Merge pull request #16612 from poettering/dissect-copy

teach systemd-dissect file copying, and make it officially supported, move to /usr/bin + man page

TODO

@@ -42,9 +42,6 @@ Features:
   mounting a subdir of the root fs as actual root. This can be used as
   fstype-agnostic version of btrfs' rootflags=subvol=foobar.
 
-* add --copy-from and --copy-to command to systemd-dissect which copies stuff
-  in and out of a disk image
-
 * Support ProtectProc= or so, using: https://patchwork.kernel.org/cover/11310197/
 
 * if /usr/bin/swapoff fails due to OOM, log a friendly explanatory message about it
@@ -112,10 +109,6 @@ Features:
 * systemd-path: add ESP and XBOOTLDR path. Add "private" runtime/state/cache dir enum,
   mapping to $RUNTIME_DIRECTORY, $STATE_DIRECTORY and such
 
-* make "systemd-dissect" an official supported tool, i.e. move to /usr/bin/ and
-  provide man page. Given that we now have a tool that can generate images like
-  this, it's useful to have one that can dump contents of them, too.
-
 * All tools that support --root= should also learn --image= so that they can
   operate on disk images directly. Specifically: bootctl, systemctl,
   coredumpctl. (Already done: systemd-nspawn, systemd-firstboot,
@@ -1153,10 +1146,6 @@ Features:
   - optionally automatically add FORWARD rules to iptables whenever nspawn is
     running, remove them when shut down.
 
-* dissect
-  - refuse mounting over a mount point
-  - automatically discover .roothash files in dissect, similarly to nspawn
-
 * machined:
   - add an API so that libvirt-lxc can inform us about network interfaces being
     removed or added to an existing machine

man/rules/meson.build

@@ -818,6 +818,7 @@ manpages = [
  ['systemd-debug-generator', '8', [], ''],
  ['systemd-delta', '1', [], ''],
  ['systemd-detect-virt', '1', [], ''],
+ ['systemd-dissect', '1', [], ''],
  ['systemd-environment-d-generator',
   '8',
   ['30-systemd-environment-d-generator'],

man/systemd-dissect.xml

@@ -0,0 +1,253 @@
+<?xml version='1.0'?> <!--*-nxml-*-->
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
+
+<refentry id="systemd-dissect"
+    xmlns:xi="http://www.w3.org/2001/XInclude">
+
+  <refentryinfo>
+    <title>systemd-dissect</title>
+    <productname>systemd</productname>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>systemd-dissect</refentrytitle>
+    <manvolnum>1</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>systemd-dissect</refname>
+    <refpurpose>Dissect file system OS images</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <cmdsynopsis>
+      <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="plain"><replaceable>IMAGE</replaceable></arg></command>
+    </cmdsynopsis>
+    <cmdsynopsis>
+      <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--mount</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg></command>
+    </cmdsynopsis>
+    <cmdsynopsis>
+      <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--copy-from</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg> <arg choice="opt"><replaceable>TARGET</replaceable></arg></command>
+    </cmdsynopsis>
+    <cmdsynopsis>
+      <command>systemd-dissect <arg choice="opt" rep="repeat">OPTIONS</arg> <option>--copy-to</option> <arg choice="plain"><replaceable>IMAGE</replaceable></arg> <arg choice="opt"><replaceable>SOURCE</replaceable></arg> <arg choice="plain"><replaceable>PATH</replaceable></arg></command>
+    </cmdsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para><command>systemd-dissect</command> is a tool for introspecting and interacting with file system OS
+    disk images. It supports four different operations:</para>
+
+    <orderedlist>
+      <listitem><para>Show general OS image information, including the image's
+      <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> data,
+      machine ID, partition information and more.</para></listitem>
+
+      <listitem><para>Mount an OS image to a local directory. In this mode it will dissect the OS image and
+      mount the included partitions according to their designation onto a directory and possibly
+      sub-directories.</para></listitem>
+
+      <listitem><para>Copy files and directories in and out of an OS image.</para></listitem>
+    </orderedlist>
+
+    <para>The tool may operate on three types of OS images:</para>
+
+    <orderedlist>
+      <listitem><para>OS disk images containing a GPT partition table envelope, with partitions marked
+      according to the <ulink url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions
+      Specification</ulink>.</para></listitem>
+
+      <listitem><para>OS disk images containing just a plain file-system without an enveloping partition
+      table. (This file system is assumed to be the root file system of the OS.)</para></listitem>
+
+      <listitem><para>OS disk images containing a GPT or MBR partition table, with a single
+      partition only. (This partition is assumed to contain the root file system of the OS.)</para></listitem>
+    </orderedlist>
+
+    <para>OS images may use any kind of Linux-supported file systems. In addition they may make use of LUKS
+    disk encryption, and contain Verity integrity information. Note that qualifying OS images may be booted
+    with <citerefentry><refentrytitle>system-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>'s
+    <option>--image=</option> switch, and be used as root file system for system service using the
+    <varname>RootImage=</varname> unit file setting, see
+    <citerefentry><refentrytitle>system.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Commands</title>
+
+    <para>If neither of the command switches listed below are passed the specified disk image is opened and
+    general information about the image and the contained partitions and their use is shown.</para>
+
+    <variablelist>
+      <varlistentry>
+        <term><option>--mount</option></term>
+        <term><option>-m</option></term>
+
+        <listitem><para>Mount the specified OS image to the specified directory. This will dissect the image,
+        determine the OS root file system — as well as possibly other partitions — and mount them to the
+        specified directory. If the OS image contains multiple partitions marked with the <ulink
+        url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>
+        multiple nested mounts are established. This command expects two arguments: a path to an image file
+        and a path to a directory where to mount the image.</para>
+
+        <para>To unmount an OS image mounted like this use <citerefentry
+        project='man-pages'><refentrytitle>umount</refentrytitle><manvolnum>8</manvolnum></citerefentry>'s
+        <option>-R</option> switch (for recursive operation), so that the OS image and all nested partition
+        mounts are unmounted.</para>
+
+        <para>When the OS image contains LUKS encrypted or Verity integrity protected file systems
+        appropriate volumes are automatically set up and marked for automatic disassembly when the image is
+        unmounted.</para>
+
+        <para>The OS image may either be specified as path to an OS image stored in a regular file or may
+        refer to block device node (in the latter case the block device must be the "whole" device, i.e. not
+        a partition device). (The other supported commands described here support this, too.)</para>
+
+        <para>All mounted file systems are checked with the appropriate <citerefentry
+        project='man-pages'><refentrytitle>fsck</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+        implementation in automatic fixing mode, unless explicitly turned off (<option>--fsck=no</option>) or
+        read-only operation is requested (<option>--read-only</option>).</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>-M</option></term>
+
+        <listitem><para>This is a shortcut for <option>--mount --mkdir</option>.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--copy-from</option></term>
+        <term><option>-x</option></term>
+
+        <listitem><para>Copies a file or directory from the specified OS image into the specified location on
+        the host file system. Expects three arguments: a path to an image file, a source path (relative to
+        the image's root directory) and a destination path (relative to the current working directory, or an
+        absolute path, both outside of the image). If the destination path is omitted or specified as dash
+        (<literal>-</literal>), the specified file is written to standard output. If the source path in the
+        image file system refers to a regular file it is copied to the destination path. In this case access
+        mode, extended attributes and timestamps are copied as well, but file ownership is not. If the source
+        path in the image refers to a directory, it is copied to the destination path, recursively with all
+        containing files and directories. In this case the file ownership is copied too.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--copy-to</option></term>
+        <term><option>-a</option></term>
+
+        <listitem><para>Copies a file or directory from the specified location in the host file system into
+        the specified OS image. Expects three arguments: a path to an image file, a source path (relative to
+        the current working directory, or an absolute path, both outside of the image) and a destination path
+        (relative to the image's root directory). If the source path is omitted or specified as dash
+        (<literal>-</literal>), the data to write is read from standard input. If the source path in the host
+        file system refers to a regular file, it is copied to the destination path. In this case access mode,
+        extended attributes and timestamps are copied as well, but file ownership is not. If the source path
+        in the host file system refers to a directory it is copied to the destination path, recursively with
+        all containing files and directories. In this case the file ownership is copied
+        too.</para>
+
+        <para>As with <option>--mount</option> file system checks are implicitly run before the copy
+        operation begins.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--json=</option><replaceable>MODE</replaceable></term>
+
+        <listitem><para>Shows output formatted as JSON. Expects one of <literal>short</literal> (for the
+        shortest possible output without any redundant whitespace or line breaks), <literal>pretty</literal>
+        (for a pretty version of the same, with indentation and line breaks) or <literal>off</literal> (to turn
+        off json output).</para></listitem>
+      </varlistentry>
+
+      <xi:include href="standard-options.xml" xpointer="help" />
+      <xi:include href="standard-options.xml" xpointer="version" />
+    </variablelist>
+
+  </refsect1>
+
+  <refsect1>
+    <title>Options</title>
+
+    <para>The following options are understood:</para>
+
+    <variablelist>
+      <varlistentry>
+        <term><option>--read-only</option></term>
+        <term><option>-r</option></term>
+
+        <listitem><para>Operate in read-only mode. By default <option>--mount</option> will establish
+        writable mount points. If this option is specified they are established in read-only mode
+        instead.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--fsck=no</option></term>
+
+        <listitem><para>Turn off automatic file system checking. By default when an image is accessed for
+        writing (by <option>--mount</option> or <option>--add</option>) the file systems contained in the OS
+        image are automatically checked using the appropriate <citerefentry
+        project='man-pages'><refentrytitle>fsck</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+        command, in automatic fixing mode. This behavior may be switched off using
+        <option>--fsck=no</option>.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--mkdir</option></term>
+
+        <listitem><para>If combined with <option>--mount</option> the directory to mount the OS image to is
+        created if it is missing. Note that the directory is not automatically removed when the disk image is
+        unmounted again.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--discard=</option></term>
+
+        <listitem><para>Takes one of <literal>disabled</literal>, <literal>loop</literal>,
+        <literal>all</literal>, <literal>crypto</literal>. If <literal>disabled</literal> the image is
+        accessed with empty block discarding turned off. if <literal>loop</literal> discarding is enabled if
+        operating on a regular file. If <literal>crypt</literal> discarding is enabled even on encrypted file
+        systems. If <literal>all</literal> discarding is unconditionally enabled.</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><option>--root-hash=</option></term>
+        <term><option>--root-hash-sig=</option></term>
+        <term><option>--verity-data=</option></term>
+
+        <listitem><para>Configure various aspects of Verity data integrity for the OS
+        image. <option>--root-hash=</option> expects a hex-encoding top-level Verity hash to use for setting
+        up the Verity integrity protection. <option>--root-hash-sig=</option> expects the path to a file
+        containing a PKCS#7 signature file for the hash. This signature is passed to the kernel during
+        activation, which will match it against signature keys available in the kernel
+        keyring. <option>--verity-data=</option> expects the path to a file with the Verity data to use for
+        the OS image, in case it is stored in a detached file. It is recommended to embed the Verity data
+        directly in the image, using the Verity mechanisms in the <ulink
+        url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>.</para></listitem>
+      </varlistentry>
+
+    </variablelist>
+
+  </refsect1>
+
+  <refsect1>
+    <title>Exit status</title>
+
+    <para>On success, 0 is returned, a non-zero failure code
+    otherwise.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>See Also</title>
+    <para>
+      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>system-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>system.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
+      <ulink url="https://systemd.io/DISCOVERABLE_PARTITIONS">Discoverable Partitions Specification</ulink>,
+      <citerefentry project='man-pages'><refentrytitle>umount</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>

meson.build

@@ -1898,8 +1898,7 @@ if conf.get('HAVE_BLKID') == 1
                 include_directories : includes,
                 link_with : [libshared],
                 install_rpath : rootlibexecdir,
-                install : true,
-                install_dir : rootlibexecdir)
+                install : true)
 endif
 
 if conf.get('ENABLE_RESOLVE') == 1

src/basic/copy.c

@@ -969,6 +969,21 @@ int copy_times(int fdf, int fdt, CopyFlags flags) {
         return 0;
 }
 
+int copy_access(int fdf, int fdt) {
+        struct stat st;
+
+        assert(fdf >= 0);
+        assert(fdt >= 0);
+
+        if (fstat(fdf, &st) < 0)
+                return -errno;
+
+        if (fchmod(fdt, st.st_mode & 07777) < 0)
+                return -errno;
+
+        return 0;
+}
+
 int copy_xattr(int fdf, int fdt) {
         _cleanup_free_ char *names = NULL;
         int ret = 0, r;

src/basic/copy.h

@@ -61,4 +61,5 @@ static inline int copy_bytes(int fdf, int fdt, uint64_t max_bytes, CopyFlags cop
 }
 
 int copy_times(int fdf, int fdt, CopyFlags flags);
+int copy_access(int fdf, int fdt);
 int copy_xattr(int fdf, int fdt);

src/basic/mkdir.c

@@ -106,7 +106,7 @@ int mkdir_parents_internal(const char *prefix, const char *path, mode_t mode, ui
         /* return immediately if directory exists */
         e = strrchr(path, '/');
         if (!e)
-                return -EINVAL;
+                return 0;
 
         if (e == path)
                 return 0;