Daniel's Notes

In what continues to be very off-brand content for me (I'm really a kernel developer, I promise!), here are some random notes on some k8s stuff that will hopefully help someone. I'll keep this post as a running log of interesting stuff as I study for the CKA exam. Deploying k8s with the Canonical Distribution of Kubernetes (CDK) Does your deployment hang forever with kubernetes-master "Waiting for kube-system pods to start"? I was using a local deployment with LXD, and I needed to do the following 3 things: Disable swap on the host. In my case, I used juju ssh to connect to a kubernetes-master unit, then kubectl get nodes|less -S . This informed me that the nodes weren't starting the container runtime. Using juju ssh to connect to a node and running sudo kubectl , I found out that the container runtime was refusing to start because the host had swap memory enabled! After disabling that with sudo swapoff -a on the host, I was able to make progress an...

What do netplan apply, netplan generate, and netplan try do? The netplan man page just talks about the YAML configuration file format and don't describe the commands. So consider this a set of draft manpages - my hope is that it will fill in the gaps. I will try to get them merged to the main repository. Background To understand the netplan commands, it's helpful to know the very basics of the netplan design. Using netplan is a 2 step process: Netplan takes YAML files - usually from /etc/netplan/*.yaml - and converts them into configuration that is read by a backend .  This backend interacts with the kernel to actually configure the devices. Netplan currently supports systemd-networkd and NetworkManager as backends. So it will convert your configuration into the configuration that they read, and then they will actually apply it to the machine. Netplan doesn't do any configuration itself. With this in mind, we can understand the components netplan generate N...

netplan  is the default network configuration system for new installs of Ubuntu 18.04 (Bionic). It uses YAML to configure network interfaces, instead of  /etc/network/interfaces . I've been testing netplan for a while, so in light of the release of Bionic, here's my set of examples, caveats, tips and tricks. Contents General tips and tricks Matching Basic IPv4 configuration MTUs Bridges, Bonds and VLANs Wifi IPv6 Supplementing or replacing netplan Going Further General tips and tricks Tabs are not allowed in YAML and currently you get a very useless error message if you use them: "Invalid YAML at //etc/netplan/10-bridge.yaml line 5 column 0: found character that cannot start any token". If you see this, check for tabs! Indentation matters in YAML. Make sure that things line up where they're supposed to. Rebooting is somewhat more reliable than netplan apply , but make sure  there are no errors in your YAML before you reboot or no network ...

netplan is the default network configuration system for new installs of Ubuntu 18.04 (Bionic). Introduced as the default in Artful, it replaces /etc/network/interfaces . One question that gets asked repeatedly is: "How do I set up an anonymous bridge in netplan?" (An anonymous bridge, I discovered, is one where the bridge doesn't have an IP address; it's more akin to a switch or hub.) It's been approached on  Launchpad , and comes up on the IRC channel. If you're trying to create a bridge without an IP address, the obvious first thing to try is this: network: version: 2 ethernets: ens8: match: macaddress: 52:54:00:f9:e9:dd ens9: match: macaddress: 52:54:00:56:0d:ce bridges: br0: interfaces: [ens8, ens9] This is neat, plausible, and wrong - the bridge will be created but will stay 'down'. Per ip a : 5: br0: <BROADCAST,MULTICAST> mtu 15...

TL;DR: Working examples of setting IPv6 addresses, nameservers and routes (static, SLAAC+RDNSS, SLAAC+stateless DHCPv6, and stateful DHCPv6), with client configuration for ifupdown (/etc/network/interfaces) and netplan, that you can run and experiment with on your own computer with minimal dependencies: github.com/daxtens/ipv6-config-demos There are quite a few ways you can set up an IPv6 connection with enough information to be useful - an address, nameserver and default route. So far I've come up with 4, listed in the table below. (I found them all very confusing to begin with - the best explanation I've found online so far is this blog post .) Method Address DNS Nameserver Default Route Static Static Static Static SLAAC + RDNSS Autogenerated by client RDNSS data in RA From RA SLAAC + Stateless DHCPv6 Autogenerated by client DHCPv6 From RA Stateful DHCPv6 Assigned by DHCPv6 server DHCPv6 ...

How do you connect to a a wifi network with netplan? I hang out on the #netplan IRC channel on Freenode, and this comes up every so often. netplan - the default network configuration tool in Ubuntu 17.10 onwards - currently supports WPA2 Personal networks, and open (unencrypted) networks only. If you need something else, consider using NetworkManager directly, or falling back to ifupdown and wpa_supplicant for a little longer. Without further ado, here are tested, working YAML files for connection to my local WPA2 and unencrypted network. The only things that have been changed are the SSIDs and password. Both networks have a router providing dhcp4. In both cases I assume there's only one wifi device in the system - if this is not true, replace match: {} with something more specific. You can drop these in  /etc/netplan and run netplan generate; netplan apply  and things should work. The network will also be brought up on subsequent boots. Note that, as always in YAML...

As an ex-IBMer, I'm still quite fond of POWER/ppc64 processors, and occasionally cross-compile kernels for 64-bit little-endian PowerPC (ppc64el/ppc64le) from my amd64 system. It's not immediately obvious what the simplest way to do this is. On Ubuntu (and I'm told, Debian) it is really very simple. Installation sudo apt install gcc-powerpc64le-linux-gnu Congrats, you now have a ppc64le cross-compiling toolchain installed! If you need other languages, g++/gccgo/gfortran/gnat/gobjc-powerpc64le-linux-gnu are also available. Kernel cd your/linux/source make ARCH=powerpc CROSS_COMPILE=powerpc64le-linux-gnu- <your usual kernel build commands here> That's it. Userspace It depends a bit on the build system. Here's how to build, for example, sed , which uses autotools ( ./configure and friends). ./configure --host powerpc64le-linux-gnu make That's it.  For a dynamically linked binary, you only need the headers for any library depende...