/usr/lib/ubuntu-release-upgrader/release-upgrade-motd is in ubuntu-release-upgrader-core 1:16.04.25.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | #!/bin/sh -e
#
# 91-release-upgrade - display upgrade message or update the cache
# in the background
#
# Copyright (C) 2010 Canonical Ltd.
#
# Authors: Dustin Kirkland <kirkland@canonical.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 3 of the License.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
stamp=/var/lib/ubuntu-release-upgrader/release-upgrade-available
if [ -f "$stamp" ]; then
# Stamp exists, see if it's expired
now=$(date +%s)
lastrun=$(stat -c %Y "$stamp") 2>/dev/null || lastrun=0
expiration=$(expr $lastrun + 86400)
if [ $now -ge $expiration ]; then
# Older than 1 day old, so update in the background
/usr/lib/ubuntu-release-upgrader/check-new-release -q > "$stamp" &
elif [ -s "$stamp" ]; then
# Less than 1 day old, and non-empty, so display now
cat "$stamp"
echo
fi
else
# No cache at all, so update in the background
/usr/lib/ubuntu-release-upgrader/check-new-release -q > "$stamp" &
fi
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