From 220222a0fecf0fbd9f49633abef552dd019ab9cd Mon Sep 17 00:00:00 2001 From: Max Reitz Date: Wed, 17 Feb 2021 12:58:44 +0100 Subject: qsd: Document FUSE exports Implementing FUSE exports required no changes to the storage daemon, so we forgot to document them there. Considering that both NBD and vhost-user-blk exports are documented in its man page (and NBD exports in its --help text), we should probably do the same for FUSE. Signed-off-by: Max Reitz Message-Id: <20210217115844.62661-1-mreitz@redhat.com> Reviewed-by: Eric Blake --- docs/tools/qemu-storage-daemon.rst | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) (limited to 'docs/tools/qemu-storage-daemon.rst') diff --git a/docs/tools/qemu-storage-daemon.rst b/docs/tools/qemu-storage-daemon.rst index 086493ebb3..3ec4bdd914 100644 --- a/docs/tools/qemu-storage-daemon.rst +++ b/docs/tools/qemu-storage-daemon.rst @@ -74,6 +74,7 @@ Standard options: .. option:: --export [type=]nbd,id=,node-name=[,name=][,writable=on|off][,bitmap=] --export [type=]vhost-user-blk,id=,node-name=,addr.type=unix,addr.path=[,writable=on|off][,logical-block-size=][,num-queues=] --export [type=]vhost-user-blk,id=,node-name=,addr.type=fd,addr.str=[,writable=on|off][,logical-block-size=][,num-queues=] + --export [type=]fuse,id=,node-name=,mountpoint=[,growable=on|off][,writable=on|off] is a block export definition. ``node-name`` is the block node that should be exported. ``writable`` determines whether or not the export allows write @@ -92,6 +93,16 @@ Standard options: ``logical-block-size`` sets the logical block size in bytes (the default is 512). ``num-queues`` sets the number of virtqueues (the default is 1). + The ``fuse`` export type takes a mount point, which must be a regular file, + on which to export the given block node. That file will not be changed, it + will just appear to have the block node's content while the export is active + (very much like mounting a filesystem on a directory does not change what the + directory contains, it only shows a different content while the filesystem is + mounted). Consequently, applications that have opened the given file before + the export became active will continue to see its original content. If + ``growable`` is set, writes after the end of the exported file will grow the + block node to fit. + .. option:: --monitor MONITORDEF is a QMP monitor definition. See the :manpage:`qemu(1)` manual page for @@ -196,6 +207,14 @@ domain socket ``vhost-user-blk.sock``:: --blockdev driver=qcow2,node-name=qcow2,file=file \ --export type=vhost-user-blk,id=export,addr.type=unix,addr.path=vhost-user-blk.sock,node-name=qcow2 +Export a qcow2 image file ``disk.qcow2`` via FUSE on itself, so the disk image +file will then appear as a raw image:: + + $ qemu-storage-daemon \ + --blockdev driver=file,node-name=file,filename=disk.qcow2 \ + --blockdev driver=qcow2,node-name=qcow2,file=file \ + --export type=fuse,id=export,node-name=qcow2,mountpoint=disk.qcow2,writable=on + See also -------- -- cgit v1.2.3