simple local file sharing

Simple Local File Sharing

Here are some simple ways to share files on hood.math (or any Unix system) without emailing them or sending through a sharing service like DropBox or GoogleDocs.

1. Copy to /tmp

The /tmp directory is writable by all users. Copy your file there and then give it read permission for others:

 % cp afile /tmp/

 % chmod o+r /tmp/afile

Now anybody else can make a copy of it:

 % cp /tmp/afile mydirectory/.

2. Expose the original

You can make your original file accessible and readable by everyone right where it is, without copying it to /tmp. Let's say your userid is jdoe and the file called afile is in a subdirectory of your account called dir1.

First make the file readable by everyone:

 % chmod o+r dir1/afile

Then enable everyone to traverse your directory to get to the file by adding execute permission for others on the directory:

 % chmod o+x dir1

This does not allow everyone to see the entire contents of your directory; it merely lets them 'cd' through the directory to get to the file. They will not have permission to "ls /u/jdoe/dir1" but they will have permission to copy /u/jdoe/dir1/afile.

3. Use group permissions on a directory in your account

To restrict sharing to groups, rather than everyone, Unix groups are needed. Ask MFCF to create a group with the required members. Let's say the group name is team-a. Anyone in the group can create a directory in his or her account for sharing, associate the directory with the group, and set group permissions to allow group members access to the directory's contents:

 % mkdir team_a_project
 % chgrp team-a team_a_project  # set the group of the directory
 % chmod g+s team_a_project     # make new files automatically have group perms
 % chmod g+rx team_a_project    # this allows group reading
 % chmod g+rwx team_a_project   # this allows writing too, if you prefer

 % ls -al team_a_project       # check permissions and group membership of
                               # everything to ensure it's the way you want

There is already a group called amfluids that you can use. Run the command

 % grep amfluids /etc/group

to see who the members are. It may or may not match your needs.

4. Use group permissions on a shared directory outside of any users' accounts

With MFCF's help you can have a directory for sharing that is not in any one user's account. For example, /fsys3/team_a_project could be a directory for all members of the team_a group to share. Permissions would be set up for you the same as in method 3.