nspawn: add ability to configure overlay mounts to .nspawn files

Fixes: #4634

4 files changed, 40 insertions, 0 deletions

diff --git a/man/systemd.nspawn.xml b/man/systemd.nspawn.xml
index b1344d6c10..7143188356 100644
--- a/man/systemd.nspawn.xml
+++ b/man/systemd.nspawn.xml
@@ -335,6 +335,17 @@
       </varlistentry>
 
       <varlistentry>
+        <term><varname>Overlay=</varname></term>
+        <term><varname>OverlayReadOnly=</varname></term>
+
+        <listitem><para>Adds an overlay mount point. Takes a colon-separated list of paths.  This option may be used
+        multiple times to configure multiple overlay mounts. This option is equivalent to the command line switches
+        <option>--overlay=</option> and <option>--overlay-ro=</option>, see
+        <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry> for details
+        about the specific options supported. This setting is privileged (see above).</para></listitem>
+      </varlistentry>
+
+      <varlistentry>
         <term><varname>PrivateUsersChown=</varname></term>
 
         <listitem><para>Configures whether the ownership of the files and directories in the container tree shall be
diff --git a/src/nspawn/nspawn-gperf.gperf b/src/nspawn/nspawn-gperf.gperf
index 3231a48d5a..c0fa4bfa1f 100644
--- a/src/nspawn/nspawn-gperf.gperf
+++ b/src/nspawn/nspawn-gperf.gperf
@@ -33,6 +33,8 @@ Files.Volatile,               config_parse_volatile_mode, 0, offsetof(Settings,
 Files.Bind,                   config_parse_bind,          0, 0
 Files.BindReadOnly,           config_parse_bind,          1, 0
 Files.TemporaryFileSystem,    config_parse_tmpfs,         0, 0
+Files.Overlay,                config_parse_overlay,       0, 0
+Files.OverlayReadOnly,        config_parse_overlay,       1, 0
 Files.PrivateUsersChown,      config_parse_tristate,      0, offsetof(Settings, userns_chown)
 Network.Private,              config_parse_tristate,      0, offsetof(Settings, private_network)
 Network.Interface,            config_parse_strv,          0, offsetof(Settings, network_interfaces)
diff --git a/src/nspawn/nspawn-settings.c b/src/nspawn/nspawn-settings.c
index 09c8f070ba..22b74d88e4 100644
--- a/src/nspawn/nspawn-settings.c
+++ b/src/nspawn/nspawn-settings.c
@@ -293,6 +293,32 @@ int config_parse_tmpfs(
         return 0;
 }
 
+int config_parse_overlay(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        Settings *settings = data;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+
+        r = overlay_mount_parse(&settings->custom_mounts, &settings->n_custom_mounts, rvalue, ltype);
+        if (r < 0)
+                log_syntax(unit, LOG_ERR, filename, line, r, "Invalid overlay file system specification %s, ignoring: %m", rvalue);
+
+        return 0;
+}
+
 int config_parse_veth_extra(
                 const char *unit,
                 const char *filename,
diff --git a/src/nspawn/nspawn-settings.h b/src/nspawn/nspawn-settings.h
index 231e6d7266..4bd0c642df 100644
--- a/src/nspawn/nspawn-settings.h
+++ b/src/nspawn/nspawn-settings.h
@@ -111,6 +111,7 @@ int config_parse_expose_port(const char *unit, const char *filename, unsigned li
 int config_parse_volatile_mode(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_bind(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_tmpfs(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_overlay(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_veth_extra(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_network_zone(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_boot(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);