ubuntu

change users listed in login screen
-----------------------------------
/etc/login.defs -> UID_MIN, GID_MIN


grub single usermode
--------------------
http://www.noah.org/wiki/Single_User_Mode

screen size in text mode
------------------------
$ vi /etc/default/grub
GRUB_CMDLINE_LINUX="vga=791"
GRUB_GFXMODE=1024x768

show boot menu
---------------
(/etc/default/grub)
GRUB_DEFAULT=0
#GRUB_HIDDEN_TIMEOUT=0
#GRUB_HIDDEN_TIMEOUT_QUIET=true
GRUB_TIMEOUT_STYLE=menu
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT=""
GRUB_CMDLINE_LINUX=""
GRUB_TERMINAL="console serial"


PXE
---
ubuntu
https://www.maketecheasier.com/configure-pxe-server-ubuntu/

redhat
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Installation_Guide/chap-installation-server-setup.html

fedora
https://docs.fedoraproject.org/en-US/Fedora/21/html/Installation_Guide/chap-pxe-server-setup.html


remote desktop
--------------
search "desktop sharing"

disable encrytion
- $ dconf-editor
- find "5900"


ui config
---------
super -> app -> unity tweak tool


auto update
-----------
sudo systemctl disable apt-daily.service # disable run when system boot
sudo systemctl disable apt-daily.timer   # disable timer run

/etc/apt/apt.conf.d/20auto-upgrades
>> APT::Periodic::Update-Package-Lists "0";
>> APT::Periodic::Unattended-Upgrade "0";


font size in text mode (ubunt-15)
---------------------------------
fonts are under /usr/share/consolefonts, to test font:
$ setfont Uni2-TerminusBold20x10

$ vi /etc/default/console-setup
Ubuntu-14:
  CODESET="Uni2"
  FONTFACE="TerminusBold"
  FONTSIZE="20x10"
Ubuntu-15:
  FONTFACE="TerminusBold"
  FONTSIZE="10x20"

For Ubuntu-15, add "setupcon" to /etc/rc.local


ftp server
----------
$sudo apt-get install pure-ftpd


>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
router
===================================================================================

network configuration
---------------------
eth0: lan, static, 172.29.0.0/16
eth1: wan, dhcp, 10.164.2.153


ip masquerading
---------------
# iptables -A FORWARD -o eth1 -i eth0 -s 172.29.0.0/16 -m conntrack --ctstate NEW -j ACCEPT
# iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT
# iptables -t nat -F POSTROUTING
# iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE

# iptables-save | sudo tee /etc/iptables.sav
add "iptables-restore < /etc/iptables.sav" into /etc/rc.local before the "exit 0" line


ip forwarding
-------------
$ sudo sh -c "echo 1 > /proc/sys/net/ipv4/ip_forward"
uncomment "net.ipv4.ip_forward=1" in /etc/sysctl.conf


port forwarding
---------------
https://tecadmin.net/setting-up-a-port-forwarding-using-iptables-in-linux/

- client wants to visit dest-server:5001 through a jump-server
- client -> jump-server:15001 -> dest-server(172.28.1.1:5001)
- client can visit dest-server:5001 by jump-server:15001

$ sudo iptables -t nat -A PREROUTING -p tcp --dport 15001 -j DNAT --to-destination 172.28.1.1:5001
$ sudo iptables -t nat -A POSTROUTING -j MASQUERADE


port mapping for libvirt vm
---------------------------
http://wiki.libvirt.org/page/Networking#Forwarding_Incoming_Connections

iptables -I FORWARD -o virbr0 -d $GUEST_IP -j ACCEPT
iptables -t nat -I PREROUTING -p tcp --dport $HOST_PORT -j DNAT --to $GUEST_IP:$GUEST_PORT


client setup
------------
$ sudo route add default gw 172.29.1.10 eth0
add "gateway 172.29.1.10" to /etc/network/interfaces under "iface eth0"

urls
----
https://help.ubuntu.com/community/Internet/ConnectionSharing
https://rbgeek.wordpress.com/2012/05/14/ubuntu-as-a-firewallgateway-router/
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<


wget
====
wget -r -np -nH --cut-dirs=4 -R index.html* http://images.maas.io/ephemeral-v2/daily/wily/arm64/ddd/

Explanation:
?It will download all files and subfolders in ddd directory:
?recursively (-r), 
?not going to upper directories (-np),
?not saving files to hostname folder "images.maas.io/" (-nH), 
?but to ddd by omitting first 4 folders "ephemeral-v2/daily/wily/arm64/" (--cut-dirs=4)
?excluding index.html files (-R index.html*)


thunderbird
===========

office365
---------
email: select imap+oauth2, works out of the box
calendar: install TbSync + "Provider for Exchange ActiveSync"

dont wrap long line
-------------------
mailnews.display.disable_format_flowed_support = true


set tab title
=============
The .bashrc solution proposed by Kirby worked for me:
set-title(){
  ORIG=$PS1
  TITLE="\e]2;$@\a"
  PS1=${ORIG}${TITLE}
}
then from my prompt: $ set-title test-title


iconize by clicking on toolbar (trusty)
=======================================
gsettings set org.compiz.unityshell:/org/compiz/profiles/unity/plugins/unityshell/ launcher-minimize-window true


enable ssh password login
==========================
$ sudo vi /etc/ssh/sshd_config
  "PasswordAuthentication yes"
  "KbdInteractiveAuthentication yes"
  "UsePAM yes"

$ sudo /etc/init.d/ssh reload


cron
====
http://www.thegeekstuff.com/2009/06/15-practical-crontab-examples/


dual ip for one nic
===================
sudo ip address add 172.29.100.100/16 dev eth0
sudo ip address del 172.29.100.100/16 dev eth0


nic offload setting
===================
sudo ethtool -k eth0  --> list settings
sudo ethtool -K eth0 rx-vlan-filter off


static dns with dhcp
====================
https://help.ubuntu.com/community/StaticDnsWithDhcp


show my public ip
=================
curl http://icanhazip.com/


dump dts
========
http://suihkulokki.blogspot.tw/2015/04/fastest-way-to-change-running-dtb.html

# apt-get install device-tree-compiler
# dtc -I fs -O dts -o current.dts /proc/device-tree/

$ dtc -I dts -O dtb -o new.dtb current.dts


initramfs
=========
The uncompressed cpio archive must be the first. Compressed cpio archives must
be after the uncompressed one.

add files
---------
https://www.kernel.org/doc/Documentation/acpi/initrd_table_override.txt
- mkdir -p kernel/firmware/acpi
- cp dsdt.aml kernel/firmware/acpi
- find kernel | cpio -H newc --create > acpi_initrd
- cat /boot/initrd.img-4.15.0-54-generic >> acpi_initrd
- mv acpi_initrd /boot/initrd.img-4.15.0-54-generic

modify
------
http://backreference.org/2010/07/04/modifying-initrdinitramfs-files/


file as /dev/sdb
================
$ dd if=/dev/zero of=virtual_hard_drive.bin bs=1M count=1024
$ mknod /dev/sdb b 7 500
$ losetup /dev/sdb virtual_hard_drive.bin


login/ssh slow
==============
try remove /etc/update-motd.d/*

https://superuser.com/questions/166359/top-causes-of-slow-ssh-logins
$ sudo systemctl restart systemd-logind


passwordless sudo
=================
$ sudo VISUAL=vim visudo
linux ALL=(ALL) NOPASSWD:ALL


system recovery
===============
http://xmodulo.com/how-to-reset-root-password-in-debian-ubuntu.html


setup apt repo
==============
https://askubuntu.com/questions/170348/how-to-create-a-local-apt-repository
$ dpkg-scanpackages . /dev/null | gzip -9c > Packages.gz


extglob
=======
$ shopt -s extglob
$ ls !(a*) -> list files NOT start with 'a'


mount whole disk image(not partition)
=====================================
$ fdisk -lu vmdisk
Device        Start      End  Sectors  Size Type
vmdisk1        2048  1050623  1048576  512M EFI System
vmdisk2     1050624 16963583 15912960  7.6G Linux filesystem
vmdisk3    16963584 20969471  4005888  1.9G Linux swap

$ sudo mount -o loop,offset=$((1050624*512)) vmdisk /mnt


create ubuntu boot usb
======================
startup disk creator


use own repo
============
deb http://wls-x86-hp07.shanghai.arm.com/debian-openstack/ ./


bridge
======
auto brAdm
iface brAdm inet static
  bridge_ports eth1
  address 192.168.234.253/24


pin package version
===================
$ sudo vi /etc/apt/preferences.d/virt

Package: libvirt-bin libvirt0
Pin: version 1.3.1-1ubuntu10.12
Pin-Priority: 900

$ sudo vi /etc/apt/preferences.d/thunderbird

Package: thunderbird*
Pin: version 1:60.9.0+build1-0ubuntu0.18.04.1
Pin-Priority: 1001

Package: xul-ext-*
Pin: version 1:60.9.0+build1-0ubuntu0.18.04.1
Pin-Priority: 1001


vlan nic
========
https://wiki.ubuntu.com/vlan


git proxy
=========
https://cms-sw.github.io/tutorial-proxy.html

ssh -f -N -D 3333 linaro@uk1
git -c "http.proxy=socks5://localhost:3333" clone https://github.com/pytorch/pytorch


resize partition
================
- fix gpt error
  # printf "fix\n" | parted ---pretend-input-tty /dev/sda print
- grow partition
  # growpart /dev/sda 2
- grow file system
  # resize2fs /dev/sda2


ssh tunnel
==========
p3OO --lan--> hp07 --vpn--> uk1 --> other side of wall
- hp07:~/$ ssh -X -f -N -D 10.169.41.138:3333 linaro@10.101.2.102
- p3OO:~/$ curl --socks5 hp07:3333 http://xxx/yyy -o yyy
- p3OO:~/$ git -c "http.proxy=socks5://hp07:3333" clone xxx


nested kvm
==========
<cpu mode='custom' match='exact'>
  <model fallback='allow'>Haswell-noTSX</model>
  <feature policy='require' name='vmx'/>
</cpu>


loop lvm
========
$ export LOOPDEV=/dev/loop2
$ sudo apt install lvm2 && sudo systemctl start lvm2-lvmetad
$ dd if=/dev/zero of=lvm1.img bs=1M count=20K
$ sudo losetup $LOOPDEV lvm1.img
$ sudo pvcreate $LOOPDEV
$ sudo vgcreate vg1 $LOOPDEV
$ sudo lvcreate -n lv1 -l 100%FREE vg1


vim
===
- check current file type
  :set ft?
- system clipboard
  "+y
  "+p


curl & run script
=================
https://stackoverflow.com/questions/4642915/passing-parameters-to-bash-when-executing-a-script-fetched-by-curl


curl & extract
==============
curl -sL https://aaa.bbb//ccc.tar.gz | tar xz


gpg
===
- create key
  $ gpg --gen-key

- list/export keys
  $ gpg -k
  $ gpg --export -a
  $ gpg -a -o yibocai.gpg --export yibo.cai@arm.com

- upload to keyserver
  $ gpg --keyserver hkp://keys.gnupg.net --send-keys 32BA38F0
  $ gpg --keyserver hkp://pgp.key-server.io:11371 --send-keys 32BA38F0
  upload manually to http://pgp.mit.edu/, https://keyserver.pgp.com/

- search keyserver by mail
  $ gpg --search-keys yibo.cai@arm.com


jenkins time format
===================
https://stackoverflow.com/questions/12472645/how-to-schedule-jobs-in-jenkins


max open files
==============
$ ulimit -Hn
$ ulimit -Sn
$ ulimit -Sn 8888


build iso
=========
genisoimage -r -V "Estuary Ubuntu Install CD" -J -l -o ubuntu-4.12.iso ./ubuntu16-4.12/


kernel
======
- install kernel debug symbol
  https://hadibrais.wordpress.com/2017/03/13/installing-ubuntu-kernel-debugging-symbols/
- get kernel source code
  * get installed kernel version: dpkg -l | grep linux-image
  * find branch/tag in https://kernel.ubuntu.com/git/ubuntu/ubuntu-focal.git
  * git clone git://kernel.ubuntu.com/ubuntu/ubuntu-disco -b tag --depth 1
- changelog
  https://launchpad.net/ubuntu/+source/linux/+changelog
  https://askubuntu.com/questions/55355/where-is-the-changelog-for-ubuntu-kernels
- mainline kernel binary
  https://kernel.ubuntu.com/~kernel-ppa/mainline/


build kernel
============
stock
-----
- https://wiki.ubuntu.com/Kernel/BuildYourOwnKernel (don't follow all)
- apply patches:
  ~ debian.master/etc/kernelconfig:   change 'archs="arm64"'
  ~ debian/rules.d/1-maintainer.mk:   delete 'rm -rf build'
  ~ debian/scripts/misc/kernelconfig: delete 'rm -rf build'
- steps:
  ~ chmod a+x debian/rules
  ~ chmod a+x debian/scripts/*
  ~ chmod a+x debian/scripts/misc/*
  ~ fakeroot debian/rules clean
  ~ fakeroot debian/rules editconfigs
  ~ cd build
  ~ make -j32 LOCALVERSION=-custom
  ~ sudo make INSTALL_MOD_STRIP=1 modules_install
  ~ sudo make install

upstream
--------
- https://wiki.ubuntu.com/KernelTeam/GitKernelBuild
- https://www.maketecheasier.com/build-custom-kernel-ubuntu/
- own build
  $ sudo apt install build-essential flex bison binutils-dev dpkg-dev \
                     libncurses5-dev libssl-dev libiberty-dev
  $ cp /boot/config-5.0.0-17-generic .config
  $ make olddefconfig
  $ sed -i 's/CONFIG_SYSTEM_TRUSTED_KEYS=.*/CONFIG_SYSTEM_TRUSTED_KEYS=""/' .config
  $ sed -i 's/CONFIG_SYSTEM_REVOCATION_KEYS=.*/CONFIG_SYSTEM_REVOCATION_KEYS=""/' .config
  $ make -j32 LOCALVERSION=-pmem
  $ sudo make INSTALL_MOD_STRIP=1 modules_install
  $ sudo make install
  $ make -C tools/perf -j8
  (# workaround libtraceevent)
  (# make -C tools/perf -j8 FEATURE_CHECK_LDFLAGS-libtraceevent=-ltraceevent)


install latest ubuntu kernel
============================
https://github.com/pimlie/ubuntu-mainline-kernel.sh


git send-email
==============
https://www.freedesktop.org/wiki/Software/PulseAudio/HowToUseGitSendEmail/
- git send-email --to cyb70289@sina.com --cc cyb70289@163.com --annotate -v2 -1


new document
============
- vi ~/.config/user-dirs.dirs
 XDG_TEMPLATES_DIR="$HOME/.Templates"
- touch ~/.Templates/"Untitled Document"


list package dependencies
=========================
apt-cache depends --recurse --no-recommends --no-suggests --no-conflicts --no-breaks --no-replaces --no-enhances --no-pre-depends ceph-osd | grep "^\w" | sort -u


disable/enable cpu
==================
- sudo chcpu -d 112-223
- sudo chcpu -e 112-223
- /sys/devices/system/cpu/{online,offline}


iconv
=====
echo -e -n "\xf1\x80\x80\x80" | iconv -f UTF-8 -t UTF-16LE - | od -t x2


set env in sudo
===============
function sudo () {
  args="$@"
  /usr/bin/sudo bash -c "source env-file && $args"
}


find multiple patterns
======================
- find . \( -name "*.c" -o -name "*.h" -o -name "*.ic" -o -name "*.cc" \)
- find . -iregex '.*\.\(c\|cc\|h\|ic\)$'


disable swap
============
sudo systemctl stop swapfile.swap
sudo systemctl mask swapfile.swap


fight with dns 127.0.0.53
=========================
cat /run/systemd/resolve/resolv.conf > /tmp/resolv.conf.real
sudo systemctl stop systemd-resolved
sudo systemctl disable systemd-resolved
sudo rm -f /etc/resolv.conf
sudo cp /tmp/resolv.conf.real /etc/resolv.conf
sudo reboot


set locale
==========
export LANG=en_US.UTF-8 LANGUAGE=en_US:en LC_ALL=en_US.UTF-8


set memlock to unlimited
========================
add to /etc/security/limits.conf

*               soft    memlock            unlimited
*               hard    memlock            unlimited
root            soft    memlock            unlimited
root            hard    memlock            unlimited

logout/login


hide desktop drive icon
=======================
gsettings set org.gnome.nautilus.desktop volumes-visible 'false'


gnome terminal
==============
- color theme
  install dconf gconf2
  https://github.com/Gogh-Co/Gogh
  [Teerb]

- windows size shrink
  dconf write /org/gnome/terminal/legacy/headerbar '@mb false'


background solid color
======================
$ gsettings set org.gnome.desktop.background picture-uri ""
$ gsettings set org.gnome.desktop.background primary-color '#0063b1'


hide volume icon on sidebar
===========================
$ git clone https://github.com/micheleg/dash-to-dock.git
$ cd dash-to-dock
$ make
$ gsettings --schemadir schemas set org.gnome.shell.extensions.dash-to-dock show-mounts false


nofitication area missing
=========================
sudo apt install gnome-shell-extension-appindicator


install python3.8 if on ubuntu 18.04
====================================
$ add-apt-repository ppa:deadsnakes/ppa
$ apt install -y python3.8 python3.8-distutils


search 64k page size arm64 kernel
=================================
sudo apt install linux-generic-64k-hwe-20.04
apt search "linux-.*64k"


install arm64 packges on x86_64
===============================
- prefer https://github.com/multiarch/qemu-user-static

- https://wiki.debian.org/Multiarch/HOWTO#Setting_up_apt_sources
  sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
  (
    (grep ^deb /etc/apt/sources.list | sed 's/deb /deb [arch=amd64] /') && \
    (grep ^deb /etc/apt/sources.list | sed 's/deb /deb [arch=arm64] /g; s/\(archive\|security\)\.ubuntu/ports.ubuntu/g; s/\/ubuntu/\/ubuntu-ports/g') \
  ) | tee /tmp/sources.list
  sudo mv /tmp/sources.list /etc/apt/sources.list
  sudo dpkg --add-architecture arm64
  sudo apt update
  sudo apt install libc6:arm64 libstdc++6:arm64

- https://wiki.debian.org/QemuUserEmulation
  sudo apt install qemu binfmt-support qemu-user-static


find peak RSS of a process
==========================
/usr/bin/time command


install latest clang
====================
curl -s https://apt.llvm.org/llvm-snapshot.gpg.key | sudo apt-key add -
sudo apt-add-repository "deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-16 main"
sudo apt update
sudo apt install clang-16

wget https://apt.llvm.org/llvm.sh
chmod u+x llvm.sh
sudo ./llvm.sh 16


ssh issue on ubuntu-22.04
=========================
append "PubkeyAcceptedKeyTypes +ssh-rsa" to /etc/ssh/ssh_config


iotop doesn't show IO
=====================
sudo sysctl -w kernel.task_delayacct=1


get primary ip
==============
hostname -I | awk '{print $1}'


recovery with install cd
========================
- boot with install iso
- edit grub menu to append "systemd.unit=rescue.target" to kernel command line
- watch console, enter recovery mode


hide mounted volumn on sidebar
==============================
gsettings set org.gnome.shell.extensions.dash-to-dock show-mounts false


debian install kernel debug symbol, source
==========================================
debug symbol
- add deb-src to /etc/apt/sources.list
- sudo apt install linux-image-$(uname -r)-dbg

source
- ad deb-src to /etc/apt/sources.list
- search & install wanted linux source package
  * apt search linux-source
  * sudo apt install linux-source-version
- extract package manually
  * cd /usr/src
  * xzcat linux-source-version.tar.xz | tar xvf -


add to favorite
===============
fix issues that some app cannot pin to favorite bar
https://averagelinuxuser.com/ubuntu_custom_launcher_dock/


install package debug symbol
============================
https://documentation.ubuntu.com/server/explanation/debugging/debug-symbol-packages/