nextboot(8)

nextboot8

Specify an alternate kernel and boot flags for the next reboot

Usage

nextboot [-aDf] [-e variable=value] [-k kernel] [-o options]

nextboot -D

Overview

The nextboot utility allows specifying some combination of an alternate kernel, boot flags, and kernel environment for the next time the machine is booted. Once the loader(8) loads in the new kernel information from the /boot/nextboot.conf file, it is disabled so in case the new kernel hangs the machine, once it is rebooted, the machine will automatically revert to its previous configuration.

The options are as follows:

-a

This option causes nextboot to append to an existing configuration in /boot/nextboot.conf. By default any existing configuration is overwritten.

-D

Invoking nextboot with this option removes an existing nextboot configuration.

-e variable=value

This option adds the provided variable and value to the kernel environment. The value is quoted when written to the nextboot configuration.

-f

This option disables the sanity checking which checks if the kernel really exists before writing the nextboot configuration.

-k kernel

This option specifies a kernel directory relative to /boot to load the kernel and any modules from.

-o options

This option allows the passing of kernel flags for the next boot.

Files

/boot/nextboot.conf

The configuration file that the nextboot configuration is written into.

Examples

To boot the GENERIC kernel with the nextboot command:

nextboot -k GENERIC

To enable into single user mode with the normal kernel:

nextboot -o "-s" -k kernel

To remove an existing nextboot configuration:

nextboot -D

Releases

83 releases since FreeBSD 2.2.2-RELEASE; the text changed 45 times.

  1. 2.2.2–2.2.6
  2. 2.2.7–2.2.8
  3. 2.2.9
  4. 3.0–3.1
  5. 3.2
  6. 3.3–3.4
  7. 3.5–3.5.1
  8. 4.0–4.2
  9. 4.3
  10. 4.4–4.7
  11. 4.8–4.11
  12. 5.0–6.3
  13. 6.4
  14. 7.0
  15. 7.1
  16. 7.2
  17. 7.3
  18. 7.4
  19. 8.0
  20. 8.1
  21. 8.2
  22. 8.3
  23. 8.4
  24. 9.0
  25. 9.1
  26. 9.2
  27. 9.3
  28. 10.0
  29. 10.1
  30. 10.2
  31. 10.3
  32. 10.4
  33. 11.0
  34. 11.1
  35. 11.2
  36. 11.3
  37. 11.4
  38. 12.0
  39. 12.1
  40. 12.2
  41. 12.3
  42. 12.4
  43. 13.0–13.1
  44. 13.2
  45. 13.3–15.0
  46. 15.1–16.0

-D since FreeBSD 5.0-RELEASE; -a since FreeBSD 11.0-RELEASE; -e since FreeBSD 9.2-RELEASE; -f since FreeBSD 5.0-RELEASE; -k since FreeBSD 5.0-RELEASE; -o since FreeBSD 5.0-RELEASE.

-b until FreeBSD 4.11-RELEASE; -d until FreeBSD 4.11-RELEASE.

History

The original nextboot manual page first appeared in FreeBSD 2.2. It used a very different interface to achieve similar results.

The current incarnation of nextboot appeared in FreeBSD 5.0.

Authors

This manual page was written by Gordon Tetlow ⟨[email protected]⟩.

Bugs

The nextboot code is implemented in the loader(8). It is not the most thoroughly tested code. It is also my first attempt to write in Forth.

Finally, it does some evil things like writing to the file system before it has been checked. If it scrambles your file system, do not blame me.

From base 16.0-CURRENT-20261027-61c70dc16a79 in FreeBSD 16.0-CURRENT (2026-10-27). Parsed by carta from the page's mdoc source.