Rapido helps you quickly test Linux kernel changes.

Quick Start

# install dracut and qemu, then...
git clone https://github.com/rapido-linux/rapido.git && cd rapido
./rapido cut simple-example # boot a throwaway VM using the host kernel

A demonstration screencast can be found here.

Setup

Clone this repository and install the following dependencies:

• Dracut:
  • Generates a VM image, with kernel-modules and minimal user-space
• QEMU:
  • Boots a given Dracut VM image and compiled Linux kernel on the local system
• systemd-networkd:
  • Configures networking within Rapido VMs (optional)
• iproute2:
  • Configures Bridge and TAP devices on the host (optional)

Rapido obtains all dependencies from the local system; no magic images or internet downloads are necessary. Individual cut scripts (e.g. cut/fstests_btrfs.sh) may require extra dependencies.

Rapido is primarily configured via rapido.conf. To boot a custom Linux kernel, copy rapido.conf.example and set the KERNEL_SRC parameter to the path of your compiled kernel source.

Network Configuration

Test VM images may be "cut" with or without network support. For networking, per-VM systemd-networkd configuration should be specified in the net-conf directory. An example is provided in net-conf.example. The rapido setup-network command should be run as root to configure a bridge network device and VM-assigned tap devices. By default, the bridge network is isolated, and isn't connected to any physical adapters.

Running

Depending on which kernel component or functionality you'd like to test, choose a cut script to generate a VM image. E.g.

./rapido cut fstests-btrfs

The cut script collects all required kernel modules and user-space dependencies from the local system and writes a VM initramfs image to initrds/myinitrd. Once generated, a VM using the image and kernel will boot immediately. Subsequent VMs can be booted manually via:

./rapido boot

Adding Your Own Tests

Rapido can be easily extended to test any kernel functionality of interest. Simply copy the cut/simple_example.sh and autorun/simple_example.sh scripts and modify them to suit your needs. The example scripts are fully annotated.

Feedback and Bug Reporting

Please raise any questions or issues upstream via https://github.com/rapido-linux/rapido/issues

Architecture

ASCII art

                                   +------------------------+
                                   |                        |
                                   | Rapido 'cut' script    |
                                   |                        |
                                   | +--------------------+ |    +-----+
                                   | |                    | |    |     |
                                   | | File manifest:     | |    |     |
+------------------------+         | | • Kernel modules   | |    |     |
|                        |         | | • User space files | |    |     |
| Userspace dependencies |         | |                    | |    |     |
| E.g.                   |         | +---------+----------+ |    |     |
| • xfstests, blktests   |         |           |            <----+     |
| • Ceph conf + binaries |         | +---------v----------+ |    |     |
| • Samba                |         | |                    | |    |     |
| • etc.                 +--->--+---->  Dracut initramfs  | |    |  r  |
|                        |      |  | |  generator         | |    |  a  |
+------------------------+      ^  | |                    | |    |  p  |
                                |  | +---------+----------+ |    |  i  |
+-------------------------+     |  |           |            |    |  d  |
|                         |     |  +------------------------+    |  o  |
| Rapido 'autorun' script +-->--+              |                 |  .  |
|                         |     |    +---------v----------+      |  c  |
+-------------------------+     |    |                    |      |  o  |
                                |    | Initramfs          |      |  n  |
                                ^    | • Includes all     |      |  f  |
+------------------------+      |    |   kernel and user  |      |     |
| Compiled Linux Kernel  |      |    |   dependencies     |      |  /  |
|                        |      |    |                    |      |     |
| +---------+            |      |    +---------+----------+      |  n  |
| | Modules +---------------->--+              |                 |  e  |
| +---------+            |         +------------------------+    |  t  |
|                        |         |           |            |    |     |
| +---------+            |         |  Rapido 'vm' script    |    |  c  |
| | bzImage +---------------->--+  |           |            |    |  o  |
| +---------+            |      |  |  +--------v----+       |    |  n  |
|                        |      |  |  |             |       <----+  f  |
+------------------------+      +-----> QEMU / KVM  |       |    |     |
                                   |  |             |       |    |     |
                                   |  +--------+----+       |    |     |
                                   |           |            |    +--+--+
                                   +------------------------+       |
   ===================                         |                    |
   | Virtual network O--------+    +-----------v---------------+    v
   =========^=========        |   ++                           |    |
            |                 |   !| Virtual Machine           |    |
            |                 |   !| • Console redirected via  |    |
            |                 +---oO   stdin and stdout        <----+
+-----------+------------+        !| • 'autorun' script        |    |
|                        |        !|   executed on boot        |    |
| Rapido "setup-network" |        !|                           |    v
|                        |        !+--------------------------++    |
+-----------^------------+        +~~~~~~~~~~~~~~~~~~~~~~~~~~~+     |
            |                                                       |
            +------------------------------<------------------------+