More Home Made Qemu KVM Recipes! — Give Each VM Its Own IP Address!

Jun 05, 2022 @ 12:14 pm

KVM logo Previously we made KVM VPses with Qemu’s default slirp networking. This time we will set up networking with Qemu so each Virtual Machine can have its own IP address. With slirp, we didn’t have to touch networking, because slirp automatically connects using its hosts’s IP address.

Here we are going to assume that our machine has a routed subnet of IP addresses and a bridge. From our subnet we can assign and configure IP addresses for each VM we make. If we don’t already have extra IP addresses, we need to get them, usually from our provider. If we don’t already have a bridge configured, Linux-KVM.org has a great tutorial. The Linux-KVM.org tutorial also covers the needed qemu-ifup script.

The approach used here is intended to be mostly independent of Linux Distribution software package systems and networking configuration utilities. The approach here also uses basic, raw qemu, with none of the excellent libraries and utilities which commonly are used to help configure Qemu KVM. Obviously, our approach here is mostly for Low End LOLs and for studying how Qemu works. It’s not for real life in production. It’s a work in pregress. The approach here should work on a VPS, on a dedicated server, or on a local machine running most Linux distributions.

Environment

From Mason Rowe’s Yabs Script

We might want to check if we have enabled hardware virtualization support. Here’s a script to check:

root@debian:~# cat cpu-virt.sh #!/bin/bash # From https://github.com/masonr/yet-another-bench-script/blob/master/yabs.sh # Lines 210-212 # Thanks to Mason and yabs developers!

CPU_VIRT=$(cat /proc/cpuinfo | grep ‘vmx\|svm’) [[ -z “$CPU_VIRT” ]] && CPU_VIRT=”\xE2\x9D\x8C Disabled” || CPU_VIRT=”\xE2\x9C\x94 Enabled” echo -e “VM-x/AMD-V : $CPU_VIRT” root@debian:~#

Libvirt

Libvirt includes a KVM environment validation utility at libvirt/tools/virt-host-validate-qemu.c

Libvirt is beyond the scope here, but, if you want to see a cool use of virt-host-validate, please take a look at Dmitrii Shcherbakov’s tutorial on running KVM inside LXC.

Install Or Compile Qemu

If Qemu is not already installed, use your distribution’s package system to install it. Alternatively, compile Qemu following the instructions on Qemu.org’s Download page. Qemu.org’s build instructions also are mentioned in a previous post on MIT’s free online Operating Systems course.

Make A Directory For The Virtual Machine

We’re going to call this VM vm206, so let’s make a directory for it.

tom@darkstar:~$ mkdir vm206 tom@darkstar:~$ cd vm206/ tom@darkstar:~/vm206$

Download And Validate An Operating System Image

Get An Image

tom@darkstar:~$ wget https://cloud.debian.org/images/cloud/sid/daily/latest/debian-sid-nocloud-amd64-daily.qcow2

[ . . . ]

tom@darkstar:~$

Get The Checksums

tom@darkstar:~/vm206$ wget https://cloud.debian.org/images/cloud/sid/daily/latest/SHA512SUMS tom@darkstar:~/vm206$

Verify The Image

tom@darkstar:~/vm206$ sha512sum --ignore-missing -c SHA512SUMS debian-sid-nocloud-amd64-daily.qcow2: OK tom@darkstar:~/vm206$

Please verify prior to booting and running an image since booting and running an image changes it.

Enable Revert

Let’s copy the image so we can revert to the original.

tom@darkstar:~/vm206$ cp debian-sid-nocloud-amd64-daily.qcow2 vm206.qcow2 tom@darkstar:~/vm206$

Resize The Image

The original downloaded image has a virtual size of 2 GiB:

tom@darkstar:~/vm206$ qemu-img info vm206.qcow2 image: vm206.qcow2 file format: qcow2 virtual size: 2 GiB (2147483648 bytes) disk size: 864 MiB cluster_size: 65536 Format specific information: compat: 1.1 compression type: zlib lazy refcounts: false refcount bits: 16 corrupt: false extended l2: false tom@darkstar:~/vm206$

Let’s resize the image:

tom@darkstar:~/vm206$ qemu-img resize vm206.qcow2 +48G Image resized. tom@darkstar:~/vm206$

Now we have a virtual size of 50 GiB:

tom@darkstar:~/vm206$ qemu-img resize vm206.qcow2 +48G Image resized. tom@darkstar:~/vm206$ qemu-img info vm206.qcow2 image: vm206.qcow2 file format: qcow2 virtual size: 50 GiB (53687091200 bytes) disk size: 864 MiB cluster_size: 65536 Format specific information: compat: 1.1 compression type: zlib lazy refcounts: false refcount bits: 16 corrupt: false extended l2: false tom@darkstar:~/vm206$

We see inconsistent results with this resizing procedure. As shown above, resizing appears to succeed on the node. However, sometimes the VM boots with the internal partition scheme seeming to recognize the resize, and sometimes not. Note that virt-resize is not yet installed on Darkstar. Alternative procedures include (1) attaching a second qcow2 file for user data or (2) not using the nocloud image and, instead, installing from Debian’s netinst.iso on a larger qcow2 file.

Script To Start The Virtual Machine

We’re going to start vm206 with this script:

tom@darkstar:~/vm206$ cat start-qemu-206.sh #!/bin/bash # Start VM on IP 206

# Run this script inside tmux

# Add route for IP 206 ip route add 66.11.114.206 dev br0

# Start qemu

/usr/local/bin/qemu-system-x86_64 \ -cpu host -smp sockets=1,cores=8,maxcpus=8 \ -enable-kvm \ -nographic \ -m 8192 \ -drive file=/home/tom/vm206/vm206.qcow2,if=virtio \ -netdev tap,id=mynet206,ifname=tap206,script=/root/qemu-ifup.sh,downscript="" \ -device virtio-net,netdev=mynet206,mac=DE:AD:00:BE:EE:06 tom@darkstar:~/vm206$

Use The Script To Start The VM Inside Tmux

tom@darkstar:~/vm206$ tmux tom@darkstar:~/vm206$ sudo ./start-qemu-206.sh

[ . . . ]

[FAILED] Failed to start OpenBSD Secure Shell server.

[ . . . ]

Debian GNU/Linux bookworm/sid localhost ttyS0

localhost login: root Linux localhost 5.17.0-3-amd64 #1 SMP PREEMPT Debian 5.17.11-1 (2022-05-26) x4

The programs included with the Debian GNU/Linux system are free software; the exact distribution terms for each program are described in the individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent permitted by applicable law. root@localhost:~#

The VM boots with the sshd server having failed and with no networking.

root@localhost:~# ping -c 2 www.google.com ping: www.google.com: Temporary failure in name resolution root@localhost:~# ping -c 2 1.1.1.1 ping: connect: Network is unreachable root@localhost:~# ping6 -c 2 2602:ffc5:105:40f::202 ping6: connect: Network is unreachable root@localhost:~#

Networking Inside the VM

Let’s add networking inside the VM.

Here are commands to start IPv4 and IPv6:

ip address add 66.11.114.206/32 dev enp0s3 ip route add 66.11.114.201 dev enp0s3 ip route add default via 66.11.114.201 dev ens3 ip -6 address add 2602:ffc5:105:40f::206/64 dev enp0s3 ip -6 route add 2602:ffc5:105:40f::1 dev enp0s3 ip -6 route add default via 2602:ffc5:105:40f::1 dev enp0s3

The network commands could be put into a script. I hear that it’s still possible to enable rc.local on Debian. Placing the script in rc.local will enable the script to run automagically during rebooting. We have this set up and working on another VM.

DNS

On this Debian VM /etc/resolv.conf is a symlink to /run/systemd/resolve/resolv.conf.

Let’s put Hurricane Electric’s resolver IP addresses in /etc/resolv.conf.

root@localhost:~# unlink /etc/resolv.conf root@localhost:~# echo nameserver 74.82.42.42 > /etc/resolv.conf root@localhost:~# echo nameserver 2001:470:20::2 >> /etc/resolv.conf root@localhost:~#

Looks like DNS and both IPv4 and IPv6 are working:

root@localhost:~# ping -c 2 lowendbox.com PING lowendbox.com(2606:4700:20::681a:1d8 (2606:4700:20::681a:1d8)) 56 data bs 64 bytes from 2606:4700:20::681a:1d8 (2606:4700:20::681a:1d8): icmp_seq=1 ttls 64 bytes from 2606:4700:20::681a:1d8 (2606:4700:20::681a:1d8): icmp_seq=2 ttls

--- lowendbox.com ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 1001ms rtt min/avg/max/mdev = 25.972/25.988/26.005/0.016 ms root@localhost:~# ping -4 -c 2 lowendbox.com PING (104.26.1.216) 56(84) bytes of data. 64 bytes from 104.26.1.216 (104.26.1.216): icmp_seq=1 ttl=58 time=21.6 ms 64 bytes from 104.26.1.216 (104.26.1.216): icmp_seq=2 ttl=58 time=21.6 ms

--- ping statistics --- 2 packets transmitted, 2 received, 0% packet loss, time 1001ms rtt min/avg/max/mdev = 21.553/21.568/21.583/0.015 ms root@localhost:~#

Looks like we have the expected IP addresses:

root@localhost:~# curl icanhazip.com 2602:ffc5:105:40f::206 root@localhost:~# curl -4 icanhazip.com 66.11.114.206 root@localhost:~#

Install Host SSL Certificates

Remember the OpenSSH server failed? That’s because it doesn’t have any host keys. Let’s fix that.

root@localhost:~# apt-get update Get:1 http://deb.debian.org/debian sid InRelease [165 kB] Get:2 http://deb.debian.org/debian sid/main Sources [9744 kB] Get:3 http://deb.debian.org/debian sid/main amd64 Packages [9204 kB] Get:4 http://deb.debian.org/debian sid/main Translation-en [6820 kB] Fetched 25.9 MB in 7s (3779 kB/s) Reading package lists... Done root@localhost:~# apt-get upgrade Reading package lists... Done Building dependency tree... Done Reading state information... Done Calculating upgrade... Done The following packages will be upgraded: cloud-guest-utils cloud-image-utils cloud-utils libnss-resolve libpam-systemd libsystemd0 libudev1 systemd systemd-sysv udev 10 upgraded, 0 newly installed, 0 to remove and 0 not upgraded. Need to get 7599 kB of archives. After this operation, 13.3 kB of additional disk space will be used. Do you want to continue? [Y/n]

[ . . . ]

root@localhost:~# dpkg-reconfigure openssh-server

[ . . . ]

Creating SSH2 ED25519 key; this may take some time ...

[ . . . ]

root@localhost:~# systemctl status sshd ● ssh.service - OpenBSD Secure Shell server Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: e> Active: active (running) since Sat 2022-06-04 03:14:27 UTC; 1min 57s ago

[ . . . ]

root@localhost:~#

If we didn’t want to use dpkg-reconfigure, ssh-keygen -A might work. Please see How To: Ubuntu / Debian Linux Regenerate OpenSSH Host Keys

Add Authorized Keys

root@localhost:~# mkdir .ssh root@localhost:~# chmod 700 .ssh/ root@localhost:~# echo ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAILySvSdulbZ4XG4K333YOoFbcwoo6ythPBOf175OIBfA chronos@localhost > .ssh/authorized_keys root@localhost:~# chmod 600 .ssh/authorized_keys

Login via SSH

How To Quit

To exit tmux while leaving the VM running, type “Ctrl-b” then “d”.
To re-enter tmux and the already running VPS:

tmux attach

To stop the VM and quit tmux:

shutdown -h now

Type “exit” when the command prompt returns following VM shutdown.

Additional Resources

A really helpful resource for me when I was first trying KVM tricks was Linux-KVM.org’s Network Configuration page.

Maybe the world’s most thorough qemu tutorial is from Dongli Zhang.

Conclusion

From our previous post we have available three ways to use qemu’s default networking tool, slirp. Now we have explored making KVM virtual machines with their own individual IP addresses.

Have fun on the Low End! 💖

Install Windows Server on any VPS or Dedicated Server without KVM/iLO or IPMI!

SoftShellWeb Offers Cheap VPS Systems in Taiwan, Amsterdam, and San Jose!

RackNerd Named Among Fastest-Growing Companies in 2024 Inc. 5000 Regionals Pacific List

How Private is Your Hosted Data, Really? Even That Encrypted Stuff...

Running LowEnd on HighEnd: Running FreeDOS on a MacBook M1 (Apple Silicon) with QEMU

KVM and OpenVZ 7 Yearly VPS Offers in USA, France, and Canada from HostNamaste!

Author
Recent Posts

Not_Oles

Contributor at Low End Box

It seems only a moment since the day, fifty years ago, when I stood in a doorway watching yard after yard of printed paper full of ascii art scrolling out of a Teletype 33 surrounded by a bunch of laughing guys!

My Low End Adventures started here at LowEndBox, when just a few years back, I found the perfect deal on a dedicated server from OVH!

These days I own my own gorgeous antique server named Darkstar. She is colocated in Dallas, Texas USA at LevelOneServers.com.

Besides writing for LowEndBox, helping as a moderator at LowEndTalk and running Darkstar, I'm trying to learn a little about programming and networking.

All these years, and, still, so much more to learn! So many people here who can teach me!

It's very, very fun here on the Low End, isn't it? :)