new file: docs/stupid_kvm_tricks.md

docs/index.md

@@ -19,6 +19,7 @@ Obviously, the commit history will reflect the time when these documents are wri
 * [Self Signed Certs](self_signed_certs.md)
 * [Selfoss on Centos7](selfoss_on_centos7.md)
 * [Stupid Package Manager Tricks](stupid_package_manager_tricks.md)
+* [Stupid KVM Tricks](stupid_kvm_tricks.md)
 
 <!---
     * [Template](Template.md)

docs/stupid_kvm_tricks.md

@@ -0,0 +1,146 @@
+# Stupid KVM Tricks
+
+## virt-install ubuntu16.04
+
+Create the disk image
+
+`qemu-img create -f qcow2 /var/lib/libvirt/images/xenial.qcow2 20G`
+
+Command to run the install
+
+```bash
+virt-install \
+    --name xenial \
+    --ram 4096 \
+    --disk path=/var/lib/libvirt/images/xenial.qcow2,size=20 \
+    --vcpus 4 \
+    --os-type linux \
+    --os-variant ubuntu16.04 \
+    --network bridge=br0 \
+    --graphics none \
+    --console pty,target_type=serial \
+    --location ./ubuntu-16.04.3-server-amd64.iso \
+    --extra-args 'console=ttyS0,115200n8 serial'
+```
+
+## Change the Network Interface
+br0 gets addresses from the network router, but what if you want
+your vm to have be on the virbr0 192.168.122.0/24 subnet?
+
+`virsh edit xenial`
+
+And then 'J' all the way down to the bottom, change the interface name from br0 to
+virbr0, 
+
+`virsh start xenial`
+
+and then look for the machine with nmap
+
+`nmap -sn 192.168.122.0/24`
+
+## Clone the VM
+
+In this case we don't have to pre-allocate the disk image because virt-clone will do that
+for us.
+
+```bash
+virt-clone --original xenial --name xenial-clone \
+    --file /var/lib/libvirt/images/xenial-clone.qcow2
+```
+
+## Clone the VM to another Machine
+
+First dump the xml that defines the virtual machine.
+
+```bash
+virsh dumpxml xenial > xenial.xml
+```
+
+Then copy both `xenial.xml` and `xenial.qcow2` to the new host machine. On the new kvm
+host you'll want to at least make sure your vm has the correct CPU architecture.
+The command to get a list of supported kvm cpu architectures is:
+
+```bash
+virsh cpu-models <arch>
+# i.e.
+virsh cpu-models x86_64
+```
+
+After you edit `xenial.xml` and update the correct cpu architecture, mv `xenial.qcow2`
+to `/var/lib/libvirt/images/`, clone it. `virt-clone` will handle generating new
+mac addresses for the network interfaces.
+
+```xml
+  <cpu mode='custom' match='exact'>
+    <model fallback='allow'>Haswell-noTSX</model>
+  </cpu>
+# i.e. change to above to
+  <cpu mode='custom' match='exact'>
+    <model fallback='allow'>SandyBridge</model>
+  </cpu>
+
+```
+
+
+```bash
+virt-clone --original-xml xenial.xml --name xenial-clone \
+    --file /var/lib/libvirt/images/xenial-clone.qcow2
+```
+
+## What is the os-type and os-variant type names?
+
+`osinfo-query os`
+
+## misc
+
+* Start the vm `virsh start xenial`  
+* List all the vms `virsh list --all`  
+* Stop the vm `virsh destroy xenial`   
+* Delete the vm `virsh undefine xenial`  
+
+## virsh help
+
+The `virsh help` command returns a long chart of help information. But each section has
+a keyword.
+
+Take for instance the command `virsh help monitor`. From this we
+see the `domiflist` subcommand (among others). Unfortunately `domifaddr` doesn't seem to
+work on the Ubuntu:16.04 host, but there are other ways to find the ip address of
+a virtual machine.
+
+So now if you want to see what host interface the vm `xenial` is attached to,
+type. 
+
+```bash
+virsh domiflist xenial
+```
+
+which returns:
+```bash
+Interface  Type       Source     Model       MAC
+-------------------------------------------------------
+vnet1      bridge     virbr0     virtio      52:54:00:58:bf:75
+```
+
+So now we can find the address of virbr0 on the host machine.
+
+```bash
+ifconfig virbr0
+```
+which returns:
+
+```bash
+virbr0    Link encap:Ethernet  HWaddr 52:54:00:38:87:38  
+          inet addr:192.168.122.1  Bcast:192.168.122.255  Mask:255.255.255.0
+          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
+          RX packets:1351 errors:0 dropped:0 overruns:0 frame:0
+          TX packets:3037 errors:0 dropped:0 overruns:0 carrier:0
+          collisions:0 txqueuelen:1000 
+          RX bytes:232346 (232.3 KB)  TX bytes:502916 (502.9 KB)
+```
+
+and thus we know what subnet to scan with nmap to find the ip address of the vm
+
+```bash
+nmap -sn 192.168.122.0/24
+```