iDRAC Tools supported on ESXi also. You can download supported iDRAC Tools from below link. Type "iDRAC Tools" is keyword and select correct operating system from drop down menu. [URL]  You can try unplugging & insert power cord. We seen it is fixing the problem most of the time. It is also depend on type of failure. Issue can persist If there are corruptions on the H/W itself.  
tired to search articles and documents but not sure about all the possible methods to update iDRAC firmware, especially after disaster. Currently I got poweredge R740 server with iDRAC9.   The easiest way I know to update iDRAC9 firmware is via the WEB UI. So simple.   What if disaster happens? Such as a brutal power cut during iDRAC update? The document (p.45)said that "If the iDRAC firmware update is interrupted, you may have to wait up to 30 minutes before attempting another firmwareupdate." But my question is, if the iDRAC web UI can no longer be accessed after the disaster described above, will the SSH + RACADM cli work to update iDRAC? Or maybe "racadm racreset soft -f"/"racadm recreset hard -f" is powerful enough to recover the iDRAC back to normal? BTW, is it doable to update/recover iDRAC firmware from BIOS?   Thanks in advance. Hope these doubts are not too stupid...
ways to update iDRAC9 firmware?