@node sec_invocation
@section Invocation

@example
@c man begin SYNOPSIS
@command{@value{qemu_system}} [@var{options}] [@var{disk_image}]
@c man end
@end example

@c man begin OPTIONS
@var{disk_image} is a raw hard disk image for IDE hard disk 0. Some
targets do not need a disk image.

@include qemu-options.texi

@c man end

@subsection Device URL Syntax
@c TODO merge this with section Disk Images

@c man begin NOTES

In addition to using normal file images for the emulated storage devices,
QEMU can also use networked resources such as iSCSI devices. These are
specified using a special URL syntax.

@table @option
@item iSCSI
iSCSI support allows QEMU to access iSCSI resources directly and use as
images for the guest storage. Both disk and cdrom images are supported.

Syntax for specifying iSCSI LUNs is
``iscsi://<target-ip>[:<port>]/<target-iqn>/<lun>''

By default qemu will use the iSCSI initiator-name
'iqn.2008-11.org.linux-kvm[:<name>]' but this can also be set from the command
line or a configuration file.

Since version Qemu 2.4 it is possible to specify a iSCSI request timeout to detect
stalled requests and force a reestablishment of the session. The timeout
is specified in seconds. The default is 0 which means no timeout. Libiscsi
1.15.0 or greater is required for this feature.

Example (without authentication):
@example
@value{qemu_system} -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \
                 -cdrom iscsi://192.0.2.1/iqn.2001-04.com.example/2 \
                 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
@end example

Example (CHAP username/password via URL):
@example
@value{qemu_system} -drive file=iscsi://user%password@@192.0.2.1/iqn.2001-04.com.example/1
@end example

Example (CHAP username/password via environment variables):
@example
LIBISCSI_CHAP_USERNAME="user" \
LIBISCSI_CHAP_PASSWORD="password" \
@value{qemu_system} -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1
@end example

@item NBD
QEMU supports NBD (Network Block Devices) both using TCP protocol as well
as Unix Domain Sockets.  With TCP, the default port is 10809.

Syntax for specifying a NBD device using TCP, in preferred URI form:
``nbd://<server-ip>[:<port>]/[<export>]''

Syntax for specifying a NBD device using Unix Domain Sockets; remember
that '?' is a shell glob character and may need quoting:
``nbd+unix:///[<export>]?socket=<domain-socket>''

Older syntax that is also recognized:
``nbd:<server-ip>:<port>[:exportname=<export>]''

Syntax for specifying a NBD device using Unix Domain Sockets
``nbd:unix:<domain-socket>[:exportname=<export>]''

Example for TCP
@example
@value{qemu_system} --drive file=nbd:192.0.2.1:30000
@end example

Example for Unix Domain Sockets
@example
@value{qemu_system} --drive file=nbd:unix:/tmp/nbd-socket
@end example

@item SSH
QEMU supports SSH (Secure Shell) access to remote disks.

Examples:
@example
@value{qemu_system} -drive file=ssh://user@@host/path/to/disk.img
@value{qemu_system} -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img
@end example

Currently authentication must be done using ssh-agent.  Other
authentication methods may be supported in future.

@item Sheepdog
Sheepdog is a distributed storage system for QEMU.
QEMU supports using either local sheepdog devices or remote networked
devices.

Syntax for specifying a sheepdog device
@example
sheepdog[+tcp|+unix]://[host:port]/vdiname[?socket=path][#snapid|#tag]
@end example

Example
@example
@value{qemu_system} --drive file=sheepdog://192.0.2.1:30000/MyVirtualMachine
@end example

See also @url{https://sheepdog.github.io/sheepdog/}.

@item GlusterFS
GlusterFS is a user space distributed file system.
QEMU supports the use of GlusterFS volumes for hosting VM disk images using
TCP, Unix Domain Sockets and RDMA transport protocols.

Syntax for specifying a VM disk image on GlusterFS volume is
@example

URI:
gluster[+type]://[host[:port]]/volume/path[?socket=...][,debug=N][,logfile=...]

JSON:
'json:@{"driver":"qcow2","file":@{"driver":"gluster","volume":"testvol","path":"a.img","debug":N,"logfile":"...",
@                                 "server":[@{"type":"tcp","host":"...","port":"..."@},
@                                           @{"type":"unix","socket":"..."@}]@}@}'
@end example


Example
@example
URI:
@value{qemu_system} --drive file=gluster://192.0.2.1/testvol/a.img,
@                               file.debug=9,file.logfile=/var/log/qemu-gluster.log

JSON:
@value{qemu_system} 'json:@{"driver":"qcow2",
@                          "file":@{"driver":"gluster",
@                                   "volume":"testvol","path":"a.img",
@                                   "debug":9,"logfile":"/var/log/qemu-gluster.log",
@                                   "server":[@{"type":"tcp","host":"1.2.3.4","port":24007@},
@                                             @{"type":"unix","socket":"/var/run/glusterd.socket"@}]@}@}'
@value{qemu_system} -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img,
@                                      file.debug=9,file.logfile=/var/log/qemu-gluster.log,
@                                      file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007,
@                                      file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket
@end example

See also @url{http://www.gluster.org}.

@item HTTP/HTTPS/FTP/FTPS
QEMU supports read-only access to files accessed over http(s) and ftp(s).

Syntax using a single filename:
@example
<protocol>://[<username>[:<password>]@@]<host>/<path>
@end example

where:
@table @option
@item protocol
'http', 'https', 'ftp', or 'ftps'.

@item username
Optional username for authentication to the remote server.

@item password
Optional password for authentication to the remote server.

@item host
Address of the remote server.

@item path
Path on the remote server, including any query string.
@end table

The following options are also supported:
@table @option
@item url
The full URL when passing options to the driver explicitly.

@item readahead
The amount of data to read ahead with each range request to the remote server.
This value may optionally have the suffix 'T', 'G', 'M', 'K', 'k' or 'b'. If it
does not have a suffix, it will be assumed to be in bytes. The value must be a
multiple of 512 bytes. It defaults to 256k.

@item sslverify
Whether to verify the remote server's certificate when connecting over SSL. It
can have the value 'on' or 'off'. It defaults to 'on'.

@item cookie
Send this cookie (it can also be a list of cookies separated by ';') with
each outgoing request.  Only supported when using protocols such as HTTP
which support cookies, otherwise ignored.

@item timeout
Set the timeout in seconds of the CURL connection. This timeout is the time
that CURL waits for a response from the remote server to get the size of the
image to be downloaded. If not set, the default timeout of 5 seconds is used.
@end table

Note that when passing options to qemu explicitly, @option{driver} is the value
of <protocol>.

Example: boot from a remote Fedora 20 live ISO image
@example
@value{qemu_system_x86} --drive media=cdrom,file=https://archives.fedoraproject.org/pub/archive/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly

@value{qemu_system_x86} --drive media=cdrom,file.driver=http,file.url=http://archives.fedoraproject.org/pub/fedora/linux/releases/20/Live/x86_64/Fedora-Live-Desktop-x86_64-20-1.iso,readonly
@end example

Example: boot from a remote Fedora 20 cloud image using a local overlay for
writes, copy-on-read, and a readahead of 64k
@example
qemu-img create -f qcow2 -o backing_file='json:@{"file.driver":"http",, "file.url":"http://archives.fedoraproject.org/pub/archive/fedora/linux/releases/20/Images/x86_64/Fedora-x86_64-20-20131211.1-sda.qcow2",, "file.readahead":"64k"@}' /tmp/Fedora-x86_64-20-20131211.1-sda.qcow2

@value{qemu_system_x86} -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on
@end example

Example: boot from an image stored on a VMware vSphere server with a self-signed
certificate using a local overlay for writes, a readahead of 64k and a timeout
of 10 seconds.
@example
qemu-img create -f qcow2 -o backing_file='json:@{"file.driver":"https",, "file.url":"https://user:password@@vsphere.example.com/folder/test/test-flat.vmdk?dcPath=Datacenter&dsName=datastore1",, "file.sslverify":"off",, "file.readahead":"64k",, "file.timeout":10@}' /tmp/test.qcow2

@value{qemu_system_x86} -drive file=/tmp/test.qcow2
@end example

@end table

@c man end