Difference between revisions of "FAQ"
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[[KTAU]] | [[ZeptoOS_Documentation|Top]] | [[KTAU]] | [[ZeptoOS_Documentation|Top]] | ||
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| + | ==How to obtain a CN node number== | ||
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| + | (some info on /proc/personality.sh) | ||
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| + | ==How to find the MPI rank from a shell script== | ||
==How to open a socket from a CN to the outside world== | ==How to open a socket from a CN to the outside world== | ||
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To enable the translation, pass <tt>ZOID_NAT_ENABLE</tt> environment variable when submitting a job. An administrator can also enable this option permanently in the [[ZOID#opt_enable_nat|config file]]. | To enable the translation, pass <tt>ZOID_NAT_ENABLE</tt> environment variable when submitting a job. An administrator can also enable this option permanently in the [[ZOID#opt_enable_nat|config file]]. | ||
| − | ==How to obtain a | + | ==How to obtain a Cobalt job ID== |
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| − | + | Cobalt passes the job id to the application processes launched on the compute nodes using the <tt>COBALT_JOBID</tt> environment variable. | |
| − | + | This variable is also accessible from the [[ZOID#User script|user script]] running on the I/O nodes, using the <tt>ZOID_JOB_ENV</tt> variable: | |
| − | == | + | <pre> |
| + | COBALT_JOBID=`echo $ZOID_JOB_ENV | sed 's/^.*COBALT_JOBID=\([^:]*\)/\1/'` | ||
| + | </pre> | ||
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[[KTAU]] | [[ZeptoOS_Documentation|Top]] | [[KTAU]] | [[ZeptoOS_Documentation|Top]] | ||
Revision as of 13:40, 28 April 2009
How to obtain a CN node number
(some info on /proc/personality.sh)
How to find the MPI rank from a shell script
How to open a socket from a CN to the outside world
ZOID provides IP packet forwarding between the compute nodes and the I/O nodes. However, because the compute nodes use non-routable IP addresses (192.168.1.x), they cannot communicate directly with the outside world.
The most transparent solution to this problem is to perform network address translation (NAT) on the I/O nodes using the Linux kernel netfilter infrastructure. We used to enable this by default, but experiments have shown it to have a detrimental effect on the overall performance of the TCP/IP stack on the I/O nodes, slowing down access to the network filesystems.
To enable the translation, pass ZOID_NAT_ENABLE environment variable when submitting a job. An administrator can also enable this option permanently in the config file.
How to obtain a Cobalt job ID
Cobalt passes the job id to the application processes launched on the compute nodes using the COBALT_JOBID environment variable.
This variable is also accessible from the user script running on the I/O nodes, using the ZOID_JOB_ENV variable:
COBALT_JOBID=`echo $ZOID_JOB_ENV | sed 's/^.*COBALT_JOBID=\([^:]*\)/\1/'`
