chmod (change access permission)

chmod (change access permission)

- Used to change access permission(or file mode) to an existing file or directory.

(Only file owners or super users are allowed to change the mode.)

- mode option is specified as a character symbol or octal number.

Options and Symbols

• the user to be changed(user target), the command to be performed (operating), and the permission to be set (access)
• Multiple option are separated using commas (,)

• options

• -R	Change the permissions of subdirectories and files (recursive)

• the user to be changed

• u	abbreviation for "user", meaning file or directory owner
  g	group owner
  o	abbreviation for "others", meaning other users
  a	abbreviation for "all", a combination of u,g,o (estimated to be all if no characters are used)

•  the command to be performed

• +	add
  -	remove
  =	specify (Existing properties disappear.)

• the permission to be set

• r	read
  w	write
  x	execute

Examples of frequently used options

+x	Add execution permission to all users (owners, groups, and others)
u+x	Add execution Permission to Owner
u-x	Remove the owner's execution permission
o-rw	Remove other users' "read and write" permissions
go=rw	assign "read, write" permissions to  groups and other users(remove if they previously had execute permissions)
u+x,go=rw	Add execution rights to owner and assign "read and write" permissions to groups and other users
a=rw	Assign "read, write" permissions to all users
g-w	Remove "write" permissions for group owners
g+w,o-x	Add "write" permissions to group owners, remove "write" permissions from other users

#chmod #permission #permission deny #linux #linux permission