Linux Frequently Asked Questions

The Linux Custer's frequently asked questions are located in the Knowledge Base in ServiceNow. Click the questions below to access their knowledge base article.

Setting Permissions on lxcluster.tlt.psu.edu

Since the migration to the new PASS space in the summer of 2008, setting permissions via "chmod" is not available, which directly effects making scripts executable. To make scripts executable follow the steps below. Also, here is a short movie version of the below steps: PASS Permissions Movie.

  1. In a browser, navigate to https://explorer.pass.psu.edu/explorer.cgi . Note, this will require you to authenticate via Web Access.
  2. Click on New Folder.
  3. Enter a new folder name. We recommend using bin for the name.
  4. Select the new folder (note you may need to click on "^-- Up One Folder") and click on Info.
  5. Click on "Go to permissions."
  6. In the "Choose Permission Type" box, click on Next.
  7. Click on the radio button for "Give Full Control" and click on Next.
  8. Click on Next without selecting either of the two radio buttons in the "Select User or Group Assignment" box.
  9. Click on Extra Permissions in the "Permissions summary for:" box.
  10. Select "Allow program files to be executed" and "Apply settings to all files and subfolders inside the (your path to the folder you created above)". This is important as any file you place in this directory will automatically inherit these permissions.
  11. Click on Confirm Change.
  12. Note that you will now see a box indicating "Success. All files in this folder and subfolders will be executable." This box is above the "Permissions summary for:" box.
  13. Watch the movie on PASS Permissions for an example of these steps. NOTE: the very last section, step 12, is displayed differently in the movie. No worries, the result is the same.

Using NFS ACL Tools to change file permissions 

We have been working with PASS system administrators and have developed a solution for setting the execution bit on files stored on PASS. Per their recommendation, we have installed some NFS4 ACL Tools on the cluster machines. These tools along with a wrapper script they’ve developed. Here is the information they supplied regarding the script and its usage:

The script at /pass/os/linux/usr/local/bin/chmod is a wrapper script PASS system administrators wrote which will attempt to do what the user probably wants when calling it as if it's a regular /bin/chmod command.

It will apply setuid, setgid and sticky bits as usual, which are not forbidden in PASS.

If it is a request to +x or -x, then it will use nfs4_setfacl from nfs4-acl-tools to set or remove execute permissions.

This script only handles a few use cases of the chmod command, and also won't cover any cases of when a file's permissions are set via chmod(2) or open(2), which compilers like gcc normally use to set file execution.

For best results, I would recommend that you provide the users instruction to call /pass/os/linux/usr/local/bin/chmod after calling the compiler command. When using make(1), use a Makefile such as for this trivial C program "myprogram" (those need to be tab indents, not spaces):

myprogram: myprogram.c

gcc -o myprogram myprogram.c

/pass/os/linux/usr/local/bin/chmod +x my program

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Last Updated September 26, 2016