Linux df command line brief examples

df is a Linux command for for reporting file system disk usage on a Linux system. While brewing coffee at home I found the following.

How to view disk usage using df command? Simple!

Simplest way is just to type df on the command line and you should get the below output:

 Filesystem     1K-blocks    Used Available Use% Mounted on
 overlay         61252420 9817828  48293424  17% /
 tmpfs              65536       0     65536   0% /dev
 tmpfs            1023564       0   1023564   0% /sys/fs/cgroup
 shm                65536       0     65536   0% /dev/shm
 /dev/sda1       61252420 9817828  48293424  17% /etc/hosts
 tmpfs            1023564       0   1023564   0% /proc/acpi
 tmpfs            1023564       0   1023564   0% /sys/firmware 

Columns explanation:

  • Filesystem – the filesystem on the machine
  • 1K-blocks – the size of the filesystem in 1K blocks
  • Used – the amount of space used in 1K blocks
  • Available – the amount of available space in 1K blocks
  • Use% – the percentage that the filesystem is in use.
  • Mounted on – where the filesystem is mounted.

Using the Linux df command ff you like to view the output in human readable use df -H

To show the filesystem type use df -T

To show only specific file system types use df -t ext4 as an example.

Runlevels Linux Learn more simple table

Hola! Each runlevel has a certain number of services stopped or started, giving the user control over the behavior of the machine. Conventionally, seven runlevels exist, numbered from zero to six. While brewing coffee at home I found the difference between runlevels in Linux. See below.

0HaltShuts down the system.
1Single-user modeDoes not configure network interfaces, start daemons or allow non-root logins.
2Multi-user modeDoes not configure network interfaces or start daemons.
3Multi-user mode with NetworkingStarts the system normally.
4UndefinedNot used.
5X11 (GUI)As runlevel 3 plus display manager.
6RebootReboots the system.

Default Apache virtual host file in Ubuntu

I was asked the other day ‘How does the default Apache virtual host file looks like?’ I was having my Peruvian coffee and decided to place below the default Apache virtual host file in this post for any future reference.

<VirtualHost *:80>
    ServerAdmin webmaster@localhost
    DocumentRoot /var/www/html
    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined

Super simple. Enjoy and remember to keep coding with coffee!

Linux File Systems ext2, ext3 and ext4

While having coffee at home I decided to put this table together regarding Linux File Systems and their differences. Let me know if I’m missing something.

Stands for Second Extended file system.Stands for Third Extended file system.Stands for Fourth Extended file system.
Introduced in 1993.Introduced in 2001.Introduced in 2008.
This was developed to overcome the
limitation of the original ext file
Starting from Kernel 2.4.15 ext3 was available.Starting from Kernel 2.6.19 ext4 was available.
Does NOT have journaling feature.Allows journaling.Supports huge individual file size and overall file system size.
Maximum individual file size can be from 16GB to 2TB.Maximum individual file size can be from 16GB to 2TB.Maximum individual file size can be from 16 GB to 16 TB.
Overall ext2 file system size can be
from 2TB to 32TB.
Overall ext2 file system size can be
from 2TB to 32TB.
Overall maximum ext4 file system size is 1 EB (exabyte).

API requests types brief explanation

API is an Application Programming Interface which is a way that allows communication between two applications using a set of rules. While having a great coffee from Bolivia I found the following API requests types.

The main Web Service APIs are:

  • SOAP (Simple Object Access Protocol) uses XML to transfer sets of information in the form of objects. Created by Microsoft in 1998.
  • XML-RPC was developed in 1997. It uses identifying tags similar to HTML and provides a rigid way to structuring data.
  • JSON-RPC was developed in 2001 and is derived from the JavaScript language. Similar to HTML its easily human readable, but can be condensed to reduce file size. JSON is now one of the most popular type of request APIs used.
  • REST (Representational State Transfer) Mainly a set of HTTP verbs. GET, POST DELETE, PUT handle the management of the server’s resources.

I hope this information about API requests types is helpful. You can also contact me if you have questions.

Difference between Inner Join and Outer Join in SQL

An inner join it is the most common kind of join, so common that SQL doesn’t actually make us say “inner join” to do one.

An outer join returns a set of records or rows that include what an inner join would return, but also includes other rows for which no corresponding match is found in the other table. There are 3 types of outer join:

  • Left join
  • Right join
  • Full join

Copying files rsync Linux use of “/” at the end of path

Hello, sometimes we need to copy files and we are not sure when to use “/ ” at the end of the path. Copying files rsync while brewing coffee at home this is what I found. Check this useful summary:

Continue reading “Copying files rsync Linux use of “/” at the end of path”

Activate File Sharing via Terminal macOS

The other day I only had access to my secondary Mac (mac mini) via the Terminal. For some reason Screen Share did not work. I needed to enabled File Sharing on my mac mini in order to transfer some backup files from my MacBook Pro to the mac mini. Coffee was brewing!

This is how I activated File Sharing via the terminal on the mac mini. I ran these two commands:

sudo launchctl load -w /System/Library/LaunchDaemons/

and then this one:

sudo defaults write /Library/Preferences/SystemConfiguration/ EnabledServices -array disk

I was then able to see the shares on my MacBook Pro. This approach is good for home use because in this case we are sharing all folders in the mac mini.

If you like to disable file sharing via terminal again run this command:

sudo launchctl unload -w /System/Library/LaunchDaemons/

Hope this post was helpful. If you like it grab a NYCMoments Coffee Mug from my sister website. Thanks!

How to Change Root Password in Ubuntu Linux

The root user is disabled by default in Ubuntu. This does not mean the account was removed. After researching while having amazing coffee from Latin America I found the following…

If for some reason, you need to enable the root account, all you need to do is to set a password for the root user. In Ubuntu, you can set or change the password of a user account with the passwd command.

To change the root password you need to run the following command as a sudo user:

sudo passwd root

You will be prompted to enter and confirm the new root password.

Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

That’s all! Now you can login to the Ubuntu system as a root. This is not the recommended way. You should always use a sudo user account instead.

What is a session in Google Analytics?

A session is defined as a group of interactions one user takes within a given time frame on your website.

For example a single session can contain multiple page views, events, social interactions, and E-Commerce transactions. A single user can open multiple sessions. Those sessions can occur on the same day, or over several days, weeks, or months. As soon as one session ends, there is then an opportunity to start a new session. There are two methods by which a session ends:

  • Time-based expiration:
    • After 30 minutes of inactivity
    • At midnight
  • Campaign change:
    • If a user arrives via one campaign, leaves, and then comes back via a different campaign.

By default, a session lasts until there’s 30 minutes of inactivity, but you can adjust this limit so a session lasts from a few seconds to several hours. See suggestions by Google in this link.