Difference between pages "UEFI Install Guide" and "Building a Kernel from Source"

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This tutorial will show you how to install Funtoo on a UEFI system. UEFI, also known as the [[Wikipedia:Unified Extensible Firmware Interface|Unified Extensible Firmware Interface]], is a new firmware interface that is used on some newer computers as a replacement for the traditional PC BIOS. It has an integrated boot loader, so setting up booting is different.
+
Setting up a proper kernel yourself - lean, mean and tailored to your hardware, is the challenge by which a linux user can graduate to becoming a Funtoo knight ;-)
  
This tutorial is meant to be an "overlay" over the Regular Funtoo Installation. Follow the normal installation and only follow steps in this tutorial when dealing with partitioning and configuring the boot loader (GRUB). All steps are otherwise identical to the regular installation process.
+
Even though many of us are using enterprise-ready kernels in datacenters, there is almost nobody who hasn't at least considered building a kernel for his laptop / PC.
 +
We are showing here how an intermediate Linux user can use an alternative to the standard beginners "genkernel" approach,  to compile a custom kernel,  in a relatively still speedy and easy set up.
  
== What Are We Doing? ==
+
=== Minimum Requirements ===
 +
You should understand the way how things work in a terminal and how to use an editor and tweak config files. This is crucial.
 +
You don't need much knowledge about the linux kernel and it's internals. Nevertheless, you have to know at least where the files are located, how they are used and what is the file logic behind the overall structure. Otherwise you should consider using a non source based linux distribution.
 +
If you are scared now, don't worry - we are going to build a kernel the Funtoo way and you will pick up everthing necessary to accomplish this challenge, step by step, so the next time you do it yourself and become a real Funtoo knight!
  
This guide will show you how to set up your UEFI system to load the GRUB boot loader, which will then load your Funtoo Linux kernel and initramfs. This is the "UEFI + GRUB" method as described on the [[Boot Methods]] page.
+
=== Assumptions ===
 +
You start from an installed Funtoo system on the disk, or at least, you are on stage3 in a chrooted environment from a live cd, following somehow the Funto [[Installation (Tutorial)|Installation Tutorial]].
  
== First Steps ==
+
In this case we are building a kernel that is booting root in LVM over encrypted LUKS container.
 +
If you don't have this setup, don't worry, you just don't need all the modules, but everything else is similar.
  
To install Funtoo Linux on a UEFI system, first you need to boot SysRescueCD in UEFI mode. To do this, enable UEFI in your BIOS, and if necessary disable legacy booting. After some fiddling, you should be able to boot SysRescueCD and get a black and white text menu instead of the traditional aqua/cyan-colored menu. The black and white menu indicates that you booted SysRescueCD in UEFI mode. Once you've accomplished this, you're ready to continue with your Funtoo Linux installation and partition your drive. See below for details.
 
  
'''If the <tt>/sys/firmware/efi</tt> directory exists, then you have successfully booted in EFI mode and will be able to configure your Funtoo system to boot in EFI mode. If the directory doesn't exist, fix this first. It is a requirement for setting up EFI booting.'''
+
= Getting everything in order to start =
  
== Partitioning ==
+
First there is the decision which linux kernel sources we need.
 +
There are plenty of them in the repositories around, often it is not easy to distinguish between them.
  
To set up your partitions for UEFI booting, you will create a ~500MB FAT32 partition on <tt>/dev/sda1</tt>, and set it to type <tt>EF00</tt> using <tt>gdisk</tt>.
+
I would always trust my distribution of choice and take what is has to offer - and funtoo has a lot to offer!
 +
 
 +
I really do recommend (especially if it is your first time) to build a debian-sourced genkernel like described in chapter 5 "Using Debian-Sources with Genkernel" in the [[Funtoo_Linux_Kernels| Funtoo Kernels Tutorial]].
 +
 
 +
From there you should have a running system booting nicely from your own build (just little bit bloated) kernel. This is more than you can expect from any other ready to go distribution.
 +
 
 +
'''Attention'''
 +
We are using RedHat's dracut in order to build a nice initramfs (containing all the necessary tools and extra drivers our kernel might need to start the system).
 +
 
 +
Although dracut is the way to go, more sophisticated and not as buggy as gentoo's genkernel approach, more and more funtoo geeks start using slashbeast's better-initramfs, which we will cover at the end of this howto!
 +
 
 +
So after having set up a genkernel from debian or gentoo sources we are going to build a kernel with either (or both) dracut or/and better-initramfs.
 +
So gentoo sources with genkernel is always my backup if anything is not working correctly on my system. For the slightly more geeky approach with my own initram I am using pf-sources, ck-sources or any other more or less heavily patched sources.
 +
 
 +
Let's go!
 +
 
 +
== Kernel Sources ==
 +
We are going to use the kernel sources from the funtoo git repository.
 +
 
 +
The source you use on your system is up to you and your needs.
 +
For a laptop or desktop system, we recommend the following:
 +
 
 +
* '''sys-kernel/pf-sources'''
 +
* '''sys-kernel/ck-sources'''
 +
* '''sys-kernel/gentoo-sources'''
 +
* '''sys-kernel/git-sources'''
 +
* '''sys-kernel/sysrescue-std-sources'''
 +
* '''sys-kernel/debian-sources'''
 +
 
 +
Please, have a look in the ebuild description, look onto their homepage and take the one that suits you best!
 +
If you are unsure for now, use sys-kernel/gentoo-sources. That's always a safe bet for a general system.
 +
 
 +
It is not a problem to have various kernels installed parallel, so go on with any one of them.
 +
 
 +
I am going to use the sys-kernel/pf-sources now, as I already had the gentoo-sources installed.
 +
 
 +
== Prerequisites ==
 +
 
 +
I don't know which tools you have already installed, so some information here might be redundant.
 +
It doesn't harm to just copy and paste and do some steps again.
 +
 
 +
First, we look into our <code>/etc/make.conf</code>:
  
 
<console>
 
<console>
Command: ##i##n ↵
+
##i### nano /etc/make.conf
Partition Number: ##i##1 ↵
+
#These compiler flags are just tweaking (optimazation) and NOT necessary:
First sector: ##i##↵
+
CFLAGS="-O2 -pipe -march=native -ftracer -fforce-addr"
Last sector: ##i##+500M ↵
+
CXXFLAGS="${CFLAGS} -fpermissive -fomit-frame-pointer"
Hex Code: ##i##EF00
+
KDIR=/usr/src/linux
 +
KERNEL="symlink build"
 +
USE="$KERNEL ....here are your use flags...."
 +
## These modules are available:
 +
## DRACUT_MODULES="dracut_modules_biosdevname dracut_modules_btrfs dracut_modules_caps dracut_modules_crypt dracut_modules_crypt-gpg dracut_modules_dmraid dracut_modules_dmsquash-live dracut_modules_gensplash dracut_modules_iscsi dracut_modules_livenet dracut_modules_lvm dracut_modules_mdraid dracut_modules_multipath dracut_modules_nbd dracut_modules_nfs dracut_modules_plymouth dracut_modules_ssh-client dracut_modules_syslog"
 +
## We will use these modules for LVM / LUKS:
 +
DRACUT_MODULES="crypt lvm plymouth biosdevname dmraid crypt-gpg dmsquash-live ssh-client syslog"
 
</console>
 
</console>
  
This partition will serve as your Funtoo <tt>/boot</tt> filesystem as well as the partition that the UEFI firmware can read to load GRUB. Then you will set up swap on <tt>/dev/sda2</tt> and your root filesystem on <tt>/dev/sda3</tt>. To create the FAT32 filesystem, type:
+
Next, we set the package keywords:
 +
<console>
 +
/etc/portage/package.use/dracut:
 +
sys-kernel/dracut dm net device-mapper crypt lvm
 +
</console>
  
 +
{{Note}} If you don't have lvm over encrypted LUKS you probably just add the "net" keyword here, or "selinux".
 +
 +
 +
After that we are going to build our packages:
 
<console>
 
<console>
# ##i##mkfs.vfat -F 32 /dev/sda1
+
# ##i##emerge -av app-portage/gentoolkit sys-kernel/pf-sources sys-kernel/dracut sys-boot/plymouth sys-boot/plymouth-openrc-plugin
 
</console>
 
</console>
  
Your <tt>/etc/fstab</tt> entry for this filesystem will also differ, and will look like this:
+
Finished? Well, then let's go on and
  
 +
== Preparing the kernel ==
 +
 +
We go now to the sources directory and enter the following commands to update the kernel's  .config  file:
 +
<console>
 +
##i### cd /usr/src/linux/
 +
##i### make clean
 +
  CLEAN  .
 +
  CLEAN  arch/x86/kernel/acpi/realmode
 +
  CLEAN  arch/x86/kernel/cpu
 +
  CLEAN  arch/x86/kernel
 +
  CLEAN  arch/x86/vdso
 +
  CLEAN  arch/x86/lib
 +
  CLEAN  drivers/gpu/drm/radeon
 +
  CLEAN  drivers/net/wan
 +
  CLEAN  drivers/scsi/aic7xxx
 +
  CLEAN  drivers/tty/vt
 +
  CLEAN  drivers/video/logo
 +
  CLEAN  firmware
 +
  CLEAN  kernel
 +
  CLEAN  lib/raid6
 +
  CLEAN  lib
 +
  CLEAN  security/apparmor
 +
  CLEAN  security/selinux
 +
  CLEAN  usr
 +
  CLEAN  arch/x86/boot/compressed
 +
  CLEAN  arch/x86/boot
 +
  CLEAN  .tmp_versions
 +
  CLEAN  vmlinux System.map .tmp_kallsyms2.S .tmp_kallsyms1.o .tmp_kallsyms2.o .tmp_kallsyms1.S .tmp_vmlinux1 .tmp_vmlinux2 .tmp_System.map
 +
##i### zcat /proc/config.gz > /usr/src/linux/.config
 +
</console>
 +
 +
<console>
 +
##i### make localmodconfig
 +
</console>
 +
 +
You will get some questions which you can answer mostly with either M (compiled as a module) or Y (compiled directly into the kernel).
 
<pre>
 
<pre>
/dev/sda1 /boot vfat noatime 1 2
+
Enable different security models (SECURITY) [Y/n/?] y
 +
Enable the securityfs filesystem (SECURITYFS) [Y/?] y
 +
Socket and Networking Security Hooks (SECURITY_NETWORK) [Y/?] y
 +
Security hooks for pathname based access control (SECURITY_PATH) [Y/?] y
 +
Low address space for LSM to protect from user allocation (LSM_MMAP_MIN_ADDR) [65536] 65536
 +
NSA SELinux Support (SECURITY_SELINUX) [Y/n/?] y
 +
  NSA SELinux boot parameter (SECURITY_SELINUX_BOOTPARAM) [N/y/?] n
 +
  NSA SELinux runtime disable (SECURITY_SELINUX_DISABLE) [N/y/?] n
 +
  NSA SELinux Development Support (SECURITY_SELINUX_DEVELOP) [Y/n/?] y
 +
  NSA SELinux AVC Statistics (SECURITY_SELINUX_AVC_STATS) [Y/n/?] y
 +
  NSA SELinux checkreqprot default value (SECURITY_SELINUX_CHECKREQPROT_VALUE) [1] 1
 +
  NSA SELinux maximum supported policy format version (SECURITY_SELINUX_POLICYDB_VERSION_MAX) [Y/n/?] y
 +
    NSA SELinux maximum supported policy format version value (SECURITY_SELINUX_POLICYDB_VERSION_MAX_VALUE) [19] 19
 +
TOMOYO Linux Support (SECURITY_TOMOYO) [Y/n/?] y
 +
  Default maximal count for learning mode (SECURITY_TOMOYO_MAX_ACCEPT_ENTRY) [2048] 2048
 +
  Default maximal count for audit log (SECURITY_TOMOYO_MAX_AUDIT_LOG) [1024] 1024
 +
  Activate without calling userspace policy loader. (SECURITY_TOMOYO_OMIT_USERSPACE_LOADER) [Y/n/?] y
 +
AppArmor support (SECURITY_APPARMOR) [Y/n/?] y
 +
  AppArmor boot parameter default value (SECURITY_APPARMOR_BOOTPARAM_VALUE) [1] 1
 +
Integrity Measurement Architecture(IMA) (IMA) [Y/n/?] y
 +
EVM support (EVM) [N/y/?] (NEW)
 +
Default security module
 +
  1. SELinux (DEFAULT_SECURITY_SELINUX)
 +
  2. TOMOYO (DEFAULT_SECURITY_TOMOYO)
 +
  3. AppArmor (DEFAULT_SECURITY_APPARMOR)
 +
> 4. Unix Discretionary Access Controls (DEFAULT_SECURITY_DAC)
 +
choice[1-4?]: 4
 +
warning: (ACPI_HOTPLUG_CPU) selects ACPI_CONTAINER which has unmet direct dependencies (ACPI && EXPERIMENTAL)
 +
warning: (MEDIA_TUNER) selects MEDIA_TUNER_TEA5761 which has unmet direct dependencies (MEDIA_SUPPORT && VIDEO_MEDIA && I2C && EXPERIMENTAL)
 +
#
 +
# configuration written to .config
 +
#
 +
warning: (GFS2_FS) selects DLM which has unmet direct dependencies (EXPERIMENTAL && INET && SYSFS && CONFIGFS_FS && (IPV6 || IPV6=n))
 +
warning: (IMA) selects TCG_TPM which has unmet direct dependencies (HAS_IOMEM && EXPERIMENTAL)
 +
warning: (MEDIA_TUNER) selects MEDIA_TUNER_TEA5761 which has unmet direct dependencies (MEDIA_SUPPORT && VIDEO_MEDIA && I2C && EXPERIMENTAL)
 +
warning: (ACPI_HOTPLUG_CPU) selects ACPI_CONTAINER which has unmet direct dependencies (ACPI && EXPERIMENTAL)
 +
root@[~src/linux] #
 +
 
 
</pre>
 
</pre>
  
Make sure you add VFAT support to your kernel if you are building it manually.
+
Now comes the most adventurous part!
  
== Boot Loader ==
+
= Building the Kernel =
 +
<console>
 +
##i### make -j8  bzImage
 +
##i### make -j8 modules
 +
##i### make modules_install
 +
##i### make install
 +
</console>
 +
 
 +
 
 +
'''Building an initramfs or not?'''
 +
 
 +
The reason to build a kernel with an initramfs is mostly for interoperability (e.g. live-cd's) and special features like an included busybox, ssh, etc.  But mostly, and that's why we are doing this here now, to have a proper kernel up and running quick'n dirty in a reasonable time without fighting hours and days until a more or less exotic hardware is perfectly run by the kernel.
 +
After having a proper basic kernel running with the help of an initramfs, I really recommend you to go a step further and build a true kernel with all features includes without an initramfs. But this could be pain in the ass and very time consuming - so we do it the funtoo way here - at least in the second example when we stick to better-initramfs instead of Red-Hat's ''dracut''.
 +
 
 +
= Option one: Initrd with dracut =
 +
 
 +
To build the initrd we just execute
 +
 
 +
<console>
 +
# ##i##dracut -f --fstab --xz /boot/initramfs-3.2.6-pf.img  3.2.6-pf
 +
</console>
  
=== Emerging GRUB ===
+
Generally, this really should be enough!
 +
If you experience booting problems like missing modules / drivers then just boot from the genkernel section and fix the initrd building. You can look into the man page to tweak the command a bit (e.g. --add-drivers "xz dm_crypt" etc...).
  
You will still use GRUB as a boot loader, but before emerging grub, you will need to enable EFI booting. To do this,
+
Ok let's go on and finish the taks, we are going to tell now grub how to boot off correctly!
add the following line to <tt>/etc/portage/make.conf</tt>:
+
  
 
<pre>
 
<pre>
GRUB_PLATFORMS="efi-64"
+
root@[~src/linux] # nano /etc/boot.conf
 +
 
 +
boot {
 +
        generate grub
 +
        default "Funtoo Linux dracut"
 +
        timeout 3
 +
}
 +
 
 +
"Funtoo Linux genkernel" {
 +
        kernel kernel-genkernel[-v]
 +
        initrd initramfs-genkernel[-v]
 +
        params = quiet rootfstype=ext4
 +
        params += luks enc_root=/dev/sda3
 +
        params += lvm root=/dev/mapper/vg-root
 +
}
 +
 
 +
"Funtoo Linux dracut" {
 +
        kernel vmlinuz[-v]
 +
## this is the better-initramfs generated initrd
 +
        initrd initramfs[-v].img
 +
        params  = quiet rootfstype=ext4
 +
        params += luks enc_root=/dev/sda3
 +
        params += lvm root=/dev/mapper/vg-root
 +
}
 +
 
 
</pre>
 
</pre>
  
Then, <tt>emerge grub</tt>. You will notice <tt>efibootmgr</tt> getting pulled in as a dependency. This is expected and good.
+
That's it almost!
  
=== Installing GRUB ===
+
Now write to the grub.cfg with the new handy boot-update script from funtoo:
 +
<console>
 +
root@[~src/linux] # boot-update -v
 +
</console>
 +
<pre>
 +
root@[~src/linux] # sudo boot-update -v
  
Now, for the magic of getting everything in place for booting. You should copy your kernel and initramfs (if you have one -- you will if you are following the default install) to <tt>/boot</tt>. GRUB will boot those. But how do we get UEFI to boot GRUB? Well, we need to run the following command:
+
boot-update 1.5.2 / Copyright 2009-2011 Funtoo Technologies
 +
 
 +
[use option "-l" for license info, "-h" for help]
 +
 
 +
* Generating config for grub...
 +
 
 +
DEFAULT > Funtoo Linux - vmlinuz-3.2.6-pf
 +
          Funtoo Linux genkernel - kernel-genkernel-x86_64-3.2.6-pf
 +
 
 +
* Completed successfully.
 +
</pre>
 +
 
 +
Okay,... here you go..! :)
 +
 
 +
Reboot and see how it works!
 +
 
 +
= Option two: using better-initramfs =
 +
 
 +
Piotr's better-initramfs is another approach that is tiny, nice and shiny and seems to become more and more a favourite among funtoo'ers. The biggest plus is that, once built it is kernel version independant.
 +
 
 +
For using this you just do the following steps:
 +
<pre>
 +
1. download sources
 +
2. build kernel with "make bzImage"
 +
3. download better-initramfs
 +
4. run better-initramfs
 +
5. adjust /etc/boot.conf
 +
</pre>
 +
 
 +
Here is how in detail:
 +
 
 +
Assuming you did install already a genkernel backup or at least you have a working bzImage + modules installed, we rush forward to step 3:
 +
 
 +
=== download better-initramfs ===
  
 
<console>
 
<console>
# ##i##grub-install --target=x86_64-efi --efi-directory=/boot /dev/sda
+
# cd /usr/src/;
 +
# git clone https://github.com/slashbeast/better-initramfs.git
 +
 
 +
# /src # cd better-initramfs
 +
# better-initramfs git:(master) ls
 +
AUTHORS    LICENSE  README.rst  bootstrap  output  sourceroot
 +
ChangeLog  Makefile  TODO        examples  scripts
 
</console>
 
</console>
This command will simply install all the stuff to <tt>/boot/EFI</tt> and <tt>/boot/grub</tt> that your system needs to boot. In particular, the <tt>/boot/EFI/grub/grubx64.efi</tt> file will be created. This is the GRUB boot image that UEFI will load and start.
 
=== Configuring GRUB ===
 
  
OK, now UEFI has the GRUB image it needs to boot. But we still need to configure GRUB itself so it finds and boots your kernel and initramfs. This is done by performing the following steps. Since boot-update doesn't yet support UEFI, we will not use boot-update directly and will create a <tt>/boot/grub/grub.cfg</tt> file manually that looks like this:
+
=== build the better-initramfs ===
 +
<console>
 +
➜ # better-initramfs git:(master) sudo bootstrap/bootstrap-all
 +
Passwort: xxx
 +
# from here go and grab a coffee
 +
➜ # sudo make prepare
 +
➜ # sudo make image
 +
➜ # sudo mv output/initramfs.cpio.gz /boot
 +
</console>
 +
 
 +
=== adjust grub ===
 +
 
 +
Taking the above setup we edit the /etc/boot.conf
 +
as I installed genkernel first, and dracut after - you see this setup:
  
 
<pre>
 
<pre>
set timeout=3
+
boot {
set gfxmode=auto
+
        generate grub
insmod efi_gop
+
        default "Funtoo Linux"
insmod efi_uga
+
        timeout 3
 +
}
 +
 
 +
# Rootfs over lvm over luks
 +
# /dev/sda3 - encrypted lvm's pv
 +
# /dev/mapper/vg-root - rootfs's lv
  
menuentry "Funtoo Linux genkernel - kernel-debian-sources-x86_64-3.2.35-2" { 
+
"Funtoo Linux" {
    insmod part_gpt
+
        kernel bzImage[-v]
    insmod fat  
+
## this is the better-initramfs generated initrd
    set root=(hostdisk//dev/sda,gpt1) 
+
        initrd initramfs.cpio.gz
    search --no-floppy --fs-uuid --set __REPLACE_UUID_OF_SDA1__
+
        params = quiet rootfstype=ext4
    linux /kernel-debian-sources-x86_64-3.2.35-2 real_root=/dev/sda3
+
        params += luks enc_root=/dev/sda3
    initrd /initramfs-debian-sources-x86_64-3.2.35-
+
        params += lvm root=/dev/mapper/vg-root
    set gfxpayload=keep
+
}
 +
 
 +
"Funtoo Linux dracut" {
 +
        kernel vmlinuz[-v]
 +
## this is the dracut generated initrd
 +
        initrd initramfs[-v].img
 +
        params  = quiet rootfstype=ext4
 +
        params += luks enc_root=/dev/sda3
 +
        params += lvm root=/dev/mapper/vg-root
 +
}
 +
 
 +
 
 +
"Funtoo Linux genkernel" {
 +
        kernel kernel-genkernel[-v]
 +
        initrd initramfs-genkernel[-v]
 +
        params = quiet rootfstype=ext4
 +
        params += luks enc_root=/dev/sda3
 +
        params += lvm root=/dev/mapper/vg-root
 
}
 
}
set default=0
 
 
</pre>
 
</pre>
 +
Okay,... here you go..! :)
  
Note the <tt>search</tt> line where it says '''<tt>__REPLACE_UUID_OF_SDA1__</tt>''' above. You will need to run '''<tt>blkid /dev/sda1</tt>''' and use the UUID value that is displayed. For example, on my system, I need to use '''<tt>C34B-19CF</tt>'''. You can also change the <tt>menuentry</tt> line text in quotes to say whatever you want, and the <tt>linux</tt> and <tt>initrd</tt> lines should reference your kernel versions in <tt>/boot</tt>. As above, use the path <tt>/</tt> instead of <tt>/boot</tt> as the path should be relative to the root of the VFAT filesystem.
+
update the grub.cfg, then reboot and see how it works!
  
== Known Issues ==
+
<console>
With pure UEFI boot mode, with legacy mode disabled, following error expected:
+
root@[~src/linux-3.2.6-pf] # boot-update -v   
* video driver not supported, boot hangs, hard reboot required.
+
 
Choose UEFI first, next legacy driver. It depends on motherboard vendor and efi bios version.
+
boot-update 1.5.2 / Copyright 2009-2011 Funtoo Technologies
In UEFI bios choose grub option, if your succeeded with above guide, additional menu should appear in Boot Menu, otherwise it boots into EFI shell:
+
 
* grub:NAME of you hard drive
+
[use option "-l" for license info, "-h" for help]
 +
 
 +
* Generating config for grub...
 +
 
 +
DEFAULT > Funtoo Linux better-initramfs - vmlinuz-3.2.6-pf
 +
          Funtoo Linux dracut - vmlinuz-3.2.6-pf
 +
          Funtoo Linux genkernel - kernel-genkernel-x86_64-3.2.6-ck
 +
 
 +
* Completed successfully.
 +
 
 +
root@[~src/linux-3.2.6-pf] #
 +
 
 +
root@[~src/linux-3.2.6-pf] # reboot
 +
 
 +
System going down for reboot!
 +
 
 +
</console>
  
=== Done! ===
 
  
Remember to follow all other steps in the regular Funtoo Install Guide. Assuming you did everything correctly, your system should now boot via UEFI! We will be adding UEFI support to boot-update soon to make this process easier.
+
[[Category:HOWTO]]
 +
[[Category:Featured]]
 +
[[Category:Kernel]]

Revision as of 15:14, 9 January 2014

Setting up a proper kernel yourself - lean, mean and tailored to your hardware, is the challenge by which a linux user can graduate to becoming a Funtoo knight ;-)

Even though many of us are using enterprise-ready kernels in datacenters, there is almost nobody who hasn't at least considered building a kernel for his laptop / PC. We are showing here how an intermediate Linux user can use an alternative to the standard beginners "genkernel" approach, to compile a custom kernel, in a relatively still speedy and easy set up.

Contents

Minimum Requirements

You should understand the way how things work in a terminal and how to use an editor and tweak config files. This is crucial. You don't need much knowledge about the linux kernel and it's internals. Nevertheless, you have to know at least where the files are located, how they are used and what is the file logic behind the overall structure. Otherwise you should consider using a non source based linux distribution. If you are scared now, don't worry - we are going to build a kernel the Funtoo way and you will pick up everthing necessary to accomplish this challenge, step by step, so the next time you do it yourself and become a real Funtoo knight!

Assumptions

You start from an installed Funtoo system on the disk, or at least, you are on stage3 in a chrooted environment from a live cd, following somehow the Funto Installation Tutorial.

In this case we are building a kernel that is booting root in LVM over encrypted LUKS container. If you don't have this setup, don't worry, you just don't need all the modules, but everything else is similar.


Getting everything in order to start

First there is the decision which linux kernel sources we need. There are plenty of them in the repositories around, often it is not easy to distinguish between them.

I would always trust my distribution of choice and take what is has to offer - and funtoo has a lot to offer!

I really do recommend (especially if it is your first time) to build a debian-sourced genkernel like described in chapter 5 "Using Debian-Sources with Genkernel" in the Funtoo Kernels Tutorial.

From there you should have a running system booting nicely from your own build (just little bit bloated) kernel. This is more than you can expect from any other ready to go distribution.

Attention We are using RedHat's dracut in order to build a nice initramfs (containing all the necessary tools and extra drivers our kernel might need to start the system).

Although dracut is the way to go, more sophisticated and not as buggy as gentoo's genkernel approach, more and more funtoo geeks start using slashbeast's better-initramfs, which we will cover at the end of this howto!

So after having set up a genkernel from debian or gentoo sources we are going to build a kernel with either (or both) dracut or/and better-initramfs. So gentoo sources with genkernel is always my backup if anything is not working correctly on my system. For the slightly more geeky approach with my own initram I am using pf-sources, ck-sources or any other more or less heavily patched sources.

Let's go!

Kernel Sources

We are going to use the kernel sources from the funtoo git repository.

The source you use on your system is up to you and your needs. For a laptop or desktop system, we recommend the following:

  • sys-kernel/pf-sources
  • sys-kernel/ck-sources
  • sys-kernel/gentoo-sources
  • sys-kernel/git-sources
  • sys-kernel/sysrescue-std-sources
  • sys-kernel/debian-sources

Please, have a look in the ebuild description, look onto their homepage and take the one that suits you best! If you are unsure for now, use sys-kernel/gentoo-sources. That's always a safe bet for a general system.

It is not a problem to have various kernels installed parallel, so go on with any one of them.

I am going to use the sys-kernel/pf-sources now, as I already had the gentoo-sources installed.

Prerequisites

I don't know which tools you have already installed, so some information here might be redundant. It doesn't harm to just copy and paste and do some steps again.

First, we look into our /etc/make.conf:

# nano /etc/make.conf
#These compiler flags are just tweaking (optimazation) and NOT necessary:
CFLAGS="-O2 -pipe -march=native -ftracer -fforce-addr"
CXXFLAGS="${CFLAGS} -fpermissive -fomit-frame-pointer"
KDIR=/usr/src/linux
KERNEL="symlink build"
USE="$KERNEL ....here are your use flags...."
## These modules are available:
## DRACUT_MODULES="dracut_modules_biosdevname dracut_modules_btrfs dracut_modules_caps dracut_modules_crypt dracut_modules_crypt-gpg dracut_modules_dmraid dracut_modules_dmsquash-live dracut_modules_gensplash dracut_modules_iscsi dracut_modules_livenet dracut_modules_lvm dracut_modules_mdraid dracut_modules_multipath dracut_modules_nbd dracut_modules_nfs dracut_modules_plymouth dracut_modules_ssh-client dracut_modules_syslog"
## We will use these modules for LVM / LUKS:
DRACUT_MODULES="crypt lvm plymouth biosdevname dmraid crypt-gpg dmsquash-live ssh-client syslog"

Next, we set the package keywords:

/etc/portage/package.use/dracut:
sys-kernel/dracut dm net device-mapper crypt lvm

Note Note: If you don't have lvm over encrypted LUKS you probably just add the "net" keyword here, or "selinux".


After that we are going to build our packages:

# emerge -av app-portage/gentoolkit sys-kernel/pf-sources sys-kernel/dracut sys-boot/plymouth sys-boot/plymouth-openrc-plugin

Finished? Well, then let's go on and

Preparing the kernel

We go now to the sources directory and enter the following commands to update the kernel's .config file:

# cd /usr/src/linux/
# make clean
  CLEAN   .
  CLEAN   arch/x86/kernel/acpi/realmode
  CLEAN   arch/x86/kernel/cpu
  CLEAN   arch/x86/kernel
  CLEAN   arch/x86/vdso
  CLEAN   arch/x86/lib
  CLEAN   drivers/gpu/drm/radeon
  CLEAN   drivers/net/wan
  CLEAN   drivers/scsi/aic7xxx
  CLEAN   drivers/tty/vt
  CLEAN   drivers/video/logo
  CLEAN   firmware
  CLEAN   kernel
  CLEAN   lib/raid6
  CLEAN   lib
  CLEAN   security/apparmor
  CLEAN   security/selinux
  CLEAN   usr
  CLEAN   arch/x86/boot/compressed
  CLEAN   arch/x86/boot
  CLEAN   .tmp_versions
  CLEAN   vmlinux System.map .tmp_kallsyms2.S .tmp_kallsyms1.o .tmp_kallsyms2.o .tmp_kallsyms1.S .tmp_vmlinux1 .tmp_vmlinux2 .tmp_System.map
# zcat /proc/config.gz > /usr/src/linux/.config
# make localmodconfig

You will get some questions which you can answer mostly with either M (compiled as a module) or Y (compiled directly into the kernel).

Enable different security models (SECURITY) [Y/n/?] y
Enable the securityfs filesystem (SECURITYFS) [Y/?] y
Socket and Networking Security Hooks (SECURITY_NETWORK) [Y/?] y
Security hooks for pathname based access control (SECURITY_PATH) [Y/?] y
Low address space for LSM to protect from user allocation (LSM_MMAP_MIN_ADDR) [65536] 65536
NSA SELinux Support (SECURITY_SELINUX) [Y/n/?] y
  NSA SELinux boot parameter (SECURITY_SELINUX_BOOTPARAM) [N/y/?] n
  NSA SELinux runtime disable (SECURITY_SELINUX_DISABLE) [N/y/?] n
  NSA SELinux Development Support (SECURITY_SELINUX_DEVELOP) [Y/n/?] y
  NSA SELinux AVC Statistics (SECURITY_SELINUX_AVC_STATS) [Y/n/?] y
  NSA SELinux checkreqprot default value (SECURITY_SELINUX_CHECKREQPROT_VALUE) [1] 1
  NSA SELinux maximum supported policy format version (SECURITY_SELINUX_POLICYDB_VERSION_MAX) [Y/n/?] y
    NSA SELinux maximum supported policy format version value (SECURITY_SELINUX_POLICYDB_VERSION_MAX_VALUE) [19] 19
TOMOYO Linux Support (SECURITY_TOMOYO) [Y/n/?] y
  Default maximal count for learning mode (SECURITY_TOMOYO_MAX_ACCEPT_ENTRY) [2048] 2048
  Default maximal count for audit log (SECURITY_TOMOYO_MAX_AUDIT_LOG) [1024] 1024
  Activate without calling userspace policy loader. (SECURITY_TOMOYO_OMIT_USERSPACE_LOADER) [Y/n/?] y
AppArmor support (SECURITY_APPARMOR) [Y/n/?] y
  AppArmor boot parameter default value (SECURITY_APPARMOR_BOOTPARAM_VALUE) [1] 1
Integrity Measurement Architecture(IMA) (IMA) [Y/n/?] y
EVM support (EVM) [N/y/?] (NEW)
Default security module
  1. SELinux (DEFAULT_SECURITY_SELINUX)
  2. TOMOYO (DEFAULT_SECURITY_TOMOYO)
  3. AppArmor (DEFAULT_SECURITY_APPARMOR)
> 4. Unix Discretionary Access Controls (DEFAULT_SECURITY_DAC)
choice[1-4?]: 4
warning: (ACPI_HOTPLUG_CPU) selects ACPI_CONTAINER which has unmet direct dependencies (ACPI && EXPERIMENTAL)
warning: (MEDIA_TUNER) selects MEDIA_TUNER_TEA5761 which has unmet direct dependencies (MEDIA_SUPPORT && VIDEO_MEDIA && I2C && EXPERIMENTAL)
#
# configuration written to .config
#
warning: (GFS2_FS) selects DLM which has unmet direct dependencies (EXPERIMENTAL && INET && SYSFS && CONFIGFS_FS && (IPV6 || IPV6=n))
warning: (IMA) selects TCG_TPM which has unmet direct dependencies (HAS_IOMEM && EXPERIMENTAL)
warning: (MEDIA_TUNER) selects MEDIA_TUNER_TEA5761 which has unmet direct dependencies (MEDIA_SUPPORT && VIDEO_MEDIA && I2C && EXPERIMENTAL)
warning: (ACPI_HOTPLUG_CPU) selects ACPI_CONTAINER which has unmet direct dependencies (ACPI && EXPERIMENTAL)
root@[~src/linux] #

Now comes the most adventurous part!

Building the Kernel

# make -j8  bzImage
# make -j8 modules
# make modules_install
# make install


Building an initramfs or not?

The reason to build a kernel with an initramfs is mostly for interoperability (e.g. live-cd's) and special features like an included busybox, ssh, etc. But mostly, and that's why we are doing this here now, to have a proper kernel up and running quick'n dirty in a reasonable time without fighting hours and days until a more or less exotic hardware is perfectly run by the kernel. After having a proper basic kernel running with the help of an initramfs, I really recommend you to go a step further and build a true kernel with all features includes without an initramfs. But this could be pain in the ass and very time consuming - so we do it the funtoo way here - at least in the second example when we stick to better-initramfs instead of Red-Hat's dracut.

Option one: Initrd with dracut

To build the initrd we just execute

# dracut -f --fstab --xz /boot/initramfs-3.2.6-pf.img  3.2.6-pf

Generally, this really should be enough! If you experience booting problems like missing modules / drivers then just boot from the genkernel section and fix the initrd building. You can look into the man page to tweak the command a bit (e.g. --add-drivers "xz dm_crypt" etc...).

Ok let's go on and finish the taks, we are going to tell now grub how to boot off correctly!

root@[~src/linux] # nano /etc/boot.conf

boot {
        generate grub
        default "Funtoo Linux dracut"
        timeout 3
}

"Funtoo Linux genkernel" {
        kernel kernel-genkernel[-v]
        initrd initramfs-genkernel[-v]
        params = quiet rootfstype=ext4
        params += luks enc_root=/dev/sda3
        params += lvm root=/dev/mapper/vg-root
}

"Funtoo Linux dracut" {
        kernel vmlinuz[-v]
## this is the better-initramfs generated initrd
        initrd initramfs[-v].img
        params  = quiet rootfstype=ext4
        params += luks enc_root=/dev/sda3
        params += lvm root=/dev/mapper/vg-root
}

That's it almost!

Now write to the grub.cfg with the new handy boot-update script from funtoo:

root@[~src/linux] # boot-update -v
root@[~src/linux] # sudo boot-update -v

 boot-update 1.5.2 / Copyright 2009-2011 Funtoo Technologies

 [use option "-l" for license info, "-h" for help]

 * Generating config for grub...

 DEFAULT > Funtoo Linux - vmlinuz-3.2.6-pf
           Funtoo Linux genkernel - kernel-genkernel-x86_64-3.2.6-pf

 * Completed successfully.

Okay,... here you go..! :)

Reboot and see how it works!

Option two: using better-initramfs

Piotr's better-initramfs is another approach that is tiny, nice and shiny and seems to become more and more a favourite among funtoo'ers. The biggest plus is that, once built it is kernel version independant.

For using this you just do the following steps:

1. download sources
2. build kernel with "make bzImage"
3. download better-initramfs
4. run better-initramfs
5. adjust /etc/boot.conf

Here is how in detail:

Assuming you did install already a genkernel backup or at least you have a working bzImage + modules installed, we rush forward to step 3:

download better-initramfs

➜ # cd /usr/src/;
➜ # git clone https://github.com/slashbeast/better-initramfs.git

➜ # /src #  cd better-initramfs
➜ # better-initramfs git:(master) ls
AUTHORS    LICENSE   README.rst  bootstrap  output   sourceroot
ChangeLog  Makefile  TODO        examples   scripts

build the better-initramfs

➜ # better-initramfs git:(master) sudo bootstrap/bootstrap-all
Passwort: xxx 
# from here go and grab a coffee
➜ # sudo make prepare
➜ # sudo make image
➜ # sudo mv output/initramfs.cpio.gz /boot

adjust grub

Taking the above setup we edit the /etc/boot.conf as I installed genkernel first, and dracut after - you see this setup:

boot {
        generate grub
        default "Funtoo Linux"
        timeout 3
}

# Rootfs over lvm over luks
# /dev/sda3 - encrypted lvm's pv
# /dev/mapper/vg-root - rootfs's lv

"Funtoo Linux" {
        kernel bzImage[-v]
## this is the better-initramfs generated initrd
        initrd initramfs.cpio.gz
        params  = quiet rootfstype=ext4
        params += luks enc_root=/dev/sda3
        params += lvm root=/dev/mapper/vg-root
}

"Funtoo Linux dracut" {
        kernel vmlinuz[-v]
## this is the dracut generated initrd
        initrd initramfs[-v].img
        params  = quiet rootfstype=ext4
        params += luks enc_root=/dev/sda3
        params += lvm root=/dev/mapper/vg-root
}


"Funtoo Linux genkernel" {
        kernel kernel-genkernel[-v]
        initrd initramfs-genkernel[-v]
        params = quiet rootfstype=ext4
        params += luks enc_root=/dev/sda3
        params += lvm root=/dev/mapper/vg-root
}

Okay,... here you go..! :)

update the grub.cfg, then reboot and see how it works!

root@[~src/linux-3.2.6-pf] # boot-update -v     

 boot-update 1.5.2 / Copyright 2009-2011 Funtoo Technologies

 [use option "-l" for license info, "-h" for help]

 * Generating config for grub...

 DEFAULT > Funtoo Linux better-initramfs - vmlinuz-3.2.6-pf
           Funtoo Linux dracut - vmlinuz-3.2.6-pf
           Funtoo Linux genkernel - kernel-genkernel-x86_64-3.2.6-ck

 * Completed successfully.

root@[~src/linux-3.2.6-pf] #

root@[~src/linux-3.2.6-pf] # reboot

System going down for reboot!