diff --git a/raspi3.yaml b/raspi3.yaml
index 42bfb20..29837de 100644
--- a/raspi3.yaml
+++ b/raspi3.yaml
@@ -66,6 +66,7 @@ steps:
   - apt: install
     packages:
     - ssh
+    - parted
     - dosfstools
     # Contains /lib/firmware/brcm/brcmfmac43430-sdio.bin (required for WiFi).
     - firmware-brcm80211
diff --git a/rpi3-resizerootfs b/rpi3-resizerootfs
index af5508d..217c20c 100755
--- a/rpi3-resizerootfs
+++ b/rpi3-resizerootfs
@@ -1,155 +1,24 @@
-#!/usr/bin/env perl
-# vim:ts=4:sw=4:et
-#
-# © 2017 Michael Stapelberg <stapelberg@debian.org>
-#
-# Extends the root partition and root file system to cover the entire remainder
-# of the device. Requires the root file system to be a block device matching
-# /.+p[0-9]$/, e.g. /dev/mmcblk0p2.
-#
-# Requires only perl-base (present on all Debian installations)
+#!/bin/sh
 
-use strict;
-use Fcntl qw(:DEFAULT :seek);
+roottmp=$(lsblk -l -o NAME,MOUNTPOINT | grep '/$')
+rootpart=/dev/${roottmp%% */}
+rootdev=${rootpart%2}
+rootdev=${rootdev%p}
 
-################################################################################
-# Find the root device by looking at what is mounted on /
-################################################################################
+flock $rootdev sfdisk -f $rootdev -N 2 <<EOF
+,+
+EOF
 
-sub slurp {
-    my ($fn) = @_;
-    open(my $fh, '<', $fn)
-        or die qq|open($fn): $!|;
-    local $/;
-    <$fh>;
-}
+sleep 5
 
-my ($rootpart) = grep { $_ ne '' } map { /([^ ]+) \/ / && $1 } split("\n", slurp(</proc/mounts>));
-my $rootdev;
-my $pno;
-if ($rootpart =~ /^(.+)p([0-9])$/) {
-    $rootdev = $1;
-    $pno = int($2);
-} else {
-    die qq|root partition "$rootpart" unexpectedly does not end in p[0-9]|;
-}
+udevadm settle
 
-################################################################################
-# Get the size of the root block device in bytes
-################################################################################
+sleep 5
 
-sub SYS_ioctl { 29; } # aarch64-specific
-sub BLKGETSIZE64 { 2148012658; }
+flock $rootdev partprobe $rootdev
 
-sysopen(my $root, $rootdev, O_RDWR)
-    or die qq|sysopen($rootdev): $!|;
+mount -o remount,rw $rootpart
 
-my $devsizep = pack("Q", ());
-$! = 0;
-syscall(SYS_ioctl(), fileno($root), BLKGETSIZE64(), $devsizep) >= 0
-    or die qq|ioctl(BLKGETSIZE64): $!|;
-my ($devsize) = unpack("Q", $devsizep);
+resize2fs $rootpart
 
-################################################################################
-# Read the partition table entry
-################################################################################
-
-sub boot_code { 446; }
-sub partition_table_entry { 16; }
-sub partition_table_start_offset { 8; }
-sub partition_table_length_offset { 12; }
-sub partition_count { 4; }
-sub partition_signature_len { 2; }
-sub tablelength { partition_table_entry() * partition_count() + partition_signature_len(); }
-
-# The contents of $original_partition_table must be updated whenever the
-# partition layout on the SD card image changes.
-# This layout matches
-# https://people.debian.org/~stapelberg/raspberrypi3/2017-10-08/2017-10-08-raspberry-pi-3-buster-PREVIEW.img.bz2
-my $original_partition_table = pack('H4' x (tablelength()/2),
-    "0020", "2100", "0c3e", "1826", "0008", "0000", "0058", "0900",
-    "003e", "1926", "833a", "2e8c", "0060", "0900", "0000", "1900",
-    "0000", "0000", "0000", "0000", "0000", "0000", "0000", "0000",
-    "0000", "0000", "0000", "0000", "0000", "0000", "0000", "0000",
-    "55aa");
-
-sub check_orig_partition_table {
-    my ($offset, $len, $bytes) = @_;
-    sysseek($root, $offset, SEEK_SET)
-        or die qq|sysseek($offset): $!|;
-    my $buf;
-    sysread($root, $buf, $len)
-        or die qq|sysread(): $!|;
-    if ($buf ne $bytes) {
-        print "Partition table already modified\n";
-        exit 0;
-    }
-}
-
-sub read_uint32_le {
-    my ($offset) = @_;
-    sysseek($root, $offset, SEEK_SET)
-        or die qq|sysseek($offset): $!|;
-    my $buf;
-    sysread($root, $buf, 4)
-        or die qq|sysread(): $!|;
-    my ($val) = unpack("V", $buf);
-    return $val;
-}
-
-# Ensure partition table has not been modified by the user.
-check_orig_partition_table(boot_code(), tablelength(), $original_partition_table);
-
-my $entry_offset = boot_code() + (partition_table_entry() * ($pno - 1));
-my $start     = 512 * read_uint32_le($entry_offset + partition_table_start_offset());
-my $oldlength = 512 * read_uint32_le($entry_offset + partition_table_length_offset());
-my $newlength = ($devsize - $start);
-if ($oldlength == $newlength) {
-    print "Partition $rootpart already at maximum size $newlength\n";
-    exit 0;
-}
-
-################################################################################
-# Change the partition length
-################################################################################
-
-sub write_uint32_le {
-    my ($offset, $val) = @_;
-    sysseek($root, $offset, SEEK_SET)
-        or die qq|sysseek($offset): $!|;
-    my $buf = pack("V", $val);
-    syswrite($root, $buf, 4)
-        or die qq|syswrite: $!|;
-}
-
-print "Resizing partition $rootpart from $oldlength to $newlength bytes\n";
-write_uint32_le($entry_offset + partition_table_length_offset(), $newlength / 512);
-
-################################################################################
-# Tell linux about the new partition size using the BLKPG ioctl (BLKRRPART
-# cannot be used when the device is mounted, even read-only).
-################################################################################
-
-sub BLKPG { 0x1269; }
-sub BLKPG_RESIZE_PARTITION { 3; }
-
-my $part = pack("q q i Z64 Z64", $start, $newlength, $pno, "devname", "volname");
-my $partb = "\x00" x length($part);
-my $op = BLKPG_RESIZE_PARTITION();
-my $ioctl_arg = pack("i i i x4 p", $op, 0, length($part), $part);
-$! = 0;
-syscall(SYS_ioctl(), fileno($root), BLKPG(), $ioctl_arg) >= 0
-    or die "ioctl(BLKPG): $!";
-
-################################################################################
-# Run resize2fs to enlarge the file system
-################################################################################
-
-# resize2fs requires the file system to be writeable.
-my @remountcmd = ('mount', '-o', 'remount,rw', $rootpart);
-system(@remountcmd) == 0
-    or die qq|system(| . join(" ", @remountcmd) . qq|): $!|;
-
-my @resizecmd = ('resize2fs', "${rootpart}");
-exec { $resizecmd[0] } @resizecmd
-    or die qq|exec(| . join(" ", @resizecmd) . qq|): $!|;
+exit 0
diff --git a/rpi3-resizerootfs.service b/rpi3-resizerootfs.service
index e90252e..02207e4 100644
--- a/rpi3-resizerootfs.service
+++ b/rpi3-resizerootfs.service
@@ -1,12 +1,13 @@
 [Unit]
 Description=resize root file system
-Before=systemd-remount-fs.service
+Before=local-fs-pre.target
 DefaultDependencies=no
 
 [Service]
 Type=oneshot
+TimeoutSec=infinity
 ExecStart=/usr/sbin/rpi3-resizerootfs
 ExecStart=/bin/systemctl --no-reload disable %n
 
 [Install]
-RequiredBy=systemd-remount-fs.service
+RequiredBy=local-fs-pre.target