Login node¶
One connects to the ASC systems through the use of "login nodes". They serve as a connection between the clusters of ASC and the outside world.
Login nodes are a shared resource that are used among all the users logged in into the system, and as such, if it becomes slow or it crashes all users are affected. For this reason we do not allow you to run anything but the most essential things on the login node. Please, don't run things that will inconvenience other users. The risk of affecting other users increases with the more CPU and memory you use, and the longer you use it.
On the login node, one can:
- Submit batch and interactive jobs.
- Copy, edit, and delete files.
- Transfer files from and to the system.
- Run applications that use small amounts of CPU and memory.
- Compile code (4 threads max).
Running on the login node
Do not run compute-, memory-, or i/o-intensive applications on login nodes. These nodes are shared resources. ASC operations may terminate processes that negatively impact other users or the systems.
If the ASC support team gets complaints from other users or by automatic monitoring about improper use of the login node, we will kill your processes. An email notification will be send if this happens.
If you notice a login node being slow or behaving unexpectedly, take a look here.
Usage Limits¶
None the less, ASC has implemented usage limits on login nodes via Linux cgroup limits with the purpose of avoiding unintentional overuse of resources and provide a better interactive experience for all ASC users.
The following memory and CPU limits have been put in place on a per-user basis (all processes combined from each user):
Additionally, all users on a node together can only use up to 80% of the available resources to allow admin access