Linux kernel supports the traditional concept of a Unix user.
Every user-space process has a user owner.
Every user-name has corresponding userid in kernel. Kernel does not know user-name.
Groups are sets of users. The primary purpose of groups is to allow a user to share file access to other users in a group.
If non-root users,
user2, are not in same user group(say
user1 cannot modify the files/directories owned by
If non-root users
user2 are in same user group(say
user1 can modify the files/directories owned by
user2 are in same group, then,
Does kernel allow
user1's process to send any signal(say
kill command) to a process owned by