Tackling group permissions on TACC

1. Once you get added to a TACC allocation, you will belong to the group (gid) associated with that allocation.

2. A user can belong to multiple groups, but will have a default group.

3. In order to make a directory and its contents readable by a group, say, 801020, do the following:

chgrp -R 801020 directoryname
chmod -R -g+rX directoryname

4. In order to avoid doing this for every file you create, add the following to your profile: This will make sure files that you generate will automatically be group readable.

umask 002

You'll also need to change from your default group to the group the client belongs to.

newgrp -G-801020

5. Alternatively, you can set the group ID on a client's directory, and then set the setgid flag on the directory so that all subdirectories and files created in the directory from that time forward inherit the same group ID:

chgrp 801020 directoryname
chmod g+s directoryname

Recursively Sharing Files In A Directory With Your Group

Taken directory from a TACC login tip:

Here's a great way to set permissions recursively to share a directory named projdir with your research group:

$ lfs find projdir | xargs chmod g+rX

Using lfs is faster and less stressful on Lustre than a recursive chmod. The capital "X" assigns group execute permissions only to files and directories for which the owner
has execute permissions

Finding The Group ID For An Allocation

A list of group IDs and users associated with the group is in the file /etc/group on Lonestar. Using grep with usernames should let you narrow down which group ID is associated with which allocation.