http://tyru.hatenablog.com/entry/2016/09/04/202117

etckeeper-setup-host.sh

#!/bin/bash
set -eu
set -x

KEY_COPY_DEST_DIR=/mnt/to/sshkeys/dir
GITLAB_HOST=gitlab-root.url
GITLAB_HOST_LIST='gitlabA gitlabB gitlabC'
GITLAB_GIT_REMOTE=git@${GITLAB_HOST}:etckeeper/etckeeper-$(hostname).git

get_gitlab_ip_list() {
	local host
	for host in $GITLAB_HOST $GITLAB_HOST_LIST; do
		getent hosts $host || true
	done | awk '$0=$1' | sort -u | paste -d , -s
}


if [ "$(id -u)" -ne 0 ]; then
  echo "Error: you must be root." >&2
  exit 1
fi

gitlab_ipaddr_list=$(get_gitlab_ip_list)
hostname=$(hostname)
sshdir=/root/.ssh
privkey=gitlab-$hostname
pubkey="$privkey.pub"
keydestdir="$KEY_COPY_DEST_DIR/$hostname/"

if [ ! -f "$keydestdir/$pubkey" ]; then
	# Make the keys to push to GitLab.
	rm -f "$sshdir/$privkey" "$sshdir/$pubkey"
	ssh-keygen -t rsa -C "${hostname}@${GITLAB_HOST}" -N '' -f "$sshdir/$privkey"
	cat <<CONFIG >>$sshdir/config
Host $GITLAB_HOST
    User $hostname
    IdentityFile $sshdir/gitlab-$hostname
CONFIG
	# Copy the public key to mounted directory.
	mkdir -p "$keydestdir"
	cp -f "$sshdir/$pubkey" "$keydestdir/$pubkey"
fi

# Update GitLab entry in known_hosts.
[ -f $sshdir/known_hosts ] && ssh-keygen -R $GITLAB_HOST
ssh-keyscan $GITLAB_HOST |
	awk -v "hosts=$gitlab_ipaddr_list" '$1 = $1 "," hosts' \
		>>$sshdir/known_hosts

# Let etckeeper push to GitLab via
# daily cron job (/etc/cron.daily/etckeeper).
etckeeper init
etckeeper vcs remote rm gitlab || true
etckeeper vcs remote add gitlab $GITLAB_GIT_REMOTE
sed -i -E 's/PUSH_REMOTE=""/PUSH_REMOTE="gitlab"/' /etc/etckeeper/etckeeper.conf

exit 0