into this directory, or you can use the ls-l View the details of an internal file

User Add Delete

Useradd  [Options] USERNAME Adding users

-U:UID Specifies the user's main ID

-G:GID Specifies the base group ID or group name (this group must first exist to be used)

-G:GID Specifies additional groups, you can specify multiple, separated by commas (this additional group first exists to use)

-C: "COMMENT" Specifies annotation information

-D: Specify the user's home directory, the default is to create a directory with the same name as the user at home.

-S: Specifies the shell, the path is finally the specified shell path in the/etc/shells file

-M: forcing the user to create a home directory

-M: Do not create home directory for new users

-r: Create a System user, system call, do not establish home directory

Userdel  [Options] USERNAME Deleting a user

-r: Delete the user and also delete the home directory

(the home directory is not deleted when no parameters are added by default)

View user Information

ID USERNAME: View user's account attribute information

-U: View UID

-G: View GID

-G: View all groups of users

-un: Displays the user name of the current user

-GN: Displays the group name of the current user

Finger USERNAME : View user account information

Modify User Properties

Usermod  [Options] USERNAME modifying account properties

-U: Modify UID

-G: Modify GID

-G: Modify additional groups

-a–g : Specify new additional groups for the user on the original additional group, without using the -A option overrides the additional group before this

- C : Modify user comment information

- D : Specify a new home directory

-d–m : Specify a new home directory, and move the previous file to the new home directory

- S : Modifies the user's default Shell

- L : Modify User name

                     -L : Lock user accounts

- u : Unlock user account

Chsh : Modify the user shell

CHFN : Modify comment Information

User Password Management

Passwd [Options] USERNAME Modifying user passwords

--stdin: Read password from standard input

-L: Lock user account

-U: Unlock user account

-D: Remove user password

-N: Minimum user password time

-X: Maximum user password usage time

PWCK: Checking user account Integrity

User Group Properties

Groupadd  [Options] GROUPNAME New Group

-G: Specify GID

-R: Added as System group

Groupmod  [Options] GROUPNAME modifying Group Properties

-G: Modify GID

-N: Modify Group name

Groupdel GROUPNAME Deleting a group

gpasswd GROUPNAME Add password to group

Modify file properties

Chown : Modify File owner (Only administrators can use this command)

Chown USERNAME file .... ( change the directory itself only )

-R: Recursive modification (Modify the properties of the directory and internal files)

Chown username:groupname file ..... Change both the owner and the group

Chown USERNAME File ... Change the owner

Chown:groupname file ... change the genus Group

Chgrp : Modify file Group

Chown USERNAME file .... ( change the directory itself only )

-R: Recursive modification (Modify the properties of the directory and internal files)

Modify file Permissions

chmod  MODE file ... Modify the file's user rights

-R: Recursive modification

modify certain permissions for a certain type of user

U: Owner

G: Genus Group

o: Other

A: All

chmod User category =mode file ....

Chmod u=wr,g=w file ....

Chmod uo=wr File ...

Modify a certain bit or some bit permission for a user of a class

Chmod User Category [-/+]mode file

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Linux Commands (ii)