Linux User and user group knowledge

1)/etc/passwd The meaning of the file field

1th Domain: User name

2nd domain: Password

3rd domain: User ID

4th domain: User group ID (0 indicates belong to root group)

5th field: Comments and text

6th domain: User home directory

7th domain: User shell type

2)/etc/group The meaning of each field of the file

1th Domain: Group name

2nd domain: Group password

3rd domain: Group ID

4th domain: The list of users under this group, NULL to indicate the same user name and group name

3 Create user examples

Useradd–d/home/users–m–g root-g qcfang–s/bin/csh Test

3) Modify User example

Usermod–d/home–s/bin/bash–g Qcfangtest

4) chown Modify the file's owner and group (root operation)

Chown-r Test a.txt– Change the owner of the file A.txt to test

Chown-r test:test a.txt-Change file A.txt's owner is test, group is test;