env/bin/rbucmd.sh

#!/bin/sh
# env
# Written in 2021 by Lucas
# CC0 1.0 Universal/Public domain - No rights reserved
#
# To the extent possible under law, the author(s) have dedicated all
# copyright and related and neighboring rights to this software to the
# public domain worldwide. This software is distributed without any
# warranty. You should have received a copy of the CC0 Public Domain
# Dedication along with this software. If not, see
# <http://creativecommons.org/publicdomain/zero/1.0/>.

usage()
{
	printf "Usage: %s [-c] [-l login_name] host backup-name\n" \
	    "${0##*/}" >&2
	exit 1
}

err()
{
	printf "%s: %s\n" "${0##*/}" "$*" >&2
	exit 1
}

login_name=$(id -nu)
agent_mode=yes
while getopts cl: flag; do
	case $flag in
	c)	agent_mode=confirm ;;
	l)	login_name=$OPTARG ;;
	*)	usage
	esac
done
shift $(($OPTIND - 1))
if [ $# -ne 2 ] || [ -z "$1" ] || [ -z "$2" ]; then
	usage
fi
host=$1
backup_name=$2

[ -f "$host/bulist" ] || err "no bulist present in \"$h/\""

if [ -z "$SSH_AUTH_SOCK" ] || [ ! -S "$SSH_AUTH_SOCK" ]; then
	eval $(ssh-agent -s)
	trap 'eval $(ssh-agent -ks)' EXIT INT QUIT TERM
fi

set -e

# Load correct key into ssh-agent.
ssh -o AddKeysToAgent=$agent_mode "$login_name@$host" true

cd "$host"
tmpdir=$(ssh "$login_name@$host" mktemp -dt rbucmd.XXXXXX)

sftp "$login_name@$host" <<EOF
put bulist $tmpdir/bulist
EOF

ssh "$login_name@$host" "cat - >\"$tmpdir/bu.sh\"" <<EOF
cd / &&
    pkg_info -mz >/tmp/pkg-info.txt &&
    doas xargs pax -wzf "$tmpdir/$backup_name.tgz" <"$tmpdir/bulist" &&
    doas chown "$login_name:$login_name" "$tmpdir/$backup_name.tgz"
EOF

# -t is needed for doas to read a password.
ssh -t "$login_name@$host" sh "$tmpdir/bu.sh"

sftp -o "user=$login_name" "$host" <<EOF
get $tmpdir/$backup_name.tgz
rm $tmpdir/*
rmdir $tmpdir/
rm /tmp/pkg-info.txt
EOF