[Samsung Galaxy Grand Quattro] Arinio:
Symbolic Mode In Details

First let us learn the THREE abbreviation used in the symbolic mode:

+ : This Add the specified permission to the existing permissions.

- : This Removes the specified permission to the existing permissions.

= : This Set the permission to the specified level. erasing all the existing permissions. [Use this with caution]

Now we know there are FOUR type of users, i.e. u, g, o and a.

So to add, take away and setting permissions we can use the chmod command as:

chmod o+rw [Other user will get Read and Write permissions for a file or folder.

chmod o-w [Other user cannot edit/delete the file or folder.

chmod a=rw [All existing permissions from All Type of users will be taken away and then All users will get ONLY Read and Write Permission.

Let me show you by example how to change permissions.

For safety we will work inside the temp folder of Ubuntu OS.

So,

arinio@ubuntu:~$ cd /

arinio@ubuntu:/$ dir

bin dev initrd.img lib32 lost+found opt run sys var

boot etc initrd.img.old lib64 media proc sbin tmp vmlinuz

cdrom home lib libx32 mnt root srv usr

arinio@ubuntu:/$ cd tmp/

arinio@ubuntu:/tmp$ ls -l

total 24

drwx------ 2 root root 4096 Jan 2 22:18 pulse-PKdhtXMmr18n

drwx------ 2 arinio arinio 4096 Jan 2 22:18 ssh-6xx4zpMOpBFj

-rw-rw-r-- 1 arinio arinio 0 Jan 2 22:18 unity_support_test.0

drwx------ 2 arinio arinio 4096 Jan 2 22:18 vmware-arinio

drwxrwxrwt 2 root root 4096 Jan 2 22:18 VMwareDnD

drwxr-xr-x 2 root root 4096 Jan 2 22:18 vmware-root

drwx------ 2 root root 4096 Jan 2 22:18 vmware-root-4013264614

Now let us pick the unity_support_test.0 file.

-rw-rw-r-- 1 arinio arinio 0 Jan 2 22:18 unity_support_test.0

The permission column shows rw-rw-r--

This means User (u) is having r (Read) and w (Write) permission.

User Group (g) is having r (Read) and w (Write) permission.

Others (o) is having r (Read) permission.

Let us assign Write (w) permission to Others (o).

So,

arinio@ubuntu:/tmp$ chmod o=w unity_support_test.0

Nowlet us observe the change:

arinio@ubuntu:/tmp$ ls -l

total 24

drwx------ 2 root root 4096 Jan 2 22:18 pulse-PKdhtXMmr18n

drwx------ 2 arinio arinio 4096 Jan 2 22:18 ssh-6xx4zpMOpBFj

-rw-rw--w- 1 arinio arinio 0 Jan 2 22:18 unity_support_test.0

drwx------ 2 arinio arinio 4096 Jan 2 22:18 vmware-arinio

drwxrwxrwt 2 root root 4096 Jan 2 22:18 VMwareDnD

drwxr-xr-x 2 root root 4096 Jan 2 22:18 vmware-root

drwx------ 2 root root 4096 Jan 2 22:18 vmware-root-4013264614

So, all permissions first taken away from Other user (o) and then Write (w) permission is set to Other user (o).

Now let us Add Read (r) and Execute (x) permission for this perticular file to Other user (o).

So,

arinio@ubuntu:/tmp$ chmod o+rx unity_support_test.0

Nowlet us observe the change:

arinio@ubuntu:/tmp$ ls -l

total 24

drwx------ 2 root root 4096 Jan 2 22:18 pulse-PKdhtXMmr18n

drwx------ 2 arinio arinio 4096 Jan 2 22:18 ssh-6xx4zpMOpBFj

-rw-rw-rwx 1 arinio arinio 0 Jan 2 22:18 unity_support_test.0

drwx------ 2 arinio arinio 4096 Jan 2 22:18 vmware-arinio

drwxrwxrwt 2 root root 4096 Jan 2 22:18 VMwareDnD

drwxr-xr-x 2 root root 4096 Jan 2 22:18 vmware-root

drwx------ 2 root root 4096 Jan 2 22:18 vmware-root-4013264614

Lastly, let us keep the file with its default permission i.e only Read (r) for Other user (u).

So, once again,

arinio@ubuntu:/tmp$ chmod o-wx unity_support_test.0

Let us observe the change:

arinio@ubuntu:/tmp$ ls -l

total 24

drwx------ 2 root root 4096 Jan 2 22:18 pulse-PKdhtXMmr18n

drwx------ 2 arinio arinio 4096 Jan 2 22:18 ssh-6xx4zpMOpBFj

-rw-rw-r-- 1 arinio arinio 0 Jan 2 22:18 unity_support_test.0

drwx------ 2 arinio arinio 4096 Jan 2 22:18 vmware-arinio

drwxrwxrwt 2 root root 4096 Jan 2 22:18 VMwareDnD

drwxr-xr-x 2 root root 4096 Jan 2 22:18 vmware-root

drwx------ 2 root root 4096 Jan 2 22:18 vmware-root-4013264614

Hope there is now no doubt to you all.