ESXi uses SYSLINUX as its boot loader and thus it is possible to add options to customize the initial SYSLINUX boot screen. In the below example we will modify syslinux.cfg to allow for a 200 second boot delay.
1) Boot your ESXi install with a Linux live CD. The SYSLINUX files are on a FAT16 partition so they should be automatically mounted. Once you have Linux running, you’ll want to run fdisk -l. You’ll want to identify the Hypervisor0 partition of your ESXi install (circled below). In my case this partition was mounted as /mnt/sda4 and that’s where the file syslinux.cfg was located.
2) Edit the file syslinux.cfg. You can run vi syslinux.cfg to start an editor. Do a search for VI editor if you haven’t used it before as the syntax for the editor can be tricky. Before you change the file it will contain the text “default safeboot.c32”. You’ll want to edit the file so that it looks like this. Note that the delay (timeout) is in 1/10 of a second so 2000 equals 200 seconds.
3) Once you have saved the file you can reboot your host. If you’ve made the changes correctly you’ll see this screen for 200 seconds. After 200 seconds ESXi will boot or you can press enter at any time to start booting ESXi immediately.