In this video I’ll show you how to enable the Vmkernel System Info Shell (vsish) on an ESX host. The vsish is normally only available on an ESXi host but in this video you will see and learn that it’s also working on ESX. With vsish you can examine the VSI (VMkernel System Information) which can be useful when troubleshooting or adjusting advanced setting that are not exposed in the vSphere Client. My virtualization friend William Lam over at virtuallyGhetto has retreived a list with all the 250 hidden advanced settings. He created a great article about “What is VMware vsish?”. I don’t have to remind you that vsish is able to damage your system so use it with caution. You can also watch the HD version of this video on <YouTube> and <ScreenCast>.
Here's some additional information I've received from Krishna Raj Raja regarding vsish:
VSISH - VSI (Vmkernel Sys Info) Shell - is the interface to access/modify live vmkernel data structures/variables.
Nearly all the configurations under the /config node in vsish are modifiable through vCenter - Software settings -> Advanced settings.
Since vsish binary access vmkernel memory data structures it is build version dependent, one cannot use a vsish binary from one ESX build onto another ESX host with a different build.
vsi_traverse binary - dumps the VSI information into binary format - vm-support script command uses this to capture the system state. When collecting performance snapshot, vm-support script captures vsi snapshot every few secs. esxtop when run in replay mode will fetch data from the VSI snapshots instead of the data from the live system. vsish -c option allow vsish to fetch information from the vsi snapshot (generated by vsi_traverse) instead of using the live system.
