File Permissions - Can Only Read

Select the external drive in the Finder and choose 'Get Info' from the File menu. Click on the triangle to the left of 'Sharing and permissions' if it is not already open. At the bottom of the window should be a padlock and if you click on that the finder will ask you to authenticate with your admin password.

After that you should be able to edit the list of users to read and write as desired.

Andy

That's odd. Is the drive formatted in HFS+? Have you connected it to a windows computer recently??

Hi Ewan Murray;

Since your external is formatted NTFS, your Mac is not able to write to it without third party software.

Allan

You can do it with terminal.

Open /Applications/Utilities/Terminal.app
(to view existing permissions)
At the prompt type
ls -aedl /Volumes/<volume_name>
#note: if volume name contains spaces, put name in quotes#
(press return)

live example:
Betsy7:~ kj$ ls -adel /Volumes/"Mac Data"
drwxrwxr-t@ 27 root admin 986 Feb 14 15:00 /Volumes/Mac Data

a. "drwxrwxr-t@" = posix permissions. in this case is "chmod 1775"
b. (owner=r/w, group=r/w, others=read),
c. "t" means sticky bit is set,
d. "@" means there are some other extended attributes.
e. root is owner, group is admin

Above is normal (usual) root directory permissions for a data drive (if everyone uses it).

to change ownership (to root as owner, group as admin):
sudo chown root:admin /Volumes/<volume_name>
example, if name is "mydata":
sudo chown root:admin /Volumes/mydata
(press return, enter admin password, press return again)
#note: additionally, "sudo" command it needed to change permissions, if you are not owner#

to change posix permissions to owner=r/w, group=r/w others=r and set sticky bit:
sudo chmod 1775 /Volumes/<volume_name>
example, if name is "mydata":
sudo chmod 1775 /Volumes/mydata
(press return, enter admin password, press return again)
#note: additionally, "sudo" command it needed to change permissions, if you are not owner#

for more info:
http://support.apple.com/kb/HT2963
http://www.takecontrolbooks.com/leopard-permissions?aff=AFL1361639390
http://aplawrence.com/Unixart/graphicalcommandline.html

paste results of these two commands if you want more help with terminal
commands to fix your permissions problems
ls -aedl /Volumes/<volume_name>
and
ls -ael /Volumes/<volume_name>

That way I can look at the permission structure of the problematic volume.

Kj ♘

KJK555
Thanks for the lesson. I never mount NTFS volumes, so it never occurred to me that it would be such a simple matter to change the permissions on one.

It is an NTFS Volume?

All that stuff I wrote won't work then.

Paragon NTFS (commercial) or NTFS 3G (freeware) will allow you to read/write.

http://www.apple.com/downloads/macosx/systemdiskutilities/ntfs3g.html

http://www.paragon-software.com/home/ntfs-mac/


Kj ♘