When not in position to go to the DC to access the ESX text mode interface use the DCUI command:
First you need to enable and start Remote Tech Support (SSH). This is done for the ESXi Host in Configuration -> Software -> Security Profile
Use an SSH client (putty) to connect to the ESXi host.
Once logged in simply run dcui
~ # dcui
To exit DCUI and return to the prompt use CTRL-C
KB article : here