#!/usr/bin/perl
# increm
# Do an incremental backup; ONLY for invocation by full !
#
# This file is part of chiark backup, a system for backing up GNU/Linux and
# other UN*X-compatible machines, as used on chiark.greenend.org.uk.
#
# chiark backup is:
#  Copyright (C) 1997-1998,2000-2001,2007
#                     Ian Jackson <ian@chiark.greenend.org.uk>
#  Copyright (C) 1999 Peter Maydell <pmaydell@chiark.greenend.org.uk>
#
# This is free software; you can redistribute it and/or modify it under the
# terms of the GNU General Public License as published by the Free Software
# Foundation; either version 3, or (at your option) any later version.
#
# This is distributed in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
# details.
#
# You should have received a copy of the GNU General Public License along
# with this program; if not, consult the Free Software Foundation's
# website at www.fsf.org, or the GNU Project website at www.gnu.org.

# We are invoked by full if the tape description file says that it is
# for an incremental backup.  We expect two commandline argument which
# is the ID string of the tape to use, and the description (which
# includes ID and function).

BEGIN {
    $etc= '/etc/chiark-backup';
    require "$etc/settings.pl";
    require 'backuplib.pl';
}

$|=1;

@ARGV==2 or die;
($tapeid,$tapedesc)= @ARGV;

print "Running incremental onto $tapedesc ...\n" or die $!;

# Just check that we weren't passed a bogus ID (the tape description
# file for incrementals is just 'incremental\nend\n')
open T,"$etc/tape.$tapeid" or die "Tape $tapeid not found: $!\n";
close T;

# This is only used for the 'next FULL backup is X' message at the end.
open NF,"next-full" or die $!;
chomp($next= <NF>);
close NF or die $!;

setstatus "FAILED during incremental";

# Read the number of the incremental involved
# (ie, (how many files are already on the tape) - 1)
open A,"increm-advance" or die $!;
chomp($advance= <A>);
close A or die $!;

# better be a decimal number
$advance =~ m/^\d+$/ or die "$advance ?";

# Get a list of all filesystems
readfsys('all');
openlog();

# Rewind the tape and if we are the first incremental on the tape then
# write the TAPEID record, otherwise skip forward to the correct point.
# (full will already have checked that this is the right tape before
# it invoked us, so no need to read the existing TAPEID record first.)
runsystem("mt -f $ntape rewind");
if ($advance == 1) {
    writetapeid($tapeid,$tapedesc);
} else {
    runsystem("mt -f $ntape fsf $advance");
    $currenttapefilenumber= $advance;
}

sub closepipes () {
    close(DUMPOR); close(BUFOR);
    close(DUMPOW); close(BUFOW);
    close(GZOR); close(GZOW);
}

setstatus "PROBLEMS during incremental dump";

for $tf (@fsys) {

    parsefsys();
    prepfsys();
    
    $bufir='DUMPOR';
    $ddcmd= "$nasty dd ibs=$softblocksizebytes obs=$blocksizebytes of=$ntape";

    pipe(DUMPOR,DUMPOW) or die $!;
    pipe(BUFOR,BUFOW) or die $!;

    $gz= $gzi if length $gzi;
    if ($gz) {
	$bufir='GZOR';
	pipe(GZOR,GZOW) or die $!;
	$ddcmd .= " conv=sync";
    }

    if ($dopt{'noinc'}) {
	pboth("Incrementals of $atf_print ($prefix) suppressed in config.\n");
    }

    if ($tm eq 'dump') {
	$dumplabel= $pcstr.$atf_print.'$';
	$dumpcmd= "dump 1Lbfu $dumplabel $softblocksizekb - $atf";
    } elsif ($tm eq 'gtar') {
	$dumpcmd= "tar NCcfl $fsidfile $atf - .";
    } else {
	pboth("Not dumping $atf_print ($prefix) - not supported.\n");
	next;
    }

    nexttapefile("inc $prefix:$atf_print");
    
    # Same trick as full uses to do a pipeline whilst keeping track
    # of all exit statuses:
    #   dump </dev/null | writebuffer | dd >/dev/null
    startprocess '</dev/null','>&DUMPOW',"$nice ".$rstr.$dumpcmd;
    if ($gz) {
	startprocess '<&DUMPOR','>&GZOW',"$nice gzip -v$gz";
    }
    startprocess "<&$bufir",'>&BUFOW',"$nasty writebuffer";
    startprocess '<&BUFOR','>/dev/null',"$nasty $ddcmd";
    closepipes();
    endprocesses();
    # advance is a file counter, so it needs to be updated for each 
    # dump we do to tape.
    $advance++;

    finfsys();
}

# Rewind the tape, and increment the counter of incremental backups.
runsystem("mt -f $tape rewind");
open IAN,">increm-advance.new" or die $!;
print IAN "$advance\n" or die $!;
close IAN or die $!;
rename 'increm-advance.new','increm-advance' or die $!;

pboth("Next FULL dump tape is $next\n");

setstatus "INCREMENTAL successful: $tapedesc, next full is $next";
exit 0;