New post, from source to Internet

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

Author: troglobit

_posts/2026-05-28-building-infix-from-source.md

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+---
+title: Building Infix from Source
+description: From git clone to pinging the internet with make run
+author: troglobit
+date: 2026-05-28 06:00:00 +0100
+categories: [howto]
+tags: [beginner, buildroot, qemu]
+---
+
+There are two ways to take Infix for a spin on your own PC.  You can
+grab a pre-built release and boot it straight away; that is what the
+[Getting Started][gs] and [Infix in GNS3][gns3] posts cover.  Or you
+can build it yourself from source and boot the result with a single
+`make run`.  This post is the second path.
+
+Building from source is the way to go when you want to change an Open
+Source component, follow the bleeding edge on `main`, hack on Infix
+itself, or simply understand how the image is put together.  It takes a
+bit longer to get going the first time, but everything after that is a
+quick edit-build-run loop.
+
+You will need an **x86_64 Linux PC** with around 30 GiB of free disk
+space.  We recommend [Debian][] based systems like [Ubuntu][] and [Linux
+Mint][].
+
+### Install the Build Tools
+
+Buildroot, which Infix is built on, needs a handful of host tools to
+bootstrap itself.  Most are already present on a typical desktop install;
+the rest can be pulled in like this on Debian/Ubuntu based systems:
+
+```bash
+$ sudo apt install bc binutils build-essential bzip2 cpio  \
+                   diffutils file findutils git gzip       \
+                   libncurses-dev libssl-dev perl patch    \
+                   python3 rsync sed tar unzip wget mtools \
+                   autopoint bison flex autoconf automake
+```
+
+For the current list of requirements, see the [Developer's Guide][dev].
+
+### Get the Source
+
+Clone the Infix tree and pull in its submodules — Buildroot itself is a
+submodule, so this step is not optional:
+
+```bash
+$ mkdir -p ~/Projects && cd ~/Projects
+$ git clone https://github.com/kernelkit/infix.git
+...
+$ cd infix/
+$ git submodule update --init
+...
+```
+
+### Configure and Build
+
+Select the target you want to build for, then kick off the build.  We
+use the `x86_64` target since it runs with acceleration in Qemu:
+
+```bash
+$ make x86_64_defconfig
+$ make
+...
+```
+
+The first build downloads all the sources and compiles the entire
+system, so it may take the better part of an hour on a typical laptop —
+now is a good time for a coffee ☕.
+
+> Curious what else is available?  `make list-defconfigs` shows every
+> supported target, and `make help` lists the most useful make targets.
+{: .prompt-tip }
+
+### First Boot with `make run`
+
+When the build finishes you have a bootable image.  Launch it in Qemu
+with:
+
+```bash
+$ make run
+...
+```
+
+Infix boots in the same terminal.  When the login prompt appears, log in
+with the default credentials, user/pass: `admin` / `admin`.  You land in
+a plain shell — this is intentional, it is meant for scripting and
+advanced debugging:
+
+```
+Run the command 'cli' for interactive OAM
+
+admin@infix-c0-ff-ee:~$
+```
+
+Type `cli` to enter the Infix command line interface:
+
+```
+admin@infix-c0-ff-ee:~$ cli
+
+See the 'help' command for an introduction to the system
+
+admin@infix-c0-ff-ee:/>
+```
+
+To shut the VM down again, you can `poweroff` from inside Infix, or use
+the Qemu escape from the terminal: press **Ctrl-a** then **x**.
+
+### Look Around
+
+You are now in the *admin-exec* context.  Tap `?` or `Tab` on an empty
+line to see what is available, and use `show` to inspect the system:
+
+```
+admin@infix-c0-ff-ee:/> show interface
+...
+admin@infix-c0-ff-ee:/> show ip brief
+...
+admin@infix-c0-ff-ee:/> show running-config
+...
+```
+
+To change something, enter the *configure* context with `configure`.
+Changes are staged in a scratch copy and only applied when you type
+`leave` (or thrown away with `abort`):
+
+```
+admin@infix-c0-ff-ee:/> configure
+admin@infix-c0-ff-ee:/config/> edit system
+admin@infix-c0-ff-ee:/config/system/> set hostname lab-switch
+admin@infix-c0-ff-ee:/config/system/> leave
+admin@lab-switch:/>
+```
+
+For a proper tour of the CLI, see the [CLI Introduction][cli] in the
+documentation.
+
+### Get It on the Network
+
+A freshly booted Infix has its ports up but no IP addresses, and the
+default user-mode networking sits behind a NAT — fine for a first boot,
+but not much fun to interact with: no inbound SSH, no pinging the VM
+from the host.  Far more interesting is to put it on a bridge, hand it
+a DHCP address, and watch it reach the internet.
+
+**1. Set up a bridge on your host.**  The easiest way is to install
+[virt-manager][], which configures a libvirt NAT network on the bridge
+`virbr0` — complete with a DHCP server and a route out to the internet:
+
+```bash
+$ sudo apt install virt-manager
+```
+
+**2. Switch Infix to bridged networking.**  The Qemu wrapper has its own
+configuration; open it with:
+
+```bash
+$ make run-menuconfig
+```
+
+Go to **Networking → Network Mode**, select **Bridged**, and confirm the
+**Bridge device** is `virbr0`.  Exit and save.
+
+> If `make run` later complains that it is not allowed to use the bridge,
+> add a line `allow virbr0` to `/etc/qemu/bridge.conf` (create the file if
+> it does not exist) — this permits Qemu's bridge helper to attach to it.
+{: .prompt-info }
+
+**3. Boot again** with `make run`.  This time the first port, `eth0`, is
+wired to `virbr0`.
+
+**4. Enable the DHCP client** on `eth0` from the CLI:
+
+```
+admin@lab-switch:/> configure
+admin@lab-switch:/config/> edit interface eth0
+admin@lab-switch:/config/interface/eth0/> set ipv4 dhcp
+admin@lab-switch:/config/interface/eth0/> leave
+```
+
+**5. Check the result.**  Within a second or two libvirt's DHCP server
+hands out a lease (typically on the `192.168.122.0/24` network), which
+you can confirm in the CLI with:
+
+```
+admin@lab-switch:/> show interface
+...
+```
+
+**6. Reach the outside.**  With an address and a default route in place,
+ping a public host:
+
+```
+admin@lab-switch:/> ping 1.1.1.1
+...
+```
+
+That round trip goes from Infix, across `virbr0`, through your host's NAT,
+and out to the internet — a virtual switch behaving exactly like the real
+thing.
+
+> These changes live in `running-config` and are gone on the next boot.
+> To keep them, save with `copy running-config startup-config`.  To wipe
+> the slate clean instead, `factory-reset` returns the system to defaults.
+{: .prompt-info }
+
+### Networking, Brick by Brick
+
+What you just did, in Lego terms, was snap an *IP* brick (with DHCP)
+onto the *Ethernet* brick called `eth0`.  That is the whole mental
+model: in Infix, every networking object is a brick, and a network is
+whatever you get by snapping bricks together.
+
+![Linux networking bricks: bridge, ip, vlan, lag, eth, veth, lo](/assets/img/lego.svg)
+_**Figure 1:** The networking bricks available in Infix._
+
+There are only a handful of brick types: physical Ethernet (`eth`),
+bridges, VLANs, IP, LAG (link aggregation), and `veth` pairs for
+containers.  They connect in two ways.  A lower brick has *one* upper
+brick on top of it — a port belongs to *one* bridge.  An upper brick
+can have *many* lowers — a bridge can swallow several ports.
+
+Those two rules are enough to describe a switch, a router, a
+VLAN-tagged uplink, a bonded link, or a container with its own private
+interface.
+
+For a tour of every brick and how they fit together, see the
+[Network Configuration][net] section of the documentation.
+
+### Handy Make Targets
+
+A few targets you will reach for often once you start hacking:
+
+| Target                 | What it does                                        |
+|------------------------|-----------------------------------------------------|
+| `make run`             | Boot the built image in Qemu                        |
+| `make run-menuconfig`  | Configure the Qemu wrapper (networking, ports, RAM) |
+| `make menuconfig`      | Configure the Infix image itself (Buildroot)        |
+| `make list-defconfigs` | List all supported targets                          |
+| `make apply-dev`       | Enable `root` login, handy while developing         |
+| `make foo-rebuild`     | Rebuild just package `foo` after changing it        |
+
+### Where to Go Next
+
+You now have a full Infix build you can boot, configure, and rebuild at
+will.  A few directions from here:
+
+ - [Getting Started with Infix][gs] — the pre-built release path, if you
+   want the quick way too
+ - [Infix in GNS3][gns3] — build multi-node topologies on a graphical
+   canvas
+ - [Inside Infix][inside] — how the system is put together, from YANG to
+   the immutable root filesystem
+ - [Developer's Guide][dev] and the [full documentation][docs] — the
+   complete reference, including the [virtual environments][virt] section
+
+Questions and feedback are always welcome in the [Discussion Forum][disc]
+and on [Discord][discord]!
+
+[gs]:          /posts/getting-started/
+[gns3]:        /posts/infix-in-gns3/
+[inside]:      /posts/inside-infix/
+[cli]:         https://www.kernelkit.org/infix/latest/cli/introduction/
+[net]:         https://www.kernelkit.org/infix/latest/networking/
+[dev]:         https://www.kernelkit.org/infix/latest/developers-guide/
+[docs]:        https://www.kernelkit.org/infix/
+[virt]:        https://www.kernelkit.org/infix/latest/virtual/
+[disc]:        https://github.com/orgs/kernelkit/discussions
+[discord]:     https://discord.gg/6bHJWQNVxN
+[virt-manager]: https://virt-manager.org/
+[Debian]:      https://www.debian.org/
+[Ubuntu]:      https://ubuntu.com/
+[Linux Mint]:  https://linuxmint.com/