Linux users and their rights management commands

/etc/passwd:

User name: Password: uid:gid: Comments: Home directory: Default Shell

/etc/group:

Group name: Password: GID: List of users with this group attached to the group

/etc/shadow:

User name: Password: Last time the password was modified: Minimum Age: Maximum Age: Warning Time: Inactive time: Expiry time:

User Management :

useradd,userdel,usermod,passwd,chsh,chfn, Finger ,ID,chage,pwck

User basic information management:

# useradd [options] USERNAME (add users)

-U UID: Specifies its UID value, greater than or equal to 1000,uid value unique

-G GID: Specifies its base group, which must exist

-G GID ... : Specifies its additional groups, if there are multiple, separated by commas with each other

-C "COMMENT": Specifying annotation information

-d/path/to/somewhere: Specify home directory (by default, create a directory with the same name as the user name in the home directory)

-S Shell: Specify the shell path, use absolute path when specified ↓(default SHELL for a user)

/etc/shells: Specifies the security shell that is available for the current system

-m-k:-m force a home directory for the user,-K copies the necessary configuration files for the new user when it is created →/etc/skel

-M: Do not create home directory for users

-e: Account expiration date

-r: Add system User (id value less than 1000)

# userdel [option] USERNAME (delete user, default does not delete their home directory)

-R: Delete the user's home directory and its associated files at the same time

-F: Forcibly delete the user's home directory and its associated files

# ID [options] [USERNAME] (view user's account attribute information)

-U/-G/-G: Displays the ID value of the specified genus Master/group/all Groups

-N: Displays the name represented by the specified ID value

To modify user account properties:

# usermod [Options] USERNAME

-U uid: Modify the original UID value

-G GID: Modify the base group value that belongs to

-a-g GID: Appends a new additional group to the user's original specified group, without using the-a option, overwriting the previous additional group

-C "Information": Add comment information

-D-M: To specify a new home directory for the user,-m to move the previous file to the new home directory

-S: Modify the user shell

-L: Modify user Name

-L: Lock the account to prevent the user from logging into the system

-U: Unlocks the account, allowing the user to log in to the system

-e: Specify the user's expiration time, format "YYYY-MM-DD"

-F: Specify inactivity Time

# Chsh USERNAME (Modify the user's default shell)

# CHFN USERNAME (Modify comment information)

Password Management:

# passwd [USERNAME] (change user password)

--stdin: Allow user passwords to be modified from standard input

-L: Lock the user against logging in

-U: Unlock the user to allow login

-D: Remove user password

# chage [OPTION] NAME

-D: Last modification time

-E: Expiration time

-M: Minimum period of use

-M: Maximum lifespan

-W: Warning time

# Pwck (check user account integrity)

Group Management :

groupadd,groupdel,groupmod,gpasswd

Create/delete Group:

# Groupadd [OPTION] GRPNAME

-G GID: Specify Group ID

-R: Added as System group (ID less than 1000)

# Groupdel GRPNAME

Modify Group Properties:

# groupmod [option] GRPNAME

-G GID: Modify Group ID

-N GRPNAME: Modify Group name

Add Password to group:

# gpasswd GRPNAME

Log in to a new group:

# newgrp GRPNAME <--> exit

Rights Management :

chown,chgrp,chmod,umask

Permission Mode:r,w,x

User category: U owner , G group , O other users . A represents all users

Change file owner: chown

# chown [OPTION] USERNAME file,... (Change the owner of the specified file to username)

-R: Modify the owner of the directory and its internal files

--reference=/path/to/somefile file,... ( changes the property contents of the specified file to the same property as the file specified in the preceding path, and the attribute includes both the owner and the group.

# chown [OPTION] [username]:[grpname] File,... (supports simultaneous modification of both owners and genera)

Changed file group: chgrp (change group)

# CHGRP [OPTION] GRPNAME file,... (Change the group of the designated documents to Grpname)

-R: Recursive modification of directory genera

--reference=/path/to/somefile file,... (IBID.)

Changing file permissions: chmod (change mode)

Modify permissions for three categories of users:

# chmod MODE File,... (also supports-R and--reference)

To modify a class of users or some class user rights:

# chmod user Category =mode,... file,...

Modify some or some bit permissions for a class of users:

# chmod user Category +/-mode,... file,...

Matte Code: Umask

Create file: 666-umask(file default cannot have Execute permission, if there is, then add 1 of its permission)

Create directory: 777-umask

# umask (shows the current user's umask)

# umask 022 (set a user's umask)

Linux users and their rights management commands