Forem: Spencer Krum

Fixing "groot must be grub root device" on ibmcloud

Spencer Krum — Mon, 04 May 2020 22:19:43 +0000

Some images on ibmcloud have an issue when installing new kernels (and thus rebuilding the initramfs and grub config files).

# apt-get upgrade
...
Processing triggers for initramfs-tools (0.130ubuntu3.9) ...
update-initramfs: Generating /boot/initrd.img-4.15.0-42-generic
I: The initramfs will attempt to resume from /dev/vdc
I: (UUID=083a8bfd-95a8-4808-bd75-ed3c1be04dd4)
I: Set the RESUME variable to override this.
Setting up ubuntu-server (1.417.4) ...
Processing triggers for linux-image-4.15.0-99-generic (4.15.0-99.100) ...
/etc/kernel/postinst.d/initramfs-tools:
update-initramfs: Generating /boot/initrd.img-4.15.0-99-generic
I: The initramfs will attempt to resume from /dev/vdc
I: (UUID=083a8bfd-95a8-4808-bd75-ed3c1be04dd4)
I: Set the RESUME variable to override this.
/etc/kernel/postinst.d/x-grub-legacy-ec2:
Searching for GRUB installation directory ... found: /boot/grub
Searching for default file ... found: /boot/grub/default
Testing for an existing GRUB menu.lst file ... found: /boot/grub/menu.lst
uuid not supported. update 'groot' in /boot/grub/menu.lst

groot must be grub root device (ie '(hd0)'). not 'LABEL=cloudimg-rootfs'

run-parts: /etc/kernel/postinst.d/x-grub-legacy-ec2 exited with return code 1
dpkg: error processing package linux-image-4.15.0-99-generic (--configure):
 installed linux-image-4.15.0-99-generic package post-installation script subprocess returned error exit status 1
Processing triggers for ureadahead (0.100.0-21) ...
Errors were encountered while processing:
 linux-image-4.15.0-99-generic
E: Sub-process /usr/bin/dpkg returned an error code (1)

Ooof. Very annoying.

Until we get a fix everywhere, you can fix this very easily yourself.

Edit: /boot/grub/menu.lst

Find this section:

...
## default grub root device
## e.g. groot=LABEL=cloudimg-rootfs
# groot=LABEL=cloudimg-rootfs

...

Change # groot=LABEL=cloudimg-rootfs to # groot=(hd0) (leaving the comment)

Then have the package manager try again

# apt-get install -f

This should succeed without issue. Then you can reboot to test the change

# reboot

PSA on Docker Images

Spencer Krum — Sun, 12 Jan 2020 05:10:30 +0000

I was surprised to find that the ubuntu:latest tag was actually quite old.

The way it seems to work is this:

ubuntu:latest points to the last LTS release (now 18.04 which is pretty outdated)
ubuntu:rolling points to the last released version of ubuntu (currently 19.10).
ubuntu:devel points to the next to-be-released version of ubuntu (currently 20.04)

My thoughts on when to use each:

Broadly ubuntu as a base image isn't what I'd use for applications anyways, I'd use a base image like node or if making something myself I'd use an alpine base image. I mostly use ubuntu base images for docker images that I'll be using short term or interactively.

ubuntu:latest I probably won't use this ever again.
ubuntu:rolling I'll use this pretty much every time. Latest packages. Won't change on me. Drops support "soon" but if it does drop support I can just rebuild and I'll be on a supported image.
ubuntu:devel I'd only use this if I was specifically trying to get access to a bleeding-edge version of a package, probably on my way to getting something else to work.

Bash Prompt snip for IBM Cloud

Spencer Krum — Wed, 11 Dec 2019 23:19:53 +0000

The below script will add a pleasing visual queue of which account and region your are targeted at with IBM Cloud. Turn off color by setting $IBMCLOUD_PS1_COLOR_NO to any value. set_prompt and PROMPT_COMMAND example below is just an example and you can use the __ibmcloud_ps1 function anywhere you'd configure your prompt.

# From Arch Wiki

txtblk='\e[0;30m' # Black - Regular
txtred='\e[0;31m' # Red
txtgrn='\e[0;32m' # Green
txtylw='\e[0;33m' # Yellow
txtblu='\e[0;34m' # Blue
txtpur='\e[0;35m' # Purple
txtcyn='\e[0;36m' # Cyan
txtwht='\e[0;37m' # White
bldblk='\e[1;30m' # Black - Bold
bldred='\e[1;31m' # Red
bldgrn='\e[1;32m' # Green
bldylw='\e[1;33m' # Yellow
bldblu='\e[1;34m' # Blue
bldpur='\e[1;35m' # Purple
bldcyn='\e[1;36m' # Cyan
bldwht='\e[1;37m' # White
unkblk='\e[4;30m' # Black - Underline
undred='\e[4;31m' # Red
undgrn='\e[4;32m' # Green
undylw='\e[4;33m' # Yellow
undblu='\e[4;34m' # Blue
undpur='\e[4;35m' # Purple
undcyn='\e[4;36m' # Cyan
undwht='\e[4;37m' # White
bakblk='\e[40m'   # Black - Background
bakred='\e[41m'   # Red
bakgrn='\e[42m'   # Green
bakylw='\e[43m'   # Yellow
bakblu='\e[44m'   # Blue
bakpur='\e[45m'   # Purple
bakcyn='\e[46m'   # Cyan
bakwht='\e[47m'   # White
txtrst='\e[0m'    # Text Reset


# Prompt snippet to show ibmcloud account status 
__ibmcloud_ps1() {
    if [ -f ~/.bluemix/config.json ]; then
        ibm_user=$(cat ~/.bluemix/config.json  | jq '.Account.Owner' | tr -d '"')
        region=$(cat ~/.bluemix/config.json  | jq '.Region' | tr -d '"')
        if [ ! -z "${IBMCLOUD_PS1_COLOR_NO}" ]; then
            echo "${ibm_user}@${region}"
        else
            echo "\[${bldpur}\]${ibm_user}\[${txtrst}\]@\[${bldylw}\]${region}\[${txtrst}\]"
        fi
    fi

}


# Just an example of where this goes
set_prompt() {
    PS1="[$(__ibmcloud_ps1)]"
    PS1+="\[${bldgrn}\]\u@\h\[${txtrst}\]:\[${bldblu}\]\w\[${txtrst}\]$ "
}

PROMPT_COMMAND=set_prompt

xtrlock

Spencer Krum — Wed, 10 Jul 2019 18:45:19 +0000

Part of the devrel life is the booth. When I'm boothing, I like to have my laptop there and open to a cool project or demo. If I'm lucky, there will be a TV or monitor for me to connect to as well.

Folks will come up and talk to me and ask me questions. That's great and literally what I am there for. But I get squeamish about being a step or two away from my unlocked computer. I also don't want to close or lock my computer. A lock screen looks weird in a booth. If my laptop is closed it is annoying to tell someone 'let me show you!' then we both wait around for an agonizing few seconds while I reconnect to wifi/ssh/whatever.

Enter xtrlock(1). This utility has existed since at least 1993 and is part of a wonderful ecosystem of old Unix/X11 tools that have been largely forgotten.

From the man page: Lock X display until password supplied, leaving windows visible. This locks the screen for input, but leaves whatever I had open visible. That means slides, terminals, or demos are still being displayed and I have peace of mind that I'm not being compromised.

Pratically, xtrlock takes effect immediately and has no option for a delay. So what I actually do is type sleep 5; xtrlock and use the five second sleep to hide/minimize whatever terminal that command was written in.

I show various things, but one thing I'm trying to do is have terminal based demo scripts that can be run without my interaction. Unlike videos, they are running against real infrastructure, and I can ^C the script and dig in deeper to the demo with an attendee if I need to. That repo is here

Hello World

Spencer Krum — Wed, 10 Jul 2019 18:29:58 +0000

Yay I made a dev.to account!