1 2In addition to using normal file images for the emulated storage 3devices, QEMU can also use networked resources such as iSCSI devices. 4These are specified using a special URL syntax. 5 6``iSCSI`` 7 iSCSI support allows QEMU to access iSCSI resources directly and use 8 as images for the guest storage. Both disk and cdrom images are 9 supported. 10 11 Syntax for specifying iSCSI LUNs is 12 "iscsi://<target-ip>[:<port>]/<target-iqn>/<lun>" 13 14 By default qemu will use the iSCSI initiator-name 15 'iqn.2008-11.org.linux-kvm[:<name>]' but this can also be set from 16 the command line or a configuration file. 17 18 Since version Qemu 2.4 it is possible to specify a iSCSI request 19 timeout to detect stalled requests and force a reestablishment of the 20 session. The timeout is specified in seconds. The default is 0 which 21 means no timeout. Libiscsi 1.15.0 or greater is required for this 22 feature. 23 24 Example (without authentication): 25 26 .. parsed-literal:: 27 28 |qemu_system| -iscsi initiator-name=iqn.2001-04.com.example:my-initiator \\ 29 -cdrom iscsi://192.0.2.1/iqn.2001-04.com.example/2 \\ 30 -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1 31 32 Example (CHAP username/password via URL): 33 34 .. parsed-literal:: 35 36 |qemu_system| -drive file=iscsi://user%password@192.0.2.1/iqn.2001-04.com.example/1 37 38 Example (CHAP username/password via environment variables): 39 40 .. parsed-literal:: 41 42 LIBISCSI_CHAP_USERNAME="user" \\ 43 LIBISCSI_CHAP_PASSWORD="password" \\ 44 |qemu_system| -drive file=iscsi://192.0.2.1/iqn.2001-04.com.example/1 45 46``NBD`` 47 QEMU supports NBD (Network Block Devices) both using TCP protocol as 48 well as Unix Domain Sockets. With TCP, the default port is 10809. 49 50 Syntax for specifying a NBD device using TCP, in preferred URI form: 51 "nbd://<server-ip>[:<port>]/[<export>]" 52 53 Syntax for specifying a NBD device using Unix Domain Sockets; 54 remember that '?' is a shell glob character and may need quoting: 55 "nbd+unix:///[<export>]?socket=<domain-socket>" 56 57 Older syntax that is also recognized: 58 "nbd:<server-ip>:<port>[:exportname=<export>]" 59 60 Syntax for specifying a NBD device using Unix Domain Sockets 61 "nbd:unix:<domain-socket>[:exportname=<export>]" 62 63 Example for TCP 64 65 .. parsed-literal:: 66 67 |qemu_system| --drive file=nbd:192.0.2.1:30000 68 69 Example for Unix Domain Sockets 70 71 .. parsed-literal:: 72 73 |qemu_system| --drive file=nbd:unix:/tmp/nbd-socket 74 75``SSH`` 76 QEMU supports SSH (Secure Shell) access to remote disks. 77 78 Examples: 79 80 .. parsed-literal:: 81 82 |qemu_system| -drive file=ssh://user@host/path/to/disk.img 83 |qemu_system| -drive file.driver=ssh,file.user=user,file.host=host,file.port=22,file.path=/path/to/disk.img 84 85 Currently authentication must be done using ssh-agent. Other 86 authentication methods may be supported in future. 87 88``Sheepdog`` 89 Sheepdog is a distributed storage system for QEMU. QEMU supports 90 using either local sheepdog devices or remote networked devices. 91 92 Syntax for specifying a sheepdog device 93 94 :: 95 96 sheepdog[+tcp|+unix]://[host:port]/vdiname[?socket=path][#snapid|#tag] 97 98 Example 99 100 .. parsed-literal:: 101 102 |qemu_system| --drive file=sheepdog://192.0.2.1:30000/MyVirtualMachine 103 104 See also https://sheepdog.github.io/sheepdog/. 105 106``GlusterFS`` 107 GlusterFS is a user space distributed file system. QEMU supports the 108 use of GlusterFS volumes for hosting VM disk images using TCP, Unix 109 Domain Sockets and RDMA transport protocols. 110 111 Syntax for specifying a VM disk image on GlusterFS volume is 112 113 .. parsed-literal:: 114 115 URI: 116 gluster[+type]://[host[:port]]/volume/path[?socket=...][,debug=N][,logfile=...] 117 118 JSON: 119 'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol","path":"a.img","debug":N,"logfile":"...", 120 "server":[{"type":"tcp","host":"...","port":"..."}, 121 {"type":"unix","socket":"..."}]}}' 122 123 Example 124 125 .. parsed-literal:: 126 127 URI: 128 |qemu_system| --drive file=gluster://192.0.2.1/testvol/a.img, 129 file.debug=9,file.logfile=/var/log/qemu-gluster.log 130 131 JSON: 132 |qemu_system| 'json:{"driver":"qcow2", 133 "file":{"driver":"gluster", 134 "volume":"testvol","path":"a.img", 135 "debug":9,"logfile":"/var/log/qemu-gluster.log", 136 "server":[{"type":"tcp","host":"1.2.3.4","port":24007}, 137 {"type":"unix","socket":"/var/run/glusterd.socket"}]}}' 138 |qemu_system| -drive driver=qcow2,file.driver=gluster,file.volume=testvol,file.path=/path/a.img, 139 file.debug=9,file.logfile=/var/log/qemu-gluster.log, 140 file.server.0.type=tcp,file.server.0.host=1.2.3.4,file.server.0.port=24007, 141 file.server.1.type=unix,file.server.1.socket=/var/run/glusterd.socket 142 143 See also http://www.gluster.org. 144 145``HTTP/HTTPS/FTP/FTPS`` 146 QEMU supports read-only access to files accessed over http(s) and 147 ftp(s). 148 149 Syntax using a single filename: 150 151 :: 152 153 <protocol>://[<username>[:<password>]@]<host>/<path> 154 155 where: 156 157 ``protocol`` 158 'http', 'https', 'ftp', or 'ftps'. 159 160 ``username`` 161 Optional username for authentication to the remote server. 162 163 ``password`` 164 Optional password for authentication to the remote server. 165 166 ``host`` 167 Address of the remote server. 168 169 ``path`` 170 Path on the remote server, including any query string. 171 172 The following options are also supported: 173 174 ``url`` 175 The full URL when passing options to the driver explicitly. 176 177 ``readahead`` 178 The amount of data to read ahead with each range request to the 179 remote server. This value may optionally have the suffix 'T', 'G', 180 'M', 'K', 'k' or 'b'. If it does not have a suffix, it will be 181 assumed to be in bytes. The value must be a multiple of 512 bytes. 182 It defaults to 256k. 183 184 ``sslverify`` 185 Whether to verify the remote server's certificate when connecting 186 over SSL. It can have the value 'on' or 'off'. It defaults to 187 'on'. 188 189 ``cookie`` 190 Send this cookie (it can also be a list of cookies separated by 191 ';') with each outgoing request. Only supported when using 192 protocols such as HTTP which support cookies, otherwise ignored. 193 194 ``timeout`` 195 Set the timeout in seconds of the CURL connection. This timeout is 196 the time that CURL waits for a response from the remote server to 197 get the size of the image to be downloaded. If not set, the 198 default timeout of 5 seconds is used. 199 200 Note that when passing options to qemu explicitly, ``driver`` is the 201 value of <protocol>. 202 203 Example: boot from a remote Fedora 20 live ISO image 204 205 .. parsed-literal:: 206 207 |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 208 209 |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 210 211 Example: boot from a remote Fedora 20 cloud image using a local 212 overlay for writes, copy-on-read, and a readahead of 64k 213 214 .. parsed-literal:: 215 216 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 217 218 |qemu_system_x86| -drive file=/tmp/Fedora-x86_64-20-20131211.1-sda.qcow2,copy-on-read=on 219 220 Example: boot from an image stored on a VMware vSphere server with a 221 self-signed certificate using a local overlay for writes, a readahead 222 of 64k and a timeout of 10 seconds. 223 224 .. parsed-literal:: 225 226 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 227 228 |qemu_system_x86| -drive file=/tmp/test.qcow2 229