Annotation of wikisrc/rumpkernel.mdwn, revision 1.8

1.1       pooka       1: **Contents**
                      3: [[!toc levels=2]]
1.5       pooka       5: This page is about rump kernels in NetBSD and assumes the reader knows
1.8     ! wiki        6: the basics of rump kernels.  [General information
        !             7: about rump kernels]( is available elsewhere.
1.5       pooka       8: 
                      9: ## System security
                     11: File system drivers are vulnerable to consistency errors in
                     12: file system images, see e.g.
                     13: [here](
                     15: What this vulnerability means is that whenever an untrusted file system
                     16: image is mounted using an in-kernel driver, system compromise should be
                     17: expected.  This untrusted images include for example ones on USB sticks.
                     18: There are heavyweight workarounds for the problem, for example including
                     19: virtual machines.
                     21: NetBSD allows transparently mounting an untrusted file system image by
                     22: running the kernel driver in a rump kernel in userspace.  The driver
                     23: is thus isolated and any damage that a malicious file system image
                     24: can directly cause is restricted to a userspace process.  From a user
                     25: perspective, mounting with the `-o rump` option is the only change
                     26: required, or `rump` in `/etc/fstab`.  Notably, even though interacting
                     27: with untrusted file systems will suffer from a minor performance penalty,
                     28: the performance of mounts from trusted file systems is completely
                     29: unaffected.
                     32: ## Automated testing
                     34: The problems of automated kernel testing are documented for example in
                     35: [The Design and Implementation of the Anykernel and Rump Kernels](
                     36: Rump kernels are used in the continuous tests run by the NetBSD project.
1.7       sevan      37: See [Release Engineering Status Site]( for the results or the NetBSD source tree
1.5       pooka      38: under `src/tests` for the test programs themselves.
                     41: ## Kernel development
                     43: On the flipside of testing is kernel development.  Rump kernels allow
                     44: developing kernel drivers in a test-driven manner, including both unit
                     45: tests and integration tests.  Since the iteration time with a rump
                     46: kernel is in the subsecond range, the development process is smoother
                     47: than with a virtual machine.  Also, the tests written during development
                     48: can be entered into the automated tests (see above), and later used
                     49: for further development.  This method avoids "throw-away" tests that
                     50: are hardcoded for one virtual machine environment and unusable in both
                     51: automated testing and further development done in another environment.
1.1       pooka      52: 
                     54: ## Source Code
                     56: You can also [browse]( the
                     57: source code history online. Code is found from all areas of the source
                     58: tree. Some examples of where to look include
                     59: [src/lib](,
                     60: [src/usr.bin]( and
                     61: [src/sys/rump](

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