#virsh

CentOS 6.4: libvirt で作った VM を自動起動する | CUBE SUGAR STORAGE

virsh console is a jarring experience. If you're running a Linux VM with libvirt, consider using virsh lxc-enter-namespace instead. I'll show you why and how.

The left screen shows two shells connecting to the same VM and you can already see that:

The escape method departs from shell norms (exit or ctrl+D)

It forces you to explicitly log in each time without telling you

The second connection doesn't display anything and writes to the first

What you can't see is that:

You need to explicitly log in but it doesn't tell you

Going over 80 characters messes up the display

I assume that these things are done for compatibility reasons as libvirt is popular and broad in scope. However, when it's not being annoying it's brazen and dangerous in how it runs against the grain of your expectations.

However, virsh can also run your shell of choice within the VM with lxc-enter-namespace. It will your expectations by leveraging your shell's familiar environment. The tool I built on the right is using that on the back end. The images above paint a stark contrast, I think.

To do this, I use this line:

sudo virsh -c lxc:/// lxc-enter-namespace <vm-id> --noseclabel -- /usr/bin/sudo -i -H -u <user> -- <command>

If you leave <command> blank then it will just load up your user's shell.

I would love to know why this is so difficult. Why can't I just run virsh shell <vm-id> --as-user <user><command>? I suggest that you toss that command into a script and use it instead of virsh console.

How to add more RAM to a KVM Virtual Machine

I have  VM running Emby that I set up a while ago on an low spec machine that had been the guest computer before everyone got Chromebooks and tablets. But it only had 2GB of RAM and I gave 1GB to the VM. So I added some new RAM to bring the system up to 8GB and wanted to start off by giving the VM 4GB to see if that improved performance.

So first I had to type

virsh edit BabyLuigi

I found the…

GRUB_TERMINAL="serial" GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1" GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,115200n8"

次に元からあった GRUB_TERMINAL_OUTPUT, GRUB_CMDLINE_LINUX をコメントアウトする。（こんな感じ)

#GRUB_TERMINAL_OUTPUT="console" #GRUB_CMDLINE_LINUX="rd.lvm.lv=fedora/root rd.lvm.lv=fedora/swap rhgb quiet"

これが終わったら

grub2-mkconfig -o /boot/grub2/grub.cfg

こうすると、grub へ設定が反映される。 これらが終わったらシャットダウンし、VirtualBoxのファイル -> 仮想アプライアンスのエクスポートで ova ファイルを作成する。 今回はその名前を fedora.ova とする。 (以下地元ネタ) それをとあるサーバーへ転送。今度はそのとあるサーバーへ ssh でログイン後、転送された fedora.ova を /media/iscsi/students/e$$/e$$$$$$ くらいにコピーする。そして、

cd /media/iscsi/students/e$$/e$$$$$$

その後、

tar -xvf fedora.ova

そしたら拡張子が vmdk (自分のは fedora-disk2.vmdk という名前だったのでここではこの名前で話を進める)が解凍されてるので、 ls コマンドで名前を確認。これを qcow2 に変換するので、

qemu-img convert -O qcow2 ./fedora-disk2.vmdk 01.qcow2

それで ls をするとわかるけど、 01.qcow2 が出来てるよね…? んでとあるサーバーには ie-virsh というのがあってそれを使う。

ie-virsh define 01 ie-virsh start 01 ie-virsh console 01

Resolved: How do I make a persistent domain with virsh? #programming #computers #answer

How do I make a persistent domain with virsh?

virsh create somefile.xml creates my machine just fine but when I shut the machine down the whole thing disappears. Machines I made with the virt-manager GUI are persistent (stick around after shutdown) and the xml file is derived from those virt-manager created machines.

Answer [by Francesco]: How do I make a persistent domain with virsh?

Use virsh…

While I've switched most of my workloads to Docker, there are still some situations where you need to manage and set up Virtual Machines (VM). These days, KVM+QEMU has more or less been established as the virtualization standard, so we'll be using that.

Setting this up on Ubuntu 14.04 (Trusty Tahr) is very straight forward. All you need to do is to run:

$ sudo apt-get install qemu-kvm libvirt-bin ubuntu-vm-builder bridge-utils

Assuming everything went well, you should now be up and running and can list your VMs (there are of course none):

$ sudo virsh list Id Name State ----------------------------------------------------

If something went wrong, take a look at the KVM installation guide.

If you only need Usermode Networking (i.e. no public IP), you're done now. If you however need your VMs to be accessible from the outside, you need to set up bridged networking.

With your system up and running, let's create a VM using vmbuilder:

$ sudo vmbuilder kvm ubuntu \ --suite trusty \ --flavour virtual \ --addpkg=linux-image-generic \ --addpkg=unattended-upgrades \ --addpkg openssh-server \ --addpkg=acpid \ --arch amd64 \ --libvirt qemu:///system \ --user ubuntu \ --name ubuntu \ --hostname=test \ --pass default

Due to this bug, you will need to use the "linux-image-generic" kernel instead of regular virtual one.

Creating the VM will take some time. Once it has been created you can start the VM using virsh with:

$ virsh start test

In order to ssh into the server, we need to find the server IP. There are a few ways to find this, but here's the best technique I've found:

$ sudo virsh dumpxml test | grep 'mac address' <mac address='XX:YY:ZZ:XX:YY:ZZ'/> $ arp -an | grep 'XX:YY:ZZ:XX:YY:ZZ' ? (192.168.122.135) at XX:YY:ZZ:XX:YY:ZZ [ether] on virbr0

Next, ssh into the VM:

$ ssh ubuntu@<the VM IP>

The password is defined above as 'default'

As you probably noticed, those are a fair amount of variables we need to pass onto virsh. The easiest solution to get around this is to create a config file. Porting the variables above into a config file would leave us with something like this:

[DEFAULT] arch = amd64 user = ubuntu name = ubuntu pass = default tmpfs = - [ubuntu] suite = trusty flavour = virtual addpkg = openssh-server, unattended-upgrades, acpid, linux-image-generic [kvm] libvirt = qemu:///system

With this config file, we can create a VM by simply running:

$ sudo vmbuilder kvm ubuntu -c myfile.cfg

A more complete config file, along with important hooks for re-generating SSH host keys on first boot can be found here.

There's a lot more to virsh and vmbuilder, but this should help you get started.

Caveats

In virsh VMs are referred to as 'domains.' This might be a bit confusing at first.

To stop and delete a VM in virsh, run destroy test and then undefine test --managed-save.

You probably want to use the --mem, --cpus and --rootsize options when using vmbuilder (see the man page).