I use qemu to virtualize appliances on my servers, and I access them over SSH. Allthough SSH supports streaming X windows so it is possible to fire up a graphical install, it is not so convenient as the connection may drop and cancel the install.
A convenient workaround is to use qemu’s curses/nographic interface, where instead of a display, a terminal is attached to the virtual machine. That way you can install and use your virtual machines directly in the SSH terminal.
To install a new system from scratch, simply define the -hda, -cdrom and -boot flags, and add the -nographic option:
qemu-system-x86_64 -hda /dev/sdc1 -m 1500 --enable-kvm -nographic -cdrom images/debian-stable.iso -boot d
The Debian installer supports headless mode, but we have to add two settings at the boot prompt to make it work with curses/nographic.
1. Fire up qemu with the command above. Wait a few seconds, the screen will turn black after loading syslinux. Hit ESC, and enter:
install fb=none vga=normal
and follow the install. Voilà, you’re installing your VM in qemu directly over ssh.
Tip: To prevent losing the install if the network connection is lost, run the commands in a screen terminal.
Recently I was deploying a service that made use of Linux’s IPTABLES feature, but this time in an LXC container. LXC containers provide an extremely lightweight virtualization technology and a simple way to separate environments.
When loading IPTABLES rules in the container I encountered the following error:
ERROR: initcaps
[Errno 2] modprobe: ERROR: ../libkmod/libkmod.c:556 kmod_search_moddep() could not open moddep file '/lib/modules/3.16.0-4-amd64/modules.dep.bin'
ip6tables v1.4.21: can't initialize ip6tables table `filter': Table does not exist (do you need to insmod?)
Perhaps ip6tables or your kernel needs to be upgraded.
This was due to the fact that on the host, the ip6table_filter module was not loaded. Usually, the iptables command will by itself load the module when needed, but LXC shares the kernel of the host system and a container is restricted from loading modules into the host’s kernel.
The solution is to simply load the kernel module on the host:
# on debian jessie, as root:
modprobe ip6table_filter
After that the container will be able to make use of the new kernel module.
Was this article useful? Leave me a comment!I’ve been waiting for an open platform where people can share the "what to know" about any product. When I buy something I want to know what impact it has, on my health, the workers, the planet.
I want to know this information from people I trust, not from the corporations themselves that don’t want me to worry about "what kind of aerosol is in that deodorant and it’s climate impact" but rather "how this is going to increase my sex-appeal."
Finally the platforms that help us gather and use consumer sourced producer information are emerging. With OpenLabel, https://theopenlabel.com/, and www.wiki-products.org (German) we are entering a buying culture where if I have the choice between two products and I happen to care about animal rights I can make a better choice. Better might not be good, but if we’re sticking with consumerism let’s send the right signals up that chain.
When advertisement and mass media lose their power, we will probably stuff this void with real information. I’m looking forward to that.
