6 files changed, 88 insertions, 6 deletions
diff --git a/hurd/translator/tmpfs.mdwn b/hurd/translator/tmpfs.mdwn
index abd47c96..0179ad6c 100644
--- a/hurd/translator/tmpfs.mdwn
+++ b/hurd/translator/tmpfs.mdwn
@@ -1,4 +1,5 @@
-[[!meta copyright="Copyright © 2007, 2008 Free Software Foundation, Inc."]]
+[[!meta copyright="Copyright © 2007, 2008, 2009 Free Software Foundation,
+Inc."]]
 
 [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
 id="license" text="Permission is granted to copy, distribute and/or modify this
@@ -13,7 +14,13 @@ is included in the section entitled
 
 It is based on [[libdiskfs]].
 
-It's not working correctly at the moment.
+Even though there are other possibilities of creating a
+[[libstore/examples/ramdisk]] and running a regular, for example, [[`ext2` file
+system|ext2fs]] on it, having a real `tmpfs` is better, as it need not deal
+with the additional block-level indirection layer that `ext2` (or any other
+disk-based file system) imposes.
+
+However, `tmpfs` is not working correctly at the moment:
 
 [[!inline
 pages="hurd/translator/tmpfs/*"
diff --git a/hurd/translator/tmpfs/notes_bing.mdwn b/hurd/translator/tmpfs/notes_bing.mdwn
index b36fc1aa..fa3eeac2 100644
--- a/hurd/translator/tmpfs/notes_bing.mdwn
+++ b/hurd/translator/tmpfs/notes_bing.mdwn
@@ -1,4 +1,5 @@
-[[!meta copyright="Copyright © 2007, 2008 Free Software Foundation, Inc."]]
+[[!meta copyright="Copyright © 2007, 2008, 2009 Free Software Foundation,
+Inc."]]
 
 [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
 id="license" text="Permission is granted to copy, distribute and/or modify this
@@ -8,6 +9,8 @@ Sections, no Front-Cover Texts, and no Back-Cover Texts.  A copy of the license
 is included in the section entitled
 [[GNU Free Documentation License|/fdl]]."]]"""]]
 
+[[!tag open_issue_hurd]]
+
 1. to run tmpfs as a regular user, /servers/default-pager must be executable by
     that user.  by default it seems to be set to read/write.
 
diff --git a/hurd/translator/tmpfs/notes_various.mdwn b/hurd/translator/tmpfs/notes_various.mdwn
index 3ec649e5..01dc87d2 100644
--- a/hurd/translator/tmpfs/notes_various.mdwn
+++ b/hurd/translator/tmpfs/notes_various.mdwn
@@ -1,5 +1,5 @@
-[[!meta copyright="Copyright © 2005, 2006, 2007, 2008 Free Software Foundation,
-Inc."]]
+[[!meta copyright="Copyright © 2005, 2006, 2007, 2008, 2009 Free Software
+Foundation, Inc."]]
 
 [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
 id="license" text="Permission is granted to copy, distribute and/or modify this
@@ -9,6 +9,8 @@ Sections, no Front-Cover Texts, and no Back-Cover Texts.  A copy of the license
 is included in the section entitled
 [[GNU Free Documentation License|/fdl]]."]]"""]]
 
+[[!tag open_issue_hurd]]
+
     <antrik> hde: what's the status on tmpfs?
     <hde> Broke
     <hde> k0ro traced the errors like the assert show above to a pager problem.
diff --git a/hurd/translator/unionfs.mdwn b/hurd/translator/unionfs.mdwn
index 8a29d0f7..6f845102 100644
--- a/hurd/translator/unionfs.mdwn
+++ b/hurd/translator/unionfs.mdwn
@@ -1,4 +1,4 @@
-[[!meta copyright="Copyright © 2008 Free Software Foundation, Inc."]]
+[[!meta copyright="Copyright © 2008, 2009 Free Software Foundation, Inc."]]
 
 [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
 id="license" text="Permission is granted to copy, distribute and/or modify this
@@ -15,3 +15,11 @@ is included in the section entitled
 # `stowfs`
 
 ... is a special mode of `unionfs`.
+
+# See Also
+
+  * [[unionmount]]
+
+# External Links
+
+  * [*Unioning file systems for Linux*](http://valerieaurora.org/union/)
diff --git a/hurd/translator/unionmount.mdwn b/hurd/translator/unionmount.mdwn
new file mode 100644
index 00000000..47a3d85d
--- /dev/null
+++ b/hurd/translator/unionmount.mdwn
@@ -0,0 +1,60 @@
+[[!meta copyright="Copyright © 2009 Free Software Foundation, Inc."]]
+
+[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
+id="license" text="Permission is granted to copy, distribute and/or modify this
+document under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no Invariant
+Sections, no Front-Cover Texts, and no Back-Cover Texts.  A copy of the license
+is included in the section entitled
+[[GNU Free Documentation License|/fdl]]."]]"""]]
+
+[[!meta title="Union Mounts"]]
+
+When setting a translator on Hurd -- similar to mounting a file system on UNIX
+-- the new node(s) exported by the translator are obscuring the original node
+where the translator is set, and any nodes below it in the directory tree. The
+translator itself can access the underlying node (which is a very nice feature,
+as it allows translators presenting the contents of the node in a different
+format); but it's no longer accessible from the "outside".
+
+Plan9 has a feature where a file system can be mounted in union mode: the new
+file system doesn't obscure the mount point in this case, but instead the
+contents are combined. (This feature has also been under discussion in Linux
+for a couple of years now, under the label "VFS-based union mounts".)
+
+This kind of union mounts is generally useful, as it's sometimes more
+convenient than unioning existing filesystem locations with unionfs -- it's not
+necessary to mount a file system that is to be unioned at some external
+location first: just union-mount it directly at the target location.
+
+But union mounts also allow creating passive translator hierarchies: If there
+is a passive translator on a parent node, and further passive translators on
+child nodes, the union mount allows the child nodes with the further translator
+settings still to be visible after the parent translator has started.
+
+This could be useful for device nodes for example: let's say we have an
+ethernet multiplexer at /dev/veth. Now the virtual subnodes could all be
+directly under /dev, i.e. /dev/veth0, /dev/veth1 etc., and explicitely refer to
+the main /dev/veth node in the translator command line. It would be more
+elegant however to store the virtual nodes direcly below the main multiplexer
+node -- /dev/veth/0, /dev/veth/1 etc.
+
+There are two possible approaches how union mounts could be implemented in the
+Hurd. The first one is to let the various translators handle union mounts
+internally, i.e. let them present the underlying nodes to the clients in
+addition to the actual nodes they export themselfs. This probably can be
+implemented as some kind of extension to the existing netfs and diskfs
+libraries.
+
+The other possible apporach is less efficient and probably more tricky, but
+probably also more generic: create a special unionmount translator, which
+serves as a kind of proxy: setting the union-mounted translator on some
+internal node; and at the actual mount location, presenting a union of the
+nodes exported by this translator, and the nodes from the underlying file
+system.
+
+The goal of this project is implementing union mounts using either of the
+approaches described above. (Though it might be useful initially to prototype
+both for comparision.) The ethernet multiplexer shall serve as an example use
+case -- any changes necessary to allow using it with the union mount
+functionality are also to be considered part of the task.
diff --git a/hurd/translator/wishlist_2.mdwn b/hurd/translator/wishlist_2.mdwn
index 3ea68999..a927db55 100644
--- a/hurd/translator/wishlist_2.mdwn
+++ b/hurd/translator/wishlist_2.mdwn
@@ -76,6 +76,8 @@ Here's an [idea](http://www.circlemud.org/~jelson/software/fusd/docs/node13.html
 
 Am I off my rocker, or does an IMAP/POP translator sound like a good idea? It would make your remote mail servers look like local ones. Or what about a translator that makes a mbox format mail spool look like a directory. Can anyone think of a good use for an SMTP translator?
 
+*Definitely: Copy my email in there to send it.* -- [[ArneBab|community/weblogs/ArneBab]]
+
 ## <a name="UUEncode"> </a> UUEncode
 
 How about a UUEncode translator for those places you can only store ASCII. Combine this with a NNTP translator and store your data in someone's Usenet archive. Or since, (as far as I know), there are no size limitations on file names in the Hurd, why not have a filesystem translator whose underlying store is a file name. (Now ls becomes cat).