Every now and then I find that I am battling permission issues in the unix environment and it usually turns out to be the permissions that are set on the directory or file. Unix has an interesting way of handling permissions. If you do a list command “ls -l” you will see a box of information on the left that looks like:
———- (10 dashes) If you see this, the file has NO rights (pretty rare).
The first position you will commonly see a “d” or “l”, the “d” is for directory, and “l” is for a link.
Position 2 to 4 are the owner permissions “rwx”, where “r” is read, “w” is write, “x” is execute
Position 5 to 7 are the group permissions “rwx”, where “r” is read, “w” is write, “x” is execute
Position 8 to 10 are the world permissions “rwx”, where “r” is read, “w” is write, “x” is execute
You can change the permissions using the command: “chmod”
To grant the read permission you give a value of 4, write permission is 2, and execute is 1. So if you want to grant read+write, you would do 4+2 = 6. And when you issue the chmod you give it a number for each permission (owner, group and world), so if you wanted to give the owner, group and world read and write access to a file you would issue the command:
chmod 666 filenametochangepermissionsto
Another useful function is the chown function, which changes the owner and/or group permission.
chown user:group filenametochangeownershipto
chown -R user:group directorytochangeownershiptorecursivelyto