numerical calculation · Episode 10: Mixed-integer secondary plan (CVXPY version)

2023-01-23   ES  

User group management

1. User group file/etc/group

[[email protected] ~]# tail -N3/ETC/Group // View data of the last three lines under the/group
testgroup:x:1001:
user2:x:1002:
grp1:x:1003:

Note: The result of the output is the same as the first three lines of/etc/passwd. Please refer to the first three lines of the previous blog post/ETC/PASSWD.

2. User backup instructions

  • Enter the command, don’t return to the car, use TAB to complete, the following effect will be displayed
[root@localhost ~]# ls /etc/shadow  // Password configuration file
shadow   shadow-           
[root@localhost ~]# ls /etc/passwd  // User configuration file
passwd   passwd-  
[root@localhost ~]# ls /etc/group  // User group file
group   group-  
[root@localhost ~]# ls /etc/gshadow  // User group password configuration file
gshadow   gshadow-  

Note: The group-, passwd-, represents the backup file of the file, if the user or the file is deleted, recover with it.

3. Added and delete user group

  1. command grammar
    groupadd [-g GID] groupname

  2. command description
    new user group

  3. command option
    -G custom GID. If you do not add -G options, you can create a group according to the default GID of the system. Like UID, GID starts from 1 1.

command example

  • Create user group
[root@localhost ~]# groupadd grpp1      // Create user group
[root@localhost ~]# tail -n1 /etc/group      // View the last line of user group files (group). (Each user group is created by default, and a line of data will be added in the last line of the group file).
grpp1:x:1004:     // Refer to the first three lines of/ETC/PASSWD
  • While creating a user group, custom GID (GID must be above 1000, and the system user group is within 1000)
[root@localhost ~]# groupadd -g 6666 grpp2
[root@localhost ~]# tail -n1 /etc/group
grpp2:x:6666:
  • Delete the user group (Groupdel)
[[email protected] ~]# groupdel grpp2
[[email protected] ~]# tail -n3 /etc/group
user2:x:1002:
grp1:x:1003:
grpp1:x:1004:

can be seen from the code that GRPP2 has been deleted.

Note: When we delete the user group, the premise is that there are no users in the user group.

source

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numerical calculation · Episode 10: Mixed-integer secondary plan (CVXPY version)

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