UNIX/LINUX File security and permissions (1)

Input ls-l xxx. xxx. xxx in the terminal as the file name). Similar information will appear, mainly including:

-Rw-r --

A total of 10 digits, including:

The-at the top of the list indicates the type.

The three rw in the middle represents the owner user)

Then the three rw-represent the group)

The last three r groups are represented by another person, other)

Then explain the nine digits below:

R indicates that the file can be read)

W indicates that the file can be written)

X indicates that the file can be executed if it is a program)

-The permission has not been granted.

Now let's talk about modifying file permissions.

Enter: chmod o + w xxx. xxx on the terminal

Grant other users the permission to write the file xxx. xxx.

Chmod go-rw xxx. xxx

Deletes the read and write permissions of group groups and other persons in xxx. xxx.

Where:

U stands for the owner user)

G indicates the group in which the owner is located)

O stands for others, but not u and g other)

A Represents all people, including u, g, and o

R indicates that the file can be read)

W indicates that the file can be written)

X indicates that the file can be executed if it is a program)

Rwx can also be replaced by numbers.

R -- 4

W -- 2

X -- 1

--- 0

After everyone understands the above, we can easily understand the following common permissions:

-Rw -- 600) only the owner has the read and write permissions.

-Rw-r -- 644) only the owner has the read and write permissions, and the group and others only have the read permission-rwx -- 700) only the owner has the read and write permissions, execution permission-rwxr-xr-x 755) only the owner has the read, write, and execute permissions, group group and others only have read and execution permissions-rwx -- x 711) only the owner has read, write, and execution permissions. Group and others only have execution permissions.

-Rw-rw-rw-666) Everyone has read and write permissions

-Rwxrwxrwx777) everyone has the read/write and execution permissions.

Source: Magicbreaker Column

Use the ls-l command, such as the following:

Total 74434

-Rwxrwxr-x 2 user dba 39921 January 16 12:50 file1

Drwxrwxr-x 2 user dba 4096 January 16 15:29 folder

Total 74434 indicates the space occupied by all files in the directory

2 indicates the number of hard links to the file

39921 indicates the length of the file, expressed in bytes. If it is not a K-byte-rwxrwxr-x, it indicates the read and write permissions of the file or directory. The first value indicates 7 types of the file)

D directory l symbolic link pointing to another file) s socket file B Device File

C character device file p name MPs queue file-Common File

The first rwx indicates the file owner permission: r, w, x)

The second rwx indicates the default group permission for the file owner: r, w, x the permissions used by the third r-x System: r, x

Note: If the attribute of a file is-r --, the file owner can still write data to the file through redirection.

Chmod command: There are two types of commands: Symbol mode and absolute mode: