Using Penn Medicine Academic Computing Services (PMACS)

Table of contents

  1. Obtaining PMACS LPC Access
  2. Logging in to PMACS LPC
  3. Submitting tickets
  4. Making a project directory
  5. Loading modules and accessing module software
  6. Requesting software installations
  7. Installing Flywheel on your PMACS account
  8. Cloning and Updating GitHub Repos on PMACS
  9. Mounting a PMACS project directory on your local machine
  10. Enabling X11 forwarding
  11. Transferring files to and from the LPC
  12. Viewing niftis
  13. Using the batch system

This section gives an overview of how to get started on PMACS Limited Performance Computing (LPC) cluster. For additional information, check out the LPC wiki.

Obtaining PMACS LPC Access

Send your PI your Pennkey, full name, and Penn email, and have them forward this information to and request access for you. When access has been granted, you will receive an email with a temporary password through SecureShare. Log in via this link with your temporary password and set a new PMACS password. Your Pennkey and new PMACS password will be used to ssh into the LPC and to access the PMACS help desk/ticketing system.

Logging in to PMACS LPC

Once you’ve set up your login credentials for the PMACS LPC, you can SSH into the LPC from anywhere (even without Penn VPN). You can SSH into PMACS as follows:

$ ssh -Y [username]

Enter PMACS password when prompted. You can submit jobs on scisub.

In general, there is a set of software libraries and tools we expect you’ll need, such as R, conda, and FSL; we’ve made these available for you in a module. To load this module, simply type the following:

$ xbash
$ source /project/bbl_projects/apps/

You can also add the source line to your bash profile (add the line in the file ~/.bash_profile) so that it loads automatically every time you sign in.

Submitting tickets

Log in to the PMACS Help Desk with PMACS credentials. Under “Quick Actions” click “Need help? Report it.” Submit ticket under appropriate category.

Making a project directory

New project directories must be created for you by PMACS LPC admin. To have a new project directory created, you need to submit a ticket. Log into the PMACS Help Desk with PMACS credentials, and submit a “Systems” ticket specifying the desired project folder name (e.g. grmpy_diffusion) and who should have read access and read/write access to the folder (e.g. bbllpc). Once made, project directories can be found in project/ (e.g. /project/grmpy_diffusion).

Loading modules and accessing module software

Environment modules are used to load and unload available software (e.g. ANTs, mrtrix, R, ITK, dcm2niix, fsl, freesurfer, etc.). Hence, in order to use most software/applications that are available on PMACS, you must first load the appropriate module. To check which modules are available on PMACS, type module avail. To load a desired module, use module load [modulename]. Finally, to see what modules you have loaded, use module list.

For example, if I want to load python:

$ module load python # automatically loads latest version
$ python
$ exit()

Modules can be loaded and unloaded both in the log in node and in an interactive shell. You can access interactive shells via ibash (standard) or xbash (used for graphics, X11 forwarding enabled). In order to use some module software, however, you must be in an interactive shell!

For example:

$ module load mrtrix3/current
$ mrstats

will return -bash: mrstats: command not found


$ ibash
$ mrstats

will now reveal help documentation for mrstats.

In what circumstances do you use ibash you ask? From the LPC wiki:

“Use the interactive shell to:

  • Prepare you submit scripts
  • Find apps, browse appl
  • Work on anything you don’t have access to on the submit host
  • Browse /project/group directory
  • Prototype code and test apps”

Requesting software installations

Open source free apps and most imaging software needs to be installed by PMACS admin. This means you can’t install R, Stata, or Python packages on your own. You can submit a “Systems” ticket at PMACS Help Desk requesting that new software be installed.

Installing Flywheel on your PMACS account

You can install the Flywheel command line interface (CLI) locally, which is helpful as the CLI version updates frequently. Follow these steps to install the Flywheel CLI and gain access to fw commands. Complete these steps on the log in node, not in an interactive shell.

  1. Install miniconda in your home directory (/home/[pmacs username]):
    $ wget
    $ bash ./ -b -p $HOME/software/pkg/miniconda3
  2. Load miniconda
    $ source $HOME/software/pkg/miniconda3/bin/activate # should be whatever folder miniconda3/bin/activate is in
  3. Create flywheel python environment and activate it
    $ conda create -n flywheel anaconda python=3
    $ conda activate flywheel
  4. Install flywheel-sdk
    $ pip install flywheel-sdk
  5. Install flywheel-cli
    $ wget
    $ unzip
  6. The fw executable should be in the linux_amd64 folder. Add this directory to your path so that the fw command is accessible from all locations
    $ echo "export PATH=\$PATH:~/linux_amd64" >> ~/.bashrc
  7. Log in to flywheel using your API key (obtained from your Flywheel User Profile)
    $ fw login$APIkey
    $ fw status
    $ You are currently logged in as $username to

Note: Sometimes fw status gets you this error message: 'Connection to timed out. (connect timeout=10)')': /api/auth/status. In this case, logging out of PMACS and logging in again should fix the issue.

Cloning and Updating GitHub Repos on PMACS

If you have already created an ssh private key for your PMACS account and have added it to both the ssh-agent on PMACS (~/.ssh/id_rsa and files) and to your GitHub account, you can clone, pull, and push git repositories using sciget and an available github module on PMACS.

Specifically, to clone and update repos you should first ssh in via sciget (rather than via scisub). Sciget allows connections to outbound networks.

$ ssh -Y [username]

Next, load a git-related module.

$ module load git/2.5.0 #or git-lfs/2.2.1

You can now use github as you normally would.

If you have not yet set up your PMACS ssh key, follow these instructions. You will only need to do this once.

  1. Generate a new ssh key using your github-associated email.
    $ ssh-keygen -t rsa -b 4096 -C "{}"
    • When promted to “Enter a file in which to save the key,” press Enter. This accepts the default file location.
    • When promted, enter a secure passphrase.
  2. Add your ssh key to the ssh-agent
    $ eval "$(ssh-agent -s)"
    $ ssh-add ~/.ssh/id_rsa
  3. Add your ssh key to your GitHub account.
    • Sign in to GitHub
    • Click on your profile photo and click Settings
    • Click SSH and GPG keys in the Settings sidebar
    • Click New SSH Key. “Title”: enter a relevant title for the new key (e.g. PMACS account). “Key”: copy the text in your ~/.ssh/ file (which should start with ssh-rsa and end with your email) and paste it into the Key text box. Click Add SSH Key.

Mounting a PMACS project directory on your local machine

  1. If you are using a Mac, first install OSXFuse and SSHFS.

  2. Make an empty mount point folder on your local machine. Make sure that only the user (not group or others) have access to this mount directory!
    $ mkdir /Users/$username/ImageData/PMACS_remote
    $ chmod 700 /Users/$username/ImageData/PMACS_remote
  3. Mount the desired PMACS directory to your newly created, local mount directory using sshfs and sciget
    $ sshfs [username]<my-folder-on-PMACS> <my-local-mount-folder> -o defer_permissions,volname=project
  4. Unmount when done! You should run this unmount command from outside of the mount point.
    $ diskutil umount force /Users/$username/ImageData/PMACS_remote

Enabling X11 forwarding

To use graphics on PMACS, make sure that you:

  • Have XQuartz installed on your local Mac
  • log in to scisub via ssh -Y
  • use xbash for your interactive shell

Transferring files to and from the LPC

  • You can transfer files to and from PMACS with This can be used with SFTP, rsync, and scp. (You cannot use transfer for ssh).
  • Sciget can be used with scp, but transfer is reccomended. As in:
    $ [apines@chead ~]$ scp /data/jux/BBL/projects/multishell_diffusion/processedData/multishellPipelineFall2017/*/*/prestats/eddy/*_msRD.nii.gz
  • Transferring from cluster-to-cluster instead of through your local machine will run orders of magnitude faster. This is particularly true if you happen to be in the midst of a global pandemic and are relying on your home wifi.
  • Make sure you have full permissions for the destination you are writing to.

Viewing niftis

  • In order to use flseyes or afni to view images on a mac, in your local terminal, type:
    $ defaults write org.macosforge.xquartz.X11 enable_iglx -bool true
  • Restart your mac and then ssh onto PMACS, you should now be able to view images

Using the batch system

PMACS uses IBM’s Load Sharing Facility (LSF) to submit and monitor jobs. This is very different from SGE used on CUBIC. The biggest differences are you will use bsub to submit jobs and bjobs to monitor jobs instead of SGE’s qsub to submit jobs and qstat to monitor jobs.

The documentation for LSF can be found here.