Access permission /opt/ in Ubuntu

Question

I want to access my /opt/ folder. I have found the following commands for giving access permission.

I am not sure what is the purpose of this commands, which one is the better to use it to maintain security and access permission both.

I want to understand the number system within this command.

sudo chmod 755 -R /opt/

sudo chmod 755 /opt/

sudo chmod 775 /opt/

sudo chmod 777 /opt/

I didn't know these commands, so what I use to do previously was gksudo nautilius then:

Right click > change the owner from root to current user group

Now I have found the chmod command I would like to better understand how this command works and how best to implement it.

Solution

The positions about numbers is in this way:

• first position -> permisions for the Owner (current user)
• second position -> permisions for the Group (set by owner)
• third position -> permisions for anyone else

So the numbers means:

0 – no permission, this person cannot read, write or execute
1 – execute only
2 – write only
3 – execute and write only (1 + 2)
4 – read only
5 – execute and read only (1 + 4)
6 – write and read only (2 + 4)
7 – execute, write and read (1 + 2 + 4)

For example:

sudo chmod 755 /opt/ 

Owner -> can execute, write and read
Current user -> can execute and read only
Anyone else -> can execute and read only

Comments

[Nir Alfasi]

did you try man chmod ? or simply google: chmod

[Admin]

@alfasin : No i have not ....wait i will try

[tripleee]

These commands are absolutely the wrong solution. The proper solution is to use sudo for the operations which require administrator privileges. If you don't have sudo access, obtain it.

[Admin]

@tripleee : I am learning commands as I am going in deeper with ubuntu ..found it amazing to use !!! have started looking in to help documentation of ubuntu... hope i will make it soon