The existing qemu-nbd --partition code claims to handle logical
partitions up to 8, since its introduction in 2008 (commit 7a5ca86).
However, the implementation is bogus (actual MBR logical partitions
form a sort of linked list, with one partition per extended table
entry, rather than four logical partitions in a single extended
table), making the code unlikely to work for anything beyond -P5 on
actual guest images. What's more, the code does not support GPT
partitions, which are becoming more popular, and maintaining device
subsetting in both NBD and the raw device is unnecessary duplication
of effort (even if it is not too difficult).
Note that obtaining the offsets of a partition (MBR or GPT) can be
learned by using 'qemu-nbd -c /dev/nbd0 file.qcow2 && sfdisk --dump
/dev/nbd0', but by the time you've done that, you might as well
just mount /dev/nbd0p1 that the kernel creates for you instead of
bothering with qemu exporting a subset. Or, keeping to just
user-space code, use nbdkit's partition filter, which has already
known both GPT and primary MBR partitions for a while, and was
just recently enhanced to support arbitrary logical MBR parititions.
Start the clock on the deprecation cycle, with examples of how
to accomplish device subsetting without using -P.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190125234837.2272-1-eblake@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
We want to be able to detect whether a given qemu NBD server is
exposing the right export(s) and dirty bitmaps, at least for
regression testing. We could use 'nbd-client -l' from the upstream
NBD project to list exports, but it's annoying to rely on
out-of-tree binaries; furthermore, nbd-client doesn't necessarily
know about all of the qemu NBD extensions. Thus, it is time to add
a new mode to qemu-nbd that merely sniffs all possible information
from the server during handshake phase, then disconnects and dumps
the information.
This patch actually implements --list/-L, while reusing other
options such as --tls-creds for now designating how to connect
as the client (rather than their non-list usage of how to operate
as the server).
I debated about adding this functionality to something akin to
'qemu-img info' - but that tool does not readily lend itself
to connecting to an arbitrary NBD server without also tying to
a specific export (I may, however, still add ImageInfoSpecificNBD
for reporting the bitmaps available when connecting to a single
export). And, while it may feel a bit odd that normally
qemu-nbd is a server but 'qemu-nbd -L' is a client, we are not
really making the qemu-nbd binary that much larger, because
'qemu-nbd -c' has to operate as both server and client
simultaneously across two threads when feeding the kernel module
for /dev/nbdN access.
Sample output:
$ qemu-nbd -L
exports available: 1
export: ''
size: 65536
flags: 0x4ed ( flush fua trim zeroes df cache )
min block: 512
opt block: 4096
max block: 33554432
available meta contexts: 1
base:allocation
Note that the output only lists sizes if the server sent
NBD_FLAG_HAS_FLAGS, because a newstyle server does not give
the size otherwise. It has the side effect that for really
old servers that did not send any flags, the size is not
output even though it was available. However, I'm not too
concerned about that - oldstyle servers are (rightfully)
getting less common to encounter (qemu 3.0 was the last
version where we even serve it), and most existing servers
that still even offer oldstyle negotiation (such as nbdkit)
still send flags (since that was added to the NBD protocol
in 2007 to permit read-only connections).
Not done here, but maybe worth future experiments: capture
the meat of NBDExportInfo into a QAPI struct, and use the
generated QAPI pretty-printers instead of hand-rolling our
output loop. It would also permit us to add a JSON output
mode for machine parsing.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Message-Id: <20190117193658.16413-20-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Document some useful qemu-nbd command lines. Mention some restrictions
on particular options, like -p being only for MBR images, or -c/-d
being Linux-only. Update some text given the recent change to no
longer serve oldstyle protocol (missed in commit 7f7dfe2a). Also,
consistently use trailing '.' in describing options.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>
Message-Id: <20190117193658.16413-4-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Having to fire up qemu, then use QMP commands for nbd-server-start
and nbd-server-add, just to expose a persistent dirty bitmap, is
rather tedious. Make it possible to expose a dirty bitmap using
just qemu-nbd (of course, for now this only works when qemu-nbd is
visiting a BDS formatted as qcow2).
Of course, any good feature also needs unit testing, so expand
iotest 223 to cover it.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20190111194720.15671-9-eblake@redhat.com>
The NBD protocol allows servers to advertise a human-readable
description alongside an export name during NBD_OPT_LIST. Add
an option to pass through the user's string to the NBD client.
Doing this also makes it easier to test commit 200650d4, which
is the client counterpart of receiving the description.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-2-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Using the --fork option, one can make qemu-nbd fork the worker process.
The original process will exit on error of the worker or once the worker
enters the main loop.
Suggested-by: Sascha Silbe <silbe@linux.vnet.ibm.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Please note, trace_init_backends() must be called in the final process,
i.e. after daemonization. This is necessary to keep tracing thread in
the proper process.
Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1466174654-30130-6-git-send-email-den@openvz.org
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Currently qemu-nbd allows an image filename to be passed on the
command line, but unless using the JSON format, it does not have
a way to set any options except the format eg
qemu-nbd https://127.0.0.1/images/centos7.iso
qemu-nbd /home/berrange/demo.qcow2
This adds a --image-opts arg that indicates that the positional
filename should be interpreted as a full option string, not
just a filename.
qemu-nbd --image-opts driver=https,url=https://127.0.0.1/images,sslverify=off
qemu-nbd --image-opts driver=file,filename=/home/berrange/demo.qcow2
This flag is mutually exclusive with the '-f' flag.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This modifies the qemu-nbd program so that it is possible to
request the use of TLS with the server. It simply adds a new
command line option --tls-creds which is used to provide the
ID of a QCryptoTLSCreds object previously created via the
--object command line option.
For example
qemu-nbd --object tls-creds-x509,id=tls0,endpoint=server,\
dir=/home/berrange/security/qemutls \
--tls-creds tls0 \
--exportname default
TLS requires the new style NBD protocol, so if no export name
is set (via --export-name), then we use the default NBD protocol
export name ""
TLS is only supported when using an IPv4/IPv6 socket listener.
It is not possible to use with UNIX sockets, which includes
when connecting the NBD server to a host device.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1455129674-17255-16-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The qemu-nbd server currently always uses the old style protocol
since it never sets any export name. This is a problem because
future TLS support will require use of the new style protocol
negotiation.
This adds "--exportname NAME" / "-x NAME" arguments to qemu-nbd
which allow the user to set an explicit export name. When an
export name is set the server will always use the new style
NBD protocol.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1455129674-17255-11-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Allow creation of user creatable object types with qemu-nbd
via a new --object command line arg. This will be used to supply
passwords and/or encryption keys to the various block driver
backends via the recently added 'secret' object type.
# printf letmein > mypasswd.txt
# qemu-nbd --object secret,id=sec0,file=mypasswd.txt \
...other nbd args...
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1455129674-17255-3-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Capitalise the first letter of sentences (and reword for grammar) the
options section of qemu-nbd.texi.
Signed-off-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Message-Id: <1451979212-25479-4-git-send-email-sitsofe@yahoo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
- Change some spacing.
- Add disconnect usage to synopsis.
- Highlight the command and its options in the synopsis.
- Fix up the grammar in the description.
- Move filename variable description out of the option table.
- Add a description of the dev variable.
- Remove duplicate entry for --format.
- Reword --discard documentation.
- Add --detect-zeroes documentation.
- Add reference to qemu man page to see also section.
Signed-off-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Message-Id: <1451979212-25479-3-git-send-email-sitsofe@yahoo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Indented lines in the texi meant the perlpod produced interpreted the
paragraph as being verbatim (thus formatting codes were not
interpreted). Fix this by un-indenting problem lines.
Signed-off-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Message-Id: <1451979212-25479-2-git-send-email-sitsofe@yahoo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Now it is possible to directly export an internal snapshot, which
can be used to probe the snapshot's contents without qemu-img
convert.
Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Currently the qemu-nbd program will auto-detect the format of
any disk it is given. This behaviour is known to be insecure.
For example, if qemu-nbd initially exposes a 'raw' file to an
unprivileged app, and that app runs
'qemu-img create -f qcow2 -o backing_file=/etc/shadow /dev/nbd0'
then the next time the app is started, the qemu-nbd will now
detect it as a 'qcow2' file and expose /etc/shadow to the
unprivileged app.
The only way to avoid this is to explicitly tell qemu-nbd what
disk format to use on the command line, completely disabling
auto-detection. This patch adds a '-f' / '--format' arg for
this purpose, mirroring what is already available via qemu-img
and qemu commands.
qemu-nbd --format raw -p 9000 evil.img
will now always use raw, regardless of what format 'evil.img'
looks like it contains
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
[Use errx, not err. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Similar to --cache and --aio, this option mimics the discard suboption
of "-drive".
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The official spelling is QEMU.
Signed-off-by: Stefan Weil <sw@weilnetz.de>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
Fix formatting for documentation of nbd command line options.
Signed-off-by: Stefan Weil <weil@mail.berlios.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5301 c046a42c-6fe2-441c-8c8c-71466251a162
