Basic Linux Basics Review command Five (users and groups)

1: Users and Groups

Core elements: allocation of resources

User Category:

Administrator: ID number 0

Normal User: ID number

System User: ID number 1-499

User ID =uid; Name resolution

Group Id=gid

[[email protected] vp-tools]# ID
Uid=0 (Root) gid=0 (root) groups=0 (root), 1034 (Avayavpgroup)

Group Category:

Administrators group: 0

System Group: 1-499

User group: Researcher

2: Permissions

• Linux all files, permissions control is actually the access to the file control.

R

W

X

• File:

R: View File contents

W: Modify File Contents

X: Start this file as a running program

• Directory:

R: LS to view the file name in the directory

W: can create files in this directory

X: You can CD to the directory, and LS-L displays the metadata for the catalog file.

[Email protected] vp-tools]# ls-l
Total 92
-r-xr-xr-x 1 root root 3866 Apr addserviceaccounts
3: User Management

• /ETC/PASSWD: User account information

For example:

Format--account:password:uid:gid:gecos:directory:shell
Account: Password: User id: Group ID: note Information: User home directory: User's default shell (operating system interface)

Example:craft:x:1032:1032::/cpic/craft:/bin/bash

• /etc/shadow: User password and related account settings

  Format: Username:passwd:lastchg:min:max:warn:inactive:expire:flag

  login : Password: Most recent password change time: Change password minimum interval: password expiration: Password expiration advance warning Time: Inactivity time : Failure time

  Example:craft:$6$1rmc/er7$hhd2rbgzhr3fyk0q6poshif5wnz8.eptr68006idexpejgiajgwixym8j5nkycxphaizfhp7cppjsqzkemg1n .: 16811:0:99999:7:::
  

• /etc/group: Account information for the group

  Format: group_name:passwd:GID:user_list

  Example:avayavpgroup:x:1034:root,craft

• /etc/gshaow: Group information, passwords and users in the group

  格式：groupname:password:admin,admin,...:member,member,...

  User group: User group Password: User Group manager: composition
  Example:avayavpgroup:!::root,craft

  4: Related commands

• Useradd

  -U: Specify UID

  -G: Specify GID or GroupName

  -G: Specify additional groups

  -C ' comment content ': Comment information

  -D: Specify home directory, if present, prompt

  [Email protected] vp-tools]# Useradd user1
  [Email protected] vp-tools]# tail-1/etc/passwd
  User1:x:1036:1036::/home/user1:/bin/bash

• Groupadd

  -g:gid

  -R: System Group

[Email protected] vp-tools]# Groupadd test
[Email protected] vp-tools]# tail-1/etc/group
test:x:1037:

• Modify Password passwd command

  Normal User: passwd

  Administrator: passwd USERNAME

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Basic Linux Basics Review command Five (users and groups)