https://blog.csdn.net/pythonw/article/details/80263428
the chmod 777 file or directory
Example: chmod 777 / etc / squid
run command, squid folder (directory) access was modified to 777 (read write executables). If Ubuntu system, you may need to add sudo to execute: sudo chmod 777 / etc / squid
specific description chmod command.
Linux system, each user's role and the division of authority is very detailed and very strict, each file (directory) has access permissions, use this mechanism to determine a user in some way to the file (directory) operate to read, write, execute and so on. Users manipulate files or directories, there are three different types: file owner, group, user, other users. MSB value represents the permissions of the file owner, the middle bit represents a group of users permission value, the lowest bit indicates other authority value of the user, so the chmod 777, three numbers above 7 correspond to three user permissions values 7. Permissions on the file or directory is divided into three kinds: read-only, write-only, executable.
In accordance with the above table, it is a combination of rights authority value corresponding to the sum, as follows: 7 = 4 + 2 + 1 = 4 write permission to run 5 + 1 and the read operation of read-only access rights 4 = 4
Thus, we will see chmod meaning the 754 filename command. Command phrase means to read and write permission to run the file filename of the file given to the owner of the rights given to read and run user group, to read the permissions granted to other users.
More official, detailed explanation, you can use the following command to see: chmod --help or man chmod
