1. How to access

We have available 3 Linux servers (40 cores and 512 GB RAM each):

In order to use them, you have to contact Hynek Baran who will create your account (you will be prompted for your CRO login, e.g., bar0001).

Terminal access by ssh

The preferred way to access these servers is a ssh connection:

  1. Activate VPN on your local machine if you are not connected to the university network directly.
  2. See the ovewiew of CPU and memory usage page to choose the proper machine.
  3. Use ssh with your CRO credentials (username and password same as at is.slu.cz). Example: 
    ssh bar0001@calc01.mic.slu.cz
  4. Hint: To enable passwordless login, use ssh keys, see e.g.:
  5. Use top or free -h to see the machine usage or available memory.

GUI access by Microsoft Remote Desktop

Alternatively, instead of the terminal ssh access, you can try Microsoft Remote Desktop client (using your CRO credentials) and run the Gnome GUI session. Unfortunately, the long-term stability of such a connection cannot be guaranteed.

User files

  1. Your home directory is shared within calc0* machines. From your local machine it can be accessed by sftp (connect by scp, Cyberduck, or WinSCP client to any of calc0* machines using CRO credentials).
  2. In addition, there is a common directory /home/share shared within all calc0* servers users.
  3. It is possible to access above shared directories by Samba client (experimental and not available by default, ask HB for the guidance).

Final cleanup

When your computations are done, please terminate them, otherwise the servers might get overloaded by unattended processes (use e.g., top, kill, or killall shell commands). You have no access rights to processes owned by the other users, so do not mind about the other people’s processes while killing yours.

2. Using tmux

tmux is a terminal screen multiplexer. It allows you to run, or keep an eye on, multiple programs within a single ssh terminal and keep the computations running even if you terminate your ssh session.

Getting In

tmux is installed and ready to use on the calc0* machines. To start a new session in tmux, simply use tmux new in your terminal

Once you are in tmux, the only thing that will be visibly different is the ever-present green bar at the bottom. All commands inside tmux are invoked by two keypresses: The prefix key (default: ctrl+b) followed by the tmux command key.

Detach

To get out of a session without exiting everything, you must detach the session. To do this, press:

ctrl+b d

This will detach the current session and return you to the normal shell. However, just because you’re out doesn’t mean your session is closed. The detached session is still available (and all the computations keep running).

List and Switch Sessions

To list all running tmux sessions, see previews, and interactively switch between them, press:

ctrl+b w

Use the up/down arrow keys and Enter to select.

If you are not in a tmux session yet, run:

tmux ls

Attach

You can go back to the last created session from the terminal with:

tmux a

To attach any other session from the terminal, list sessions using tmux ls. Each tmux session has a number associated with it, which can be used to attach. For example, to re-attach session number 3:

tmux a -t 3

Alternatively, inside a tmux session, press ctrl+b w and choose the window to attach.

Naming Sessions

You can rely on session numbers, but naming sessions makes them easier to manage. To start a new session with a specific name:

tmux new -s [name]

To reattach to a named session:

tmux a -t [name]

Exit

To exit a session, attach it and use the standard:

exit

To kill a session (including all its windows):

tmux kill-session -t [session]

Inside tmux, you can also press:

ctrl+b :

Then type kill-session to terminate the current session.

Note: These commands may not terminate all child processes. Please kill abandoned computations manually (e.g., with kill, killall, or top).

Final Overview

Command Line:

Keyboard Shortcuts (inside a tmux session):