Display brightness level in i3status bar

I’ve been using Linux for a long time, but I was never entirely happy with the desktop environment options available. Until last year, Xfce was the closest to what I consider a good compromise between features and performance. Then I found i3, an amazing piece of software that changed my life.

i3 is a tiling window manager. The goal of a window manager is to control the appearance and placement of windows in a windowing system. Window managers are often used as part a full-featured desktop environment (such as GNOME or Xfce), but some can also be used as standalone applications.

i3status don’t have an option to display brightness level by default. But by tweaking some configuration we can easily achieve this.

Follow this method

  1. copy the script to /usr/local/bin

net-speed-and-brightness.sh

#!/bin/sh

# Authors:
# - Moritz Warning <[email protected]> (2016)
# - Zhong Jianxin <[email protected]> (2014)
# - Akhil Jalagam <[email protected]> (2019)
#
# See file LICENSE at the project root directory for license information.
#
# i3status.conf should contain:
# general {
#   output_format = i3bar
# }
#
# i3 config looks like this:
# bar {
#   status_command exec /usr/share/doc/i3status/contrib/net-speed.sh
# }
#
# Single interface:
# ifaces="eth0"
#
# Multiple interfaces:
# ifaces="eth0 wlan0"
#

# Auto detect interfaces
#ifaces=$(ls /sys/class/net | grep -E '^(eth|wlan|enp|wlp)')
ifaces="enp2s0 wlp3s0"

last_time=0
last_rx=0
last_tx=0
rate=""

readable() {
  local bytes=$1
  local kib=$(( bytes >> 10 ))
  if [ $kib -lt 0 ]; then
    echo "? K"
  elif [ $kib -gt 1024 ]; then
    local mib_int=$(( kib >> 10 ))
    local mib_dec=$(( kib % 1024 * 976 / 10000 ))
    if [ "$mib_dec" -lt 10 ]; then
      mib_dec="0${mib_dec}"
    fi
    echo "${mib_int}.${mib_dec} M"
  else
    echo "${kib} K"
  fi
}

update_rate() {
  local time=$(date +%s)
  local rx=0 tx=0 tmp_rx tmp_tx

  for iface in $ifaces; do
    read tmp_rx < "/sys/class/net/${iface}/statistics/rx_bytes"
    read tmp_tx < "/sys/class/net/${iface}/statistics/tx_bytes"
    rx=$(( rx + tmp_rx ))
    tx=$(( tx + tmp_tx ))
  done

  local interval=$(( $time - $last_time ))
  if [ $interval -gt 0 ]; then
    rate="$(readable $(( (rx - last_rx) / interval )))↓ $(readable $(( (tx - last_tx) / interval )))↑"
  else
    rate=""
  fi
  # show brightness
  brightness=$(cat /sys/class/backlight/intel_backlight/brightness)

  last_time=$time
  last_rx=$rx
  last_tx=$tx
}

i3status | (read line && echo "$line" && read line && echo "$line" && read line && echo "$line" && update_rate && while :
do
  read line
  update_rate
  echo ",[{\"full_text\":\"${rate} | Sun: $(($brightness/75))% \" },${line#,\[}" || exit 1
done)

In the above script you can change /sys/class/backlight/intel_backlight/brightness based on your backlight model.

2. update i3 config with the following

# control brightness
bindsym XF86MonBrightnessUp exec intelbacklight -inc 500 # increase screen brightness
bindsym XF86MonBrightnessDown exec intelbacklight -dec 500 # decrease screen brightness

# status bar
bar {
        status_command  /usr/local/bin/net-speed-and-brightness.sh
}

Now reload the i3 config using Mod+Shift+r

Finally, you will see the net speed and brightness in status bar

If you don’t want to see net speed just remove {rate} from the echo command in above script

storing multiple users and hosts in .my.cnf(MySQL)

When you run MySQL commands MySQL, mysqlcheck, mysqdump and psql, psqldump, etc; they will pick username & password from this file if you do not provide them as argument (-u and -p). It can save you time.

Of course, if you specify username and password explicitly as part of the command’s arguments, they will be used.

.my.cnf ( for MySQL client )

[clienthost1]   # Note: client + host1
user=myuser
password=mypass
database=dbname
host=server.location.com

Quick Install latest git from source

git-install-latest-from-src.sh

wget https://github.com/git/git/archive/master.zip
unzip master.zip && rm master.zip
cd master
make configure
./configure --prefix=/usr
make install

PHP 7 Installation in CentOS 7

PHP installation script

yum install -y http://rpms.remirepo.net/enterprise/remi-release-7.rpm
yum install -y yum-utils
# yum-config-manager --enable remi-php70
# yum-config-manager --enable remi-php71
# yum-config-manager --enable remi-php72
yum-config-manager --enable remi-php73
yum -y install php # php-mcrypt php-cli php-gd php-curl php-mysql php-ldap php-zip php-fileinfo 
php -v

storing multiple users and hosts in .pgpass(psql)

When you run MySQL commands MySQL, mysqlcheck, mysqdump and psql, psqldump etc; they will pick username & password from this file if you do not provide them as argument (-u and -p). It can save you time.

Of course, if you specify username and password explicitly as part of the command’s arguments, they will be used.

.pgpass ( for psql client )

test.net:5432:testdb:testuser:testpass
test1.net:5432:testdb1:testuser1:testpass1
test2.net:5432:testdb2:testuser2:testpass2

Exploring the Logrotate Configuration

Logrotate is a system utility that manages the automatic rotation and compression of log files. If log files were not rotated, compressed, and periodically pruned, they could eventually consume all available disk space on a system.

Logrotate’s configuration information can generally be found in two places:

/etc/logrotate.conf: this file contains some default settings and sets up the rotation for a few logs that are not owned by any system packages. It also uses an include statement to pull in configuration from any file in the /etc/logrotate.d directory.

/etc/logrotate.d/: this is where any packages you install that need help with log rotation will place their Logrotate configuration. On a standard install, you should already have files here for basic system tools like apt, dpkg, rsyslog and so on.

Example

/var/log/apt/history.log {
  rotate 12
  monthly
  compress
  missingok
  notifempty
  create 0640 www-data www-data
  sharedscripts
  postrotate
      systemctl reload example-app
  endscript
}

Explanation:

  • rotate 12: keep twelve old log files.
  • monthly: rotate once a month.
  • compress: compress the rotated files. this uses gzip by default and results in files ending in .gz. The compression command can be changed using the compresscmd option.
  • missingok: don’t write an error message if the log file is missing.
  • notifempty: don’t rotate the log file if it is empty.
  • create 0640 www-data www-data: this creates a new empty log file after rotation, with the specified permissions (0640), owner (www-data), and group (also www-data).
  • sharedscripts: this flag means that any scripts added to the configuration are run only once per run, instead of for each file rotated. Since this configuration would match two log files in the example-app directory, the script specified in postrotate would run twice without this option.
  • postrotate to endscript: this block contains a script to run after the log file is rotated. In this case we’re reloading our example app. This is sometimes necessary to get your application to switch over to the newly created log file. Note that postrotate runs before logs are compressed. Compression could take a long time, and your software should switch to the new logfile immediately. For tasks that need to run after logs are compressed, use the lastaction block instead.

MySQL – install, configure, create user and database with permissions

MySQL is an open-source relational database management system. Its name is a combination of “My”, the name of co-founder Michael Widenius’s daughter, and “SQL”, the abbreviation for Structured Query Language.

Download and Install MySQL from the following link

https://dev.mysql.com/downloads/

rpm -ih mysql80-community-release-el7-3.noarch.rpm
yum update -y
yum install -y mysql-server

Configure

systemctl enable mysqld
systemctl start mysqld
mysql_secure_installation
# default password
grep -oP 'temporary password(.*): \K(\S+)' /var/log/mysqld.log

Create user and database with permissions

mysql -u root -p
# mysql > 
CREATE DATABASE dbname;
CREATE USER 'myuser'@'localhost' IDENTIFIED BY 'mypass';
GRANT ALL PRIVILEGES ON dbname.* TO 'myuser'@'%';
FLUSH PRIVILEGES;

Starting with MySQL 8 you no longer can (implicitly) create a user using the GRANT command. Use CREATE USER instead, followed by the GRANT statement:

CREATE USER 'root'@'%' IDENTIFIED BY 'root';
GRANT ALL PRIVILEGES ON . TO 'root'@'%' WITH GRANT OPTION;

Postgresql – install, configure, create user and database with permissions

postgresql

PostgreSQL: The World’s Most Advanced Open Source Relational Database

PostgreSQL is arguably the most advance and powerful opensource enterprise class relational database system. It is the object relational database system and provides the most standard compliant system for the Database designers. It provides the complete support for reliable transactions that is (ACID complaint) where ACID stands for Atomicity, Consistency, Isolation and Durability.

Its advance underlying technology makes it extremely powerful and programmable. Support for concurrency is one of its key feature. It is one of the most important technology you will learn and will greatly affect the way you work with Databases. It is the ultimate RDBM system which will allow you to create complex web apps which works flawlessly even for very large number of users.

1. Download and Install Postgresql from the following link

https://www.postgresql.org/download/

2. Configure

service postgresql initdb
systemctl enable postgresql
systemctl start postgresql

Edit the file /etc/postgresql/8.4/main/pg_hba.conf and replace ident or peer by either md5 or trust, depending on whether you want it to ask for a password on your own computer or not. Then reload the configuration file with:

/etc/init.d/postgresql reload

pg_hba.conf

local   all             all                                     peer
# IPv4 local connections:
host    all             all             127.0.0.1/32            password  
# IPv6 local connections:
host    all             all             ::1/128                 password

3. Create user and database with permissions

sudo -u postgres psql
postgres=# create database mydb;
postgres=# create user myuser with encrypted password 'mypass';
postgres=# grant all privileges on database mydb to myuser;

Grub repair on a dual boot with Windows

Grub 2 typically gets overridden when you install Windows or another Operating System. To make Ubuntu control the boot process, you need Reinstall (Repair/Restore) Grub using a Linux Live CD.

ROOT_DISK='/dev/sda2'
BOOT_DISK='/dev/sda1' # optional
DISK='/dev/sda'

mount $ROOT_DISK /mnt
mount $BOOT_DISK /mnt/boot/efi # optional

for i in /dev /dev/pts /proc /sys /sys/firmware/efi/efivars /run; do sudo mount -B $i /mnt$i; done

chroot /mnt
grub-install $DISK
update-grub

# don't forget to update UUID in /mnt/etc/fstab using blkid