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-rw-r--r--man/systemd-nspawn.xml46
1 files changed, 46 insertions, 0 deletions
diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml
index 88b5758d91..3a2af2711c 100644
--- a/man/systemd-nspawn.xml
+++ b/man/systemd-nspawn.xml
@@ -565,6 +565,52 @@
</varlistentry>
<varlistentry>
+ <term><option>--overlay=</option></term>
+ <term><option>--overlay-ro=</option></term>
+
+ <listitem><para>Combine multiple directory trees into one
+ overlay file system and mount it into the container. Takes a
+ list of colon-separated paths to the directory trees to
+ combine and the destination mount point.</para>
+
+ <para>If three or more paths are specified, then the last
+ specified path is the destination mount point in the
+ container, all paths specified before refer to directory trees
+ on the host and are combined in the specified order into one
+ overlay file system. The left-most path is hence the lowest
+ directory tree, the second-to-last path the highest directory
+ tree in the stacking order. If <option>--overlay-ro=</option>
+ is used instead of <option>--overlay=</option> a read-only
+ overlay file system is created. If a writable overlay file
+ system is created all changes made to it are written to the
+ highest directory tree in the stacking order, i.e. the
+ second-to-last specified.</para>
+
+ <para>If only two paths are specified, then the second
+ specified path is used both as the top-level directory tree in
+ the stacking order as seen from the host, as well as the mount
+ point for the overlay file system in the container. At least
+ two paths have to be specified.</para>
+
+ <para>For details about overlay file systems, see <ulink
+ url="https://www.kernel.org/doc/Documentation/filesystems/overlayfs.txt">overlayfs.txt</ulink>. Note
+ that the semantics of overlay file systems are substantially
+ different from normal file systems, in particular regarding
+ reported device and inode information. Device and inode
+ information may change for a file while it is being written
+ to, and processes might see out-of-date versions of files at
+ times. Note that this switch automatically derives the
+ <literal>workdir=</literal> mount option for the overlay file
+ system from the top-level directory tree, making it a sibling
+ of it. It is hence essential that the top-level directory tree
+ is not a mount point itself (since the working directory must
+ be on the same file system as the top-most directory
+ tree). Also note that the <literal>lowerdir=</literal> mount
+ option receives the paths to stack in the opposite order of
+ this switch.</para></listitem>
+ </varlistentry>
+
+ <varlistentry>
<term><option>--setenv=</option></term>
<listitem><para>Specifies an environment variable assignment