Table of contents
Minimal image
Below is minimal Buster image for RPI4. Download it, uncompress and write it to SDcard. Image is for 8GiB card. If your card is bigger than that, you can use fdisk /dev/mmcblk0 to remove the second partition and recreate it same start sector but highest possible end sector and after boot resize2fs /dev/mmcblk0p2 to expand the filesystem. In case your card is smaller, bad luck.
Debian Buster (aarch64) 2020-02-29.img.gz
The image contains very stripped and cleaned down Buster image with sane minimal set of packages. It also runs sleek, very trimmed down kernel with only minimal set of features. Features are built in to core image, not as modules. The only module is brcmfmac (ie. Pi's wifi). It didn't work as builtin.
Generally image is suitable for server use. If you need graphical UI, probably there exists better options. Personally I like to strip down everything possible to minimal to save every clock cycle I have. If you feel same, this image is for you.
Features included are basically :
- Image is 64bit (aarch64) with 64-bit userland. (Not 32bit, like in Raspbian)
- Basic framebuffer console and support for usb-keyboard.
- Login is root with password pass
- Wireless works once you adapt /etc/network/interfaces to you needs
- There's openssh running, so it's possible to ssh in without attaching keyboard and monitor since eth0 boots with static address 192.168.11.2/24
- Once you have root-logged in, create your personal user account and add it to adm group. Once you are in that group, sudo works.
Kernel building
Generally, please follow process and instructions for RPI3. Below are short instructions more or less specific to RPI4.
Instructions below are for image above. Process for other images are probably the same, but image's name used for booting is probably different. For example Raspbian uses name kernel8.img. Name used here is kernel8-p4.img and defined in /boot/config.txt.
In case you are using ready prepared image downloaded above, it already contains sources. Of course sources are probable old, but I'd suggest to first experiment with these without pulling newer version from repository. If you pull newer version, upstream sources might have changed and example config below does not fit perfect any more. When you have succeeded and booted with your own once, it's easier to begin experiment freely.
Steps
If you are using image other than above, first clone sources from official Raspberry Pi git. I haven't tested against stock kernel. Might work, might not.
But you are using the provided image, it already had sources and minimal config on places just waiting for make -j4. In this case skip directly to building. Of course you can git pull it to sync it to current.
rpi4:/usr/src$ git clone --depth=1 https://github.com/raspberrypi/linux rpi-linux Cloning into 'rpi-linux'... remote: Enumerating objects: 66210, done. remote: Counting objects: 100% (66210/66210), done. remote: Compressing objects: 100% (61674/61674), done. remote: Total 66210 (delta 5235), reused 16512 (delta 3610), pack-reused 0 Receiving objects: 100% (66210/66210), 177.89 MiB | 3.93 MiB/s, done. Resolving deltas: 100% (5235/5235), done. Checking out files: 100% (62367/62367), done.
Pick up minimal config from here and check it if you want to feel sure.
rpi4:/usr/src$ cd rpi-linux/ rpi4:/usr/src/rpi-linux$ wget -qO .config http://sub.nanona.fi/rpi4/minimal_kernel_config_4.19 rpi4:/usr/src/rpi-linux$ md5sum .config 07ad42cc380a1484811e4dc2695dcdbc .config rpi4:/usr/src/rpi-linux$ ls -l .config -rw-r--r-- 1 juhar juhar 67881 helmi 28 10:54 .config
Do menuconfig once, and exit from dialog.
rpi4:/usr/src/rpi-linux$ make menuconfig HOSTCC scripts/basic/fixdep UPD scripts/kconfig/.mconf-cfg HOSTCC scripts/kconfig/mconf.o YACC scripts/kconfig/zconf.tab.c LEX scripts/kconfig/zconf.lex.c HOSTCC scripts/kconfig/zconf.tab.o HOSTCC scripts/kconfig/lxdialog/checklist.o HOSTCC scripts/kconfig/lxdialog/inputbox.o HOSTCC scripts/kconfig/lxdialog/menubox.o HOSTCC scripts/kconfig/lxdialog/textbox.o HOSTCC scripts/kconfig/lxdialog/util.o HOSTCC scripts/kconfig/lxdialog/yesno.o HOSTLD scripts/kconfig/mconf scripts/kconfig/mconf Kconfig *** End of the configuration. *** Execute 'make' to start the build or try 'make help'.
Build it.
rpi4:/usr/src/rpi-linux$ make -j4 HOSTCC scripts/kconfig/conf.o HOSTLD scripts/kconfig/conf scripts/kconfig/conf --syncconfig Kconfig WRAP arch/arm64/include/generated/uapi/asm/errno.h WRAP arch/arm64/include/generated/uapi/asm/ioctl.h WRAP arch/arm64/include/generated/uapi/asm/ioctls.h WRAP arch/arm64/include/generated/uapi/asm/ipcbuf.h WRAP arch/arm64/include/generated/uapi/asm/kvm_para.h WRAP arch/arm64/include/generated/uapi/asm/mman.h WRAP arch/arm64/include/generated/uapi/asm/msgbuf.h WRAP arch/arm64/include/generated/uapi/asm/poll.h WRAP arch/arm64/include/generated/uapi/asm/resource.h WRAP arch/arm64/include/generated/uapi/asm/sembuf.h WRAP arch/arm64/include/generated/uapi/asm/shmbuf.h WRAP arch/arm64/include/generated/uapi/asm/socket.h UPD include/generated/uapi/linux/version.h WRAP arch/arm64/include/generated/uapi/asm/sockios.h WRAP arch/arm64/include/generated/uapi/asm/swab.h WRAP arch/arm64/include/generated/uapi/asm/termbits.h ... LD [M] net/netfilter/xt_nat.ko LD [M] net/netfilter/xt_pkttype.ko LD [M] net/netfilter/xt_quota.ko LD [M] net/netfilter/xt_state.ko LD [M] net/netfilter/xt_tcpmss.ko LD [M] net/netfilter/xt_tcpudp.ko rpi4:/usr/src/rpi-linux$
Install modules.
rpi4:/usr/src/rpi-linux$ sudo make modules_install INSTALL arch/arm64/crypto/aes-arm64.ko INSTALL arch/arm64/crypto/aes-neon-blk.ko INSTALL arch/arm64/crypto/aes-neon-bs.ko INSTALL crypto/cryptd.ko INSTALL crypto/crypto_simd.ko INSTALL drivers/block/nbd.ko INSTALL drivers/input/evdev.ko INSTALL drivers/input/ff-memless.ko INSTALL drivers/input/input-polldev.ko INSTALL drivers/input/matrix-keymap.ko INSTALL drivers/net/dummy.ko INSTALL drivers/net/wireless/broadcom/brcm80211/brcmfmac/brcmfmac.ko INSTALL drivers/net/wireless/broadcom/brcm80211/brcmutil/brcmutil.ko INSTALL fs/binfmt_misc.ko INSTALL fs/fuse/fuse.ko INSTALL net/ipv4/netfilter/ip_tables.ko INSTALL net/ipv4/netfilter/ipt_MASQUERADE.ko INSTALL net/ipv4/netfilter/ipt_REJECT.ko INSTALL net/ipv4/netfilter/iptable_filter.ko INSTALL net/ipv4/netfilter/iptable_nat.ko INSTALL net/ipv4/netfilter/nf_defrag_ipv4.ko INSTALL net/ipv4/netfilter/nf_log_ipv4.ko INSTALL net/ipv4/netfilter/nf_nat_ipv4.ko INSTALL net/ipv4/netfilter/nf_reject_ipv4.ko INSTALL net/ipv6/netfilter/ip6_tables.ko INSTALL net/ipv6/netfilter/ip6t_MASQUERADE.ko INSTALL net/ipv6/netfilter/ip6t_NPT.ko INSTALL net/ipv6/netfilter/ip6t_REJECT.ko INSTALL net/ipv6/netfilter/ip6table_filter.ko INSTALL net/ipv6/netfilter/ip6table_nat.ko INSTALL net/ipv6/netfilter/nf_defrag_ipv6.ko INSTALL net/ipv6/netfilter/nf_log_ipv6.ko INSTALL net/ipv6/netfilter/nf_nat_ipv6.ko INSTALL net/ipv6/netfilter/nf_reject_ipv6.ko INSTALL net/netfilter/nf_conntrack.ko INSTALL net/netfilter/nf_log_common.ko INSTALL net/netfilter/nf_nat.ko INSTALL net/netfilter/x_tables.ko INSTALL net/netfilter/xt_LOG.ko INSTALL net/netfilter/xt_addrtype.ko INSTALL net/netfilter/xt_comment.ko INSTALL net/netfilter/xt_hashlimit.ko INSTALL net/netfilter/xt_iprange.ko INSTALL net/netfilter/xt_length.ko INSTALL net/netfilter/xt_limit.ko INSTALL net/netfilter/xt_mac.ko INSTALL net/netfilter/xt_nat.ko INSTALL net/netfilter/xt_pkttype.ko INSTALL net/netfilter/xt_quota.ko INSTALL net/netfilter/xt_state.ko INSTALL net/netfilter/xt_tcpmss.ko INSTALL net/netfilter/xt_tcpudp.ko DEPMOD 4.19.106-minimal1+
...and finally kernel...
rpi4:/usr/src/rpi-linux$ sudo cp arch/arm64/boot/Image /boot/kernel8-p4.img
After installing the core image, sync and reboot. It should come up with with kernel you compiled.
rpi4:/usr/src/rpi-linux$ sync rpi4:/usr/src/rpi-linux$ sudo /sbin/reboot
Once you have done that, you have the baseline and you can start adding features you need to your own custom kernel. Strong suggestion is to keep backup of this initial working kernel and also bump up revision number on make menuconfig's Local version under General setup -menu. By this way you don't overwrite working kernel's /lib/modules/4.19.106-minimal1+ module directory with notworking one.
Image internals
Packages on image
adduser add and remove users and groups apt commandline package manager apt-utils package management related utility programs base-files Debian base system miscellaneous files base-passwd Debian base system master password and group f bash GNU Bourne Again SHell bc GNU bc arbitrary precision calculator language binutils GNU assembler, linker and binary utilities binutils-aarch64-linux-gnu GNU binary utilities, for aarch64-linux-gnu ta binutils-common:arm64 Common files for the GNU assembler, linker and bison YACC-compatible parser generator bsdmainutils collection of more utilities from FreeBSD bsdutils basic utilities from 4.4BSD-Lite build-essential Informational list of build-essential packages bzip2 high-quality block-sorting file compressor - u ca-certificates Common CA certificates console-setup console font and keymap setup program console-setup-linux Linux specific part of console-setup coreutils GNU core utilities cpio GNU cpio -- a program to manage archives of fi cpp GNU C preprocessor (cpp) cpp-8 GNU C preprocessor cron process scheduling daemon dash POSIX-compliant shell dbus simple interprocess messaging system (daemon a debconf Debian configuration management system debconf-i18n full internationalization support for debconf debian-archive-keyring GnuPG archive keys of the Debian archive debianutils Miscellaneous utilities specific to Debian deborphan program that can find unused packages, e.g. li diffutils File comparison utilities discover hardware identification system discover-data Data lists for Discover hardware detection sys dmidecode SMBIOS/DMI table decoder dmsetup Linux Kernel Device Mapper userspace library dpkg Debian package management system dpkg-dev Debian package development tools e2fsprogs ext2/ext3/ext4 file system utilities fdisk collection of partitioning utilities file Recognize the type of data in a file using ma findutils utilities for finding files--find, xargs flex fast lexical analyzer generator g++ GNU C++ compiler g++-8 GNU C++ compiler gcc GNU C compiler gcc-8 GNU C compiler gcc-8-base:arm64 GCC, the GNU Compiler Collection (base package gdbm-l10n GNU dbm database routines (translation files) git fast, scalable, distributed revision control s git-man fast, scalable, distributed revision control s gpgv GNU privacy guard - signature verification too grep GNU grep, egrep and fgrep groff-base GNU troff text-formatting system (base system gzip GNU compression utilities hostname utility to set/show the host name or domain na htop interactive processes viewer ifupdown high level tools to configure network interfac init metapackage ensuring an init system is install init-system-helpers helper tools for all init systems installation-report system installation report iproute2 networking and traffic control tools iptables administration tools for packet filtering and iputils-ping Tools to test the reachability of network host isc-dhcp-client DHCP client for automatically obtaining an IP isc-dhcp-common common manpages relevant to all of the isc-dhc joe user friendly full screen text editor kbd Linux console font and keytable utilities keyboard-configuration system-wide keyboard preferences kmod tools for managing Linux kernel modules less pager program similar to more locales GNU C Library: National Language (locale) data login system login tools logrotate Log rotation utility lsb-base Linux Standard Base init script functionality m4 macro processing language make utility for directing compilation man-db on-line manual pager mawk a pattern scanning and text processing languag mlocate quickly find files on the filesystem based on mount tools for mounting and manipulating filesystem nano small, friendly text editor inspired by Pico ncdu ncurses disk usage viewer ncurses-base basic terminal type definitions ncurses-bin terminal-related programs and man pages net-tools NET-3 networking toolkit netbase Basic TCP/IP networking system ntpdate client for setting system time from NTP server openssh-client secure shell (SSH) client, for secure access t openssh-server secure shell (SSH) server, for secure access f openssh-sftp-server secure shell (SSH) sftp server module, for SFT openssl Secure Sockets Layer toolkit - cryptographic u passwd change and administer password and group data patch Apply a diff file to an original pciutils Linux PCI Utilities perl Larry Wall's Practical Extraction and Report L perl-base minimal Perl system perl-modules-5.28 Core Perl modules procps /proc file system utilities readline-common GNU readline and history libraries, common fil rsyslog reliable system and kernel logging daemon saidar curses-based program which displays live syste sed GNU stream editor for filtering/transforming t sensible-utils Utilities for sensible alternative selection ssh secure shell client and server (metapackage) sudo Provide limited super user privileges to speci systemd system and service manager systemd-sysv system and service manager - SysV links sysvinit-utils System-V-like utilities tar GNU version of the tar archiving utility tzdata time zone and daylight-saving time data ucf Update Configuration File(s): preserve user ch udev /dev/ and hotplug management daemon usb.ids USB ID Repository usbutils Linux USB utilities util-linux miscellaneous system utilities util-linux-locales locales files for util-linux vim-common Vi IMproved - Common files vim-tiny Vi IMproved - enhanced vi editor - compact ver wamerican American English dictionary words for /usr/sha wget retrieves files from the web whiptail Displays user-friendly dialog boxes from shell wireless-tools Tools for manipulating Linux Wireless Extensio wpasupplicant client support for WPA and WPA2 (IEEE 802.11i) xkb-data X Keyboard Extension (XKB) configuration data xxd tool to make (or reverse) a hex dump xz-utils XZ-format compression utilities zlib1g:arm64 compression library - runtime
/boot -partition
Boot partition contains these files. Probably all are not necessary, but I haven't bothered to clean these.
rpi4:~$ ls /boot/ armstub8-gic.bin COPYING.linux kernel8-p4.img start_db.elf bcm2710-rpi-3-b.dtb fixup4cd.dat LICENCE.broadcom start.elf bcm2710-rpi-3-b-plus.dtb fixup4.dat overlays startup.sh bcm2710-rpi-cm3.dtb fixup4db.dat RECOVERY.000 start_x.elf bcm2711-rpi-4-b.dtb fixup4x.dat start4cd.elf vl805.bin bcm2837-rpi-3-b.dtb fixup_cd.dat start4db.elf vl805.sig bootcode.bin fixup.dat start4.elf cmdline.txt fixup_db.dat start4x.elf config.txt fixup_x.dat start_cd.elf
Configs are simplified as :
rpi4:~$ cat /boot/config.txt # For more options and information see # http://www.raspberrypi.org/documentation/configuration/config-txt.md # Some settings may impact device functionality. See link above for details disable_overscan=1 dtparam=spi=on dtparam=audio=on dtoverlay=vc4-fkms-v3d gpu_mem=32 start_x=0 arm_64bit=1 [pi4] max_framebuffers=2 kernel=kernel8-p4.img disable_overscan:1=1 [all]
rpi4:~$ cat /boot/cmdline.txt dwc_otg.lpm_enable=0 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes usbhid.mousepoll=0 rootwait
If you are booting for external drive (and to do that change root to root=/dev/sda1), the rootwait is absolutety required so that boot process waits disks to spin up before trying to mount root from them.
/lib/firmware -directory
Required firmwares are manually added. These are required only for wireless to operate.
rpi4:~$ find /lib/firmware -type f /lib/firmware/brcm/brcmfmac43455-sdio.bin /lib/firmware/brcm/brcmfmac43455-sdio.clm_blob /lib/firmware/brcm/brcmfmac43455-sdio.txt /lib/firmware/regulatory.db
/etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).
source /etc/network/interfaces.d/*
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
allow-hotplug eth0
iface eth0 inet static
address 192.168.11.2
netmask 255.255.255.0
#allow-hotplug wlan0
iface wlan0 inet dhcp
wpa-ssid MY_SSID
wpa-psk MY_SSID_PASS
wpa-key-mgmt WPA-PSK
Notes & bugs
- If you want to tune this even a bit further, you can remove wireless support if you don't need it. Remove wireless options from :
Device Drivers --->
[*] Network device support --->
[ ] Wireless LAN --->
[*] Networking support --->
[ ] Wireless --->
mmc0: Timeout waiting for hardware interrupt. mmc0: sdhci: ============ SDHCI REGISTER DUMP =========== mmc0: sdhci: Sys addr: 0x00000000 | Version: 0x00001002 mmc0: sdhci: Blk size: 0x00007200 | Blk cnt: 0x00000000 mmc0: sdhci: Argument: 0x00000000 | Trn mode: 0x00000023 mmc0: sdhci: Present: 0x1fff0000 | Host ctl: 0x00000017 mmc0: sdhci: Power: 0x0000000f | Blk gap: 0x00000080 mmc0: sdhci: Wake-up: 0x00000000 | Clock: 0x00000107 mmc0: sdhci: Timeout: 0x0000000e | Int stat: 0x00000000 mmc0: sdhci: Int enab: 0x03ff100b | Sig enab: 0x03ff100b mmc0: sdhci: ACmd stat: 0x00000000 | Slot int: 0x00000000 mmc0: sdhci: Caps: 0x45ee6432 | Caps_1: 0x0000a525 mmc0: sdhci: Cmd: 0x00000c1b | Max curr: 0x00080008 mmc0: sdhci: Resp[0]: 0x00000c00 | Resp[1]: 0x003bad7f mmc0: sdhci: Resp[2]: 0x325b5900 | Resp[3]: 0x00400e00 mmc0: sdhci: Host ctl2: 0x00000000 mmc0: sdhci: ADMA Err: 0x00000000 | ADMA Ptr: 0xded2d240 mmc0: sdhci: ============================================