EFI boot manager; or, well, an EFI bootorder compiler.

7fba144 Replace ucf for /etc/klapki/description with just the usual conffile mechanism

5 months ago

3d88e7d Manpage update by job 1113475

6 months ago

#klapki builds.sr.ht badge

EFI boot manager; or, well, an EFI bootorder compiler.

#Manpage (PDF)

screenshot of OVMF Boot Manager Nenu, showing an entry called "zoot", four similar entries starting with "Debian GNU/Linux" grouped by two kernel versions, the bottom entry of each version being suffixed with "(graphical)", then "Linux Boot Manager" screenshot of Dell R710 UEFI Boot Manager menu, showing a set of entries under the Embedded SATA Port B Disk, designated "Debian GNU/Linux 11 (bullseye)" grouped by two kernel versions, the bottom entry of each version being suffixed with "(rd.break=pre-pivot emergency)", then an entry fot the Port A Optical drive, then Front USB


You need to boot Linux somehow, but you don't really need any EFI-side code to do it if you configure your kernel right and have something tell the firmware about it. This is that something.

klapki stores neither code nor data (well, except the kernel and initrds) on the ESP, making it SecureBoot-compatible out-of-box, and instead generates entries for the host's kernels and manages them during their lifetime from the host itself.

Because of this, entries for each host can be trivially placed anywhere in the boot order (in the screenshot they're at {bootpos 1}, preceded by the "zoot" entry).

As seen in the screenshot, additional boot variants (just "graphical" in that case) are also supported, generating another entry for each kernel; OVMF doesn't show it, but the difference can be seen from this listing of /etc/klapki/cmdline used to generate those entries (the description is a tad verbose to match convention):

echo root=ZFS=zoot/root
[ "$2" = "graphical" ] || echo console=ttyS0

The second screenshot goes for the radical

echo root=zfs:AUTO intel_iommu=on zfs.zfs_arc_max=85899345920 "$2"


You'll need libmd-dev, libefi{var,boot}-dev, doctest-dev, libfmt-dev, zlib1g-dev, and make should hopefully Just Work™ if you have a C++20-capable compiler.

These are searched for with pkgconf if available. zlib is optional but, if it's beneficial, can thin out the state variable 12%-50%.

mandoc is required for HTML manpages. Set MANDOC=: when building to remove this dependency.

Note that klapki uses Linux-specific sendfile(), and as such building it will fail on other systems. Upstream libefivar only supports Linux anyway (and FreeBSD carries a port, though the usefulness of this within any classic UNIX distribution is doubtful).


Copy out/klapki to /sbin and write a /etc/klapki/{description,cmdline}, as seen in the manual.

#From Debian repository

The following line in /etc/apt/sources.list or equivalent:

deb [signed-by=/etc/apt/keyrings/nabijaczleweli.asc] https://debian.nabijaczleweli.xyz sid main

With my PGP key (the two URLs are interchangeable, or pull with WKD):

sudo wget -O/etc/apt/keyrings/nabijaczleweli.asc https://debian.nabijaczleweli.xyz/nabijaczleweli.gpg.key
sudo wget -O/etc/apt/keyrings/nabijaczleweli.asc https://nabijaczleweli.xyz/pgp.txt

(you may need to create /etc/apt/keyrings on apt <2.4.0 (<=bullseye) manually).

Then the usual

sudo apt update
sudo apt install klapki

will work on amd64, x32, and i386.

See the repository README for more information.

#From tar-ball

Release tarballs are signed with nabijaczleweli@nabijaczleweli.xyz (pull with WKD, but 7D69 474E 8402 8C5C C0C4 4163 BCFD 0B01 8D26 58F1). аnd stored in git notes as-if via the example program and are thus available on the refs listing/tag page as .tar.gz.asc.


Remove the variable corresponding to the host under the klapki GUID (a8a9ad3a-f831-11ea-946d-674ccd7415cc).

For example, on Linux, with host "zoot":

chattr -i /sys/firmware/efi/efivars/zoot-a8a9ad3a-f831-11ea-946d-674ccd7415cc
rm        /sys/firmware/efi/efivars/zoot-a8a9ad3a-f831-11ea-946d-674ccd7415cc

This will abandon any previously-managed entries by removing all state, so either run {delkernel ver} for all versions you had registered beforehand, or remove the entries and files later with efibootmgr(8)/EFI shell/the firmware UI.

#Reporting bugs

There's the tracker, but also see the list below.


Send a patch inline, as an attachment, or a git link and a ref to pull from to the list (~nabijaczleweli/klapki@lists.sr.ht) or me directly. I'm not picky, just please include the repo name in the subject prefix.


Please use the tracker, the list, or mastussy (formerly Twitter).

#Special thanks

To all who support further development on Patreon, in particular:

  • ThePhD
  • Embark Studios
  • Jasper Bekkers
  • EvModder