Difference between pages "Emerge" and "Building a Kernel from Source"

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== Getting started with emerge ==
+
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 ;-)
Emerge is the front-end for funtoo's portage package manager. With emerge it is easy to install, update or remove packages.
+
 
 +
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 speedy and easy set up.
 +
 
 +
== Minimum Requirements ==
 +
* '''Understand the command line'''
 +
* '''Know where the kernel files are located'''
 +
 
 +
== 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]].
 +
 
 +
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_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.
 +
 
 +
{{Note}} 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>:
  
=== Update package database ===
 
'''Sync local package database. This will update your local Portage tree with the latest Funtoo ebuilds.'''
 
 
<console>
 
<console>
###i## emerge --sync
+
###i## 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"
 
</console>
 
</console>
  
=== Search packages ===
+
Next, we set the package keywords:
'''Search packages by name.'''
+
 
<console>
 
<console>
###i## emerge -s firefox
+
###i## nano /etc/portage/package.use/dracut
###i## emerge --search firefox
+
sys-kernel/dracut dm net device-mapper crypt lvm
 
</console>
 
</console>
  
'''Search packages by description.'''
+
{{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## emerge -S web browser
+
###i## emerge -av app-portage/gentoolkit sys-kernel/pf-sources sys-kernel/dracut sys-boot/plymouth sys-boot/plymouth-openrc-plugin
###i## emerge --searchdesc web browser
+
 
</console>
 
</console>
  
=== Install packages ===
+
Finished? Well, then let's go on and
'''Install package.'''
+
 
 +
== Preparing the kernel ==
 +
 
 +
We go now to the sources directory and enter the following commands to update the kernel'.config  file:
 
<console>
 
<console>
###i## emerge firefox
+
###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>
  
'''Install multiple packages.'''
 
 
<console>
 
<console>
###i## emerge firefox thunderbird
+
###i## make localmodconfig
 
</console>
 
</console>
  
'''Install package. Ask for confirmation before performing any changes. Show verbose output.'''
+
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>
 +
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>
 +
 
 +
Now comes the most adventurous part!
 +
 
 +
= Building the Kernel =
 
<console>
 
<console>
###i## emerge -av firefox
+
###i## make -j8  bzImage
###i## emerge --ask firefox
+
###i## make -j8 modules
 +
###i## make modules_install
 +
###i## make install
 
</console>
 
</console>
  
=== Remove packages ===
+
 
'''Remove package.'''
+
'''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>
 
<console>
###i## emerge -C firefox
+
# ##i##dracut -f --fstab --xz /boot/initramfs-3.2.6-pf.img  3.2.6-pf
###i## emerge --unmerge firefox
+
 
</console>
 
</console>
  
'''Remove package. Ask for confirmation before performing any changes.'''
+
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!
 +
 
 
<console>
 
<console>
###i## emerge -aC firefox
+
###i## 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
 +
}
 
</console>
 
</console>
  
'''Remove orphaned packages. Ask for confirmation before performing any changes.'''
+
That's it almost!
 +
 
 +
Now write to the <code>grub.cfg</code> with the new handy boot-update script from funtoo:
 
<console>
 
<console>
###i## emerge -a --depclean
+
###i## 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.
 
</console>
 
</console>
  
=== Update packages ===
+
Okay,... here you go..! :)
'''Update all packages.'''
+
 
 +
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:
 +
 
 +
=== Downloading Better-initramfs ===
 +
 
 
<console>
 
<console>
###i## emerge -uDN @world
+
###i## cd /usr/src/;
 +
###i## git clone https://github.com/slashbeast/better-initramfs.git
 +
###i## /src #  cd better-initramfs
 +
###i## better-initramfs git:(master) ls
 +
AUTHORS    LICENSE  README.rst  bootstrap  output  sourceroot
 +
ChangeLog  Makefile  TODO        examples  scripts
 
</console>
 
</console>
  
'''Update all packages. Ask for confirmation before performing any changes. Show verbose output.'''
+
=== Build Better-Initramfs ===
 
<console>
 
<console>
###i## emerge -uavDN @world
+
###i## better-initramfs git:(master) sudo bootstrap/bootstrap-all
 +
###i## sudo make prepare
 +
###i## sudo make image
 +
###i## sudo mv output/initramfs.cpio.gz /boot
 
</console>
 
</console>
  
== Emerge options ==
+
=== adjust grub ===
  
; --sync
+
Taking the above setup we edit the /etc/boot.conf
: Updates the portage tree that is located in /usr/portage by default.
+
as I installed genkernel first, and dracut after - you see this setup:
  
; --search -s
+
<pre>
: Searches  for  matches  of  the  supplied  string in the portage tree.
+
boot {
 +
        generate grub
 +
        default "Funtoo Linux"
 +
        timeout 3
 +
}
  
; --searchdesc -S
+
# Rootfs over lvm over luks
: Matches the search string against the description field as well as the package name.
+
# /dev/sda3 - encrypted lvm's pv
 +
# /dev/mapper/vg-root - rootfs's lv
  
; --ask -a
+
"Funtoo Linux" {
: Ask for confirmation before performing any changes.
+
        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
 +
}
  
; --pretend -p
+
"Funtoo Linux dracut" {
: Instead of actually performing the merge, simply display what *would* have been installed if --pretend weren't used.
+
        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
 +
}
  
; --unmerge -C
 
: Removes all matching packages.
 
  
; --update -u
+
"Funtoo Linux genkernel" {
: Updates  packages to the best version available, which may not always be the  highest version number due to masking for testing and development.
+
        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
 +
}
 +
</pre>
 +
Okay,... here you go..! :)
  
; --deep [DEPTH] -D
+
update the grub.cfg, then reboot and see how it works!
: force  emerge  to  consider  the entire  dependency tree of packages, instead of checking only the immediate dependencies of the packages.
+
  
; --newuse -N
+
<console>
: Tells emerge to include installed packages where USE flags have changed since compilation.
+
root@[~src/linux-3.2.6-pf] # boot-update -v   
  
; --depclean -c
+
boot-update 1.5.2 / Copyright 2009-2011 Funtoo Technologies
: Remove orphaned packages. Cleans the system by removing packages that are not associated with explicitly merged packages.
+
  
; --autounmask-write
+
[use option "-l" for license info, "-h" for help]
: Automatically write package.use settings as necessary to satisfy dependencies.
+
  
; --resume -r
+
  * Generating config for grub...
: Resumes the  most recent merge list that has been aborted due to an error.
+
  
; --jobs[=JOBS] -j [JOBS]
+
DEFAULT > Funtoo Linux better-initramfs - vmlinuz-3.2.6-pf
: Specifies the number of packages to build simultaneously.
+
          Funtoo Linux dracut - vmlinuz-3.2.6-pf
 +
          Funtoo Linux genkernel - kernel-genkernel-x86_64-3.2.6-ck
  
; --load-average [LOAD]
+
  * Completed successfully.
: Specifies that  no  new  builds should be started if there are other builds running and the load average is at least LOAD (a floating-point number).
+
  
== Configuration ==
+
root@[~src/linux-3.2.6-pf] #
=== make.conf ===
+
Emerge can be configured with <code>/etc/portage/make.conf</code>
+
<console>
+
###i## nano /etc/portage/make.conf
+
CFLAGS="-march=native -O2 -pipe"
+
CXXFLAGS="-march=native -O2 -pipe"
+
  
MAKEOPTS="-j2"
+
root@[~src/linux-3.2.6-pf] # reboot
EMERGE_DEFAULT_OPTS="--jobs 2 --load-average 2"
+
INPUT_DEVICES="evdev synaptics"
+
VIDEO_CARDS="intel i965"
+
LINGUAS="en en_US en_GB"
+
ACCEPT_LICENSE="*"
+
  
USE="mmx mmxext sse sse2 sse3 ssse3 threads alsa X gtk xcb dri opengl vaapi udev \
+
System going down for reboot!
    svg x264 xvid gstreamer webm vpx icu bash-completion vim-pager \
+
    -gnome -xscreensaver -cups -fortran -deprecated -iptables -ipv6 -geoloc \
+
    -mta -sendmail -kmod -tiff -live -quicktime -real -gpm -themes"
+
</console>
+
  
=== package.use ===
 
Per-package use flags can be configured with <code>/etc/portage/package.use</code>
 
<console>
 
###i## nano /etc/portage/package.use
 
x11-wm/dwm savedconfig
 
media-sound/ncmpcpp visualizer clock taglib
 
 
</console>
 
</console>
  
=== package.accept_keywords ===
 
If you want to install package that has not been tested on your architecture you need to edit <code>/etc/portage/package.accept_keywords</code>
 
<console>
 
###i## nano /etc/portage/package.accept_keywords
 
=app-misc/screenfetch-9999 **
 
</console>
 
 
== Further info ==
 
For further info see emerge man page.
 
<console>$##i## man emerge</console>
 
 
[[Category:Portage]]
 
  
 
[[Category:HOWTO]]
 
[[Category:HOWTO]]
[[Category:Tutorial]]
+
[[Category:Featured]]
[[Category:System]]
+
[[Category:Kernel]]

Revision as of 01:56, 11 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 speedy and easy set up.

Contents

Minimum Requirements

  • Understand the command line
  • Know where the kernel files are located

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.

Note Note: 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:

# nano /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!

# 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:

# 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:

Downloading 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 Better-Initramfs

# better-initramfs git:(master) sudo bootstrap/bootstrap-all
# 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!