I agree the Linaro instructions are a little confusing, they take you to too many places and have too many options. Additionally they have instructions for booting from SDCard to run Linux, and booting from SDCard to install into the eMMC.
Based on the fact that you are getting a command prompt, I think you have copied the wrong image onto your SDCard. You can figure out which image you need by looking at the file sizes. The smaller SDCard image just boots from the SDCard to a command prompt . The larger SDCard image boots to the installer screen, and then has all of the files that need to be copied over to the eMMC. You want the larger image.
For Build 283 the two files I am discussing are:
- dragonboard410c_sdcard_install_debian-283.zip this is a 1.1G file and when unziped is about 3GB
- dragonboard410c_sdcard_developer_debian-283.zip this is a 450M file and when unziped is about 1.4GB.
You want to copy the larger unziped file to your SDCard. As you can see it is (roughly) double the size, this is because it contains two copies of Debian, the copy it boots from, and the copy it transfers to the eMMC.
Assuming you get to the installer screen, simply select the image, and click OK to get it to copy the image onto the eMMC. After the copy is complete remove the SDCard, throw it away, and boot directly form onboard eMMC, the SDCard is no longer required.
I hope this solves your problem.
Full Disclosure: I am an employee of Qualcomm Canada, any opinions I may have expressed in this or any other post may not reflect the opinions of my employer.