[linux-base] 04/04: Add linux-update-symlinks command for use by package maintainer scripts
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Mon May 30 17:53:34 UTC 2016
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benh pushed a commit to branch benh/maint-script-helpers
in repository linux-base.
commit af7c52a66d513d7d67abc803d1b36c53e4463bc4
Author: Ben Hutchings <ben at decadent.org.uk>
Date: Mon May 30 18:41:42 2016 +0100
Add linux-update-symlinks command for use by package maintainer scripts
This is simpler than the current logic in the linux maintainer
scripts:
- Now that I know that hard-linking and copying to the default locations
were broken, I only need to worry about making symlinks
- The logic for updating on installation/upgrade and removal is kept
together rather than divided across two scripts
- It uses existing functions in the DebianLinux module
But it's also smarter: it builds a list of versions and the files that
belong to them, prioritised based on the current type of change, the
existing symlinks and version sorting. So it can always point the
symlinks somewhere sensible, unless the last image is being removed.
---
bin/linux-update-symlinks | 206 ++++++++++++++++++++++++++++++++++++++++++++++
debian/changelog | 1 +
debian/linux-base.install | 1 +
3 files changed, 208 insertions(+)
diff --git a/bin/linux-update-symlinks b/bin/linux-update-symlinks
new file mode 100755
index 0000000..3722222
--- /dev/null
+++ b/bin/linux-update-symlinks
@@ -0,0 +1,206 @@
+#!/usr/bin/perl
+
+# Copyright 2016 Ben Hutchings
+#
+# 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, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+
+use strict;
+use warnings;
+use File::Spec;
+use POSIX ();
+
+use DebianLinux qw(image_stem image_list read_kernelimg_conf version_cmp);
+
+sub usage {
+ my $fh = shift;
+ print $fh (<< "EOT");
+Usage: $0 {install|upgrade|remove} VERSION IMAGE-PATH
+
+This command is intended to be called from the postinst and postrm
+maintainer scripts of Linux kernel packages. The postinst script must
+pass the first argument 'install' or 'upgrade' depending on whether a
+fresh installation or an upgrade has taken place.
+
+The VERSION argument must be the kernel version string as shown by
+'uname -r' and used in filenames.
+
+The IMAGE-PATH argument must be the absolute filename of the kernel
+image.
+EOT
+}
+
+sub usage_error {
+ usage(*STDERR{IO});
+ exit 2;
+}
+
+sub update_symlink {
+ my ($source, $dest) = @_;
+
+ $source = File::Spec->abs2rel($source, (File::Spec->splitpath($dest))[1]);
+
+ # Don't make unnecessary changes
+ my $old_source = readlink($dest);
+ if (defined($old_source) && $old_source eq $source) {
+ return;
+ }
+
+ # Create a symlink with a temporary name
+ my $rand;
+ while (($rand = int(rand(1000000))) && !symlink($source, "$dest.$rand")) {
+ if ($! != POSIX::EEXIST) {
+ die "Failed to create symlink to $source: $!";
+ }
+ }
+
+ # Move it into place atomically
+ if (!rename("$dest.$rand", $dest)) {
+ my $err = "$!";
+ unlink("$dest.$rand");
+ die "Failed to create or replace $dest: $err";
+ }
+
+ print "I: $dest is now a symlink to $source\n";
+}
+
+sub promote_default {
+ my ($sorted_images, $link) = @_;
+
+ # Get the absolute path
+ my $image_path = readlink($link);
+ if (!defined($image_path)) {
+ return;
+ }
+ $image_path = File::Spec->rel2abs($image_path,
+ (File::Spec->splitpath($link))[1]);
+
+ # If it's already on the list, move it to the end. (If it's not,
+ # presumably the symlink is broken.)
+ for my $i (0..$#$sorted_images) {
+ if ($sorted_images->[$i]->[1] eq $image_path) {
+ my $tmp = $sorted_images->[$i];
+ splice @$sorted_images, $i, 1;
+ push @$sorted_images, $tmp;
+ last;
+ }
+ }
+}
+
+sub update_all {
+ my ($change, $version, $image_path) = @_;
+ my $conf = read_kernelimg_conf();
+
+ # Check whether symlinks are actually wanted
+ if (!$conf->{do_symlinks}) {
+ exit 0;
+ }
+
+ my $default_dir = $conf->{image_dest};
+ $default_dir =~ s|/*$|/|; # tidy up
+
+ my $image_stem = image_stem();
+
+ # We build a list of [version, image_path, initrd_path] in
+ # ascending priority order, then update the symlinks to match it.
+
+ # Start with a list of existing images sorted by version, adding any
+ # existing initrds.
+ my @sorted_images = sort({version_cmp($a->[0], $b->[0])} image_list());
+ for my $i (0..$#sorted_images) {
+ my $exist_version = $sorted_images[$i]->[0];
+ if (-f "/boot/initrd.img-$exist_version") {
+ $sorted_images[$i]->[2] = "/boot/initrd.img-$exist_version";
+ }
+ }
+
+ # The files for this version may not actually have been
+ # installed/removed yet (e.g. on installation the initrd will
+ # probably be built later). Also, on installation this version
+ # should have the highest priority, not dependent on version
+ # ordering. So ensure that this version is included (for
+ # for upgrade) or excluded (otherwise).
+ my $initrd_path = ((exists($ENV{INITRD}) && $ENV{INITRD} eq 'No') ?
+ undef : "/boot/initrd.img-$version");
+ for my $i (0.. at sorted_images) {
+ my $diff = ($i < @sorted_images ?
+ version_cmp($version, $sorted_images[$i]->[0]) : -1);
+ if ($diff == 0) {
+ if ($change eq 'upgrade') {
+ $sorted_images[$i] = [$version, $image_path, $initrd_path];
+ } else {
+ splice @sorted_images, $i, 1;
+ }
+ last;
+ } elsif ($diff < 0) {
+ if ($change eq 'upgrade') {
+ splice @sorted_images, $i, 0,
+ [$version, $image_path, $initrd_path];
+ }
+ last;
+ }
+ }
+
+ # Any existing non-broken symlinks have higher priority.
+ promote_default(\@sorted_images, "${default_dir}${image_stem}.old");
+ promote_default(\@sorted_images, "${default_dir}${image_stem}");
+
+ # In case of installation, this version has highest priority.
+ if ($change eq 'install') {
+ push @sorted_images, [$version, $image_path, $initrd_path];
+ }
+
+ if (@sorted_images) {
+ # Take the two highest priority entries on the list. In case there
+ # is only one entry, use it twice!
+ my ($old_version, $old_image_path, $old_initrd_path) =
+ @{$sorted_images[@sorted_images >= 2 ? -2 : -1]};
+ my ($cur_version, $cur_image_path, $cur_initrd_path) =
+ @{$sorted_images[-1]};
+
+ update_symlink($old_image_path, "${default_dir}${image_stem}.old");
+ if (defined($old_initrd_path)) {
+ update_symlink($old_initrd_path, "${default_dir}initrd.img.old");
+ } else {
+ unlink("${default_dir}initrd.img.old");
+ }
+ update_symlink($cur_image_path, "${default_dir}${image_stem}");
+ if (defined($cur_initrd_path)) {
+ update_symlink($cur_initrd_path, "${default_dir}initrd.img");
+ } else {
+ unlink("${default_dir}initrd.img");
+ }
+ } else {
+ print STDERR "W: Last kernel image has been removed, so removing the default symlinks\n";
+ unlink("${default_dir}${image_stem}.old");
+ unlink("${default_dir}initrd.img.old");
+ unlink("${default_dir}${image_stem}");
+ unlink("${default_dir}initrd.img");
+ }
+
+ exit 0;
+}
+
+if (@ARGV == 0) {
+ usage_error();
+}
+
+my $change = $ARGV[0];
+if ($change eq 'help' or grep({$_ eq '--help'} @ARGV)) {
+ usage(*STDOUT{IO});
+ exit 0;
+} elsif ($change =~ /^(?:install|upgrade|remove)$/ && @ARGV == 3) {
+ update_all(@ARGV);
+}
+usage_error();
diff --git a/debian/changelog b/debian/changelog
index 2319f3c..cb4eef5 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -4,6 +4,7 @@ linux-base (4.1) UNRELEASED; urgency=medium
- Add .gitignore files
- debian/control: Update Vcs-* fields (Closes: #824748)
* Add image_stem() and read_kernelimg_conf() functions to Perl module
+ * Add linux-update-symlinks command for use by package maintainer scripts
-- Ben Hutchings <ben at decadent.org.uk> Tue, 11 Aug 2015 19:12:59 +0200
diff --git a/debian/linux-base.install b/debian/linux-base.install
index 55d565a..4e35cb1 100644
--- a/debian/linux-base.install
+++ b/debian/linux-base.install
@@ -1,3 +1,4 @@
+bin/linux-update-symlinks usr/bin
bin/linux-version usr/bin
bin/perf usr/bin
lib/DebianLinux.pm usr/share/perl5
--
Alioth's /usr/local/bin/git-commit-notice on /srv/git.debian.org/git/kernel/linux-base.git
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