srvbackup

commit 9c0be458fde1577549ac916ebfd40a5ce4259dec
Author: Jacob R. Edwards <jacob@jacobedwards.org>
Date:   Thu, 27 Apr 2023 19:32:47 -0700

Add srvbackup script and Makefile

Diffstat:
A
Makefile
 | 
7
+++++++
A
srvbackup
 | 
81
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

2 files changed, 88 insertions(+), 0 deletions(-)
diff --git a/Makefile b/Makefile
@@ -0,0 +1,7 @@
+install:
+	install -o root -g bin -m 0755 srvbackup /usr/local/bin/srvbackup
+
+uninstall:
+	rm -f /usr/local/bin/backup
+	# You may also wish to run
+	# 	# rm -rf /var/backup
diff --git a/srvbackup b/srvbackup
@@ -0,0 +1,81 @@
+#!/bin/sh
+# Copyright 2023 Jacob R. Edwards
+# srvbackup, a server backup script
+#
+# This script is to be put on the server and is meant to be used
+# by both the server to generate the backup and by clients connecting
+# through ssh(1) to retrive the backup.
+#
+# The backup is available to everyone (permissions-wise) but will
+# in the future be able to be encrypted with an age(1) key if
+# /etc/backup/key exists.
+#
+# Example usage:
+#
+# Make a backup at the beginning of every day using
+# a crontab(5):
+#	0 0 * * * srvbackup make
+#
+# Update 'local-backup.tar.age' from the 'server.dom':
+#	ssh unprivledged@server.dom srvbackup get "$(sha256 < local-backup.tar.age)" > tmp
+#	(test -s tmp && mv tmp local-backup.tar.age) || rm tmp
+
+set -e
+
+dir=/var/backup
+backup="$dir"/backup.tar
+checksum="$dir"/sha256
+
+createdir() {
+	! test -d "$dir" &&
+		mkdir -m 0755 "$dir" # not -p
+}
+
+update() (
+	IFS='
+	'
+	cd /
+	pax -w -uf "$backup" $(</etc/backup/list)
+)
+
+if test $# -eq 0; then
+	c=make
+else
+	c="$1"
+	shift
+fi
+
+case "$c" in
+(make)
+	createdir
+	update "$backup"
+	sha256 < "$backup" > "$checksum"
+	;;
+(path)
+	echo "$backup"
+	;;
+(sha256)
+	cat "$checksum"
+	;;
+(get)
+	if test "$1" -a "$1" = -c
+	then
+		shift
+		write=compress
+	else
+		write=cat
+	fi
+	test "$1" -a "$1" = "$(<"$checksum")" &&
+		exit 0
+	$write < "$backup"
+	;;
+(*)
+	{
+		echo "$c: Command not known"
+		echo "usage: srvbackup make
+                 path
+                 sha256 
+                 get [-c] [sha256] # (compress(1) if -c is given, only if checksums differ)"
+	} 1>&2
+	exit 1
+esac