A while back I bought a 1TB USB external drive. I formatted it ext4 in Ubuntu and copied a bunch of files / folders to it from several machines, all to /home/machinename/whatever, respectively.
At some point I ran a chmod -R shell command on it to change the permissions. That was months ago and I don't remember what I typed but it made the drive so I could only access its /home folder as root. This wasn't a problem because I could still access everything, but today I decided to try to fix it.
I went to my shell as root, went to that drive and typed:
chown -R rick:rick ./
chmod -R 666 ./
It seemed to work. That home directory and everything else in it now shows up as rw for each:
rick@rick64:/media/aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee$ ls -l
drw-rw-rw- 7 rick rick 4096 2012-03-04 13:08 home
So, if I try to access that directory with the shell, I get:
rick@rick64:/media/aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee$ ls -l
drw-rw-rw- 7 rick rick 4096 2012-03-04 13:08 home
rick@rick64:/media/aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee$ cd home
bash: cd: home: Permission denied
rick@rick64:/media/aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee$ _
When I access it with nautilus I can see the multiple machine names within the /home/ folder, but they all appear with a file icon. I can right-click on them and choose "Properties" but it won't let me see the permissions.
Am baffled. Why can't I access that folder? I'm the owner? I'm even the group. I have r/w privileges. What am I doing wrong?
You're neither trying to read (list) nor write (create a new entry) the directory. You want to enter it, therefore you need (slightly misnamed in the case of directories) exexute permissions.
来源：https://stackoverflow.com/questions/10565367/why-cant-i-access-this-folder