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linux

List of Contents:

Useful Commands

chroot

Opens a new TTY on given root directory.

dialog

You can create UI dialogs with it on command-line easily. For example;

usernameDialog () {
    username=$(dialog --stdout \
                      --title "Creating Users" \
                      --backtitle "Happy Hacking Linux" \
                      --ok-label "Done" \
                      --nocancel \
                      --inputbox "Choose your username" 8 50)
}

fc-list

Lists fonts available in the system.

fc-list | grep Monaco

nl

Adds line numbers to beginning of each line.

cat foobar.txt | nl

powertop

Lists processes by their energy consume.

yes

Approve all confirmations

yes | pacman -S yolo

du

Checks size of a folder.

du -sh /

ncdu

Disk usage analyzer with CLI UI with ncurses.

expac

Data extraction tool for ALPM (Arch Linux Package Management).

To list packages by their size;

expac "%n %m" -l'\n' -Q $(pacman -Qq) | sort -rhk 2 | less
yes | pacman -S yolo

ip

List network interfaces in the system:

ip link show

Manage routing tables:

ip r

pkill

Kill a process partially matching given pattern;

pkill -f pattern

sed

Uncomment matching line:

sed -i -e '/^#en_US/s/^#//' /etc/locale.

Slugify a string:

sed -e 's/[^[:alnum:]]/-/g' | tr -s '-' | tr A-Z a-z

awk

Select particular columns and print out;

lsblk | awk '{print $1,$4}'
# sda 8GB

file

Returns file info. It's especially useful on images;

file logo.png
# PNG image data, 16 x 16, 8-bit/color RGBA, non-interlaced

date

Get unix timestamp:

date +%s

Get date & time nicely formatted;

date '+%d %h %H:%M'
# 22 Jun 01:42

Tmux

On command-line:

  • tmux a -t [name] Open a session
  • tmux ls List available sessions

On session:

  • C-z $ Rename session
  • C-z d Detach session

Windows

  • S-[left] Select the next window
  • S-[right] Select the previous window
  • C-[left] Move window to left
  • C-[right] Move window to right
  • C-z c Open new window
  • C-z x Close current window
  • C-z C-z Open last window
  • C-z :swap-window -t -1 Move current window to left
  • C-z , Rename window
  • C-z n Next window
  • C-z p Previous window

Status Bar

  • C-z b Toggle status bar

Other

  • C-z :source-file ~/.tmux.conf Reload config

htop

Interactive process viewer. Useful keybindings:

  • / Search
  • \ Filter
  • , Choose the sorting criteria
  • k Send kill signal to selected process
  • u Filter results by user
  • t Open/close tree mode
  • - or + Collapse/uncollapse process trees
  • H Turn off displaying threads

iotop

Sorts processes by disk writes, and show how much and how frequently programs are writing to the disk.

nethogs

htop for network. lists processes by their network traffic.

systemctl

Use systemctl command to control the services. Example;

systemctl restart slim.service

Some useful systemctl commands:

  • start
  • stop
  • restart
  • reload
  • status
  • is-enabled
  • enable
  • disable
  • mask
  • unmask
  • list-units

Restart systemd scanning for new or changed units;

systemctl daemon-reload

Toggle a service with one-liner:

if [[  "`systemctl is-active NetworkManager`" != "active" ]]; then sudo systemctl start NetworkManager; else sudo systemctl stop NetworkManager; fi

See which units are failing;

systemctl list-units --state=failed

See logs of a specific unit;

sudo journalctl -xu dhcpcd@enp0s3.service --since today

systemd-analyze

Analysize the boot time:

$ systemd-analyze

List the started unit files, sorted by the time each of them took to start up:

$ systemd-analyze blame

See boot units as chain:

$ systemd-analyze critical-chain

tee

It's used for splitting the output of a program so we can both display it and also save it.

For example, add a new entry to hosts file;

echo "127.0.0.1 foobar" | sudo tee -a /etc/hosts

find

List files by extension;

find . -type f -name *.strings

Using -or:

find . -type f \( -name "*.strings" -or -name "*.txt" \)

Executing a command per file;

find . -type f -name *.strings -exec sed -i '' -e "s/foo/bar/" {} \;

tree

Lists contents of a directory in tree-like format.

tree

Show hidden files:

tree -a

Show only directories:

tree -d

xev

Creates a window and lets you see the keyboard events. Useful when you modify keybindings.

setxkbmap

Sets the keyboard layout:

setxkbmap tr -variant alt -option lv3:ralt

pidof

Find process id of a running program:

pidof nginx

It might return multiple pids (e.g nginx have worker processes). Specify -s parameter to get only one pid:

pidof -s nginx

Networking

Get the name of the actively used network interfaces

route | grep '^default' | grep -o '[^ ]*$'

Get Internal IP Address:

ifconfig | grep -Eo 'inet (addr:)?([0-9]*\.){3}[0-9]*' | grep -Eo '([0-9]*\.){3}[0-9]*' | grep -v '127.0.0.1'

Get Sent/Received Bytes

cat /sys/class/net/eth0/statistics/rx_bytes
cat /sys/class/net/eth0/statistics/rx_packets
cat /sys/class/net/eth0/statistics/tx_packets
cat /sys/class/net/eth0/statistics/tx_bytes

Check If You're Online

ping -q -w 1 -c 1 $gateway> /dev/null && echo 1 || echo 0

Get Gateway IP

ip r | grep default | cut -d ' ' -f 3

Mount Swap Partition

Create a Swap partition using partitioning tools like cfdisk or parted. Then format the partition as swap;

$ mkswap /dev/sdXY

Enable it;

$ swapon /dev/sdXY

Get UUID of the partition:

$ sudo blkid /dev/sdXY

And add following line into /etc/fstab

UUID=? none   swap    sw      0       0

List swap devices and their sizes:

$ swapon -s

See which swap devices are being used:

$ cat /proc/swaps

See total, used and free swap space:

$ cat /proc/meminfo | grep Swap

Or:

$ cat /proc/swaps

Swapiness

The swappiness sysctl parameter represents the kernel's preference (or avoidance) of swap space. Swappiness can have a value between 0 and 100, the default value is 60. A low value causes the kernel to avoid swapping, a higher value causes the kernel to try to use swap space. Using a low value on sufficient memory is known to improve responsiveness on many systems. To check the current swappiness value:

$ cat /proc/sys/vm/swappiness

To temporarily set the swappiness value:

$ sysctl vm.swappiness=10

To set the swappiness value permanently, edit a sysctl configuration file:

echo "vm.swappiness=10" > /etc/sysctl.d/99-sysctl.conf

Irssi

  • Auto-connect to a network: /server ADD -auto -network NetworkName irc.host.com 6667
  • Auto-join to channels: /channel ADD -auto #channel NetworkName password
  • Switch to a window: M-[number] use letters when for windows beyond 9: M-[q|w|e|r|t|y]
  • Close window: /wc
  • Save config: /save
  • Load a script: /script load awm
  • Set theme: /set theme weed

Xmonad

  • After making a change hit xmonad --recompile to check errors, then mod+r to reload the config.

How to submit a package to AUR ?

Arch Linux Installation

Download ISO and create a bootable USB stick;

In Linux:

dd bs=4M if=/path/to/archlinux.iso of=/dev/sdx status=progress && sync

In OSX:

sudo dd if=path/to/arch.iso of=/dev/rdiskX bs=1m

After booting the USB, follow these steps;

  • Create Partitions
  • Make sure boot (/mnt/boot) & root (/mnt) mounted.
  • Run pacstrap to install the base: pacstrap /mnt
  • Update FS Tab: genfstab -U /mnt >> /mnt/etc/fstab
  • Switch to the new root: arch-chroot /mnt
  • Install GRUB
  • Localize:
    • Select timezone
    • Generate /etc/adjtime: hwclock --systohc
    • Uncomment en_US lines in /etc/locale.gen: sed -i -e '/^#en_US/s/^#//' /etc/locale.gen
    • Generate locales with locale-gen
    • echo "LANG=en_US.UTF-8" >> /etc/locale.conf
    • echo "FONT=Lat2-Terminus16" >> /etc/vconsole.conf
  • Create users
  • Done

Partitioning

  • Command-line tools: parted, fdisk, cfdisk (with UI)
  • List disks and partitions by fdisk -l or lsblk
  • The simple and popular layout is boot & root;
parted /dev/sda --script mklabel msdos \
    mkpart primary ext4 1MiB 512MiB \
    set 1 boot on \
    mkpart primary ext4 512MiB 100%
  • Don't forget formatting them as ext4: yes | mkfs.ext4 /dev/sda1

Creating Users

This bash function I wrote for happy-hacker-linux installer shows the steps of creating a user.

createUser () {
    useradd -m -s /usr/bin/zsh $1
    echo "$1:$2" | chpasswd

    echo "$1 ALL=(ALL) NOPASSWD: ALL" >> /etc/sudoers
    echo $1 > /etc/hostname
    echo "127.0.1.1	$1.localdomain	$1" >> /etc/hosts
}

Timezones

View your time info:

timedatectl

List all regions:

find /usr/share/zoneinfo/. -maxdepth 1 -type d | cut -d "/" -f6 | sed '/^$/d'

Or, select your timezone interactively:

tzselect

Then set your timezone:

timedatectl set-timezone Asia/Makassar

date

Print current date formatted:

date '+%d %h %H:%M'

Set current date:

date --set="23 June 1988 10:00:00"

Or time:

date --set="10:00:00"

Building Custom Arch ISO

Step 1: Create Chroot Base System

$ pacman -S devtools git make --needed
$ mkarchroot /tmp/chroot base
$ git clone git://projects.archlinux.org/archiso.git
$ make -C archiso/archiso DESTDIR=/tmp/chroot install
$ arch-chroot /tmp/chroot

Step 2: Customize

mknod /dev/loop0 b 7 0
echo 'Server = http://ftp.osuosl.org/pub/archlinux/$repo/os/x86_64' >> /etc/pacman.d/mirrorlist
pacman -S devtools libisoburn squashfs-tools

And install necessary packages.

Step 3: Build The ISO

cp -r /usr/share/archiso/configs/baseline /tmp
cd /tmp/baseline
./build.sh
exit

Now, you will be out of your chroot, with the built ISO at the file path of:

/tmp/chroot/tmp/baseline/out/<iso>