Linux Blimp

Welcome to this exclusive edition “BEGINNER’S GUIDE FOR LINUX” by TecMint, this course module is specially designed and compiled for those beginners, who want to make their way into Linux learning process and do the best in today’s IT organizations. This courseware is created as per requirements of industrial environment with complete entrance to Linux, which will help you to build a great success in Linux.

We have given special priority to Linux commands and switches, scripting, services and applications, access control, process control, user management, database management, web services, etc. Even though Linux command-line provides thousands of commands, but only a few of basic commands you need to learn to perform a day-to-day Linux tasks.

Prerequisites:

All students must have a little understanding of computers and passion to learn new technology.

Distributions:

This courseware is presently supported on the latest releases of Linux distributions like Red Hat Enterprise Linux, CentOS, Debian, Ubuntu, etc.

Course Objectives

Section 1: Introduction To Linux and OS Installations

1. Linux Boot Process
2. Linux File System Hierarchy
3. Installation of CentOS 7
4. Installation of Various Linux Distributions including Debian, RHEL, Ubuntu, Fedora, etc
5. Installation of CentOS on VirtualBox
6. Dual Boot Installation of Windows and Linux

Section 2: Essentials of Basic Linux Commands

1. List Files and Directories Using ‘ls’ Command
2. Switch Between Linux Directories and Paths with ‘cd’ Command
3. How to Use ‘dir’ Command with Different Options in Linux
4. Find Out Present Working Directory Using ‘pwd’ Command
5. Create Files using ‘touch’ Command
6. Copy Files and Directories using ‘cp’ Command
7. View File Content with ‘cat’ Command
8. Check File System Disk Space Usage with ‘df’ Command
9. Check Files and Directories Disk Usage with ‘du’ Command
10. Find Files and Directories using find Command
11. Find File Pattern Searches using grep Command

Section 3: Essentials of Advance Linux Commands

1. Quirky ‘ls’ Commands Every Linux User Must Know
2. Manage Files Effectively using head, tail and cat Commands in Linux
3. Count Number of Lines, Words, Characters in File using ‘wc’ Command
4. Basic ‘sort’ Commands to Sort Files in Linux
5. Advance ‘sort’ Commands to Sort Files in Linux
6. Pydf an Alternative “df” Command to Check Disk Usage
7. Check Linux Ram Usage with ‘free’ Command
8. Advance ‘rename’ Command to Rename Files and Directories
9. Print Text/String in Terminal using ‘echo’ Command

Section 4: Some More Advance Linux Commands

1. Switching From Windows to Nix – 20 Useful Commands for Newbies – Part 1
2. 20 Advanced Commands for Middle Level Linux Users – Part 2
3. 20 Advanced Commands for Linux Experts – Part 3
4. 20 Funny Commands of Linux or Linux is Fun in Terminal – Part 1
5. 6 Interesting Funny Commands of Linux (Fun in Terminal) – Part 2
6. 51 Useful Lesser Known Commands for Linux Users
7. 10 Most Dangerous Commands – You Should Never Execute on Linux

Section 5: User, Group and File Permissions Management

1. How to Add or Create New Users using ‘useradd’ Command
2. How to Modify or Change Users Attributes using ‘usermod’ Command
3. Managing Users & Groups, File Permissions & Attributes – Advance Level
4. Difference Between su and sudo – How to Configure sudo – Advance Level
5. How to Monitor User Activity with psacct or acct Tools

Section 6: Linux Package Management

1. Yum Package Management – CentOS, RHEL and Fedora
2. RPM Package Management – CentOS, RHEL and Fedora
3. APT-GET and APT-CACHE Package Management – Debian, Ubuntu
4. DPKG Package Management – Debian, Ubuntu
5. Zypper Package Management – Suse and OpenSuse
6. Linux Package Management with Yum, RPM, Apt, Dpkg, Aptitude and Zypper – Advance Level
7. 27 ‘DNF’ (Fork of Yum) Commands for RPM Package Management – New Update

Section 7: System Monitoring & Cron Scheduling

1. Linux Process Monitoring with top Command
2. Linux Process Management with Kill, Pkill and Killall Commands
3. Linux File Process Management with lsof Commands
4. Linux Job Scheduling with Cron
5. 20 Command Line Tools to Monitor Linux Performance – Part 1
6. 13 Linux Performance Monitoring Tools – Part 2
7. Nagios Monitoring Tool for Linux – Advance Level
8. Zabbix Monitoring Tool for Linux – Advance Level
9. Shell Script to Monitor Network, Disk Usage, Uptime, Load Average and RAM – New Update

Section 8: Linux Archiving/Compression, Backup/Sync and Recovery

Archiving/Compression Files

1. How to Archive/Compress Linux Files and Directories using ‘tar’ Command
2. How to Open, Extract and Create RAR Files in Linux
3. 5 Tools to Archive/Compress Files in Linux
4. How to Archive/Compress Files and Setting File Attributes – Advance Level

Backup/Sync Files and Directories in Linux

1. How to Copy/Synchronize Files and Directories Locally/Remotely with rsync
2. How to Transfer Files/Folders in Linux using scp
3. Rsnapshot (Rsync Based) – A Local/Remote File System Backup Tool
4. Sync Two Apache Web Servers/Websites Using Rsync – Advance Level

Backup/Recovery Linux Filesystems

1. Backup and Restore Linux Systems using Redo Backup Tool
2. How to Clone/Backup Linux Systems Using – Mondo Rescue Disaster Recovery Tool
3. How to Recover Deleted Files/Folders using ‘Scalpel’ Tool
4. 8 “Disk Cloning/Backup” Softwares for Linux Servers

Section 9: Linux File System / Network Storage Management

1. What is Ext2, Ext3 & Ext4 and How to Create and Convert Linux File Systems
2. Understanding Linux File System Types
3. Linux File System Creation and Configurations – Advance Level
4. Setting Up Standard Linux File Systems and Configuring NFSv4 Server – Advance Level
5. How to Mount/Unmount Local and Network (Samba & NFS) Filesystems – Advance Level
6. How to Create and Manage Btrfs File System in Linux – Advance Level
7. Introduction to GlusterFS (File System) and Installation – Advance Level

Section 10: Linux LVM Management

1. Setup Flexible Disk Storage with Logical Volume Management
2. How to Extend/Reduce LVM’s (Logical Volume Management)
3. How to Take Snapshot/Restore LVM’s
4. Setup Thin Provisioning Volumes in LVM
5. Manage Multiple LVM Disks using Striping I/O
6. Migrating LVM Partitions to New Logical Volume

Section 11: Linux RAID Management

1. Introduction to RAID, Concepts of RAID and RAID Levels
2. Creating Software RAID0 (Stripe) on ‘Two Devices’ Using ‘mdadm
3. Setting up RAID 1 (Mirroring) using ‘Two Disks’ in Linux
4. Creating RAID 5 (Striping with Distributed Parity) in Linux
5. Setup RAID Level 6 (Striping with Double Distributed Parity) in Linux
6. Setting Up RAID 10 or 1+0 (Nested) in Linux
7. Growing an Existing RAID Array and Removing Failed Disks in Linux
8. Assembling Partitions as RAID Devices – Creating & Managing System Backups

Section 12: Manage Services in Linux

1. Configure Linux Services to Start and Stop Automatically
2. How to Stop and Disable Unwanted Services in Linux
3. How to Manage ‘Systemd’ Services Using Systemctl in Linux
4. Managing System Startup Process and Services in Linux

Section 13: Linux System Security and Firewall

Linux Security and Tools

1. 25 Hardening Security Tips for Linux Servers
2. 5 Best Practices to Secure and Protect SSH Server
3. How to Password Protect Grub in Linux
4. Protect SSH Logins with SSH & MOTD Banner Messages
5. How to Audit Linux Systems using Lynis Tool
6. Secure Files/Directories using ACLs (Access Control Lists) in Linux
7. How to Audit Network Performance, Security, and Troubleshooting in Linux
8. Mandatory Access Control Essentials with SELinux – New Update

Linux Firewall and Tools

1. Basic Guide on IPTables (Linux Firewall) Tips / Commands
2. How To Setup an Iptables Firewall in Linux
3. How to Configure ‘FirewallD’ in Linux
4. Useful ‘FirewallD’ Rules to Configure and Manage Firewall in Linux
5. How to Install and Configure UFW – An Un-complicated FireWall
6. Shorewall – A High-Level Firewall for Configuring Linux Servers
7. Install ConfigServer Security & Firewall (CSF) in Linux
8. How to Install ‘IPFire’ Free Firewall Linux Distribution
9. How to Install and Configure pfSense 2.1.5 (Firewall/Router) in Linux
10. 10 Useful Open Source Security Firewalls for Linux Systems

Section 14: LAMP (Linux, Apache, MySQL/MariaDB and PHP) Setup’s

1. Installing LAMP in RHEL/CentOS 6.0
2. Installing LAMP in RHEL/CentOS 7.0
3. Ubuntu 14.04 Server Installation Guide and Setup LAMP
4. Installing LAMP in Arch Linux
5. Setting Up LAMP in Ubuntu Server 14.10
6. Installing LAMP in Gentoo Linux
7. Creating Your Own Webserver and Hosting A Website from Your Linux Box
8. Apache Virtual Hosting: IP Based and Name Based Virtual Hosts in Linux
9. How to Setup Standalone Apache Server with Name-Based Virtual Hosting with SSL Certificate
10. Creating Apache Virtual Hosts with Enable/Disable Vhosts Options in RHEL/CentOS 7.0
11. Creating Virtual Hosts, Generate SSL Certificates & Keys and Enable CGI Gateway in Gentoo Linux
12. Protect Apache Against Brute Force or DDoS Attacks Using Mod_Security and Mod_evasive Modules
13. 13 Apache Web Server Security and Hardening Tips
14. How to Sync Two Apache Web Servers/Websites Using Rsync
15. How to Install ‘Varnish’ (HTTP Accelerator) and Perform Load Testing Using Apache Benchmark
16. Installing and Configuring LAMP/LEMP Stack on Debian 8 Jessie – New Update

Section 15: LEMP (Linux, Nginx, MySQL/MariaDB and PHP) Setup’s

1. Install LEMP in Linux
2. Installing FcgiWrap and Enabling Perl, Ruby and Bash Dynamic Languages on Gentoo LEMP
3. Installing LEMP in Gentoo Linux
4. Installing LEMP in Arch Linux

Section 16: MySQL/MariaDB Administration

1. MySQL Basic Database Administration Commands
2. 20 MySQL (Mysqladmin) Commands for Database Administration in Linux
3. MySQL Backup and Restore Commands for Database Administration
4. How to Setup MySQL (Master-Slave) Replication
5. Mytop (MySQL Database Monitoring) in Linux
6. Install Mtop (MySQL Database Server Monitoring) in Linux
7. https://www.tecmint.com/mysql-performance-monitoring/

Section 17: Basic Shell Scripting

1. Understand Linux Shell and Basic Shell Scripting Language Tips – Part I
2. 5 Shell Scripts for Linux Newbies to Learn Shell Programming – Part II
3. Sailing Through The World of Linux BASH Scripting – Part III
4. Mathematical Aspect of Linux Shell Programming – Part IV
5. Calculating Mathematical Expressions in Shell Scripting Language – Part V
6. Understanding and Writing functions in Shell Scripts – Part VI
7. Deeper into Function Complexities with Shell Scripting – Part VII
8. Working with Arrays in Linux Shell Scripting – Part 8
9. An Insight of Linux “Variables” in Shell Scripting Language – Part 9
10. Understanding and Writing ‘Linux Variables’ in Shell Scripting – Part 10
11. Nested Variable Substitution and Predefined BASH Variables in Linux – Part 11

Section 18: Linux Interview Questions

1. 15 Interview Questions on Linux “ls” Command – Part 1
2. 10 Useful ‘ls’ Command Interview Questions – Part 2
3. Basic Linux Interview Questions and Answers – Part 1
4. Basic Linux Interview Questions and Answers – Part 2
5. Linux Interview Questions and Answers for Linux Beginners – Part 3
6. Core Linux Interview Questions and Answers
7. Useful Random Linux Interview Questions and Answers
8. Interview Questions and Answers on Various Commands in Linux
9. Useful Interview Questions on Linux Services and Daemons
10. Basic MySQL Interview Questions for Database Administrators
11. MySQL Database Interview Questions for Beginners and Intermediates
12. Advance MySQL Database “Interview Questions and Answers” for Linux Users
13. Apache Interview Questions for Beginners and Intermediates
14. VsFTP Interview Questions and Answers – Part 1
15. Advance VsFTP Interview Questions and Answers – Part 2
16. Useful SSH (Secure Shell) Interview Questions and Answers
17. Useful “Squid Proxy Server” Interview Questions and Answers in Linux
18. Linux Firewall Iptables Interview Questions – New Update
19. Basic Interview Questions on Linux Networking – Part 1 – New Update

Section 19: Shell Scripting Interview Questions

1. Useful ‘Interview Questions and Answers’ on Linux Shell Scripting
2. Practical Interview Questions and Answers on Linux Shell Scripting

Section 20: Free Linux Books for Learning

1. Complete Linux Command Line Cheat Sheet
2. The GNU/Linux Advanced Administration Guide
3. Securing & Optimizing Linux Servers
4. Linux Patch Management: Keeping Linux Up To Date
5. Introduction to Linux – A Hands on Guide
6. Understanding the Linux® Virtual Memory Manager
7. Linux Bible – Packed with Updates and Exercises
8. A Newbie’s Getting Started Guide to Linux
9. Linux from Scratch – Create Your Own Linux OS
10. Linux Shell Scripting Cookbook, Second Edition
11. Securing & Optimizing Linux: The Hacking Solution
12. User Mode Linux – Understanding and Administration
13. Bash Guide for Linux Beginners – New Update

Section 21: Linux Certifications – Prepration Guides

1. RHCSA (Red Hat Certified System Administrator) Certification Guide
2. LFCS (Linux Foundation Certified Sysadmin) Certification Guide
3. LFCE (Linux Foundation Certified Engineer) Certification Guide

Source

A checksum is a digit which serves as a sum of correct digits in data, which can be used later to detect errors in the data during storage or transmission. MD5 (Message Digest 5) sums can be used as a checksum to verify files or strings in a Linux file system.

MD5 Sums are 128-bit character strings (numerals and letters) resulting from running the MD5 algorithm against a specific file. The MD5 algorithm is a popular hash function that generates 128-bit message digest referred to as a hash value, and when you generate one for a particular file, it is precisely unchanged on any machine no matter the number of times it is generated.

It is normally very difficult to find two distinct files that results in same strings. Therefore, you can use md5sumto check digital data integrity by determining that a file or ISO you downloaded is a bit-for-bit copy of the remote file or ISO.

Suggested Read: Progress – Monitor Progress for (cp, mv, dd, tar, etc.) Commands in Linux

In Linux, the md5sum program computes and checks MD5 hash values of a file. It is a constituent of GNU Core Utilities package, therefore comes pre-installed on most, if not all Linux distributions.

Take a look at the contents of /etc/group saved as groups.cvs below.

root:x:0:
daemon:x:1:
bin:x:2:
sys:x:3:
adm:x:4:syslog,aaronkilik
tty:x:5:
disk:x:6:
lp:x:7:
mail:x:8:
news:x:9:
uucp:x:10:
man:x:12:
proxy:x:13:
kmem:x:15:
dialout:x:20:
fax:x:21:
voice:x:22:
cdrom:x:24:aaronkilik
floppy:x:25:
tape:x:26:
sudo:x:27:aaronkilik
audio:x:29:pulse
dip:x:30:aaronkilik

The md5sums command below will generate a hash value for the file as follows:

$ md5sum groups.csv

bc527343c7ffc103111f3a694b004e2f  groups.csv

When you attempt to alter the contents of the file by removing the first line, root:x:0: and then run the command for a second time, try to observe the hash value:

$ md5sum groups.csv

46798b5cfca45c46a84b7419f8b74735  groups.csv

You will notice that the hash value has now changed, indicating that the contents of the file where altered.

Now, put back the first line of the file, root:x:0: and rename it to group_file.txt and run the command below to generate its hash value again:

$ md5sum groups_list.txt

bc527343c7ffc103111f3a694b004e2f  groups_list.txt

From the output above, the hash value is still the same even when the file has been renamed, with its original content.

Important: md5 sums only verifies/works with the file content rather than the file name.

The file groups_list.txt is a duplicate of groups.csv, so, try to generate the hash value of the files at the same time as follows.

You will see that they both have equal hash values, this is because they have the exact same content.

$ md5sum groups_list.txt  groups.csv 

bc527343c7ffc103111f3a694b004e2f  groups_list.txt
bc527343c7ffc103111f3a694b004e2f  groups.csv

You can redirect the hash value(s) of a file(s) into a text file and store, share them with others. For the two files above, you can issues the command below to redirect generated hash values into a text file for later use:

$ md5sum groups_list.txt  groups.csv > myfiles.md5

To check that the files have not been modified since you created the checksum, run the next command. You should be able to view the name of each file along with “OK”.

Suggested Read: Find Top 15 Processes by Memory Usage in Linux

The -c or --check option tells md5sums command to read MD5 sums from the files and check them.

$ md5sum -c myfiles.md5

groups_list.txt: OK
groups.csv: OK

Remember that after creating the checksum, you can not rename the files or else you get a “No such file or directory” error, when you try to verify the files with new names.

For instance:

$ mv groups_list.txt new.txt
$ mv groups.csv file.txt
$ md5sum -c  myfiles.md5

md5sum: groups_list.txt: No such file or directory
groups_list.txt: FAILED open or read
md5sum: groups.csv: No such file or directory
groups.csv: FAILED open or read
md5sum: WARNING: 2 listed files could not be read

The concept also works for strings alike, in the commands below, -n means do not output the trailing newline:

$ echo -n "Tecmint How-Tos" | md5sum - 

afc7cb02baab440a6e64de1a5b0d0f1b  -

$ echo -n "Tecmint How-To" | md5sum - 

65136cb527bff5ed8615bd1959b0a248  -

In this guide, I showed you how to generate hash values for files, create a checksum for later verification of file integrity in Linux. Although security vulnerabilities in the MD5 algorithm have been detected, MD5 hashes still remains useful especially if you trust the party that creates them.

Verifying files is therefore an important aspect of file handling on your systems to avoid downloading, storing or sharing corrupted files. Last but not least, as usual reach us by means of the comment form below to seek any assistance, you can as well make some important suggestions to improve this post.

Source

Have you ever wondered why a given binary or package installed on your system does not work according to you expectations, meaning it does not function correctly as it is supposed to do, perhaps it can not event start at all.

While downloading packages, you may face challenges of unsteady network connections or unexpected power blackouts, this can result into installation of corrupted package.

Considering this as an important factor in maintaining uncorrupted packages on your system, it is therefore a vital step to verify the files on the file system against the information stored in the package by using following article.

Suggested Read: Learn How to Generate and Verify Files with MD5 Checksum in Linux

How to Verify Installed Debian Packages Against MD5 Checksums

On Debian/Ubuntu systems, you can use the debsums tool to check the MD5 sums of installed packages. If you want to know the information about debsums package before installing it, you can use APT-CACHE like so:

$ apt-cache search debsums

Next, install it using apt command as follows:

$ sudo apt install debsums

Now its time to learn how to use debsums tool to verify MD5sum of installed packages.

Note: I have used sudo with all the commands below because certain files may not have read permissions for regular users.

In addition, the output from the debsums command shows you the file location on the left and the check results on the right. There are three possible results you can get, they include:

1. OK – indicates that a file’s MD5 sum is good.
2. FAILED – shows that a file’s MD5 sum does not match.
3. REPLACED – means that the specific file has been replaced by a file from another package.

When you run it without any options, debsums checks every file on your system against the stock md5sum files.

$ sudo debsums

/usr/bin/a11y-profile-manager-indicator                                       OK
/usr/share/doc/a11y-profile-manager-indicator/copyright                       OK
/usr/share/man/man1/a11y-profile-manager-indicator.1.gz                       OK
/usr/share/accounts/providers/facebook.provider                               OK
/usr/share/accounts/qml-plugins/facebook/Main.qml                             OK
/usr/share/accounts/services/facebook-microblog.service                       OK
/usr/share/accounts/services/facebook-sharing.service                         OK
/usr/share/doc/account-plugin-facebook/copyright                              OK
/usr/share/accounts/providers/flickr.provider                                 OK
/usr/share/accounts/qml-plugins/flickr/Main.qml                               OK
/usr/share/accounts/services/flickr-microblog.service                         OK
/usr/share/accounts/services/flickr-sharing.service                           OK
/usr/share/doc/account-plugin-flickr/copyright                                OK
/usr/share/accounts/providers/google.provider                                 OK
/usr/share/accounts/qml-plugins/google/Main.qml                               OK
/usr/share/accounts/services/google-drive.service                             OK
/usr/share/accounts/services/google-im.service                                OK
/usr/share/accounts/services/picasa.service                                   OK
/usr/share/doc/account-plugin-google/copyright                                OK
/lib/systemd/system/accounts-daemon.service                                   OK
/usr/lib/accountsservice/accounts-daemon                                      OK
/usr/share/dbus-1/interfaces/org.freedesktop.Accounts.User.xml                OK
/usr/share/dbus-1/interfaces/org.freedesktop.Accounts.xml                     OK
/usr/share/dbus-1/system-services/org.freedesktop.Accounts.service            OK
/usr/share/doc/accountsservice/README                                         OK
/usr/share/doc/accountsservice/TODO                                           OK
....

To enable checking of every file and configuration files for each package for any changes, include the -a or --all option:

$ sudo debsums --all

/usr/bin/a11y-profile-manager-indicator                                       OK
/usr/share/doc/a11y-profile-manager-indicator/copyright                       OK
/usr/share/man/man1/a11y-profile-manager-indicator.1.gz                       OK
/etc/xdg/autostart/a11y-profile-manager-indicator-autostart.desktop           OK
/usr/share/accounts/providers/facebook.provider                               OK
/usr/share/accounts/qml-plugins/facebook/Main.qml                             OK
/usr/share/accounts/services/facebook-microblog.service                       OK
/usr/share/accounts/services/facebook-sharing.service                         OK
/usr/share/doc/account-plugin-facebook/copyright                              OK
/etc/signon-ui/webkit-options.d/www.facebook.com.conf                         OK
/usr/share/accounts/providers/flickr.provider                                 OK
/usr/share/accounts/qml-plugins/flickr/Main.qml                               OK
/usr/share/accounts/services/flickr-microblog.service                         OK
/usr/share/accounts/services/flickr-sharing.service                           OK
/usr/share/doc/account-plugin-flickr/copyright                                OK
/etc/signon-ui/webkit-options.d/login.yahoo.com.conf                          OK
/usr/share/accounts/providers/google.provider                                 OK
/usr/share/accounts/qml-plugins/google/Main.qml                               OK
/usr/share/accounts/services/google-drive.service                             OK
/usr/share/accounts/services/google-im.service                                OK
/usr/share/accounts/services/picasa.service                                   OK
/usr/share/doc/account-plugin-google/copyright                                OK
...

It is as well possible to check only the configuration file excluding all other package files by using the -e or --config option:

$ sudo debsums --config

/etc/xdg/autostart/a11y-profile-manager-indicator-autostart.desktop           OK
/etc/signon-ui/webkit-options.d/www.facebook.com.conf                         OK
/etc/signon-ui/webkit-options.d/login.yahoo.com.conf                          OK
/etc/signon-ui/webkit-options.d/accounts.google.com.conf                      OK
/etc/dbus-1/system.d/org.freedesktop.Accounts.conf                            OK
/etc/acpi/asus-keyboard-backlight.sh                                          OK
/etc/acpi/events/asus-keyboard-backlight-down                                 OK
/etc/acpi/ibm-wireless.sh                                                     OK
/etc/acpi/events/tosh-wireless                                                OK
/etc/acpi/asus-wireless.sh                                                    OK
/etc/acpi/events/lenovo-undock                                                OK
/etc/default/acpi-support                                                     OK
/etc/acpi/events/ibm-wireless                                                 OK
/etc/acpi/events/asus-wireless-on                                             OK
/etc/acpi/events/asus-wireless-off                                            OK
/etc/acpi/tosh-wireless.sh                                                    OK
/etc/acpi/events/asus-keyboard-backlight-up                                   OK
/etc/acpi/events/thinkpad-cmos                                                OK
/etc/acpi/undock.sh                                                           OK
/etc/acpi/events/powerbtn                                                     OK
/etc/acpi/powerbtn.sh                                                         OK
/etc/init.d/acpid                                                             OK
/etc/init/acpid.conf                                                          OK
/etc/default/acpid                                                            OK
...

Next, to only display changed files in the output of debsums, use the -c or --changed option. I didn’t found any changed files in my system.

$ sudo debsums --changed

The next command prints out files that do not have md5sum info, here we use the -l and --list-missingoption. On my system, the command does not show any file.

$ sudo debsums --list-missing

Now it’s time to verify the md5 sum of a single package by specifying its name:

$ sudo debsums apache2 

/lib/systemd/system/apache2.service.d/apache2-systemd.conf                    OK
/usr/sbin/a2enmod                                                             OK
/usr/sbin/a2query                                                             OK
/usr/sbin/apache2ctl                                                          OK
/usr/share/apache2/apache2-maintscript-helper                                 OK
/usr/share/apache2/ask-for-passphrase                                         OK
/usr/share/bash-completion/completions/a2enmod                                OK
/usr/share/doc/apache2/NEWS.Debian.gz                                         OK
/usr/share/doc/apache2/PACKAGING.gz                                           OK
/usr/share/doc/apache2/README.Debian.gz                                       OK
/usr/share/doc/apache2/README.backtrace                                       OK
/usr/share/doc/apache2/README.multiple-instances                              OK
/usr/share/doc/apache2/copyright                                              OK
/usr/share/doc/apache2/examples/apache2.monit                                 OK
/usr/share/doc/apache2/examples/secondary-init-script                         OK
/usr/share/doc/apache2/examples/setup-instance                                OK
/usr/share/lintian/overrides/apache2                                          OK
/usr/share/man/man1/a2query.1.gz                                              OK
/usr/share/man/man8/a2enconf.8.gz                                             OK
/usr/share/man/man8/a2enmod.8.gz                                              OK
/usr/share/man/man8/a2ensite.8.gz                                             OK
/usr/share/man/man8/apache2ctl.8.gz                                           OK

Assuming that you are running debsums as a regular user without sudo, you can treat permission errors as warnings by employing the --ignore-permissions option:

$ debsums --ignore-permissions 

How To Generate MD5 Sums from .Deb Files

The -g option tells debsums to generate MD5 sums from deb contents, where:

1. missing – instruct debsums to generate MD5 sums from the deb for packages which don’t provide one.
2. all – directs debsums to ignore the on disk sums and use the one present in the deb file, or generated from it if none exists.
3. keep – tells debsums to write the extracted/generated sums to /var/lib/dpkg/info/package.md5sums file.
4. nocheck – means the extracted/generated sums are not checked against the installed package.

When you look at the contents of the directory /var/lib/dpkg/info/, you will see md5sums for various files that packages as in the image below:

$ cd /var/lib/dpkg/info
$ ls *.md5sums

a11y-profile-manager-indicator.md5sums
account-plugin-facebook.md5sums
account-plugin-flickr.md5sums
account-plugin-google.md5sums
accountsservice.md5sums
acl.md5sums
acpid.md5sums
acpi-support.md5sums
activity-log-manager.md5sums
adduser.md5sums
adium-theme-ubuntu.md5sums
adwaita-icon-theme.md5sums
aisleriot.md5sums
alsa-base.md5sums
alsa-utils.md5sums
anacron.md5sums
apache2-bin.md5sums
apache2-data.md5sums
apache2.md5sums
apache2-utils.md5sums
apg.md5sums
apparmor.md5sums
app-install-data.md5sums
app-install-data-partner.md5sums
...

Remember that using -g option is the same as --generate=missing, you can try to generate a md5 sum for apache2 package by running the following command.

$ sudo debsums --generate=missing apache2 

Since apache2 package on my system already has md5 sums, it will show the output below, which is the same as running:

$ sudo debsums apache2

For more interesting options and usage info, look through the debsums man page.

$ man debsums

In this article, we shared how to verify installed Debian/Ubuntu packages against MD5 checksums, this can be useful in order to avoid installing and executing corrupted binaries or package files on your system by checking the files on the file system against the information stored in the package.

For any questions or feedback, take advantage of the comment form below. Imaginably, you can as well offer one or two suggestions to make this post better.

Source

Fkill-cli is a free open source, simple and cross-platform command line tool designed to interactively kill processes in Linux, developed using Nodejs. It also runs on Windows and MacOS X operating systems. It requires a process ID (PID) or process name to kill it.

Requirements:

1. Install Nodejs 8 and NPM in Linux

In this article, we will explain how to install and use fkill to interactively kill processes in Linux systems.

How to Install fkill-cli in Linux Systems

To install fkill-cli tool, first you need to install required packages Nodejs and NPM on your Linux distributions using following commands.

Install Nojejs and NPM in Debian/Ubuntu

--------------- Install Noje.js 8 --------------- 
$ curl -sL https://deb.nodesource.com/setup_8.x | sudo -E bash -
$ sudo apt install -y nodejs

--------------- or Install Noje.js 10 ---------------
$ curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -
$ sudo apt install -y nodejs

Install Nojejs and NPM in CentOS/RHEL & Fedora

--------------- Install Noje.js 8 --------------- 
$ curl --silent --location https://rpm.nodesource.com/setup_8.x | sudo bash -
$ sudo yum -y install nodejs

--------------- or Install Noje.js 10 ---------------
$ curl --silent --location https://rpm.nodesource.com/setup_10.x | sudo bash -
$ sudo yum -y install nodejs

Once Nodejs and NPM packages are installed, now you can install fkill-cli package using npm command using the -g option, which enables installing it globally.

$ sudo npm install -g fkill-cli

Once you have installed fkill-cli on your system, use the fkill command to launch it in interactive mode by running it without any arguments. Once you have select the process you want to kill, press Enter.

$ fkill  

You can also provide a PID or process name from the command line, the process name is case insensitive, here are some examples.

$ fkill 1337
$ fkill firefox

To kill a port, prefix it with a colon, for example: :19999.

$ fkill :19999

You can use the -f flag to force an operation and -v allows for displaying process arguments.

$ fkill -f 1337
$ fkill -v firefox

To view the fkill help message, use the following command.

$ fkill --help

Also check out examples of how to kill processes using traditional Linux tools such as kill, pkill and killall:

1. A Guide to Kill, Pkill and Killall Commands to Terminate a Process in Linux
2. How to Find and Kill Running Processes in Linux
3. How to Kill Linux Processes/Unresponsive Applications Using ‘xkill’ Command

Fkill-cli Github repository: https://github.com/sindresorhus/fkill-cli

That’s it! In this article, we have explained how to install and use fkill-cli tool in Linux with examples. Use the comment form below to ask any questions, or share your thoughts about it.

Source

I am always fascinated by the things going on behind the scenes when I boot a Linux system and log on. By pressing the power button on a bare metal or starting a virtual machine, you put in motion a series of events that lead to a fully-functional system – sometimes in less than a minute. The same is true when you log off and / or shutdown the system.

What makes this more interesting and fun is the fact that you can have the operating system execute certain actions when it boots and when you logon or logout.

In this distro-agnostic article we will discuss the traditional methods for accomplishing these goals in Linux.

Note: We will assume the use of Bash as main shell for logon and logout events. If you happen to use a different one, some of these methods may or may not work. If in doubt, refer to the documentation of your shell.

Executing Linux Scripts During Reboot or Startup

There are two traditional methods to execute a command or run scripts during startup:

Method #1 – Use a cron Job

Besides the usual format (minute / hour / day of month / month / day of week) that is widely used to indicate a schedule, cron scheduler also allows the use of @reboot. This directive, followed by the absolute path to the script, will cause it to run when the machine boots.

However, there are two caveats to this approach:

1. a) the cron daemon must be running (which is the case under normal circumstances), and
2. b) the script or the crontab file must include the environment variables (if any) that will be needed (refer to this StackOverflow thread for more details).

Method #2 – Use /etc/rc.d/rc.local

This method is valid even for systemd-based distributions. In order for this method to work, you must grant execute permissions to /etc/rc.d/rc.local as follows:

# chmod +x /etc/rc.d/rc.local

and add your script at the bottom of the file.

The following image shows how to run two sample scripts (/home/gacanepa/script1.sh and /home/gacanepa/script2.sh) using a cron job and rc.local, respectively, and their respective results.

#!/bin/bash
DATE=$(date +'%F %H:%M:%S')
DIR=/home/gacanepa
echo "Current date and time: $DATE" > $DIR/file1.txt

#!/bin/bash
SITE="Tecmint.com"
DIR=/home/gacanepa
echo "$SITE rocks... add us to your bookmarks." > $DIR/file2.txt

Keep in mind that both scripts must be granted execute permissions previously:

$ chmod +x /home/gacanepa/script1.sh
$ chmod +x /home/gacanepa/script2.sh

Executing Linux Scripts at Logon and Logout

To execute a script at logon or logout, use ~.bash_profile and ~.bash_logout, respectively. Most likely, you will need to create the latter file manually. Just drop a line invoking your script at the bottom of each file in the same fashion as before and you are ready to go.

Summary

In this article we have explained how to run script at reboot, logon, and logout. If you can think of other methods we could have included here, feel free to use the comment form below to point them out. We look forward to hearing from you!

Source

The easiest way to determine the type of a file on any operating system is usually to look at its extension (for instance .xml, .sh, .c, .tar etc..). What if a file doesn’t have an extension, how can you determine its type?

Read Also: 7 Ways to Find Out File System Types in Linux

Linux has a useful utility called file which carry out some tests on a specified file and prints the file type once a test is successful. In this short article, we will explain useful file command examples to determine a file type in Linux.

Note: To have all the options described in this article, you should be running file version 5.25 (available in Ubuntu repositories) or newer. CentOS repositories have an older version of file command (file-5.11) which lacks some options.

You can run following command to verify the version of file utility as shown.

$ file -v

file-5.33
magic file from /etc/magic:/usr/share/misc/magic

Linux file Command Examples

1. The simplest file command is as follows where you just provide a file whose type you want to find out.

$ file etc

2. You can also pass the names of the files to be examined from a file (one per line), which you can specify using the -f flag as shown.

$ file -f files.list

3. To make file work faster you can exclude a test (valid tests include apptype, ascii, encoding, tokens, cdf, compress, elf, soft and tar) from the list of tests made to determine the file type, use the -e flag as shown.

$ file -e ascii -e compress -e elf etc

4. The -s option causes file to also read block or character special files, for example.

$ file -s /dev/sda

/dev/sda: DOS/MBR boot sector, extended partition table (last)

5. Adding the -z options instructs file to look inside compressed files.

$ file -z backup

6. If you want to report information about the contents only not the compression, of a compressed file, use the -Z flag.

$ file -Z backup

7. You can tell file command to output mime type strings instead of the more traditional human readable ones, using the -i option.

$ file -i -s /dev/sda

/dev/sda: application/octet-stream; charset=binary

8. In addition, you can get a slash-separated list of valid extensions for the file type found by adding the –extension switch.

$ file --extension /dev/sda

For more information and usage options, consult the file command man page.

$ man file

That’s all! file command is a useful Linux utility to determine the type of a file without an extension. In this article, we shared some useful file command examples. If you have any questions or thoughts to share, use the feedback form below to reach us.

Source

System administration involves numerous tasks including managing users/groups and under user management, some of the minor tasks involved are adding, modifying, suspending, or deactivating user accounts, and many more.

This article will explain one of the critical user account management functions, how to set or change user password expiration and aging in Linux using the chage command.

Read Also: How to Manage Users and Groups in Linux

The chage command is used to modify user password expiry information. It enables you to view user account aging information, change the number of days between password changes and the date of the last password change.

Once you have set password expiry and aging information, this information is used by the system to determine when a user must change his/her password. Normally, companies or organizations have certain security polices that demand users to change passwords regularly: this can be a simple way to enforce such policies as we explained below.

To view a user account aging information, use the -l flag as shwon.

# chage -l ravi

To set the date or number of days (since January 1, 1970) when the password was last changed, use the -dflag as follows.

# chage -d 2018-02-11 ravi

Next, you can also set the date or number of days (since January 1, 1970) on which the user’s account will no longer be accessible by using the -E switch as shown in the following command.

In this case, once a user’s account is locked, he/she is required to contact the system administrator before being able to use the system again.

# chage -E 2018-02-16 ravi

Then, the -W option allows you to set the number of days of warning before a password change is required. Considering the command below, the user ravi will be warned 10 days prior to his password expiring.

# chage -W 10 ravi

In addition, you can set the number of days of inactivity after a password has expired before the account is locked. This example means that after user ravi’s password expires, his account will be inactive for 2 days before it is locked.

When the account becomes inactive, he must contact the system administrator before being able to use the system again.

# chage -I 2 ravi

For more information, refer to the chage man page.

# man chage

Note that you can also change a user’s password expiration and aging information using the usermod command, which is actually intended for modifying a user account.

Also check out:

1. Managing Users & Groups, File Permissions & Attributes on User Accounts
2. 11 Ways to Find User Account Info and Login Details in Linux

That’s it for now. Hoping you find this article informative and useful, if you have any questions to ask, use the feedback form below.

Source

On the internet you will find plenty of tools for checking disk space utilization in Linux. However, Linux has a strong built in utility called ‘df‘. The ‘df‘ command stand for “disk filesystem“, it is used to get full summary of available and used disk space usage of file system on Linux system.

Using ‘-h‘ parameter with (df -h) will shows the file system disk space statistics in “human readable” format, means it gives the details in bytes, mega bytes and gigabyte.

This article explain a way to get the full information of Linux disk space usage with the help of ‘df‘ command with their practical examples. So, you could better understand the usage of df command in Linux.

1. Check File System Disk Space Usage

The “df” command displays the information of device name, total blocks, total disk space, used disk space, available disk space and mount points on a file system.

[root@tecmint ~]# df

Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/cciss/c0d0p2     78361192  23185840  51130588  32% /
/dev/cciss/c0d0p5     24797380  22273432   1243972  95% /home
/dev/cciss/c0d0p3     29753588  25503792   2713984  91% /data
/dev/cciss/c0d0p1       295561     21531    258770   8% /boot
tmpfs                   257476         0    257476   0% /dev/shm

2. Display Information of all File System Disk Space Usage

The same as above, but it also displays information of dummy file systems along with all the file system disk usage and their memory utilization.

[root@tecmint ~]# df -a

Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/cciss/c0d0p2     78361192  23186116  51130312  32% /
proc                         0         0         0   -  /proc
sysfs                        0         0         0   -  /sys
devpts                       0         0         0   -  /dev/pts
/dev/cciss/c0d0p5     24797380  22273432   1243972  95% /home
/dev/cciss/c0d0p3     29753588  25503792   2713984  91% /data
/dev/cciss/c0d0p1       295561     21531    258770   8% /boot
tmpfs                   257476         0    257476   0% /dev/shm
none                         0         0         0   -  /proc/sys/fs/binfmt_misc
sunrpc                       0         0         0   -  /var/lib/nfs/rpc_pipefs

3. Show Disk Space Usage in Human Readable Format

Have you noticed that above commands displays information in bytes, which is not readable yet all, because we are in a habit of reading the sizes in megabytes, gigabytes etc. as it makes very easy to understand and remember.

The df command provides an option to display sizes in Human Readable formats by using ‘-h’ (prints the results in human readable format (e.g., 1K 2M 3G)).

[root@tecmint ~]# df -h

Filesystem            Size  Used Avail Use% Mounted on
/dev/cciss/c0d0p2      75G   23G   49G  32% /
/dev/cciss/c0d0p5      24G   22G  1.2G  95% /home
/dev/cciss/c0d0p3      29G   25G  2.6G  91% /data
/dev/cciss/c0d0p1     289M   22M  253M   8% /boot
tmpfs                 252M     0  252M   0% /dev/shm

4. Display Information of /home File System

To see the information of only device /home file system in human readable format use the following command.

[root@tecmint ~]# df -hT /home

Filesystem		Type    Size  Used Avail Use% Mounted on
/dev/cciss/c0d0p5	ext3     24G   22G  1.2G  95% /home

5. Display Information of File System in Bytes

To display all file system information and usage in 1024-byte blocks, use the option ‘-k‘ (e.g. –block-size=1K) as follows.

[root@tecmint ~]# df -k

Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/cciss/c0d0p2     78361192  23187212  51129216  32% /
/dev/cciss/c0d0p5     24797380  22273432   1243972  95% /home
/dev/cciss/c0d0p3     29753588  25503792   2713984  91% /data
/dev/cciss/c0d0p1       295561     21531    258770   8% /boot
tmpfs                   257476         0    257476   0% /dev/shm

6. Display Information of File System in MB

To display information of all file system usage in MB (Mega Byte) use the option as ‘-m‘.

[root@tecmint ~]# df -m

Filesystem           1M-blocks      Used Available Use% Mounted on
/dev/cciss/c0d0p2        76525     22644     49931  32% /
/dev/cciss/c0d0p5        24217     21752      1215  95% /home
/dev/cciss/c0d0p3        29057     24907      2651  91% /data
/dev/cciss/c0d0p1          289        22       253   8% /boot
tmpfs                      252         0       252   0% /dev/shm

7. Display Information of File System in GB

To display information of all file system statistics in GB (Gigabyte) use the option as ‘df -h‘.

[root@tecmint ~]# df -h

Filesystem            Size  Used Avail Use% Mounted on
/dev/cciss/c0d0p2      75G   23G   49G  32% /
/dev/cciss/c0d0p5      24G   22G  1.2G  95% /home
/dev/cciss/c0d0p3      29G   25G  2.6G  91% /data
/dev/cciss/c0d0p1     289M   22M  253M   8% /boot
tmpfs                 252M     0  252M   0% /dev/shm

8. Display File System Inodes

Using ‘-i‘ switch will display the information of number of used inodes and their percentage for the file system.

[root@tecmint ~]# df -i

Filesystem            Inodes   IUsed   IFree IUse% Mounted on
/dev/cciss/c0d0p2    20230848  133143 20097705    1% /
/dev/cciss/c0d0p5    6403712  798613 5605099   13% /home
/dev/cciss/c0d0p3    7685440 1388241 6297199   19% /data
/dev/cciss/c0d0p1      76304      40   76264    1% /boot
tmpfs                  64369       1   64368    1% /dev/shm

9. Display File System Type

If you notice all the above commands output, you will see there is no file system type mentioned in the results. To check the file system type of your system use the option ‘T‘. It will display file system type along with other information.

[root@tecmint ~]# df -T

Filesystem		Type   1K-blocks  Used      Available Use% Mounted on
/dev/cciss/c0d0p2	ext3    78361192  23188812  51127616  32%   /
/dev/cciss/c0d0p5	ext3    24797380  22273432  1243972   95%   /home
/dev/cciss/c0d0p3	ext3    29753588  25503792  2713984   91%   /data
/dev/cciss/c0d0p1	ext3    295561     21531    258770    8%    /boot
tmpfs			tmpfs   257476         0    257476    0%   /dev/shm

10. Include Certain File System Type

If you want to display certain file system type use the ‘-t‘ option. For example, the following command will only display ext3 file system.

[root@tecmint ~]# df -t ext3

Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/cciss/c0d0p2     78361192  23190072  51126356  32% /
/dev/cciss/c0d0p5     24797380  22273432   1243972  95% /home
/dev/cciss/c0d0p3     29753588  25503792   2713984  91% /data
/dev/cciss/c0d0p1       295561     21531    258770   8% /boot

11. Exclude Certain File System Type

If you want to display file system type that doesn’t belongs to ext3 type use the option as ‘-x‘. For example, the following command will only display other file systems types other than ext3.

[root@tecmint ~]# df -x ext3

Filesystem           1K-blocks      Used Available Use% Mounted on
tmpfs                   257476         0    257476   0% /dev/shm

12. Display Information of df Command.

Using ‘–help‘ switch will display a list of available option that are used with df command.

[root@tecmint ~]# df --help

Usage: df [OPTION]... [FILE]...
Show information about the file system on which each FILE resides,
or all file systems by default.

Mandatory arguments to long options are mandatory for short options too.
  -a, --all             include dummy file systems
  -B, --block-size=SIZE use SIZE-byte blocks
  -h, --human-readable  print sizes in human readable format (e.g., 1K 234M 2G)
  -H, --si              likewise, but use powers of 1000 not 1024
  -i, --inodes          list inode information instead of block usage
  -k                    like --block-size=1K
  -l, --local           limit listing to local file systems
      --no-sync         do not invoke sync before getting usage info (default)
  -P, --portability     use the POSIX output format
      --sync            invoke sync before getting usage info
  -t, --type=TYPE       limit listing to file systems of type TYPE
  -T, --print-type      print file system type
  -x, --exclude-type=TYPE   limit listing to file systems not of type TYPE
  -v                    (ignored)
      --help     display this help and exit
      --version  output version information and exit

SIZE may be (or may be an integer optionally followed by) one of following:
kB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G, T, P, E, Z, Y.

Report bugs to <bug-coreutils@gnu.org>.

Read Also :

1. 10 fdisk Commands to Manage Linux Disk Partitions
2. 10 Useful “du” Commands to Find Disk Usage of Files and Directories

Source

In our last article, we have explained how to use df (disk filesystem) utility to report file system disk space usage in Linux. We have discovered yet a another great utility for the same purpose but with a prettier output, called discus.

Discus is a df-like, highly configurable utility for checking disk space utilization in Linux, intended to make dfprettier with fancy features such as colored output, bar graphs, and smart formatting of numbers. To configure it, you may copy its main configuration file /etc/discusrc to ~/.discusrc and do your customization in there.

Read Also: Pydf an Alternative “df” Command to Check Disk Usage in Different Colours

The package discus is available to install from the default system repositories using package manager on Linux distribution as shown.

$ sudo apt install discus	#Debian/UBuntu
$ sudo yum install discus	#RHEL/CentOS
$ sudo dnf install discus	#Fedora 22+

After installing discus, learn how to use discus with the following examples.

Discus Command Examples

Run the discus command with the default settings.

$ discus

To disable the color, use the -c flag.

$ discus -c

To display device names instead of graphs, use the -d flag:.

$ discus -d

If do not want to use smart formatting, you can disable it using the -s switch as shown.

$ discus -s

You can specify the number of digits to right of decimal place using the -p flag.

$ discus -p 3

To display sizes in kilobytes, gigabytes, megabytes, or terabytes use the -k, -g, -m, or -t flags respectively. For example.

$ discus -m

Last but not least, if you want to configure it to your preference, copy its main configuration file /etc/discusrc to ~/.discusrc as shown.

$ sudo cp /etc/discusrc ~/.discusrc

Then open the newly created file and perform your customization.

$ vim ~/.discusrc

For more information, see the discus man page.

$ man discus 

You may also like to read these following useful articles on Linux disk space usage.

1. 10 Useful du (Disk Usage) Commands to Find Disk Usage of Files and Directories
2. How to Find Out Top Directories and Files (Disk Space) in Linux

That’s all! Discus is a simple utility intended to make df command prettier. Try it out and let us know of thoughts in the comments section below.

Source

The easiest way to count number of files and subdirectories in a directory using a tree command, which is best known for displaying files and directories in tree-like form.

Although you can always enable quotas to restrict disk space and inode usage to avoid user abuse, this command may be useful anyway. By default, the current working directory is assumed if no arguments are given:

$ tree -iLf 1

Sample Output

.
./10-Top-Linux-Distributions-of-2015.png
./adobe-flash-player-alternative.jpg
./CentOS-7-Security-Hardening-Guide.png
./coding.png
./d-logo-sketch.png
./Experts-Share-Thoughts-on-25th-Anniversary-of-the-World-Wide-Web-431806-2.jpg
./Get-Default-OS-Logo.png
./InstallCinnamonDesktoponUbuntuandFedora720x345.png
./Install-Nagios-in-CentOS.jpg
./Install-Vmware-Workstation-12-in-Linux.png
./Install-WordPress-on-CentOS-Fedora.png
./Linux-Essentials-Bundle-Course.png
./Linux-Online-Training-Courses.png
./Linux-PDF-Readers-Viewers-Tools.png
./linux-play-game.jpg
./logo.png
./nrpe-3.0.tar.gz
./Python-and-Linux-Administration-Course.png
./Ravi
./teamviewer 11 0 57095 i386
./Telegram
./tsetup.0.10.1.tar.xz
./VBoxGuestAdditions_5.0.0.iso
./Vivaldi-About.png
./VMware-Workstation-Full-12.1.1-3770994.x86_64.bundle

3 directories, 22 files

If you want to view the same information for /var/log, do:

$ tree -iLf 1 /var/log

Sample Output

/var/log
/var/log/alternatives.log
/var/log/apt
/var/log/aptitude
/var/log/auth.log
/var/log/boot.log
/var/log/bootstrap.log
/var/log/btmp
/var/log/btmp.1
/var/log/ConsoleKit
/var/log/cups
/var/log/dmesg
/var/log/dpkg.log
/var/log/faillog
/var/log/fontconfig.log
/var/log/fsck
/var/log/gpu-manager.log
/var/log/hp
/var/log/installer
/var/log/kern.log
/var/log/lastlog
/var/log/mdm
/var/log/mintsystem.log
/var/log/mintsystem.timestamps
/var/log/ntpstats
/var/log/samba
/var/log/speech-dispatcher
/var/log/syslog
/var/log/syslog.1
/var/log/teamviewer11
/var/log/unattended-upgrades
/var/log/upstart
/var/log/vbox-install.log
/var/log/wtmp
/var/log/wtmp.1
/var/log/Xorg.0.log
/var/log/Xorg.0.log.old

13 directories, 23 files

Type the command below to view information about files and subdirectories in the directory ISOs.

$ tree -iLf 1 ISOs 

Sample Output

ISOs
ISOs/CentOS-6.5-x86_64-minimal.iso
ISOs/CentOS-7.0-1406-x86_64-Minimal.iso
ISOs/CentOS-7-x86_64-DVD-1503-01
ISOs/ces-standard-3.3-x86_64.iso
ISOs/debian-8.1.0-amd64-CD-1.iso
ISOs/kali-linux-2.0-i386
ISOs/openSUSE-13.2-DVD-x86_64.iso
ISOs/rhel-server-7.0-x86_64-dvd.iso
ISOs/ubuntu-14.04.2-desktop-amd64.iso
ISOs/ubuntu-14.04.3-server-amd64.iso
ISOs/VL-7.1-STD-FINAL.iso
ISOs/Win10_1511_1_English_x32.iso
ISOs/Win10_1511_1_Spanish_64.iso

2 directories, 11 files

Explaining tree options used in the command above:

1. -i – its a graphical option that enables tree to print out indentation lines
2. -L – specifies the level of depth of the directory tree to be displayed, which in the case above is 1
3. -f – makes tree print the full path prefix for every file

As you can view from the image above, after listing all the files and subdirectories, tree shows you the total number of directories and files in the directory you specified.

Suggested Read: Encrypt and Decrypt Files and Directories Using Tar and OpenSSL

You can refer to the tree man page to discover more useful options, some configuration files and environment variables to better understand how it works.

Conclusion

Here, we covered an important tip that can help you use the tree utility in a different way as compared to its traditional use, for displaying files and directories in a tree-like form.

You can can build new tips by using the numerous tree options from the man page. Do you have any useful tip concerning the use of tree? Then share it with millions of Linux users around the world through the feedback form below.

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