Although there are already a lot of good security features built into Linux-based systems, based upon the need for proper permissions. Wrong file permission may open a door for attackers in your system.
Group Permission
Owner—The Owner permissions apply only the owner of the file or directory; they will not impact the actions of other users.
Group—The Group permissions apply only to the group that has been assigned to the file or directory; they will not affect the actions of other users.
All User/Other—The All Users permissions apply to all other users on the system; this is the permission group that you want to watch the most.
Each file or directory has three basic permission types:
Read—The Read permission refers to a user’s capability to read the contents of the file.
Write—The Write permissions refer to a user’s capability to write or modify a file or directory.
Execute—The Execute permission affects a user’s capability to execute a file or view the contents of a directory.
File permission is in following format.
Owner Group Other/all
root@Net:~# ls -al
We will talk about aforementioned command later on in this post.
-rwxr-xr-x 1 net tut 77 Oct 24 11:51 auto run
drwx------ 2 ali tut 4096 Oct 25 2012 cache
File auto run permission
-—No special permissions
rwx—Owner (net) having read, write, and execute permission while group (tut) having read and execute and other also having same permission.
File cahe permission
d—Represent directory
rwx—Owner (ali) having read, write, and execute permission while group (tut) and other/all does not have any permission for accessing or reading this file.
Linux Advance/Special Permission
l—The file or directory is a symbolic link
s—This indicated the setuid/setgid permissions. Represented as a s in the read portion of the owner or group permissions.
t—This indicates the sticky bit permissions. Represented as a t in the executable portion of the all users permissions
i—chatter Making file unchangeable
There are two more which mostly used by devices.
c—Character device
b—Block device (i.e., hdd)
some examples
Link Permission
root@net:~#ln -s new /root/link
root@net:~#ls -a
lrwxrwxrwx 1 ali ali 3 Mar 18 08:09 link -> new
link is created for a file name called new (link is symbolic for file name new)
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