Linux in RAM: debirf way

You want to have absolute disk speed? Let's see how it can be done in 2018 with versioning and automation.

before run this tutorial

you must know

• linux essential
• difference between bash and sh (debirf writen on sh)
• how to format usb key (any way)
• what drivers you need for your hardware (or you can debug it via dmesg|lspci)
• how to automate you desires via 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 prepare

(optional) enable non-free components for basic installation

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

for start:

Let's think, our flash drive:

• must be fast. recommend to use 8+ class, or booting will take many of your 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)

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, not needed)
• mount usb key to mount point (on GUI-powered systems enabled auto-mount, not 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 names is important. In file network the resolving file will be changed to the system-resolved, and you can not 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

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.