Build a patched snapd

build-snapd.sh

#!/bin/bash
# Build snapd with longer time between forced refresh, effectively
# allowing systems to prevent any refreshes at all, "easily".

# While it's possible to defer updates to a later date, like this:
# $ sudo snap set system refresh.hold="$(/usr/bin/date --iso-8601=seconds -d '+30 days')"
# After 60 days, snapd will eventually force refresh, even if you run 
# the above command every day to push the refresh time back continuously.

# All this script does is build snapd with a way longer interval between
# 'forced' refreshes.

# To undo this, we patch snapd, rebuild and install it
# Allow us to push updates long into the future (1825 days, 5 years)
# Set maxPostponement = 1825 * 24 * time.hour
# Set maxInhibition = 1825 * 24 * time.Hour

# Patch only on Tuesday
# Set defaultRefreshSchedule = "tue,12:00"

# Temp dir to do the work in
WORKING_DIR="$PWD"
SNAPD_BUILDDIR=$(mktemp -d -p "$WORKING_DIR")

# What snap store channel should we yoink the snapd version from
SNAPD_CHANNEL="latest/candidate"

# Push updates back a ludicrous amount of time. Five years should do.
MAXPOSTPONEMENT="1825"
MAXINHIBITION="1825"

# When should refreshes happen, if they do
# Default is every day, four times a day
REFRESHTIME="tue,12:00"

# Get version in snap store from candidate, we build that
# That way we stay a little ahead of the stable channel, sometimes
CANDIDATE="$(snap info snapd | grep "$SNAPD_CHANNEL" | awk -F ' ' '{print $2}')"

# snap source is in github
SNAPD_SOURCE="https://github.com/snapcore/snapd.git"

# Clone the upstream source
cd "$SNAPD_BUILDDIR" || exit 8
if git clone -q $SNAPD_SOURCE; then
	echo "*** Cloned"
else
	echo "*** Failed to clone"
	exit 1
fi
cd snapd || exit 7
if git checkout -q "$CANDIDATE"; then
	echo "*** Checked out $CANDIDATE"
else
	echo "*** Failed to check out $CANDIDATE"
	exit 2
fi

# Patch things
if sed -i "s|const maxPostponement = 60|const maxPostponement = $MAXPOSTPONEMENT|" overlord/snapstate/autorefresh.go; then
	echo "*** Patched maxPostponement"
else
	echo "*** Failed to patch maxPostponement"
	exit 3
fi
if sed -i "s|const maxInhibition = 7|const maxInhibition = $MAXINHIBITION|" overlord/snapstate/autorefresh.go; then
	echo "*** Patched maxInhibition"
else
	echo "*** Failed to patch maxInhibition"
	exit 4
fi
if sed -i "s|00:00~24:00/4|$REFRESHTIME|" overlord/snapstate/autorefresh.go; then
	echo "*** Patched autorefresh default time"
else
	echo "*** Failed to patch autorefresh default time"
	exit 5
fi

# Build snapd remotely in the cloud!
# This means it'll build for whatever architecture you run this
# script on, and will not consume resources on your computer.
# In my experience when the builders aren't all busy, it takes
# ~30 minutes to build snapd
# Check it at https://launchpad.net/builders to see builder 'queue'
if snapcraft remote-build --launchpad-accept-public-upload --build-on amd64,armhf,arm64; then
    mv snapd_*.snap "$WORKING_DIR"
    mv snapd_*.txt "$WORKING_DIR"
    # Back from where we came
    cd "$WORKING_DIR" || exit 9
    # Remove the build temporary folder
    rm -rf "$SNAPD_BUILDDIR"
    ls -l1 snapd_*
else
	echo "Failed to build"
	exit 6
fi