Clever Geek Handbook

Creating an Ubuntu ARM "from scratch" image

When development is just starting, it is often not yet clear which packages will go to the target rootfs.



In other words, it's too early to grab LFS, buildroot, or yocto (or something else), but you need to start. For the rich (I have 4GB eMMC on pilot samples), there is a way to distribute to developers a distribution kit that will allow them to quickly deliver something that is missing at the moment, and then we can always collect package lists and form a list for the target rootfs.



This article is not new and is a simple copy-paste instruction.



The purpose of the article is to build Ubuntu rootfs for ARM boards (in my case, based on Colibri imx7d).



Assembling the image



Build target rootfs for replication.



Unpacking Ubuntu Base



We choose the release ourselves based on the need and our own preferences. Here I have given 20.



$ mkdir ubuntu20
$ cd ubuntu20
$ mkdir rootfs
$ wget http://cdimage.ubuntu.com/ubuntu-base/releases/20.04/release/ubuntu-base-20.04-base-armhf.tar.gz
$ tar xf ubuntu-base-20.04-base-armhf.tar.gz -C rootfs


Checking BINFMT support in the kernel



If you have a widespread distribution kit, then BINFMT_MISC support is there and everything is configured, if not, then I'm sure you know how to enable BINFMT support in the kernel.



Make sure BINFMT_MISC is enabled in the kernel:



$ zcat /proc/config.gz | grep BINFMT
CONFIG_BINFMT_ELF=y
CONFIG_COMPAT_BINFMT_ELF=y
CONFIG_BINFMT_SCRIPT=y
CONFIG_BINFMT_MISC=y


Now you need to check the settings:



$ ls /proc/sys/fs/binfmt_misc
qemu-arm  register  status
$ cat /proc/sys/fs/binfmt_misc/qemu-arm
enabled
interpreter /usr/bin/qemu-arm
flags: OC
offset 0
magic 7f454c4601010100000000000000000002002800
mask ffffffffffffff00fffffffffffffffffeffffff


You can register manually using, for example, this instruction .



Qemu static arm setup



Now we need a statically compiled qemu instance.



!!! !!!

, :

https://sourceware.org/bugzilla/show_bug.cgi?id=23960

https://bugs.launchpad.net/qemu/+bug/1805913

x86_64 host arm guest i386 qemu:

http://ftp.ru.debian.org/debian/pool/main/q/qemu/qemu-user-static_5.0-13_i386.deb


$ wget http://ftp.debian.org/debian/pool/main/q/qemu/qemu-user-static_5.0-13_amd64.deb
$ alient -t qemu-user-static_5.0-13_amd64.deb
#   rootfs        /proc/sys/fs/binfmt_misc/qemu-arm
$ mkdir qemu
$ tar xf qemu-user-static-5.0.tgz -C qemu
$ file qemu/usr/bin/qemu-arm-static
qemu/usr/bin/qemu-arm-static: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, BuildID[sha1]=be45f9a321cccc5c139cc1991a4042907f9673b6, for GNU/Linux 3.2.0, stripped
$ cp qemu/usr/bin/qemu-arm-static rootfs/usr/bin/qemu-arm
$ file rootfs/usr/bin/qemu-arm
rootfs/usr/bin/qemu-arm: ELF 64-bit LSB executable, x86-64, version 1 (GNU/Linux), statically linked, BuildID[sha1]=be45f9a321cccc5c139cc1991a4042907f9673b6, for GNU/Linux 3.2.0, stripped


Chroot



:



ch-mount.sh 
#!/bin/bash

function mnt() {
    echo "MOUNTING"
    sudo mount -t proc /proc ${2}proc
    sudo mount --rbind /sys ${2}sys
    sudo mount --make-rslave ${2}sys
    sudo mount --rbind /dev ${2}dev
    sudo mount --make-rslave ${2}dev
    sudo mount -o bind /dev/pts ${2}dev/pts
    sudo chroot ${2}
}

function umnt() {
    echo "UNMOUNTING"
    sudo umount ${2}proc
    sudo umount ${2}sys
    sudo umount ${2}dev/pts
    sudo umount ${2}dev

}

if [ "$1" == "-m" ] && [ -n "$2" ] ;
then
    mnt $1 $2
elif [ "$1" == "-u" ] && [ -n "$2" ];
then
    umnt $1 $2
else
    echo ""
    echo "Either 1'st, 2'nd or both parameters were missing"
    echo ""
    echo "1'st parameter can be one of these: -m(mount) OR -u(umount)"
    echo "2'nd parameter is the full path of rootfs directory(with trailing '/')"
    echo ""
    echo "For example: ch-mount -m /media/sdcard/"
    echo ""
    echo 1st parameter : ${1}
    echo 2nd parameter : ${2}
fi


:



$ ./ch-mount.sh -m rootfs/
# cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04 LTS"
VERSION_ID="20.04"
HOME_URL="https://www.ubuntu.com/"
SUPPORT_URL="https://help.ubuntu.com/"
BUG_REPORT_URL="https://bugs.launchpad.net/ubuntu/"
PRIVACY_POLICY_URL="https://www.ubuntu.com/legal/terms-and-policies/privacy-policy"
VERSION_CODENAME=focal
UBUNTU_CODENAME=focal
# uname -a
Linux NShubin 5.5.9-gentoo-x86_64 #1 SMP PREEMPT Mon Mar 16 14:34:52 MSK 2020 armv7l armv7l armv7l GNU/Linux


( ) :



# du -d 0 -h / 2>/dev/null
63M     /


:



# apt update
# apt upgrade --yes


:



# SYSTEMD_IGNORE_CHROOT=yes apt install --yes autoconf kmod socat ifupdown ethtool iputils-ping net-tools ssh g++ iproute2 dhcpcd5 incron ser2net udev systemd gcc minicom vim cmake make mtd-utils util-linux git strace gdb libiio-dev iiod


, , . , , , device tree Ubuntu . , .



- , .



# apt install --yes linux-headers-generic


, :



# apt clean
# du -d 0 -h / 2>/dev/null
770M    /


.





$ sudo tar -C rootfs --transform "s|^./||" --numeric-owner --owner=0 --group=0 -c ./ | tar --delete ./ | gzip > rootfs.tar.gz


etckeeper autopush



, , .



etckeeper.



:

  • force push
  • .. ...




# ssh-keygen
# apt install etckeeper
# etckeeper init
# cd /etc
# git remote add origin ...


autopush



( , ).



# cat /etc/etckeeper/etckeeper.conf
PUSH_REMOTE="origin"


...





- , ( MAC — ):



cat /proc/cpuinfo 
# cat /proc/cpuinfo
processor       : 0
model name      : ARMv7 Processor rev 5 (v7l)
BogoMIPS        : 60.36
Features        : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm 
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xc07
CPU revision    : 5

processor       : 1
model name      : ARMv7 Processor rev 5 (v7l)
BogoMIPS        : 60.36
Features        : half thumb fastmult vfp edsp neon vfpv3 tls vfpv4 idiva idivt vfpd32 lpae evtstrm 
CPU implementer : 0x41
CPU architecture: 7
CPU variant     : 0x0
CPU part        : 0xc07
CPU revision    : 5

Hardware        : Freescale i.MX7 Dual (Device Tree)
Revision        : 0000
Serial          : 06372509


:



# cat /proc/cpuinfo | grep Serial | cut -d':' -f 2 | tr -d [:blank:]
06372509


:



# cat /etc/etckeeper/commit.d/40myown-push
#!/bin/sh
set -e

if [ "$VCS" = git ] && [ -d .git ]; then
  branch=$(cat /proc/cpuinfo | grep Serial | cut -d':' -f 2 | tr -d [:blank:])
  cd /etc/
  git push origin master:${branch}
fi


— .





BINFMT_MISC

Kernel Support for miscellaneous Binary Formats (binfmt_misc)

Compiling with qemu user chroot

Building Ubuntu rootfs for ARM

How to create a custom Ubuntu live from scratch

Crossdev qemu-static-user-chroot

etckeeper



getdents64 problem



readdir () returns NULL (errno = EOVERFLOW) for 32-bit user-static qemu on 64-bit host

Ext4 64 bit hash breaks 32 bit glibc 2.28+

compiler_id_detection fails for armhf when using QEMU user-mode emulation

CMake doesn't work properly under qemu-arm



More articles:


All Articles