[A recent breaking change upstream in Golang's crypto
library](e4e2799dd7)
has broken SSH connectivity for a few builders:
```
==> qemu: Waiting for SSH to become available...
2017/05/20 16:23:58 ui: ==> qemu: Waiting for SSH to become available...
2017/05/20 16:23:58 packer: 2017/05/20 16:23:58 [INFO] Attempting SSH connection...
2017/05/20 16:23:58 packer: 2017/05/20 16:23:58 reconnecting to TCP connection for SSH
2017/05/20 16:23:58 packer: 2017/05/20 16:23:58 handshaking with SSH
2017/05/20 16:23:58 packer: 2017/05/20 16:23:58 handshake error: ssh: must specify HostKeyCallback
2017/05/20 16:23:58 packer: 2017/05/20 16:23:58 [DEBUG] SSH handshake err: ssh: must specify HostKeyCallback
2017/05/20 16:24:05 packer: 2017/05/20 16:24:05 [INFO] Attempting SSH connection...
2017/05/20 16:24:05 packer: 2017/05/20 16:24:05 reconnecting to TCP connection for SSH
2017/05/20 16:24:05 packer: 2017/05/20 16:24:05 handshaking with SSH
2017/05/20 16:24:05 packer: 2017/05/20 16:24:05 handshake error: ssh: must specify HostKeyCallback
2017/05/20 16:24:05 packer: 2017/05/20 16:24:05 [DEBUG] SSH handshake err: ssh: must specify HostKeyCallback
```
Specifying HostKeyCallback as insecure should make things work again
and would make sense for packer's use case.
If using a builder that has an http server set up for file transfer,
expose the connection info to the shell provisioner through the environment
variable PACKER_HTTP_ADDR.
Closes#2869
This option allows to set the extension of the ISO file after download.
Defaults to "iso". It makes sense for building Mac OS X guests, where the
bootable image is actually a DMG, not an ISO.
In particular, it is important for "parallels-iso" builder to set the right extension.
To enable nested virtualization, mac spoofing, no dynamic memory and at least 4gb of ram should be set for the vm. Set warning if this has not been done.
Detected Virtualization Extensions are supported by the machine your are running on, as it only works for Windows 10 and Windows Server 2016 onwards.
<leftAlt>
<leftCtrl>
<leftShift>
<rightAlt>
<rightCtrl>
<rightShift>
Add type support for combinations of ctr, alt, shift with (only use lower case characters with this):
<leftAltOn>
<leftCtrlOn>
<leftShiftOn>
<leftAltOff>
<leftCtrlOff>
<leftShiftOff>
<rightAltOn>
<rightCtrlOn>
<rightShiftOn>
<rightAltOff>
<rightCtrlOff>
<rightShiftOff>
