Raspberry Pi Conservative Expand Rootfs Raspi Config Wrapper

Introduction

• since SD-card sizes of the "same" size but different vendors vary, up to "full - ~256MByte"
  • do it by hand, using fdisk and resize2fs or
  • or with this conservative_expand-rootfs wrapper script extending the original raspi-config http://github.com/asb/raspi-config (see LICENSE file for copyright and license details) to only expand up to the afore mentioned maximum:

Code

#!/usr/bin/perl -w
#
# Author: P.Zumbruch@gsi.de 
# January 22, 2016

use strict;
use File::Temp qw/ tempfile tempdir /;

#find location of 'raspi-config'
open CMD,'-|', 'which raspi-config'
   or die $@;
my $raspiConfigLocation = <CMD>;
close CMD;

#read 'raspi-config'
open FILE, $raspiConfigLocation
   or die "Cannot open '$raspiConfigLocation': $!";
my $raspiConfig = do { local $/; <FILE> };
close FILE;

###
#define additional code segments to leave some space of 256MB at the very end of the SD card
# - size calculations
my $partSizeCommands = << 'EOF';

#additional code segment to leave some space of 256MB at the very end of the SD card
if [ -z "$PART_SIZE" ]
then 
    local DEVICE_SIZE=$(parted MY_DEVICE -ms unit s p | grep MY_DEVICE | cut -d: -f 2 | sed -e 's/[A-Z]//ig');
    local DEVICE_SECTOR_SIZE=$(parted MY_DEVICE -ms unit s p | grep MY_DEVICE | cut -d: -f 4 | sed -e 's/[A-Z]//ig');
    local PART_SIZE=$(( $DEVICE_SIZE - ( 1 + 256 * 1024 * 1024 / $DEVICE_SECTOR_SIZE) ));
fi
EOF
;
#replace dummy "MY_DEVICE" by real device name used in 'raspi-config'
my $partSizeCommandsDevice = $raspiConfig =~ s/.+parted (\/dev\/.+?)\s.+/$1/sr;
$partSizeCommands =~ s/MY_DEVICE/$partSizeCommandsDevice/g;

# - unmodified fdisk sequence 
my $fdiskCommands = << 'EOF';
p
d
$PART_NUM
n
p
$PART_NUM
$PART_START

p
w
EOF
;

# generate modified fdisk sequence including PART_SIZE
my $fdiskCommandsInsert = $fdiskCommands =~ s/(\$PART_NUM\n\$PART_START\n)(\n)/$1\$PART_SIZE$2/rm;
# generate search pattern
my $fdiskCommandsSearch = $fdiskCommands =~ s/\$/\\\$/rg;

#replace fdisk sequence
$raspiConfig =~ s/(.*?\n)$fdiskCommandsSearch/$partSizeCommands$1$fdiskCommandsInsert/m;
#print $raspiConfig;

#create new enhanced 'raspi-config' to temporary file
my $filename;
(undef, $filename) = tempfile( "", SUFFIX => '.raspi-config', TMPDIR => 1, OPEN => 1 );

open OUTPUT, ">$filename" or die "Cannot create output file: $!";
print OUTPUT $raspiConfig ."\n";
close OUTPUT;

chmod 0755, "$filename";

#execute vi sudo new 'raspi-config'
!system "sudo $filename --expand-rootfs" or warn "sudo $filename --expand-rootfs failed:$!\n";

#delete temporary 'raspi-config' file
unlink $filename or warn "failed removing $filename: $!\n";