Comment 5 for bug 1495207

an empty channel.ini file is certainly not right. You can copy the one from the other device you have. It should look something like

 adb shell system-image-cli -i

current build number: 25
device name: krillin
channel: ubuntu-touch/stable/bq-aquaris.en
last update: 2015-09-09 09:13:11
version version: 25
version ubuntu: 20150825.1
version device: 20150821-736d127
version custom: 20150821-887-33-32-vivid

If you want to be sure you actually have all of r25 ota6 you could do this after restoring the channel.ini file

sudo system-image-cli -b 0

This will reinstallll the entire image but not remove any data