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nbdkit-vddk-plugin(1) NBDKIT nbdkit-vddk-plugin(1)

NAME

nbdkit-vddk-plugin - nbdkit VMware VDDK plugin

SYNOPSIS

 nbdkit vddk file=FILENAME [config=FILENAME] [libdir=LIBRARY]
             [vm=moref=ID] [server=HOSTNAME] [user=USERNAME]
             [password=PASSWORD | password=- | password=+FILENAME]
             [cookie=COOKIE] [thumbprint=THUMBPRINT]
             [port=PORT] [nfchostport=PORT] [single-link=true]
             [snapshot=MOREF] [transports=MODE:MODE:...]
             [unbuffered=true]
 nbdkit vddk --dump-plugin

DESCRIPTION

"nbdkit-vddk-plugin" is an nbdkit(1) plugin that serves files from local VMware VMDK files, VMware ESXi servers, VMware VCenter servers, and other sources. It requires VMware's proprietary VDDK library that you must download yourself separately.

The plugin can serve read-only (if the -r option is used) or read/write.

LIBRARY AND CONFIG FILE LOCATIONS

If the VDDK library (libvixDiskLib.so.N) is located on a non-standard path, you may need to set "LD_LIBRARY_PATH" or modify /etc/ld.so.conf before this plugin will work. In addition you may want to set the "libdir" parameter so that the VDDK library can load plugins like Advanced Transport.

For 64 bit platforms pass the lib64 subdirectory:

 export LD_LIBRARY_PATH=/path/to/vmware-vix-disklib-distrib/lib64

For 32 bit platforms pass the lib32 subdirectory:

 export LD_LIBRARY_PATH=/path/to/vmware-vix-disklib-distrib/lib32

Then pass the VDDK distribution directory as "libdir" along with other parameters as required:

 nbdkit vddk \
     libdir=/path/to/vmware-vix-disklib-distrib \
     file=file.vmdk

VDDK itself looks in a few default locations for the optional configuration file, usually including /etc/vmware/config and $HOME/.vmware/config, but you can override this using the "config" parameter.

PARAMETERS

All parameters are optional except:

"file"
is required for opening a local VMDK file.
"server"
"thumbprint"
"user"
"password"
"vm"
"file"
When making a remote connection you must supply all 6 of these parameters.

See the "EXAMPLES" section below for local and remote command lines.

The name of the VDDK configuration file.
Cookie from existing authenticated session on the host.
Set the name of the VMDK file to serve.

For local files you must supply an absolute path.

For remote files this is usually a path on the VMware server with the format "[datastore] path/to/file.vmdk". You can find the path using virsh(1). For ESXi:

 virsh -c 'esx://esxi.example.com?no_verify=1' dumpxml guestname

For vCenter:

 virsh -c 'vpx://vcenter.example.com/Datacenter/esxi.example.com?no_verify=1' \
       dumpxml guestname

If a VM has multiple disks, nbdkit can only serve one at a time. To serve more than one you must run multiple copies of nbdkit. (See "NOTES" below).

This sets the path of the VMware VDDK distribution.

VDDK uses this to load its own plugins, if this path is unspecified or wrong then VDDK will work with reduced functionality.

If the parameter is not given, then a hard-coded path determined at compile time is used, see "DUMP-PLUGIN OUTPUT" below.

Port used to establish an NFC connection to ESXi. Defaults to 902.

(Only supported in VDDK ≥ 5.5.5 and ≥ 6.0.1)

Set the password to use when connecting to the remote server.

Note that passing this on the command line is not secure on shared machines.

Ask for the password (interactively) when nbdkit starts up.
Read the password from the named file. This is the most secure method to supply a password, as long as you set the permissions on the file appropriately.
The port on the VCenter/ESXi host. Defaults to 443.
The hostname or IP address of VCenter or ESXi host.
Open the current link, not the entire chain. This corresponds to the "VIXDISKLIB_FLAG_OPEN_SINGLE_LINK" flag.
The Managed Object Reference of the snapshot.
The SSL (SHA1) thumbprint for validating the SSL certificate.

The format is "xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx:xx" (20 hex digit pairs).

See "THUMBPRINTS" below for how to get this.

List of one or more transport modes to use. Possible values include ‘nbd’, ‘nbdssl’, ‘san’, ‘hotadd’, ‘file’ (there may be others). If not given, VDDK will try to choose the best transport mode.
Disable host caching. This corresponds to the "VIXDISKLIB_FLAG_OPEN_UNBUFFERED" flag.
The username to connect to the remote server as.
The Managed Object Reference ("moref") of the virtual machine.

For VMware ESXi hypervisors, this is a number (eg. "vm=moref=2"). For VMware VCenter, this is a string beginning with "vm-") (eg. "vm=moref=vm-16"). Across ESXi and vCenter the numbers are different even for the same virtual machine.

If you have libvirt ≥ 3.7, the moref is available in the virsh(1) "dumpxml" output:

 $ virsh -c 'esx://esxi.example.com?no_verify=1' dumpxml guestname
 ...
 <vmware:moref>2</vmware:moref>
 ...

or:

 $ virsh -c 'vpx://vcenter.example.com/Datacenter/esxi.example.com?no_verify=1' \
       dumpxml guestname
 ...
 <vmware:moref>vm-16</vmware:moref>
 ...

An alternative way to find the moref of a VM is using the "moRefFinder.pl" script written by William Lam (http://www.virtuallyghetto.com/2011/11/vsphere-moref-managed-object-reference.html https://blogs.vmware.com/vsphere/2012/02/uniquely-identifying-virtual-machines-in-vsphere-and-vcloud-part-2-technical.html).

This parameter is ignored for backwards compatibility.

EXAMPLES

Open a local VMDK file

 nbdkit vddk file=/absolute/path/to/file.vmdk

Note that when opening local files the "file=" parameter must be an absolute path.

Because VDDK needs to take a lock on this file, the file must be on a writable filesystem (unless you use the -r option).

Open a file on a remote VMware ESXi hypervisor

Connect directly to a VMware ESXi hypervisor and export a particular file:

 nbdkit vddk user=root password=+/tmp/rootpw \
             server=esxi.example.com thumbprint=xx:xx:xx:... \
             vm=moref=2 \
             file="[datastore1] Fedora/Fedora.vmdk"

"user" and "password" must be specified. Use "password=+FILENAME" to provide the password securely in a file.

"server" is the hostname of the ESXi server. "thumbprint" is the thumb print for validating the SSL certificate. How to find the thumb print of a server is described in "THUMBPRINTS" below.

"vm" is the Managed Object Reference ("moref") of the virtual machine. To find this using virsh(1) or the "moRefFinder.pl" script, see "PARAMETERS" above. Note that it is different from the moref used by vCenter, and is just a single number.

"file" is the actual file you want to open, usually in the form "[datastore] vmname/vmname.vmdk". You can find this from virsh(1) as described in "PARAMETERS" above.

Open a file on a remote VMware vCenter server

Connect via VMware vCenter and export a particular file:

 nbdkit vddk user=root password=vmware \
             server=vcenter.example.com thumbprint=xx:xx:xx:... \
             vm=moref=vm-16 \
             file="[datastore1] Fedora/Fedora.vmdk"

"user" and "password" must be specified. Use "password=+FILENAME" to provide the password securely in a file.

"server" is the hostname of the vCenter server. "thumbprint" is the thumb print for validating the SSL certificate. How to find the thumb print of a server is described in "THUMBPRINTS" below.

"vm" is the Managed Object Reference ("moref") of the virtual machine. To find this using virsh(1) or the "moRefFinder.pl" script, see "PARAMETERS" above. Note that it is different from the moref used by ESXi, and always begins with the prefix "vm-".

"file" is the actual file you want to open, usually in the form "[datastore] vmname/vmname.vmdk". You can find this from virsh(1) as described in "PARAMETERS" above.

THUMBPRINTS

The thumbprint is a 20 byte string containing the SSL (SHA1) fingerprint of the remote VMware server and it is required when making a remote connection. There are two ways to obtain this.

Extracting thumbprint from ESXi or vCenter server

To extract the thumbprint, log in to the ESXi hypervisor shell and run this command:

 # openssl x509 -in /etc/vmware/ssl/rui.crt -fingerprint -sha1 -noout

For VMware vCenter servers the thumbprint is printed on the text console of the server or is available by logging in to the server and using this command:

 # openssl x509 -in /etc/vmware-vpx/ssl/rui.crt -fingerprint -sha1 -noout

Trick: Get VDDK to tell you the thumbprint

Another (easier) way to get the thumbprint of a server is to connect to the server using a bogus thumbprint with debugging enabled:

 nbdkit -f -v vddk server=esxi.example.com [...] thumbprint=12
 qemu-img info nbd:localhost:10809

The nbdkit process will try to connect (and fail because the thumbprint is wrong). However in the debug output will be a message such as this:

 nbdkit: debug: VixDiskLibVim: Failed to verify SSL certificate: actual thumbprint=B2:31:BD:DE:9F:DB:9D:E0:78:EF:30:42:8A:41:B0:28:92:93:C8:DD expected=12

This gives you the server’s real thumbprint. Of course this method is not secure since it allows a Man-in-the-Middle (MITM) attack.

DUMP-PLUGIN OUTPUT

To query more information about the plugin (and whether it is working), use:

 nbdkit vddk --dump-plugin

If the plugin is not present, not working or the library path is wrong you will get an error.

If it works the output will include:

"vddk_default_libdir=..."
The compiled-in library path. Use "libdir=PATHNAME" to override this at runtime.
"vddk_has_nfchostport=1"
If this is printed then the "nfchostport=PORT" parameter is supported by this build.
"vddk_dll=..."
Prints the full path to the VDDK shared library. Since this requires a glibc extension it may not be available in all builds of the plugin.

DEBUGGING VDDK

Debugging messages can be very helpful if you have problems connecting to VMware servers, or to find the list of available transport modes, or to diagnose SAN problems.

Run nbdkit like this to see all debugging messages:

 nbdkit -f -v vddk file=FILENAME [...]

NOTES

Sector size limitation

The VDDK plugin can only answer read/write requests on whole 512 byte sector boundaries. This is because the VDDK Read and Write APIs only take sector numbers.

The plugin could be extended in future to support byte granularity, but common NBD clients don't need it so it's not a priority.

Threads

Handling threads in the VDDK API is complex and does not map well to any of the thread models offered by nbdkit (see "THREADS" in nbdkit-plugin(3)). The plugin uses the nbdkit "SERIALIZE_ALL_REQUESTS" model, but technically even this is not completely safe. This is a subject of future work.

Export names

For VMs with multiple disks, it would be nice to map the disk names to NBD export names. However nbdkit core will need to be extended to support this.

Out of memory errors

In the verbose log you may see errors like:

 nbdkit: vddk[3]: error: [NFC ERROR] NfcFssrvrProcessErrorMsg:
 received NFC error 5 from server: Failed to allocate the
 requested 2097176 bytes

This seems especially common when there are multiple parallel connections open to the VMware server.

These can be caused by resource limits set on the VMware server. You can increase the limit for the NFC service by editing /etc/vmware/hostd/config.xml and adjusting the "<maxMemory>" setting:

 <nfcsvc>
   <path>libnfcsvc.so</path>
   <enabled>true</enabled>
   <maxMemory>50331648</maxMemory>
   <maxStreamMemory>10485760</maxStreamMemory>
 </nfcsvc>

and restarting the "hostd" service:

 # /etc/init.d/hostd restart

For more information see https://bugzilla.redhat.com/1614276.

SUPPORTED VERSIONS OF VDDK

This plugin requires VDDK ≥ 5.1.1.

It has been tested with all versions up to 6.7 (but should work with future versions).

VDDK ≥ 6.0 should be used if possible. This is the first version which added Flush support which is crucial for data integrity when writing.

SEE ALSO

nbdkit(1), nbdkit-plugin(3), virsh(1), https://www.vmware.com/support/developer/vddk/

AUTHORS

Richard W.M. Jones

COPYRIGHT

Copyright (C) 2013-2018 Red Hat Inc.

LICENSE

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

  • Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
  • Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
  • Neither the name of Red Hat nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

2019-08-16 nbdkit-1.14.2