I have created a file and set the permission to read and write only for user and group. Here is how I did it:

chmod filename 660

I used ls -l to see and the changes are right so, why is it saying permission denied when I try to change into it. When I type cd filename, I am told permission denied. Why?

Directories need execute permissions.
Try...

chmod 770 dirname

Yeah I tried with execution, even 700 it works. But I don't understand because this is homework given us by the teacher and unless it is a mistake, it is stated clearly that we should create three directories and then change their permission to read and write only for user and group. And then they said we should change to one of the directories. Maybe it was a mistake?

the correct syntax is
chmod 660 filename

also, make sure you(user) is the owner or belong to the group of the filename.


cheers,
Devaraj Takhellambam

Sorry, my mistake but I wrote it as chmod 660 filename. And yes, the PC belongs to me.

access permissions take a different meaning for directories. Here's what they mean:

• Read determines if a user can view the directory's contents, i.e. do ls in it.
• Write determines if a user can create new files or delete file in the directory. (Note here that this essentially means that a user with write access to a directory can delete files in the directory even if he/she doesn't have write permissions for the file! So be careful with this.)
• eXecute determines if the user can cd into the directory.
To be safe you should keep R and X together on directories.


in your case you have no "X" and so cant CD into the directory.