Linux Learning Note Four

Unit Five

########################## User Action command #################

(i) use of ID

ID User name # # View user Information

ID - u # # user uid(userid)

- G # # user gid(initial group ID, only one)

-A # # users All information

- G # # # User IDs for all groups (including universities,Linux groups, etc.)

-un # # user name

-GN # # user Initial group name

-GN # # # users All group names

Execute vim/etc/login.dafs, the user's uid default is !

The operating conditions are:

[Email protected] desktop]$ echo $PATH

/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin

[[email protected] desktop]$ which LS

Alias ls= ' ls--color=auto '

/usr/bin/ls

(ii) Switch User's environment

Echo $PATH # # # View the user environment for the current user, which displays the current PATH environment variable, which consists of a series of colon-delimited directory names.

Echo $USER # # # Displays information about the current user

Su-username # # # Toggles the environment used by the current user

# #kiosk原本的环境

[Kiosk Echo $PATH

/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/kiosk/.local/bin:/home/kiosk/bin

# #root原本的环境

[Root Echo $PATH

/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bi N

# #root用su-kiosk Switch to kiosk while switching to Kiosk's own environment variable

[Root Su-kiosk

[Kiosk echo $PATH

/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/home/kiosk/.local/bin:/home/kiosk/bin

# #root用su Kiosk switches to kiosk, but still root path, no path to the kiosk

[Root su Kiosk

[Kiosk Echo $PATH

/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

The difference between SU student and su-student when switching users :

1.su-student Switch User, and user's environment, add "-" environment variable also changed;

2. do not add "-" that is, su student just switch users.

(iii) actions for users and Groups

1. User

① User Type

A. Administrator Root: A user with all permissions,the value ofuid is 0

B. Normal User: Normally created user,uid is ~60000

c. system users: To ensure that the system operation of users, generally do not provide password login system,the UID is 1~499

② user-related files

A. /etc/passwd# # User information file

stores the user's basic properties, from which all users of Linux can be viewed . The format is:

"User name: Password: User ID: Owner group ID:user description (e.g. name, age, phone, etc.): User root: User programming environment ( Shell used ) "

Each user group has one primary group (private group), one or more additional groups.

B. /etc/shadow# # user authentication information

Some strategies for storing user passwords in the form of:

"User name: Password: the date of the most recent password change: The number of days the password cannot be changed: Warning period before password change: Password expiration Grace time: Account expiration Date: Reserved"

c. /home/username# User home directory

d. /etc/skel/.*# # User's basic information configuration

③ User Commands

A. New User:useradd-d Root - G Main group - G Append group list (comma separated) user name

B. Reset password:passwd user name

c. Modify User:usermod-d Root - G Main group - G Append group list (comma separated) user name ———— The-G of the command moves the user from the original additional group and can use the-a parameter indicates the new mode

D. Deleting a User:userdel-r Delete a user name together with the root directory

E. View all users:cat/etc/passwd

F. Viewing individual user details:ID user name

G. View all currently logged-in users:WHHO

2. user groups

The user group is the user's container, and the user can inherit permissions from the user group.

① user Group type

A. Common user groups: can join multiple users

B. System user group: Generally add some system users

c. Private user group: When a user is created, a user group with the same name will be created for that user if no user group is indicated. A private user group is actually a common user group.

② user group related files

A. /etc/group# # user group Information

Basic information about the storage group. The format is;

"group name: Group Password: group ID: User list"

B. /etc/gshadow

similar to the shadow of the user group

③ User Group commands

A. New group:groupadd-g uid number group name ———— if uid is not specified Automatic generation of the number

Groupadd-g 888 Test(Specify uid as 888)

Groupadd hehe(uid not specified )

B. Modify Group:gruopmod-n new group name ———— can be used to group names

Groupmod-n Jack Jaak

c. Delete Group:groupdel Group name ———— cannot be deleted if there are users in the group

d. View all groups + view users within a group:cat/etc/gruop

E. Viewing the user's group information:ID user name

Output:

Uid=0 (Root) gid=0 (root) groups=0 (root)

UID is the primary group,gruops is the additional group

F. adding users to a group:gpasswd-a user name Group name

G. Removing a user from a group:gpasswd-d user name Group name

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(iv) detailed operation of the user

Useradd # # New user

- u # # # Specify uid for user

- G # # # Specify user initial group, this group must exist

- G # # # Specifies additional groups, and groups also exist

- C # # User Description

- D # # # Specify user plus directory

- S # # # Specify the shellThe user uses,shell type See /etc/shells

Userdel - R # # # Delete users

Groupadd - G # # # New Group,-g indicates the ID of the specified group

Groupdel # # # Delete Group

passwd # # # change user password

"Example"useradd-u 1016(existing group number) - G 1016(existing group number) test(user name)

################## First, listen passwd . ###########

Watch-n1 Tail-n 3/etc/passwd

1.

Useradd Add test User

Useradd Test

When a process is in use and cannot delete test :

Kill + The process number

And then again:

Userdel-r Test

So that we can remove it successfully.

2.

User uid and gid can be specified at the same time

Useradd-u 888-g 888 Test

3.

Add user instructions (to delete test before it can be established)

Useradd-c "Test User" test

4.

Specify User home Directory

useradd-d/mnt/test Test

5.

Specify the shell type used by the user

Useradd test-s/bin/tcsh

6.

See the types of shells

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Linux Learning Note Four