Need a way to drive GRUB over serial port

[Loïc Minier]

Hi,

currently, our snappy x86 images default to setting up GRUB without serial port; to locally enable this, people are remounting the fs read-write and changing:
- "/mnt/rootfs/etc/default/grub.d/50-system-image.cfg" to have:
console=ttyS1,115200n8 instead of console=ttyS0

- "/mnt/rootfs/etc/grub.d/00_header" to have following after the first instance of the line "cat << EOF":
serial --port=0x2f8 --speed=115200 --word=8 --parity=no --stop=1

I'm not sure which way we would support this in snappy; perhaps ubuntu-core config?

Cheers,

[Michael Vogt (mvo)]

I wonder if we could simply enable this by default? Or is there a (security) risk here?

[Loïc Minier (lool)]

I suspect the serial port name might differ (e.g. ttyS0 and ttyS1) and that people might want to disable that if they actually need the serial port for something else.

It kind of feel like a deployment option to me: headless servers where you want to use an existing serial port, but some platforms wont have it; perhaps there's a smart way to detect it though, like "press space now to enable serial console" during grub startup?

[David Duffey (dduffey)]

I made an onie-installer, and I do a couple of things, I created an "isntaller.conf" that contains serial port settings that are read at the time snappy is laid down onto an ONIE device.

It modifies grub.cfg in system-boot as well as the snap space in system-a, and this seems to persist across reboots and ubuntu-core updates.

http://bazaar.launchpad.net/~david-duffey/+junk/snappy-onie-installer/revision/3