Edit: /usr/sbin/dpkg-fsys-usrunmess (12399B)
#!/usr/bin/perl
#
# dpkg-fsys-usrunmess - Undoes the merged-/usr-via-aliased-dirs mess
#
# Copyright © 2020-2021 Guillem Jover
#
# This program 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 2 of the License, or
# (at your option) any later version.
#
# This program 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, see
use strict;
use warnings;
use feature qw(state);
our ($PROGNAME) = $0 =~ m{(?:.*/)?([^/]*)};
our $PROGVERSION = '1.20.9';
our $ADMINDIR = '/var/lib/dpkg';
use POSIX;
use Getopt::Long qw(:config posix_default bundling_values no_ignorecase);
eval q{
pop @INC if $INC[-1] eq '.';
use File::FcntlLock;
};
if ($@) {
fatal('missing File::FcntlLock module; please install libfile-fcntllock-perl');
}
my $opt_noact = length $ENV{DPKG_USRUNMESS_NOACT} ? 1 : 0;
my $opt_prompt = 0;
my @options_spec = (
'help|?' => sub { usage(); exit 0; },
'version' => sub { version(); exit 0; },
'dry-run|no-act|n' => \$opt_noact,
'prompt|p' => \$opt_prompt,
);
{
local $SIG{__WARN__} = sub { usageerr($_[0]) };
GetOptions(@options_spec);
}
my @aliased_dirs;
#
# Scan all dirs under / and check whether any are aliased to /usr.
#
foreach my $path (glob '/*') {
debug("checking symlink? $path");
next unless -l $path;
debug("checking merged-usr symlink? $path");
my $symlink = readlink $path;
next unless $symlink eq "usr$path" or $symlink eq "/usr$path";
debug("merged-usr breakage, queueing $path");
push @aliased_dirs, $path;
}
if (@aliased_dirs == 0) {
print "System is fine, no aliased directories found, congrats!\n";
exit 0;
}
#
# dpkg consistency checks
#
debug('checking dpkg database consistency');
system(qw(dpkg --audit)) == 0
or fatal("cannot audit the dpkg database: $!");
debug('checking whether dpkg has been interrupted');
if (glob "$ADMINDIR/updates/*") {
fatal('dpkg is in an inconsistent state, please fix that');
}
my $aliased_regex = '^(' . join('|', @aliased_dirs) . ')/';
#
# Get a list of all paths (including diversion) under the aliased dirs.
#
my @search_args;
my %aliased_pathnames;
foreach my $dir (@aliased_dirs) {
push @search_args, "$dir/*";
}
open my $fh_paths, '-|', 'dpkg-query', '--search', @search_args
or fatal("cannot execute dpkg-query --search: $!");
while (<$fh_paths>) {
if (m/^diversion by [^ ]+ from: .*$/) {
# Ignore.
} elsif (m/^diversion by [^ ]+ to: (.*)$/) {
if (-e $1) {
add_pathname($1, 'diverted pathname');
}
} elsif (m/^.*: (.*)$/) {
add_pathname($1, 'pathname');
}
}
close $fh_paths;
#
# Get a list of all update-alternatives under the aliased dirs.
#
my @selections = qx(update-alternatives --get-selections);
foreach my $selection (@selections) {
my $name = (split(' ', $selection))[0];
my $slaves = 0;
open my $fh_alts, '-|', 'update-alternatives', '--query', $name
or fatal("cannot execute update-alternatives --query: $!");
while (<$fh_alts>) {
if (m/^\s*$/) {
last;
} elsif (m/^Link: (.*)$/) {
add_pathname($1, 'alternative link');
} elsif (m/^Slaves:\s*$/) {
$slaves = 1;
} elsif ($slaves and m/^\s\S+\s(\S+)$/) {
add_pathname($1, 'alternative slave');
} else {
$slaves = 0;
}
}
close $fh_alts;
}
my $sroot = '/.usrunmess';
my @relabel;
#
# Create a shadow hierarchy under / for the new unmessed dir:
#
debug("creating shadow dir = $sroot");
mkdir $sroot
or sysfatal("cannot create directory $sroot");
foreach my $dir (@aliased_dirs) {
debug("creating shadow dir = $sroot$dir");
mkdir "$sroot$dir"
or sysfatal("cannot create directory $sroot$dir");
push @relabel, "$sroot$dir";
}
#
# Populate the split dirs with hardlinks or copies of the objects from
# their counter-parts in /usr.
#
foreach my $pathname (sort keys %aliased_pathnames) {
my (@meta) = lstat $pathname
or sysfatal("cannot lstat object $pathname for shadow hierarchy");
if (-d _) {
my $mode = $meta[2];
my ($uid, $gid) = @meta[4, 5];
my ($atime, $mtime, $ctime) = @meta[8, 9, 10];
debug("creating shadow dir = $sroot$pathname");
mkdir "$sroot$pathname"
or sysfatal("cannot mkdir $sroot$pathname");
chmod $mode, "$sroot$pathname"
or sysfatal("cannot chmod $mode $sroot$pathname");
chown $uid, $gid, "$sroot$pathname"
or sysfatal("cannot chown $uid $gid $sroot$pathname");
utime $atime, $mtime, "$sroot$pathname"
or sysfatal("cannot utime $atime $mtime $sroot$pathname");
push @relabel, "$sroot$pathname";
} elsif (-f _) {
debug("creating shadow file = $sroot$pathname");
copy("/usr$pathname", "$sroot$pathname");
} elsif (-l _) {
my $target = readlink "/usr$pathname";
debug("creating shadow symlink = $sroot$pathname");
symlink $target, "$sroot$pathname"
or sysfatal("cannot symlink $target to $sroot$pathname");
push @relabel, "$sroot$pathname";
} else {
fatal("unhandled object type for '$pathname'");
}
}
#
# Prompt at the point of no return, if the user requested it.
#
if ($opt_prompt) {
print "Shadow hierarchy created at '$sroot', ready to proceed (y/N)? ";
my $reply = ;
chomp $reply;
if ($reply ne 'y' and $reply ne 'yes') {
print "Aborting migration, shadow hierarchy left in place.\n";
exit 0;
}
}
#
# Mark all packages as half-configured so that we can force a mass
# reconfiguration, to trigger any code in maintainer scripts that might
# create files.
#
# XXX: We do this manually by editing the status file.
# XXX: We do this for packages that might not have maintscripts, or might
# not involve affected directories.
#
debug('marking all dpkg packages as half-configured');
if (not $opt_noact) {
open my $fh_lock, '>', "$ADMINDIR/lock"
or sysfatal('cannot open dpkg database lock file');
my $fs = File::FcntlLock->new(l_type => F_WRLCK);
$fs->lock($fh_lock, F_SETLKW)
or sysfatal('cannot get a write lock on dpkg database');
my $file_db = "$ADMINDIR/status";
my $file_dbnew = $file_db . '.new';
open my $fh_dbnew, '>', $file_dbnew
or sysfatal('cannot open new dpkg database');
open my $fh_db, '<', $file_db
or sysfatal('cannot open dpkg database');
while (<$fh_db>) {
if (m/^Status: /) {
s/ installed$/ half-configured/;
}
print { $fh_dbnew } $_;
}
close $fh_db;
$fh_dbnew->flush() or sysfatal('cannot flush new dpkg database');
$fh_dbnew->sync() or sysfatal('cannot fsync new dpkg database');
close $fh_dbnew or sysfatal('cannot close new dpkg database');
rename $file_dbnew, $file_db
or sysfatal('cannot rename new dpkg database');
}
#
# Replace things as quickly as possible:
#
foreach my $dir (@aliased_dirs) {
debug("making dir backup = $dir.aliased");
if (not $opt_noact) {
rename $dir, "$dir.aliased"
or sysfatal("cannot make backup directory $dir.aliased");
}
debug("renaming $sroot$dir to $dir");
if (not $opt_noact) {
rename "$sroot$dir", $dir
or sysfatal("cannot install fixed directory $dir");
}
}
mac_relabel();
#
# Re-configure all packages, so that postinst maintscripts are executed.
#
debug('reconfigured all packages');
if (not $opt_noact) {
local $ENV{DEBIAN_FRONTEND} = 'noninteractive';
system(qw(dpkg --configure --pending)) == 0
or fatal("cannot reconfigure packages: $!");
}
#
# Cleanup backup directories.
#
foreach my $dir (@aliased_dirs) {
debug("removing backup = $dir.aliased");
if (not $opt_noact) {
unlink "$dir.aliased"
or sysfatal("cannot cleanup backup directory $dir.aliased");
}
}
my %deferred_dirnames;
#
# Cleanup moved objects.
#
foreach my $pathname (sort keys %aliased_pathnames) {
my (@meta) = lstat $pathname
or sysfatal("cannot lstat object $pathname for cleanup");
if (-d _) {
# Skip directories as this might be shared by a proper path under the
# aliased hierearchy. And so that we can remove them in reverse order.
debug("deferring merged dir cleanup = /usr$pathname");
$deferred_dirnames{"/usr$pathname"} = 1;
} else {
debug("cleaning up pathname = /usr$pathname");
next if $opt_noact;
unlink "/usr$pathname"
or sysfatal("cannot unlink object /usr$pathname");
}
}
#
# Cleanup deferred directories.
#
debug("cleaning up shadow deferred dir = $sroot");
my $arg_max = POSIX::sysconf(POSIX::_SC_ARG_MAX) // POSIX::_POSIX_ARG_MAX;
my @batch_dirs;
my $batch_size = 0;
foreach my $dir (keys %deferred_dirnames) {
my $dir_size = length($dir) + 1;
if ($batch_size + $dir_size < $arg_max) {
$batch_size += length($dir) + 1;
push @batch_dirs, $dir;
} else {
next;
}
next if length $batch_size == 0;
open my $fh_dirs, '-|', 'dpkg-query', '--search', @batch_dirs
or fatal("cannot execute dpkg-query --search: $!");
while (<$fh_dirs>) {
if (m/^.*: (.*)$/) {
# If the directory is known by its aliased name, it should not be
# cleaned up.
if (exists $deferred_dirnames{$1}) {
delete $deferred_dirnames{$1};
}
}
}
close $fh_dirs;
@batch_dirs = ();
$batch_size = 0;
}
if (not $opt_noact) {
foreach my $dirname (reverse sort keys %deferred_dirnames) {
rmdir $dirname
or sysfatal("cannot remove shadow directory $dirname");
}
}
if (not $opt_noact) {
debug("cleaning up shadow root dir = $sroot");
rmdir $sroot
or sysfatal("cannot remove shadow directory $sroot");
}
print "Done, hierarchy unmessed, congrats!\n";
print "(Note: you might need to run 'hash -r' in your shell.)\n";
1;
##
## Functions
##
sub debug
{
my $msg = shift;
print { \*STDERR } "D: $msg\n";
}
sub fatal
{
my $msg = shift;
die "error: $msg\n";
}
sub sysfatal
{
my $msg = shift;
fatal("$msg: $!");
}
sub copy
{
my ($src, $dst) = @_;
# Try to hardlink first.
return if link $src, $dst;
# If we are on different filesystems, try a copy.
if ($! == POSIX::EXDEV) {
# XXX: This will not preserve hardlinks, these would get restored
# after the next package upgrade.
system('cp', '-a', $src, $dst) == 0
or fatal("cannot copy file $src to $dst: $?");
} else {
sysfatal("cannot link file $src to $dst");
}
}
sub mac_relabel
{
my $has_cmd = 0;
foreach my $path (split /:/, $ENV{PATH}) {
if (-x "$path/restorecon") {
$has_cmd = 1;
last;
}
}
return unless $has_cmd;
foreach my $pathname (@relabel) {
system('restorecon', $pathname) == 0
or fatal("cannot restore MAC context for $pathname: $?");
}
}
sub add_pathname
{
my ($pathname, $origin) = @_;
if ($pathname =~ m/$aliased_regex/) {
debug("adding $origin = $pathname");
$aliased_pathnames{$pathname} = 1;
}
}
sub version()
{
printf "Debian %s version %s.\n", $PROGNAME, $PROGVERSION;
}
sub usage
{
printf
'Usage: %s [