NERSCPowering Scientific Discovery Since 1974


PDSF runs Scientific Linux 6.2 as its native operating system. The native operation system is not intended for general use. Instead, the chos utility is used to create a Scientific Linux environment on both the interactive nodes and in batch jobs. Currently Scientific Linux 6.4 (sl64) is the default.

You can use the chosenv command to see what chos you are in.

To automatically select a system version you need to create a file in your home directory named .chos (with the dot at the beginning). In this file you should have one and only one line:

In your .chos file:The operating system you get:
sl53 64-bit Scientific Linux 5.3
sl62 64-bit Scientific Linux 6.2
sl64 64-bit Scientific Linux 6.4

When you log in you should have a full, working environment with the system of your choice.

By default your batch jobs will run under the CHOS system version you submitted them from. If you want your batch jobs to run under a different CHOS environment from the one you are interactively working in, you can set the CHOS variable to the environment you want while submitting the job. This can be done as follows:

qsub -v CHOS=sl62 script_name

You can switch also "live" between system versions. This is intended for testing scripts and environments. It is generally recommended that users change chos by altering their ".chos" file and logging back in to the system. However, in some cases, it may be usefult to do some fast testing in the same shell. To do that, set the CHOS variable to the value for the desired CHOS and run the "chos" command. For example:

setenv CHOS sl62