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Michael Stapelberg
2017-10-08 22:18:48 +02:00
commit 331f68931a
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rpi3-resizerootfs Executable file
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#!/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]$/, e.g. /dev/mmcblk0p2.
#
# Requires only perl-base (present on all Debian installations)
use strict;
use Fcntl qw(:DEFAULT :seek);
################################################################################
# Find the root device by looking at what is mounted on /
################################################################################
sub slurp {
my ($fn) = @_;
open(my $fh, '<', $fn)
or die qq|open($fn): $!|;
local $/;
<$fh>;
}
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]|;
}
################################################################################
# Get the size of the root block device in bytes
################################################################################
sub SYS_ioctl { 29; } # aarch64-specific
sub BLKGETSIZE64 { 2148012658; }
sysopen(my $root, $rootdev, O_RDWR)
or die qq|sysopen($rootdev): $!|;
my $devsizep = pack("Q", ());
$! = 0;
syscall(SYS_ioctl(), fileno($root), BLKGETSIZE64(), $devsizep) >= 0
or die qq|ioctl(BLKGETSIZE64): $!|;
my ($devsize) = unpack("Q", $devsizep);
################################################################################
# Read the partition table entry
################################################################################
sub boot_code { 446; }
sub partition_table_entry { 16; }
sub partition_table_start_offset { 8; }
sub partition_table_length_offset { 12; }
sub read_uint32_le {
my ($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;
}
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|): $!|;