summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
-rw-r--r--man/systemd-nspawn.xml27
-rw-r--r--src/nspawn/nspawn-mount.c45
-rw-r--r--src/nspawn/nspawn-mount.h1
3 files changed, 57 insertions, 16 deletions
diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml
index 84fa9cadef..cd0a90d82f 100644
--- a/man/systemd-nspawn.xml
+++ b/man/systemd-nspawn.xml
@@ -741,16 +741,18 @@
<term><option>--bind-ro=</option></term>
<listitem><para>Bind mount a file or directory from the host into the container. Takes one of: a path
- argument — in which case the specified path will be mounted from the host to the same path in the container —,
- or a colon-separated pair of paths — in which case the first specified path is the source in the host, and the
- second path is the destination in the container —, or a colon-separated triple of source path, destination path
+ argument — in which case the specified path will be mounted from the host to the same path in the container, or
+ a colon-separated pair of paths — in which case the first specified path is the source in the host, and the
+ second path is the destination in the container, or a colon-separated triple of source path, destination path
and mount options. The source path may optionally be prefixed with a <literal>+</literal> character. If so, the
- source path is taken relative to the images root directory. This permits setting up bind mounts within the
- container image. Mount options are comma-separated and currently, only "rbind" and "norbind" are allowed,
- controlling whether to create a recursive or a regular bind mount. Defaults to "rbind". Backslash escapes are
- interpreted, so <literal>\:</literal> may be used to embed colons in either path. This option may be specified
- multiple times for creating multiple independent bind mount points. The <option>--bind-ro=</option> option
- creates read-only bind mounts.</para></listitem>
+ source path is taken relative to the image's root directory. This permits setting up bind mounts within the
+ container image. The source path may be specified as empty string, in which case a temporary directory below
+ the host's <filename>/var/tmp</filename> directory is used. It is automatically removed when the container is
+ shut down. Mount options are comma-separated and currently, only <option>rbind</option> and
+ <option>norbind</option> are allowed, controlling whether to create a recursive or a regular bind
+ mount. Defaults to "rbind". Backslash escapes are interpreted, so <literal>\:</literal> may be used to embed
+ colons in either path. This option may be specified multiple times for creating multiple independent bind
+ mount points. The <option>--bind-ro=</option> option creates read-only bind mounts.</para></listitem>
</varlistentry>
<varlistentry>
@@ -805,7 +807,12 @@
two paths have to be specified.</para>
<para>The source paths may optionally be prefixed with <literal>+</literal> character. If so they are taken
- relative to the image's root directory.</para>
+ relative to the image's root directory. The uppermost source path may also be specified as empty string, in
+ which case a temporary directory below the host's <filename>/var/tmp</filename> is used. The directory is
+ removed automatically when the container is shut down. This behaviour is useful in order to make read-only
+ container directories writable while the container is running. For example, use the
+ <literal>--overlay=+/var::/var</literal> option in order to automatically overlay a writable temporary
+ directory on a read-only <filename>/var</filename> directory.</para>
<para>For details about overlay file systems, see <ulink
url="https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt">overlayfs.txt</ulink>. Note
diff --git a/src/nspawn/nspawn-mount.c b/src/nspawn/nspawn-mount.c
index 291a88a9ac..3a069cf0e0 100644
--- a/src/nspawn/nspawn-mount.c
+++ b/src/nspawn/nspawn-mount.c
@@ -75,6 +75,11 @@ void custom_mount_free_all(CustomMount *l, unsigned n) {
free(m->work_dir);
}
+ if (m->rm_rf_tmpdir) {
+ (void) rm_rf(m->rm_rf_tmpdir, REMOVE_ROOT|REMOVE_PHYSICAL);
+ free(m->rm_rf_tmpdir);
+ }
+
strv_free(m->lower);
}
@@ -142,6 +147,24 @@ int custom_mount_prepare_all(const char *dest, CustomMount *l, unsigned n) {
free(m->source);
m->source = s;
+ } else {
+ /* No source specified? In that case, use a throw-away temporary directory in /var/tmp */
+
+ m->rm_rf_tmpdir = strdup("/var/tmp/nspawn-temp-XXXXXX");
+ if (!m->rm_rf_tmpdir)
+ return log_oom();
+
+ if (!mkdtemp(m->rm_rf_tmpdir)) {
+ m->rm_rf_tmpdir = mfree(m->rm_rf_tmpdir);
+ return log_error_errno(errno, "Failed to acquire temporary directory: %m");
+ }
+
+ m->source = strjoin(m->rm_rf_tmpdir, "/src");
+ if (!m->source)
+ return log_oom();
+
+ if (mkdir(m->source, 0755) < 0)
+ return log_error_errno(errno, "Failed to create %s: %m", m->source);
}
if (m->type == CUSTOM_MOUNT_OVERLAY) {
@@ -207,8 +230,11 @@ int bind_mount_parse(CustomMount **l, unsigned *n, const char *s, bool read_only
return -ENOMEM;
}
- if (!source_path_is_valid(source))
+ if (isempty(source))
+ source = NULL;
+ else if (!source_path_is_valid(source))
return -EINVAL;
+
if (!path_is_absolute(destination))
return -EINVAL;
@@ -288,19 +314,26 @@ int overlay_mount_parse(CustomMount **l, unsigned *n, const char *s, bool read_o
if (!destination)
return -ENOMEM;
} else {
- int i;
+ char **i;
/* If more than two parameters are specified, the last one is the destination, the second to last one
* the "upper", and all before that the "lower" directories. */
- for (i = 0; i < k - 1; i++)
- if (!source_path_is_valid(lower[i]))
- return -EINVAL;
-
destination = lower[k - 1];
upper = lower[k - 2];
lower[k - 2] = NULL;
+ STRV_FOREACH(i, lower)
+ if (!source_path_is_valid(*i))
+ return -EINVAL;
+
+ /* If the upper directory is unspecified, then let's create it automatically as a throw-away directory
+ * in /var/tmp */
+ if (isempty(upper))
+ upper = NULL;
+ else if (!source_path_is_valid(upper))
+ return -EINVAL;
+
if (!path_is_absolute(destination))
return -EINVAL;
}
diff --git a/src/nspawn/nspawn-mount.h b/src/nspawn/nspawn-mount.h
index dc8be438ac..467082a737 100644
--- a/src/nspawn/nspawn-mount.h
+++ b/src/nspawn/nspawn-mount.h
@@ -56,6 +56,7 @@ typedef struct CustomMount {
char *options;
char *work_dir;
char **lower;
+ char *rm_rf_tmpdir;
} CustomMount;
CustomMount* custom_mount_add(CustomMount **l, unsigned *n, CustomMountType t);