Linux in RAM: debirf way 2018

Linux in RAM: debirf way


Do you want to have absolute disk speed nowadays, don’t you? Let's revise how it could be done with versioning and automation in 2018.


От модератора: нам в Песочницу пришла статья на английском языке. Мы её прочитали и и в качестве пятничного эксперимента решили опубликовать. Не судите строго, всем peace and happy Friday! Let's come together! Короче, фром зе боттом оф ауа хартс.

Changelog:


  • The language of the article is corrected in English
  • sample repository introduced at github
  • Added test params
  • added asciicast

You must know before running this tutorial:


  • linux essential
  • the main difference between bash and sh (debirf written on sh, so I recommend to follow the style)
  • how to format usb key (in any way)
  • what drivers are needed for your hardware (or you can debug it via dmesg|lspci)
  • how to gain your task purposes via the scripting

you can replace:


  • usb letter from /dev/sdb to any else (/dev/sdd)
  • working directory from /root/Projects/debirf/ to your choice (/home/username/Documents/debirf)
  • mountpoint from /media/root/8B46-1189 to /media/username/myflashdrive

Steps to preparing


They are (optional) enable non-free components for basic installation. In addition, I think, you will need the non-free repository.


  • open line number 107 of file /usr/bin/debirf like nano +107 $(which debirf)
  • find function create_debootstrap
  • find line like local OPTS="
  • add --components main,contrib,non-free in brackets

Up to start:


Let's imagine, our flash drive:


  • must to be fast, so it is recommended to use 8+ class, or booting will take enough time
  • /dev/sdb
  • formated
  • mounted at /media/root/8B46-1189.
  • our working directory /root/Projects/debirf/

Install debirf


apt-get install -yq debirf mtools genisoimage

  • mtools needed for create iso via debirf (not working, but needed)
  • genisoimage needed for create real working iso (optional)

Prepare debirf working directory


mkdir -p /root/Projects/debirf
tar xzf /usr/share/doc/debirf/example-profiles/rescue.tgz -C /root/Projects/debirf
cd /root/Projects/debirf/rescue

And configure /root/Projects/debirf/rescue/debirf.conf


DEBIRF_LABEL="debirf-rescue"
DEBIRF_SUITE=stretch
DEBIRF_DISTRO=debian
DEBIRF_MIRROR=http://ftp.ru.debian.org/debian/

Create LiR


  • Run debirf make . and go away. It need many time, at minimal 15 minutes on top hardware.
  • Run debirf makeiso . for create not working iso (needed for grub.cfg file)

Test it


  • Install qemu
    • for linux: apt-get install -yq qemu
    • for macos: brew install qemu
  • decide which resources will be allocated for VM
    • -smp 1 1 real kernel
    • -m 1G 1G memory
  • additional
    • -nographic will launch VM in current terminal window
    • --enable-kvm enables hardware accelation
    • -kernel vmlinuz-* permit directly pass kernel
    • -initrd *.cgz direct access to .cgz file with initramfs
    • -append allows bypass kernel params, here are the parameters for running without a graphical shell

The command to start the virtual machine:


qemu-system-x86_64 --enable-kvm -kernel vmlinuz-* -initrd *.cgz -append "console=tty0 console=ttyS0,115200n8" -m 1G -smp 1 -net nic,vlan=0 -net user -nographic

Test sample


asciicast


Install grub to flash drive and copy LiR on it


I recommend you use bios legacy boot and package grub-pc. Not tested with UEFI, but must work. Next lines will be do:


  • create mount point (on GUI-powered systems enabled auto-mount it isn't needed)
  • mount usb key to mount point (on GUI-powered systems enabled auto-mount it isn't needed)
  • install grub
  • copy grub file
  • copy initramfs (system)
  • copy vmlinuz (kernel)
  • unmount usb key
  • remove mount point

mkdir -p /media/root/8B46-1189
mount /dev/sdb1 /media/root/8B46-1189
grub-install --boot-directory=/media/root/8B46-1189/boot /dev/sdb
cp /root/Projects/debirf/rescue/iso/boot/grub/grub.cfg /media/root/8B46-1189/boot/grub/
cp /root/Projects/debirf/rescue/*.cgz /media/root/8B46-1189
cp /root/Projects/debirf/rescue/vmlinuz-* /media/root/8B46-1189
umount /media/root/8B46-1189
rm -rf /media/root/8B46-1189

Create bootable iso (optional)


  • download isolinux.bin
  • create isolinux config file
  • create iso

mkdir -p rescue/iso/isolinux/
wget -O rescue/iso/isolinux/isolinux.bin 'http://mirror.yandex.ru/centos/7/os/x86_64/isolinux/isolinux.bin'
cat << EOF > rescue/iso/isolinux/isolinux.cfg
TIMEOUT 5
DEFAULT lir
LABEL lir
  LINUX /vmlinuz-4.9.0-7-amd64
  INITRD /debirf-rescue_stretch_4.9.0-7-amd64.cgz
EOF
genisoimage -b isolinux/isolinux.bin -c isolinux/boot.cat -no-emul-boot -boot-load-size 4 -boot-info-table -l -input-charset default -V LiR -A "Linux in RAM" -o rescue/rescue.iso rescue/iso/

Check result


  • Install QEMU hypervisor apt-get install -yq qemu
  • run qemu-system-x86_64 -enable-kvm -m 512 -hda /dev/sdb
  • if previous command fails, remove -enable-kvm
  • VM will be started, booted from usb key
  • you must see two menu items, difference in end: console and serial. Select first entry.
  • in ~minute you will see many lines. after it ends — press enter to see welcome message
  • login: root, no password

Customize it: Create custom debirf module


Module — executable sh script for running during LiR creating


  • create module file
  • the order of file’s names is important. In file network the resolving file will be changed to the system-resolved, and you can’t work with the network;
  • lines from 1 to 3 must be present, line 3 must present file name
  • if you want install package — use construction #DEBIRF_PACKAGE>+
  • if you want work with rootfs — use $DEBIRF_ROOT
  • if you want to run command in fakeroot — use debirf_exec

Sample:


cat <<< EOF > rescue/modules/mi
#!/bin/sh -e
# debirf module: mi
# prepare to run on mi notebook
#
# This script were written by
# Eduard Generalov <eduard@generalov.net>
#
# They are Copyright 2018, and published under the MIT,
#DEBIRF_PACKAGE>+firmware-iwlwifi
#DEBIRF_PACKAGE>+firmware-misc-nonfree
#DEBIRF_PACKAGE>+wpasupplicant
echo 'iwlwifi' >> $DEBIRF_ROOT/etc/modules
cat << EOF > $DEBIRF_ROOT/etc/wpa_supplicant/wpa_supplicant-wlp1s0.conf
ctrl_interface=/run/wpa_supplicant
update_config=1
network={
        ssid="WiFi_SSID"
        psk="WIFIPASSWORD"
}
EOF
cat << EOF > $DEBIRF_ROOT/etc/systemd/network/wireless.network
[Match]
Name=wlp1s0
[Network]
DHCP=ipv4
[DHCP]
RouteMetric=20
EOF

and replace line with resolved in file rescue/modules/network with debirf_exec systemctl enable wpa_supplicant@wlp1s0.service systemd-networkd.service systemd-resolved.service


Bonus: lxc on LiR


module rescue/modules/lxc


#!/bin/sh -e
# debirf module: lxc
# prepare lxc
#
# This script were written by
# Eduard Generalov <eduard@generalov.net>
#
# They are Copyright 2018, and published under the MIT,
#DEBIRF_PACKAGE>+lxc
mkdir -p $DEBIRF_ROOT/root/.ssh/
ssh-keygen -b 2048 -t rsa -f $DEBIRF_ROOT/root/.ssh/id_rsa -q -N ""
cp $DEBIRF_ROOT/root/.ssh/id_rsa $DEBIRF_ROOT/root/.ssh/authorized_keys
chmod 400 $DEBIRF_ROOT/root/.ssh/authorized_keys
debirf_exec systemctl enable lxc-net
cat << EOF > $DEBIRF_ROOT/etc/lxc/default.conf
lxc.network.type = veth
lxc.network.link = lxc
lxc.network.name = eth0
lxc.network.flags = up
lxc.network.hwaddr = 00:FF:AA:FF:xx:xx
lxc.mount.entry=/var/cache/apt var/cache/apt none bind,rw 0 0
lxc.mount.entry = /root/.ssh/ root/.ssh none bind,create=dir 0 0
EOF
cat << EOF > $DEBIRF_ROOT/etc/default/lxc-net 
USE_LXC_BRIDGE="true"
LXC_BRIDGE="lxc"
LXC_ADDR="10.0.3.1"
LXC_NETMASK="255.255.255.0"
LXC_NETWORK="10.0.3.0/24"
LXC_DHCP_RANGE="10.0.3.2,10.0.3.254"
LXC_DHCP_MAX="253"
LXC_DHCP_CONFILE=""
LXC_DOMAIN="lxc"
EOF

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