Package: mmdebstrap
Version: 0.7.5-2
Severity: wishlist
File: /usr/bin/mmdebstrap
Tags: patch upstream
Hi josch,
I noticed that asking mmdebstrap to output to /dev/null can be a
reasonably common thing to do when the desired artifact resides inside
the chroot and is transferred via special hooks. Indeed, I think it is
so common that mmdebstrap should optimize this use case by skipping the
tar creation. To that end, I propose adding a new --format called
"null", which is automatically selected when the target is literally
"/dev/null". I'm attaching a patch with my implementation.
Helmut
--- a/mmdebstrap
+++ b/mmdebstrap
@@ -4384,7 +4384,8 @@
if ($format eq 'dir') {
$format = 'directory';
}
- my @valid_formats = ('auto', 'directory', 'tar', 'squashfs', 'ext2');
+ my @valid_formats = ('auto', 'directory', 'tar', 'squashfs', 'ext2',
+ 'null');
if (none { $_ eq $format } @valid_formats) {
error "invalid format. Choose from " . (join ', ', @valid_formats);
}
@@ -5086,7 +5087,9 @@
# figure out the right format
if ($format eq 'auto') {
- if ($options->{target} ne '-' and -d $options->{target}) {
+ if ($options->{target} eq '/dev/null') {
+ $format = 'null';
+ } elsif ($options->{target} ne '-' and -d $options->{target}) {
$format = 'directory';
} elsif (
defined $tar_compressor
@@ -5157,30 +5160,32 @@
info "automatically chosen format: $format";
}
- if ($options->{target} eq '-' and $format ne 'tar') {
+ if ($options->{target} eq '-' and $format ne 'tar' and $format ne 'null') {
error "the $format format is unable to write to standard output";
}
- if (any { $_ eq $format } ('tar', 'squashfs', 'ext2')) {
- if ( any { $_ eq $options->{variant} } ('extract', 'custom')
- and any { $_ eq $options->{mode} } ('fakechroot', 'proot')) {
- info "creating a tarball or squashfs image or ext2 image in"
- . " fakechroot mode or proot mode might fail in extract and"
- . " custom variants because there might be no tar inside the"
- . " chroot";
- }
- # try to fail early if target tarball or squashfs image cannot be
- # opened for writing
- if ($options->{target} ne '-') {
- if ($options->{dryrun}) {
- if (-e $options->{target}) {
- info "not overwriting $options->{target} because in"
- . " dry-run mode";
+ if (any { $_ eq $format } ('tar', 'squashfs', 'ext2', 'null')) {
+ if ($format ne 'null') {
+ if ( any { $_ eq $options->{variant} } ('extract', 'custom')
+ and any { $_ eq $options->{mode} } ('fakechroot', 'proot')) {
+ info "creating a tarball or squashfs image or ext2 image in"
+ . " fakechroot mode or proot mode might fail in extract and"
+ . " custom variants because there might be no tar inside the"
+ . " chroot";
+ }
+ # try to fail early if target tarball or squashfs image cannot be
+ # opened for writing
+ if ($options->{target} ne '-') {
+ if ($options->{dryrun}) {
+ if (-e $options->{target}) {
+ info "not overwriting $options->{target} because in"
+ . " dry-run mode";
+ }
+ } else {
+ open my $fh, '>', $options->{target}
+ or error "cannot open $options->{target} for writing: $!";
+ close $fh;
}
- } else {
- open my $fh, '>', $options->{target}
- or error "cannot open $options->{target} for writing: $!";
- close $fh;
}
}
# since the output is a tarball, we create the rootfs in a temporary
@@ -5332,7 +5337,7 @@
= sprintf("%06o\0", unpack("%16C*", $entry));
$devtar .= $entry;
}
- } elsif ($format eq 'directory') {
+ } elsif (any { $_ eq $format } ('directory', 'null')) {
# nothing to do
} else {
error "unknown format: $format";
@@ -5435,7 +5440,7 @@
or error "tar failed: $?";
info "done";
- } elsif ($format eq 'directory') {
+ } elsif (any { $_ eq $format } ('directory', 'null')) {
# nothing to do
} else {
error "unknown format: $format";
@@ -5537,7 +5542,7 @@
}
info "done";
- } elsif ($format eq 'directory') {
+ } elsif (any { $_ eq $format } ('directory', 'null')) {
# nothing to do
} else {
error "unknown format: $format";
@@ -5608,7 +5613,7 @@
if ($options->{dryrun}) {
# nothing to do
- } elsif ($format eq 'directory') {
+ } elsif (any { $_ eq $format } ('directory', 'null')) {
# nothing to do
} elsif (any { $_ eq $format } ('tar', 'squashfs', 'ext2')) {
# we use eval() so that error() doesn't take this process down and
@@ -5706,7 +5711,7 @@
# change signal handler message
$waiting_for = "cleanup";
- if ($format eq 'directory') {
+ if (any { $_ eq $format } ('directory', 'null')) {
# nothing to do
} elsif (any { $_ eq $format } ('tar', 'squashfs', 'ext2')) {
if (!-e $options->{root}) {
@@ -5894,8 +5899,8 @@
=item B<--format>=I<name>
Choose the output format. Valid format I<name>s are B<auto>, B<directory>,
-B<tar>, B<squashfs>, and B<ext2>. The default format is B<auto>. See the
-section B<FORMATS> for more information.
+B<tar>, B<squashfs>, B<ext2> and B<null>. The default format is B<auto>. See
+the section B<FORMATS> for more information.
=item B<--aptopt>=I<option>|I<file>
@@ -6331,7 +6336,8 @@
When selecting this format (the default), the actual format will be inferred
from the I<TARGET> positional argument. If I<TARGET> was not specified, then
-the B<tar> format will be chosen. If I<TARGET> is an existing directory, and
+the B<tar> format will be chosen. If I<TARGET> happens to be F</dev/null>, then
+the B<null> format will be chosen. If I<TARGET> is an existing directory, and
does not equal to C<->, then the B<directory> format will be chosen. If
I<TARGET> ends with C<.tar> or with one of the filename extensions listed in
the section B<COMPRESSION>, or if I<TARGET> equals C<->, or if I<TARGET> is a
@@ -6387,6 +6393,14 @@
extents,uninit_bg,dir_index,has_journal TARGET>. Since C<genext2fs> does not
support extended attributes, the resulting image will not contain them.
+=item B<null>
+
+A temporary chroot directory will be created in C<$TMPDIR> or F</tmp> if
+C<$TMPDIR> is not set. After the bootstrap is complete, the temporary chroot
+will be deleted without being part of the output. This is most useful when the
+desired artifact is generated inside the chroot and it is transferred using
+special hooks such as B<sync-out>.
+
=back
=head1 HOOKS
