s (setuid) means set user ID upon execution. If setuid bit turned on a file, user executing that executable file gets the permissions of the individual or group that owns the file.

What does S mean in permissions Linux?

SUID is a special file permission for executable files which enables other users to run the file with effective permissions of the file owner. Instead of the normal x which represents execute permissions, you will see an s (to indicate SUID) special permission for the user.

What is S in chmod command?

chmod has the following syntax: chmod [options] mode file(s) The ‘mode’ part specifies the new permissions for the file(s) that follow as arguments. A mode specifies which user’s permissions should be changed, and afterwards which access types should be changed.