shared: add new IMAGE_VERSION=/IMAGE_ID= field to /etc/os-release

This specifes two new optional fields for /etc/os-release:
IMAGE_VERSION= and IMAGE_ID= that are supposed to identify the image of
the current booted system by name and version.

This is inspired by the versioning stuff in
https://github.com/systemd/mkosi/pull/683.

In environments where pre-built images are installed and updated as a
whole the existing os-release version/distro identifier are not
sufficient to describe the system's version, as they describe only the
distro an image is built from, but not the image itself, even if that
image is deployed many times on many systems, and even if that image
contains more resources than just the RPMs/DEBs.

In particular, "mkosi" is a tool for building disk images based on
distro RPMs with additional resources dropped in. The combination of all
of these together with their versions should also carry an identifier
and version, and that's what IMAGE_VERSION= and IMAGE_ID= is supposed to
be.

9 files changed, 62 insertions, 5 deletions

diff --git a/man/os-release.xml b/man/os-release.xml
index e6162bdacf..e8462500f2 100644
--- a/man/os-release.xml
+++ b/man/os-release.xml
@@ -346,6 +346,28 @@
         <literal>SYSEXT_LEVEL=15.14</literal>.</para></listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><varname>IMAGE_ID=</varname></term>
+
+        <listitem><para> A lower-case string (no spaces or other characters outside of 0–9, a–z, ".", "_" and
+        "-"), identifying a specific image of the operating system. This is supposed to be used for
+        environments where OS images are prepared, built, shipped and updated as comprehensive, consistent OS
+        images. This field is optional and may not be implemented on all systems, in particulary not on those
+        that are not managed via images but put together and updated from individual packages and on the
+        local system.  Examples: <literal>IMAGE_ID=vendorx-cashier-system</literal>,
+        <literal>IMAGE_ID=netbook-image</literal> </para></listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><varname>IMAGE_VERSION=</varname></term>
+
+        <listitem><para>A lower-case string (mostly numeric, no spaces or other characters outside of 0–9,
+        a–z, ".", "_" and "-") identifying the OS image version. This is supposed to be used together with
+        <varname>IMAGE_ID</varname> described above, to discern different versions of the same
+        image. Examples: <literal>IMAGE_VERSION=33</literal>,
+        <literal>IMAGE_VERSION=47.1rc1</literal> </para></listitem>
+      </varlistentry>
+
     </variablelist>
 
     <para>If you are reading this file from C code or a shell script
diff --git a/man/repart.d.xml b/man/repart.d.xml
index 66debd336f..b6346b3f85 100644
--- a/man/repart.d.xml
+++ b/man/repart.d.xml
@@ -543,11 +543,13 @@
           </thead>
           <tbody>
             <xi:include href="standard-specifiers.xml" xpointer="a"/>
+            <xi:include href="standard-specifiers.xml" xpointer="A"/>
             <xi:include href="standard-specifiers.xml" xpointer="b"/>
             <xi:include href="standard-specifiers.xml" xpointer="B"/>
             <xi:include href="standard-specifiers.xml" xpointer="H"/>
             <xi:include href="standard-specifiers.xml" xpointer="l"/>
             <xi:include href="standard-specifiers.xml" xpointer="m"/>
+            <xi:include href="standard-specifiers.xml" xpointer="M"/>
             <xi:include href="standard-specifiers.xml" xpointer="o"/>
             <xi:include href="standard-specifiers.xml" xpointer="v"/>
             <xi:include href="standard-specifiers.xml" xpointer="w"/>
diff --git a/man/standard-specifiers.xml b/man/standard-specifiers.xml
index 40bb6cc3ea..f1666365b9 100644
--- a/man/standard-specifiers.xml
+++ b/man/standard-specifiers.xml
@@ -4,16 +4,21 @@
 <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
 
 <tbody>
-  <row id='b'>
-    <entry><literal>%b</literal></entry>
-    <entry>Boot ID</entry>
-    <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
-  </row>
   <row id='a'>
     <entry><literal>%a</literal></entry>
     <entry>Architecture</entry>
     <entry>A short string identifying the architecture of the local system. A string such as <constant>x86</constant>, <constant>x86-64</constant> or <constant>arm64</constant>. See the architectures defined for <varname>ConditionArchitecture=</varname> in <citerefentry><refentrytitle>systemd.unit</refentrytitle><manvolnum>5</manvolnum></citerefentry> for a full list.</entry>
   </row>
+  <row id='A'>
+    <entry><literal>%A</literal></entry>
+    <entry>Operating system image version</entry>
+    <entry>The operating system image version identifier of the running system, as read from the <varname>IMAGE_VERSION=</varname> field of <filename>/etc/os-release</filename>. If not set, resolves to an empty string. See <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information.</entry>
+  </row>
+  <row id='b'>
+    <entry><literal>%b</literal></entry>
+    <entry>Boot ID</entry>
+    <entry>The boot ID of the running system, formatted as string. See <citerefentry><refentrytitle>random</refentrytitle><manvolnum>4</manvolnum></citerefentry> for more information.</entry>
+  </row>
   <row id='B'>
     <entry><literal>%B</literal></entry>
     <entry>Operating system build ID</entry>
@@ -34,6 +39,11 @@
     <entry>Machine ID</entry>
     <entry>The machine ID of the running system, formatted as string. See <citerefentry><refentrytitle>machine-id</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information.</entry>
   </row>
+  <row id='M'>
+    <entry><literal>%M</literal></entry>
+    <entry>Operating system image identifier</entry>
+    <entry>The operating system image identifier of the running system, as read from the <varname>IMAGE_ID=</varname> field of <filename>/etc/os-release</filename>. If not set, resolves to an empty string. See <citerefentry><refentrytitle>os-release</refentrytitle><manvolnum>5</manvolnum></citerefentry> for more information.</entry>
+  </row>
   <row id='o'>
     <entry><literal>%o</literal></entry>
     <entry>Operating system ID</entry>
diff --git a/man/systemd.dnssd.xml b/man/systemd.dnssd.xml
index 96a14b1ba5..be2e873efb 100644
--- a/man/systemd.dnssd.xml
+++ b/man/systemd.dnssd.xml
@@ -90,10 +90,12 @@
                 </thead>
                 <tbody>
                   <xi:include href="standard-specifiers.xml" xpointer="a"/>
+                  <xi:include href="standard-specifiers.xml" xpointer="A"/>
                   <xi:include href="standard-specifiers.xml" xpointer="b"/>
                   <xi:include href="standard-specifiers.xml" xpointer="B"/>
                   <xi:include href="standard-specifiers.xml" xpointer="H"/>
                   <xi:include href="standard-specifiers.xml" xpointer="m"/>
+                  <xi:include href="standard-specifiers.xml" xpointer="M"/>
                   <xi:include href="standard-specifiers.xml" xpointer="o"/>
                   <xi:include href="standard-specifiers.xml" xpointer="v"/>
                   <xi:include href="standard-specifiers.xml" xpointer="w"/>
diff --git a/man/systemd.unit.xml b/man/systemd.unit.xml
index 42dcbac72c..631658d88a 100644
--- a/man/systemd.unit.xml
+++ b/man/systemd.unit.xml
@@ -1872,6 +1872,7 @@
             <entry>Architecture</entry>
             <entry>A short string identifying the architecture of the local system. A string such as <constant>x86</constant>, <constant>x86-64</constant> or <constant>arm64</constant>. See the architectures defined for <varname>ConditionArchitecture=</varname> above for a full list.</entry>
           </row>
+          <xi:include href="standard-specifiers.xml" xpointer="A"/>
           <xi:include href="standard-specifiers.xml" xpointer="b"/>
           <xi:include href="standard-specifiers.xml" xpointer="B"/>
           <row>
@@ -1944,6 +1945,7 @@ Note that this setting is <emphasis>not</emphasis> influenced by the <varname>Us
             <entry>This is either <filename>/var/log</filename> (for the system manager) or the path <literal>$XDG_CONFIG_HOME</literal> resolves to with <filename index="false">/log</filename> appended (for user managers).</entry>
           </row>
           <xi:include href="standard-specifiers.xml" xpointer="m"/>
+          <xi:include href="standard-specifiers.xml" xpointer="M"/>
           <row>
             <entry><literal>%n</literal></entry>
             <entry>Full unit name</entry>
diff --git a/man/sysusers.d.xml b/man/sysusers.d.xml
index e15c1b2eee..fd67c1f078 100644
--- a/man/sysusers.d.xml
+++ b/man/sysusers.d.xml
@@ -259,11 +259,13 @@ r     -        500-900
         </thead>
         <tbody>
           <xi:include href="standard-specifiers.xml" xpointer="a"/>
+          <xi:include href="standard-specifiers.xml" xpointer="A"/>
           <xi:include href="standard-specifiers.xml" xpointer="b"/>
           <xi:include href="standard-specifiers.xml" xpointer="B"/>
           <xi:include href="standard-specifiers.xml" xpointer="H"/>
           <xi:include href="standard-specifiers.xml" xpointer="l"/>
           <xi:include href="standard-specifiers.xml" xpointer="m"/>
+          <xi:include href="standard-specifiers.xml" xpointer="M"/>
           <xi:include href="standard-specifiers.xml" xpointer="o"/>
           <xi:include href="standard-specifiers.xml" xpointer="T"/>
           <xi:include href="standard-specifiers.xml" xpointer="v"/>
diff --git a/man/tmpfiles.d.xml b/man/tmpfiles.d.xml
index 4adbf6bb0a..55b763e26d 100644
--- a/man/tmpfiles.d.xml
+++ b/man/tmpfiles.d.xml
@@ -635,6 +635,7 @@ w- /proc/sys/vm/swappiness - - - - 10</programlisting></para>
           </thead>
           <tbody>
             <xi:include href="standard-specifiers.xml" xpointer="a"/>
+            <xi:include href="standard-specifiers.xml" xpointer="A"/>
             <xi:include href="standard-specifiers.xml" xpointer="b"/>
             <xi:include href="standard-specifiers.xml" xpointer="B"/>
             <row>
@@ -665,6 +666,7 @@ w- /proc/sys/vm/swappiness - - - - 10</programlisting></para>
               <entry>In <option>--user</option> mode, this is the same as <varname>$XDG_CONFIG_HOME</varname> with <filename index="false">/log</filename> appended, and <filename>/var/log</filename> otherwise.</entry>
             </row>
             <xi:include href="standard-specifiers.xml" xpointer="m"/>
+            <xi:include href="standard-specifiers.xml" xpointer="M"/>
             <xi:include href="standard-specifiers.xml" xpointer="o"/>
             <row>
               <entry><literal>%S</literal></entry>
diff --git a/src/shared/specifier.c b/src/shared/specifier.c
index 24e8781805..6edf4a215c 100644
--- a/src/shared/specifier.c
+++ b/src/shared/specifier.c
@@ -234,6 +234,14 @@ int specifier_os_variant_id(char specifier, const void *data, const void *userda
         return specifier_os_release_common("VARIANT_ID", ret);
 }
 
+int specifier_os_image_id(char specifier, const void *data, const void *userdata, char **ret) {
+        return specifier_os_release_common("IMAGE_ID", ret);
+}
+
+int specifier_os_image_version(char specifier, const void *data, const void *userdata, char **ret) {
+        return specifier_os_release_common("IMAGE_VERSION", ret);
+}
+
 int specifier_group_name(char specifier, const void *data, const void *userdata, char **ret) {
         char *t;
 
diff --git a/src/shared/specifier.h b/src/shared/specifier.h
index 1323b41d98..6735a7a363 100644
--- a/src/shared/specifier.h
+++ b/src/shared/specifier.h
@@ -25,6 +25,8 @@ int specifier_os_id(char specifier, const void *data, const void *userdata, char
 int specifier_os_version_id(char specifier, const void *data, const void *userdata, char **ret);
 int specifier_os_build_id(char specifier, const void *data, const void *userdata, char **ret);
 int specifier_os_variant_id(char specifier, const void *data, const void *userdata, char **ret);
+int specifier_os_image_id(char specifier, const void *data, const void *userdata, char **ret);
+int specifier_os_image_version(char specifier, const void *data, const void *userdata, char **ret);
 
 int specifier_group_name(char specifier, const void *data, const void *userdata, char **ret);
 int specifier_group_id(char specifier, const void *data, const void *userdata, char **ret);
@@ -41,11 +43,13 @@ int specifier_var_tmp_dir(char specifier, const void *data, const void *userdata
  *
  * COMMON_SYSTEM_SPECIFIERS:
  * %a: the native userspace architecture
+ * %A: the OS image version, according to /etc/os-release
  * %b: the boot ID of the running system
  * %B: the OS build ID, according to /etc/os-release
  * %H: the hostname of the running system
  * %l: the short hostname of the running system
  * %m: the machine ID of the running system
+ * %M: the OS image ID, according to /etc/os-release
  * %o: the OS ID according to /etc/os-release
  * %v: the kernel version
  * %w: the OS version ID, according to /etc/os-release
@@ -64,16 +68,19 @@ int specifier_var_tmp_dir(char specifier, const void *data, const void *userdata
 
 #define COMMON_SYSTEM_SPECIFIERS                  \
         { 'a', specifier_architecture,    NULL }, \
+        { 'A', specifier_os_image_version,NULL }, \
         { 'b', specifier_boot_id,         NULL }, \
         { 'B', specifier_os_build_id,     NULL }, \
         { 'H', specifier_host_name,       NULL }, \
         { 'l', specifier_short_host_name, NULL }, \
         { 'm', specifier_machine_id,      NULL }, \
+        { 'M', specifier_os_image_id,     NULL }, \
         { 'o', specifier_os_id,           NULL }, \
         { 'v', specifier_kernel_release,  NULL }, \
         { 'w', specifier_os_version_id,   NULL }, \
         { 'W', specifier_os_variant_id,   NULL }
 
+
 #define COMMON_CREDS_SPECIFIERS                   \
         { 'g', specifier_group_name,      NULL }, \
         { 'G', specifier_group_id,        NULL }, \