Q. We have a small graphics department with 4 Macs with external hard drives and no server. We use each otherâ€™s files often but we have a problem with permissions. The files are often locked so we canâ€™t open them and save them. Itâ€™s very frustrating. How can we get rid of permissions?
A. The problem is that you can’t get rid of permissions. Since MacOS X is Unix, file permissions are at the core of every file. Every file and process on the Mac belongs to a user and a group. Permissions are set up to protect the system from the users and to protect each userâ€™s files.
However, you can get around them or get them to work for you. If you log into the other Macs as “guest” or as a valid user then you can change the permission on a folder (and it’s contents) to be accessible by that user.
Simply stated to change the permissions select the file or folder in the Finder and choose “Get Info” from the â€œFileâ€ menu. Under â€œOwnership & Permissionsâ€ click the triangle to expand and see the Details. You should see the â€œshortnameâ€ of the â€œOwnerâ€, the â€œGroupâ€ of the owner and â€œOthersâ€. In order for someone to be able to open (read) and save (write) changes, they either have to be the owner or a member of the group to whom the file belongs.
The easiest way to control a file remotely is to login as the owner. However then you have the same access as the owner â€“ this means you have to be careful. You can create a generic log in to the Mac, such as â€œmacuserâ€ and use the same login on all the Macs â€“ but you would have to do this when youâ€™re setting up the Macs. The installer that sets up the computer doesnâ€™t explain this very well â€“ again to protect the computerâ€¦
Another choice you have is to create a second login user on each Mac and then change the permission for the group â€œstaffâ€™ on the folder you want to share. Every user login account on the Mac belongs to the group named â€œstaffâ€. In order to share a file in the folder, change the permissions for the group to be â€œstaffâ€ and set to â€œRead and Writeâ€. Also choose â€œApply to enclosed itemsâ€¦â€ to have the permission change all of the files and folders inside â€“ we refer to this as â€œrecursivelyâ€. The only drawback is that new file will only be â€œread onlyâ€ to staff until you change permissions.
There is also a shareware program called â€œSharePointsâ€ (www.hornware.com) which emulates the way that a MacOS X sever handles sharing. On a MacOS X Server, you set up folders as â€œshare pointsâ€ which allow all users in a group to have equal access to the files. This is the same way that MacOS 9 did file sharing as well.
Changing permissions on the command line
Of course, you can also change permissions on the command line. (You have been reading All of my articles – havenâ€™t you?) To change permissions, you have to change a fileâ€™s mode using the â€œchmodâ€ command. To change a fileâ€™s owner or group you use the â€œchownâ€ command.
To begin, open the Terminal app (Applications/Utilities/Terminal). You should then navigate to the folder that contains the file, using the â€œcdâ€ command. When you open the Terminal you are inside your home folder. (Type â€œpwdâ€ and Return to see the current or â€œpresent working directoryâ€.) You can list the files with â€œlsâ€ to see the files and folders. Use â€œls â€“laâ€ (thatâ€™s list with the options â€œlongâ€ and â€œallâ€) to see a long list:
timmitra@TimsG4  ls -la
-rw-r–r– 1 timmitra staff 87444 15 Nov 2005 Configuring.pdf
drwxr-xr-x 141 timmitra staff 4794 7 Jun 16:27 Desktop
drwxr-xr-x 47 timmitra staff 1598 18 Apr 13:16 Documents
-rw-r–r– 1 timmitra staff 3033258 6 Oct 2005 EngStudio 05.pdf
The first part shows the permissions (â€œdâ€ or â€œ-â€œ means a directory or file)
The â€œrwxâ€ is read, write or execute for owner, group and others.
Listed next are the Ownerâ€™s short name and group.
To change permissions so all can read and write use the command â€œchmod 755â€ and then the file or folder name. If you use the recursive option, â€œchmod â€“R 755â€ on a file then all the fileâ€™s contents will be made available. (Remember to be careful and you are opening all the files to be accessible.) If you want to make all files inherit the permissions of the folder, you can use â€œchmod 1755â€ and the folder (or â€œchmod g+s foldernameâ€). This turns on the sticky bit and all new files will have the same permissions.