There are three types of permissions: rwx, which stand for read, write, and execute.
Files correspond to three object groups. Each object group protects the three types of permissions: rwx.
The three object groups are the owner’s permissions, the group’s permissions, and the permissions for other users in the system.
Binary representation of permissions:
r 100
w 010
x 001
Octal representation of permissions:
r 4
w 2
x 1
The command chmod can modify file permissions using either characters or numbers.
Permissions can be represented using ugo to indicate the object.
Use + or – to add or remove rwx from a file or path.
Use = to directly assign permissions.
Use -R to modify permissions recursively.
chmod 554 file modifies the permissions of file to r-xr-xr--.