Specifically, uname -r is the command to be run. In this case, the IP address of the target remote node is listed ( 192.168.1.250). The -w option means that the IP address of the target’s node(s) is specified. This simple test gets the kernel version of a different node using the IP address of the other node. First pdsh CommandsĪ quick test ensures that pdsh is working correctly. If for some reason you see the following when you try running pdsh, then you have built it with rsh: can either rebuild pdsh without rsh or use the environment variable in your. bashrc file: export PDSH_RCMD_TYPE=sshīe sure to source your. If you happened to build pdsh with rsh and do not or cannot rebuild it, you can override rsh and make ssh the default by adding the following line to your. L list info on all loaded modules and exitĪvailable rcmd modules: ssh,exec (default: ssh) N disable hostname: labels on output lines select one or more misc modules to initialize first u seconds set command timeout (no default) t seconds set connect timeout (default is 10 sec) d enable extra debug information from ^C status b disable ^C status feature (batch mode) S return largest of remote command return values If rsh wasn't excluded, it would be listed here, too, and it would be the default however, it is highly recommended that you not build pdsh with rsh because it is such a security hole. Notice the available rcmd modules (rcmd is the “remote command” used by pdsh ) at the bottom of Listing 1 states that only ssh and exec are available. By default, pdsh uses rsh, which is not secure and should never be used. You might notice that I used the - without-rsh option in the configure command. Also, to make life easier, I put the directory on a filesystem that is shared with the compute nodes, which allows pdsh to run regardless of what system you are using. For production work, I would put them in /opt or the like just be sure the directory is in your path. These three lines put the binaries into /usr/local/, which is fine for testing purposes. Building and Installing pdshīuilding and installing pdsh is really simple if you have built code using GNU’s autoconfigure before. Using ssh inside the cluster should alleviate your fears about not using passwords. However, you need the ability to ssh to any node without a password (i.e., passwordless ssh). Only the client nodes need to have ssh installed, which is pretty typical for HPC systems. It allows you to run commands on multiple nodes using only SSH, so the data transmission is encrypted. The pdsh tool is arguably one of the most popular parallel shells. The shell I typically use – and that I have found a large number of other people using – is pdsh. Some of the tools are perhaps not as appropriate or useful for HPC but may be good for other tasks. However, some techniques will allow you to run parallel commands on a large number of nodes.Īmong the parallel shells available, many are written in Python, which has become a very popular DevOps tool. Parallel shells are more practical when used on a smaller number of nodes, on specific nodes (e.g., those associated with a specific job in a resource manager), or for gathering information that varies somewhat slowly. However, for those that might be asking if they can use parallel shells on their 50,000-node clusters, the answer is that you can, but the time skew in the results will be large enough that the results might not be useful (which is a completely different subject). Anything you want to do on a single node can be done on a large number of nodes using a parallel shell tool. This list is just the short version the real list is extensive.
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