In the “Disk Selection” step of the installation, make sure that the boot disk (the internal IDE/SATA disk of your host system) is NOT in the list of “Selected Disks” on which to lay out the file systems.
The steps to install Solaris 10 x86 on an external USB HD go something like this: I used Windows XP’s Disk Management tool (“Control Panel -> Administrative Tools -> Computer Management”, then “Storage -> Disk Management”) to delete existing partitions on my external USB HD. it should appear as unformatted, unpartitioned space to the installer. Make sure that the USB HD to install to has no existing partitions on it i.e.Make sure to run the Sun Device Detection Tool from whatever OS is installed on your system, as it will give you a very accurate indication of hardware device driver issues both before and after the installation.Make sure that your system supports booting from an external USB (storage) device otherwise this will be an exercise in testing the Solaris 10 installer!.Prior to booting from the Solaris 10 x86 installation DVD: I used the latest version of Solaris 10 x86 available, which as of June 09 was Solaris 10 x86 5/09 (U7), and used the full installation DVD. 80Gb Maxtor IDE hard drive (6L080P0) inside a Vantec NexStar 2 3.5″ IDE to USB 2.0 external hard drive enclosure.Dell Latitude D830 laptop with an Intel Core2Duo CPU and NVidia graphics.
In a nutshell, Solaris 10 x86 5/09 (also known as Solaris 10 x86 U7 or Update 7) is easy to install and boot off of an external USB HD. Since I came across very little information on whether or not such a setup was possible or even any information about how easy or difficult the process would be, I thought I’d document my experience of installing Solaris 10 x86 on an external USB hard drive. However, since it has a small HD and no spare partitions on it nor any capability for a 2nd HD the only choice was to try and install it on an external USB hard drive and boot off of the external USB-attached HD. I needed to install Solaris 10 x86 on a 64-bit system for testing some 64-bit compatibility issues in an existing app/system, and my Dell laptop was as good a choice as any.