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Linux

Linux#

Bash Scripting#

AWK#

https://www.gnu.org/software/gawk/manual/gawk.html

include/source/import#

https://gist.github.com/toransahu/0a816af786b7d0b98ab1e7079bf0426f

String Comparison#

  • use = or ==
  • keep proper square spacing between operators & brackets (most imp)
  • use double quote for strings and variables
  • sometime we need to use brackets to access env variables

https://gist.github.com/toransahu/4fd3abc369bb5c8a1ee424af07cb1563

Sub-String Comparison#

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string="$(hostname)"
substr="mint"
if [ -z "${string##*$substr*}" ]; then

https://gist.github.com/toransahu/f812260a37947a299c5c26adddfa4cfa

If, elif, else, fi#

  • Source: https://ryanstutorials.net/bash-scripting-tutorial/bash-if-statements.php

Switch Case#

https://www.shellscript.sh/case.html

UNIX Commands#

mv all files/dir to a subdir#

BASH

  • https://askubuntu.com/questions/91740/how-to-move-all-files-in-current-folder-to-subfolder
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TODO: zsh

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setopt extended_glob
mv

Get System Informations#

Set deafult shell#

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sudo chsh -s /bin/zsh
then logout

In Github:linux-tweaks/guides

xclip#

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xclip -sel clip <file>

ls prefixed commands#

ls lsA lsblk lscpu lshw lsipc lslogins lsof lspcmcia lss16toppm lsusb
lsa lsattr lsb_release lsdiff lsinitramfs lslocks lsmod lspci lspgpot lss3

find#

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find <dir> <type> <test> <expression> <action>

find /Ray/ -type f -name "*.pyc" -delete

Set hostname#

1. at /etc/hosts#

127.0.1.1 mint-ThinkPad-L440

2. at /etc/hostname#

write mint-ThinkPad-L440

3. then tell the machine#

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sudo hostname mint-ThinkPad-L440

CPU Info#

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cat flags /proc/cpuinfo

CPU Temperature#

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sudo apt-get install lm-sensors
After installation type the following in terminal
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sudo sensors-detect
You may also need to run 
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sudo service kmod start
It will ask you few questions. Answer Yes for all of them. Finally to get your CPU temperature type sensors in your terminal.
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sensors

  • ifconfig
  • ip addr
  • hostname -I

ssh#

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In case of AWS EC2 SSH#

Connection freezes frequently on inactivity - source https://www.quora.com/Why-does-ssh-to-amazon-ec2-instance-gets-frozen-after-sometime - Solution - sudo vim /etc/ssh/ssh_config - add TCPKeepAlive yes - add ServerAliveInterval 5 where 5 is minute - sudo service sshd restart

sftp#

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sftp [email protected]


put local_file



get remote_file
files will upload/download @ home

sshfs#

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sudo mkdir /mnt/pi


sudo sshfs -o allow_other  [email protected]:/ /mnt/pi/

Device connected to the Network#

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nmap -sP 192.168.1.0/24

dd (Disk Dump) commands#

Create a backup#

dd if=/dev/sda of=/opt/backup_sda.img

Restore a backup#

dd if=/opt/backup_sda.img of=/dev/sda

Clone a hard disk#

dd if=/dev/sdb of=/dev/sdc

Transfer a disk image#

dd if=/dev/sdb | ssh root@target "(cat > backup.img)"

Create an iso image of a CD/DVD#

dd if=/dev/cdrom of=cdimage.iso

Burn an iso image of a CD/DVD#

dd if=cdimage.iso of=/dev/cdrom obs=32k seek=0

Rescue a file that contains bad blocks#

dd if=movie.avi of=rescued_movie.avi conv=noerror

Create your own bootloader#

dd conv=notrunc if=bootloader of=qemu.img

Create a backup of your MBR#

dd if=/dev/sdb of=mbr_backup bs=512 count=1

Restore a backup of your MBR#

dd if=mbr_backup of=/dev/sdb bs=512 count=1

Mount dd image of and entire disk#

You must use the start number of the partition. fdisk -u -l disk_image

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Disk /mnt/storage/disk_image: 0 MB, 0 bytes255 heads, 63 sectors/track, 0 cylinders, total 0 sectors
Units = sectors of 1 * 512 = 512 bytesDisk identifier: 0x41172ba5

Device                      Boot    Start    End       Blocks   Id  System
/mnt/storage/disk_image1            63       64259     32098+   de  Dell Utility
/mnt/storage/disk_image2    *       64260    78108029  39021885 7   HPFS/NTFS

Partition 2 has different physical/logical endings:phys=(1023, 254, 63) logical=(4861, 254, 63)

Then take the start of the partition that you want to edit, 64260 (disk_image2) in this case, and multiply it by 512

Ex: 512 * 64260 = 32901120

mount -o loop,offset=32901120 -t auto /mnt/storage/disk_image /mnt/image_partition_2

When the hard disk has errors#

Get the dd_rescue tool dd_rescue /dev/sdb /opt/backup_sdb.img

Network Clone#

  • Destination: nc -l -p 2222 | dd of=/dev/sda bs=16M

  • Source: dd if=/dev/sda bs=16M | nc Destination 2222

Network speed test#

dd if=/dev/zero bs=1M count=100 | ssh user@machine 'cat > /dev/null'

  • Symbolic link ln -s original link

  • Hard Link ln original link

Task Autorun/Automation#

  • src1 : https://developer.toradex.com/knowledge-base/how-to-autorun-application-at-the-start-up-in-linux

Daemons#

Shells#

Graphical#

Cron Jobs#

Intro#

The cron service (daemon) runs in the background and constantly checks the /etc/crontab file, and /etc/cron.*/ directories. It also checks the /var/spool/cron/ directory.

Source

  • create cron job
    • crontab -e and edit the opened file
      • add your task (in cron format)
    • or, create a new cron job under /etc/cron.*/
      • add your task (in cron format)
Syntax#
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SHELL=/bin/bash
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
MAILTO=""
1 2 3 4 5 /path/to/command arg1 arg2
# or  
1 2 3 4 5 /root/backup.sh`

  • to automate tasks based on time like

    • on boot: @reboot
    • hourly: @hourly or “0 * * * *”
    • daily : @daily or @midnight or “0 0 * * *”
    • weekly: @weekly or “0 0 * * 0”
    • monthly: @monthly or “0 0 1 * *”

    • yearly: @yearly or @annually or “0 0 1 1 *”

            • command to be executed

    | | | | |
    | | | | ----- Day of week (0 - 7) (Sunday=0 or 7)
    | | | ------- Month (1 - 12)
    | | --------- Day of month (1 - 31)
    | ----------- Hour (0 - 23)
    ------------- Minute (0 - 59)

Operations#
  • start: sudo service cron start
  • stop: sudo service cron stop
  • restart: sudo service cron restart
  • status: sudo service cron status
  • list: crontab -l or crontab -u USERNAME -l
  • delete all: crontab -r or crontab -u USERNAME -r
Type#
  • System Level
    • need to define USERNAME
    • 1 2 3 4 5 USERNAME /path/to/command arg1 arg2
  • User Level
    • by default takes USERNAME of creator
    • 1 2 3 4 5 /path/to/command arg1 arg2
Operators#
  • asterisk (*)
    • every [minute/hour/day/month/day of week]
  • comma (,)
    • list of values
    • like, on this days: 1,2,3,4,5
  • dash (-)
    • range
    • like, on this days: 1-5
  • seperator (/)
    • stepper
    • like, */2 in hour field means: every 2 hours
misc#
  • print names of all valid files: run-parts --list /etc/cron.d
  • print script names which would run, but don't run them: run-parts --test /etc/cron.d

Services#

.desktop file#

  • Works on boot
  • put .desktop file with some script in ~/.config/autostart/
  • write script like 
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    [Desktop Entry]
Type=Application
Exec=sh /home/toran/Applications/linux_tweaks/LowBatterySound/LowBattery.sh
X-GNOME-Autostart-enabled=false
NoDisplay=false
Hidden=false
Name[en_IN]=Low Battery Warning
Comment[en_IN]=Warning sound on battery less than 15%
X-GNOME-Autostart-Delay=20

using /etc/rc.local#

using /etc/init.d#

fdisk#

  • manupulate disk partition table
  • list devices: sudo fdisk -l

lsblk#

  • lists block devices

blkid#

  • locate/ print block device attributes

df#

  • reports filesystem disk space usage

du#

  • estimate file space usage
    • Summarize disk usage of the set of FILEs, recursively for directories.

GRUB#

Edit grub configs#

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vim /etc/default/grub

grub update#

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sudo update-grub

Reboot into other OS#

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sudo grub-reboot 2

Problems & Solutions#

Make Anaconda Python Default#

  • put following in .bashrc or .zshrc 
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export PATH="/home/toran/anaconda3/bin:$PATH"

If cinnamon freezes#

  • go to tty0 or tty1 using Alt + Ctrl + F1 or F2
  • login
  • type w and enter
  • look under FROM column, where row is related to cinnamon session
  • note the value for that cell, in my case its :0 (with colon)
  • note type export DISPLAY=:0 cinnamon & and enter

sudo: unable to resolve host Ray: Connection timed out#

  • Two things to check (assuming your machine is called my-machine, you can change this as appropriate):
  • That the /etc/hostname file contains just the name of the machine.
  • That /etc/hosts has an entry for localhost. It should have something like:

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 127.0.0.1    localhost.localdomain localhost
 127.0.1.1    my-machine
- If either of these files aren't correct (since you can't sudo), you may have to reboot the machine into recovery mode and make the modifications, then reboot to your usual environment.

nemo context menu "open in terminal" not working#

source: https://forums.linuxmint.com/viewtopic.php?t=204933

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gsettings set org.cinnamon.desktop.default-applications.terminal exec mate-terminal

Speedup mouse scroll#

Source: https://forums.linuxmint.com/viewtopic.php?t=221526 

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sudo apt install imwheel
then use mousewheel.sh to adjust the speed.

Utilities#

Multitouch Gesture#

  • src: https://github.com/toransahu/libinput-gestures - by bulletmark
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sudo gpasswd -a toran input
sudo apt-get install xdotool wmctrl libinput-tools
git clone http://github.com/toransahu/libinput-gestures
cd libinput-gestures
sudo ./libinput-gestures-setup install

cd ~/libinput-gestures

#edit the created libinput-gestures.conf:

vim libinput-gestures.conf

#set following:

gesture swipe down  xdotool key ctrl+alt+Up
gesture swipe up    xdotool key ctrl+alt+Down
gesture swipe right xdotool key ctrl+super+Left
gesture swipe left  xdotool key ctrl+super+Right

sudo make install (or sudo ./libinput-gestures-setup install)

libinput-gestures-setup autostart
libinput-gestures-setup start

Battery Monitor#

  • Source: http://battery-monitor.maateen.me/

Battery Optimization#

SATA Power Management#

  • source: https://askubuntu.com/questions/809127/how-to-turn-off-one-of-sata-hdds-installed-in-the-computer-to-save-power

  • Using hdparm utility.

    • It allows you to control your hard drives' power settings, apart from benchmarking and other stuff.

  • put the disk into standby mode

    • whenever you access the disk, it should automatically wake up and work back again 
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      hdparm -y /dev/sdX

  • deeper resting mode

    • may need to restart your computer in order to make the HDD work again 
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      hdparm -Y /dev/sdX

PowerTop by Intel (Recommanded)#

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sudo apt-get update
sudo apt-get install powertop
sudo powertop --auto-tune
sudo powertop --calibrate

TLP (Emergency)#

  • Source: https://linrunner.de/en/tlp/docs/tlp-linux-advanced-power-management.html
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sudo apt install tlp

#restart

#or
sudo tlp start

Mono#

Install#

https://www.mono-project.com/download/stable/#download-lin

Verify#

Source: https://www.mono-project.com/docs/getting-started/mono-basics/ Scripts:

Thinkpad Touchpad Middle Button#

Install#

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sudo apt install xserver-xorg-input-libinput

Config#

  • restart
  • alter touchpad setting and choose use multiple fingers in click actions

Finger Print Reader#

  • src: https://launchpad.net/~fingerprint/+archive/ubuntu/fingerprint-gui

Installation#

  1. First of all, if you have installed Fingerprint GUI manually before, get rid of it completely. Remove all binaries, shared libraries, any other files and undo all the changes you have made to your system config files (especially to files under /etc/pam.d/).

  2. Add this PPA to your sources: 

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        sudo add-apt-repository ppa:fingerprint/fingerprint-gui
    sudo apt-get update

  3. Install the packages: 

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  4. Log out of your session and log back in (we need the new session defaults to be picked up).

Uninstallation#

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    sudo apt-get remove fingerprint-gui

ZSH#

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sudo apt install zsh

oh-my-zsh#

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sh -c "$(curl -fsSL https://raw.githubusercontent.com/robbyrussell/oh-my-zsh/master/tools/install.sh)"

#OR

sh -c "$(wget https://raw.githubusercontent.com/robbyrussell/oh-my-zsh/master/tools/install.sh -O -)"

VIM#

Vundle#

  • VIM plugin manager (VIM + Bundle)
  • install from : https://github.com/VundleVim/Vundle.vim
  • i.e. git clone https://github.com/VundleVim/Vundle.vim.git ~/.vim/bundle/Vundle.vim
Using Vundle#
  • Mention bundle names (as a github repo) in .vimrc file
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Plugin 'VundleVim/Vundle.vim'
Plugin 'morhetz/gruvbox'
Plugin 'itchyny/lightline.vim'
Plugin 'itchyny/vim-gitbranch'
Plugin 'scrooloose/nerdtree.git'
Plugin 'aperezdc/vim-template'
Plugin 'davidhalter/jedi-vim'
Plugin 'editorconfig/editorconfig-vim'
Plugin 'tpope/vim-abolish'
  • Install using command
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:PluginInstall

VIM as Python IDE#

Source: http://chrisstrelioff.ws/sandbox/2016/09/21/vim_and_vundle_on_ubuntu_16_04.html

  • ~/.vimrc & ~/.editorconfig config files @ https://gist.github.com/toransahu/66c69903649f3d417d8ba4dc78324f60

  • cheat sheet: https://gist.github.com/toransahu/4a921c6fb73274479dbdfbcfe6dda483

Tmux#

Tmux Package Manager#

Source: https://github.com/tmux-plugins/tpm

~/.tmux.conf : https://gist.github.com/toransahu/53a523d973a212f52ce53474417e01b1

Tmux Plugins:#

  • Sidebar: https://tmuxcheatsheet.com/tmux-plugins-tools/?full_name=tmux-plugins%2Ftmux-sidebar

Commands#

  • abbr.

    • prefix: ctrl + b

  • help: ctrl + b ?

  • select, copy, paste within tmux

    • enter scroll mode: ctrl + b [
    • enter select mode: ctrl + space
    • move cursor to select text
    • copy to tmux buffer: alt + w
    • copy to system clip: ctrl + b - y
    • paste to any tmux: ctrl + b ]

  • create/split pane

    • vertical split: prefix %
    • hor split: prefix "

  • convert a pane to window: prefix !

  • move to pane: prefix arrows

  • close current pane: prefix x

Load .bashrc with tmux#

By default tmux runs a login shell. When bash is invoked as an interactive login shell, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile. So you have to put source ~/.bashrc in one of those files.

Another way to solve this issue is to put in your file .tmux.conf the line:

set-option -g default-shell "/bin/bash"

KeyBoard Custom Shortcuts Bindings#

Emulate right click from keyboard#

  • install xdotool 

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    sudo apt install xdotool

  • bind keyboard shortcut with command: xdotool click 3

Backup & Restore Cinnamon settings#

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sudo apt install dconf-cli

#backup
dconf dump /org/cinnamon/ > cinnamon_backup

#restore
dconf load /org/cinnamon/ < cinnamon_backup


#reset to default
dconf reset -f /org/cinnamon/

Raspberry Pi#

OS#

Raspbian with RPD Desktop#

  • prepare https://www.raspberrypi.org/forums/viewtopic.php?t=135316

Raspbian Lite (without GUI)#

Install Desktop for Lite#

Source: https://www.raspberrypi.org/forums/viewtopic.php?t=133691

Enable ssh & enter SSID/WiFi details without keyboard#

Source: https://medium.com/@danidudas/install-raspbian-jessie-lite-and-setup-wi-fi-without-access-to-command-line-or-using-the-network-97f065af722e

Ubuntu Core/Snap#

Windows IoT#

Display#

Touch Screeen Config#

  • 5 inch capacitive 800*480

/boot/config.txt 

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framebuffer_width=800
framebuffer_height=480
hdmi_force_hotplug=1
hdmi_group=2
hdmi_mode=87
hdmi_cvt 800 480 60 6 0 0 0

Backup Image from Burnt Image#

On a different linux PC using USB.#

  • It won't work on the raspi!, it will get trapped in infinit loop
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#list disk
sudo fdisk -l

#backup SD card
sudo dd bs=4M if=/dev/sdb | gzip > /home/your_username/image`date +%d%m%y`.gz

#restore the backup on SD card
sudo gzip -dc /home/your_username/image.gz | dd bs=4M of=/dev/sdb

In Raspberry Itself using rsync#

Network Drive Mount (sshfs)#

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#Install SSHFS

sudo apt-get install sshfs

#First, create a directory on your host computer:

mkdir pi

#Then mount the Raspberry Pi's filesystem to this location:

sudo sshfs -o allow_other [email protected]:/ pi

#Now enter this directory as if it is a regular folder; you should be able to see and access the contents of the Raspberry Pi:

cd pi/
ls

Remote Audio#

bluetooth#

Way 1#
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sudo apt-get install bluetooth  blueman bluez python-gobject python-gobject-2 pulseaudio-module-bluetooth

sudo systemctl status bluetooth
pulseaudio --start
  • https://gist.github.com/mill1000/74c7473ee3b4a5b13f6325e9994ff84c
  • https://raspberrypi.stackexchange.com/questions/48140/raspberry-pi-3-connecting-to-bluetooth-audio-device-on-raspbian-jessie
  • https://markus.jarvisalo.dy.fi/2017/12/making-the-raspberry-pi-3-a-bluetooth-audio-receiver/
Way 2#
  • https://www.instructables.com/id/Turn-your-Raspberry-Pi-into-a-Portable-Bluetooth-A/ 
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wifi#

  • shareport
  • https://thepi.io/how-to-set-up-a-raspberry-pi-airplay-receiver/

enable ssh from card#

  • put empty ssh file inside /boot/

set wifi/ssid from card#

  • change inside /etc/network/interface
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    auto lo

    iface lo inet loopback
    iface eth0 inet dhcp

    allow-hotplug wlan0
    auto wlan0


    iface wlan0 inet dhcp
            wpa-ssid "Connecting..."
            wpa-psk "PrideValencia_A704"

wifi to ethernet#

src: https://www.instructables.com/id/Share-WiFi-With-Ethernet-Port-on-a-Raspberry-Pi/

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sudo apt install dnsmasq -y
cd
wget https://raw.githubusercontent.com/arpitjindal97/raspbian-recipes/master/wifi-to-eth-route.sh
chmod +x ~/wifi-to-eth-route.sh
sudo crontab -e
@reboot bash /home/pi/wifi-to-eth-route.sh &  # add it to crontab file