Conversation
jarkko

Jarkko Sakkinen

Edited 6 months ago

Just wanted try out what I minimally need for qemu-system-x86_64 -kernel arch/x86/boot/bzImage: 

#!/usr/bin/env bash

set -e

make defconfig
scripts/config --set-str CONFIG_INITRAMFS_SOURCE "initramfs.txt"
yes '' | make oldconfig

cat > initramfs.txt << EOF
dir /dev 755 0 0
nod /dev/console 644 0 0 c 5 1
nod /dev/loop0 644 0 0 b 7 0
dir /bin 755 1000 1000
slink /bin/sh busybox 777 0 0
file /bin/busybox initramfs/busybox 755 0 0
dir /proc 755 0 0
dir /sys 755 0 0
dir /mnt 755 0 0
file /init initramfs/init.sh 755 0 0
EOF

mkdir initramfs

curl -sSf https://dl-cdn.alpinelinux.org/alpine/edge/main/x86_64/busybox-static-1.36.1-r25.apk | tar zx --strip-components 1
cp busybox.static initramfs/busybox

cat > initramfs/init.sh << EOF
#!/bin/sh
mount -t proc none /proc
mount -t sysfs none /sys
sh
EOF

“linux from scratch” in 32 lines :-)

#linux #kernel #alpine

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r1w1s1@mastodon.social

Ric🐧☕

Reply to @jarkko

@jarkko nice :)

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jarkko

Jarkko Sakkinen

Reply to @r1w1s1@mastodon.social
glad you liked it :-)
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noflcl@mastodon.social

Stephen McNamara

Reply to @jarkko

@jarkko

I love how after decades of Linux use... This is human readable lol

Very nice

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jarkko

Jarkko Sakkinen

Reply to @noflcl@mastodon.social

@noflcl it’s missing the last command tho: make -j$(nproc) but just a minor detail ;-)

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jarkko

Jarkko Sakkinen

Reply to @jarkko
Edited 6 months ago
kudos to @ncopa again for the static busybox binary tip! i'll refine this at some point to multi-arch with toolchains from https://toolchains.bootlin.com/. i.e. one arg for arch and it will download the toolchain and matching busybox binary. #bootlin #buildroot
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