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Sync users across nodes

Any time you add a new user on your cluster’s head node or make changes to an existing user, you will need to synchronize those changes across the entire cluster. Advanced Clustering makes this a simple task by using our act_authsync utility. This utility takes all system user configuration files and pushes them out to […]

Installing Libraries for Python Outside of System Directories

Python is being used more frequently in HPC applications. Whether a job is being run by the scheduler or pre/post-processing on login nodes, there’s a chance you may run into it. With Python comes the need for libraries. Installing the libraries in system directories normally isn’t possible, but there is a good solution for that. […]

Taking Compute Nodes Down for Maintenance

When taking your compute nodes down for any reason, it’s good to take that node out of any job queues in which it may be a member. Nodes coming up temporarily may start new jobs, only to be shut down again, killing the user’s job. Here’s how to safely pull a node out of service […]

Pinpoint a failed drive in your array

If you see that your LSI RAID array has a failed disk, but you’re not sure which physical disk in the machine it is, use the MegaCli command line utility to flash the drive’s LEDs: Command syntax: MegaCli64 -PdLocate <-start|-stop> -physdrv[<enclosure#>:<disk#>] -a<adapter#> In this example, we will locate disk 0 on adapter 0 (the first […]

Getting package information

By using the ‘rpm’ command (RPM Package Manager) is is possible to get a lot of information about installed packages on your system. To start, say we want to see if we have a specific package name installed on our system. We can search all the currently installed packages for a package named ‘actutil’ by: […]

Viewing your system’s event log through IPMI

If your system has IPMI (Intelligent Platform Management Interface), it can be useful to pull its system event log when encountering odd behavior. If you have a cluster installed with our act_utils software tools, you can use the act_ipmi_log command (replace “node01″ with the hostname of the machine you wish to query): $ act_ipmi_log -n […]

Using VNC to Speed Up Slow X-forwarded Sessions

Most of you know that you can use X-forwarding built into SSH to run a graphical application on a remote host: laptop$ ssh -X head.mycluster head$ firefox & (Firefox session displays on your laptop, running on the remote host) But sometimes these programs run very slowly over the network. Firefox can be slow to render, […]

Use Screen to Run Long Processes

Tech TipScreen is a Linux utility that allows you to run multiple terminals all within a single terminal window manager. It can be used for many things and greatly increases workflow. Screen enables you to run your long scripts/processes within a screen session. If you want to execute a script that generally takes a very […]

Update Initrd

Have you blacklisted a kernel module, but it’s still showing up at boot? You probably need to update your initrd, a compressed filesystem used to bootstrap the OS. Simply run “dracut –force”, and the initrd will be recreated, taking into account any configuration changes made in your /etc filesystem. Then reboot. Your changes are now […]

Re-imaging a compute node back to a working state

If you accidentally misconfigure software on a cluster compute node you can always revert it back to a working image. In order to prepare a node for imaging you first set it to boot into the cloner3 image the next time it powers on: $ act_netboot -n <node name> -set=cloner3 Next you simply reboot the machine […]

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