Category Archives: Linux

Discover DevOps roles and learn Linux from basics to advanced at DevOpsRoles.com. Detailed guides and in-depth articles to master Linux for DevOps careers.

Linux

RPM query installed packages in Centos RHEL and Fedora

10/31/2018 HuuPV Leave a comment

In this tutorial, I using the rpm command to query lists the packages installed on the system. How do I use “rpm query installed packages in Centos, RHEL, and Fedora“. Linux the essential for DevOps Roles.

RPM query installed packages

List of the only package installed your system.

$ rpm -qa --qf "%{NAME}\n"

Example, List of the package installed on “Server A”. After then, How to install the package from “Server A” for “Server B”

Server A $ rpm -qa --qf "%{NAME}\n" > packaged.list
Server B # xargs yum -y < packaged.list

Display the package names, versions and releases with this command

[huupv@huupv devopsroles]$ rpm -qa --qf '%{NAME}-%{VERSION}-%{RELEASE} (%{ARCH})\n'

The screen output terminal as below

Conclusion

Thought the article, How to use “RPM query installed packages in Centos RHEL and Fedora” as above. I hope will this your helpful. Thank you for reading the DevopsRoles page!

Linux

bad interpreter: /bin/sh^M: no such file or directory solve problem

10/31/2018 HuuPV Leave a comment

In this tutorial, How to solve bad interpreter when running the shell exit with “bad interpreter: /bin/sh^M: no such file or directory“. I will be using three methods. Linux the essential for DevOps Roles.

bad interpreter: /bin/sh^M: no such file or directory fixed

Method 1: Using vim editor

Open vim and insert the following command

:set fileformat=unix
:x

:set ff=unix
:x

Method 2: Using sed command

[huupv@huupv devopsroles]$ sed -i 's/\r//' FILE_NAME

Method 3: I Using dos2unix command

[huupv@huupv devopsroles]$ dos2unix FILE_NAME

Conclusion

Thought the article, You have solved the problem “bad interpreter: /bin/sh^M: no such file or directory” as above. I hope will this your helpful. Thank you for reading the DevopsRoles page!

Linux

How to kill specific processes in Linux

10/19/2018 HuuPV Leave a comment

Introduction

This guide will walk you through how to kill specific processes in Linux, from basic commands to advanced techniques, with practical examples. Whether you’re new to Linux or looking to refine your skills, mastering these commands can save you time and enhance system stability.

Linux is a powerful and flexible operating system, used in a variety of environments, from personal desktops to complex server systems. One essential aspect of managing a Linux system effectively is understanding how to handle running processes, especially when they behave unexpectedly or consume too many resources.

Why Kill Processes in Linux?

Processes in Linux are essentially tasks or programs that are currently running on the system. Sometimes, these processes can become unresponsive, hog system resources, or even cause the system to crash. In such cases, killing the process becomes essential to free up resources and maintain the smooth operation of the system. This article provides a comprehensive look at various ways to kill processes based on different criteria, allowing you to manage your Linux system with greater efficiency.

How to View Running Processes

Before killing any process, it’s crucial to know how to view the processes running on your system. You can use several commands to list active processes.

Using ps

The ps command provides a static snapshot of all currently running processes:

ps aux

a: Shows processes for all users.
u: Displays processes in a user-oriented format.
x: Lists processes not connected to a terminal.

Using `top` and `htop`

The top and htop commands give a real-time view of running processes.

top

For a more user-friendly interface, install and use htop:

htop

kill specific processes in Linux

For example, kill all PID of the browser Firefox. But not kill line “grep –color=auto firefox” as the picture below

Use ps command with “-ef” option the display PID of browser Firefox.

[huupv@huupv devopsroles]$ ps -ef | grep firefox

The only display PID of Firefox as command below

[huupv@huupv devopsroles]$ ps -ef | grep firefox | grep -v "grep" | awk '{print $2}'

The screen output terminal as below

Using kill command to kill all Processes for Firefox as command line below

[huupv@huupv devopsroles]$ sudo kill -9 $(ps -ef | grep firefox | grep -v "grep" | awk '{print $2}')

Frequently Asked Questions (FAQ)

How do I kill a process without knowing its PID?

You can use pkill or killall to kill a process by name.

What’s the difference between `kill` and kill -9?

The default kill (SIGTERM) requests a graceful shutdown, while kill -9 (SIGKILL) forcefully stops the process.

Is there any risk in using kill -9?

kill -9 terminates a process immediately without cleanup, so unsaved data may be lost. Use it only when necessary.

How can I kill processes that belong to another user?

To kill processes owned by another user, you need root privileges. Use sudo pkill -u [username].

Why is xkill not working on my Linux distribution?

Some distributions don’t have xkill installed by default. You can install it using your package manager.

External Resources

Linux Command Line Basics
GNU Kill Command Documentation
The ps Command – Process Status

Conclusion

Managing processes in Linux is a fundamental skill that improves your efficiency and control over the system. This guide has covered essential commands for killing specific processes, from using kill and pkill to more advanced techniques. Practice these commands to confidently handle any unresponsive or resource-consuming processes on your system. Remember to exercise caution, especially with kill -9, and ensure you understand the implications of terminating critical processes. By mastering these techniques, you’ll be better equipped to maintain a smooth-running Linux environment. Thank you for reading the DevopsRoles page!

Linux

scp command example: A Comprehensive Guide to Secure File Transfers

10/13/2018 HuuPV Leave a comment

Introduction

How to use the SCP command in Linux to copy a file from one server to another. it is used to securely copy a file to or from a remote server.

Discover the simplicity and power of using the SCP command in Linux for secure file transfers. This tutorial will guide you through various examples of how to utilize SCP to copy files and directories between servers securely. Whether you are a beginner or an experienced administrator, mastering the SCP command is crucial for managing remote file transfers efficiently.

SCP command example

Copy file from one client location to another server location

$ scp /tmp/local.conf huupv@192.168.1.22:/home/huupv

Use the “-r” recursive option to copy the directory and sub-directories.

$ scp -r huupv@192.168.1.22:/home/huupv/* ./your-workspace

To copy the remote file to the local directory

$ scp huupv@192.168.1.22:/home/huupv/file-remote.txt /local/folder

Copying a local file to a remote directory

$ scp local-text.txt huupv@192.168.1.22:/home/huupv

Using key files like SSH command 🙂

$ scp -i your_key.pem local-text.txt huupv@192.168.1.22:/home/huupv

Conclusion

With the SCP command, transferring files between servers becomes a seamless task. This guide has shown you several practical examples to help you understand how to use SCP effectively. By integrating these techniques into your workflow, you’ll enhance your server management skills and ensure secure data handling. I hope will this your helpful. Thank you for reading the DevopsRoles page!

Linux

Linux list services

10/13/2018 HuuPV Leave a comment

In this tutorial, How do I list all services running in Linux distribution? List running service on Ubuntu Or Systemd service management. Linux the essential for DevOps Roles.

Linux list services

Systemd service management

Listing services

Listing running services.

[huupv@huupv devopsroles]$ systemctl

The screen output terminal

Listing the “failed” services

[huupv@huupv devopsroles]$ systemctl --failed

The screen output terminal

Managing targets

To find the default target for your system.

[huupv@huupv devopsroles]$ systemctl get-default

Setting the default target for your system

$ sudo systemctl set-default <target-name>

Managing to autostart of services

Showing a service is enabled on system boot.
$ sudo systemctl is-enabled [service-name]

To show a service is currently active (running).
$ sudo systemctl is-active [service-name]

Enabling a service on system boot.
$ sudo systemctl enable [service-name]

Disabling a service on system boot.
$ sudo systemctl disable [service-name]

Managing services at runtime

Starting a service

$ systemctl start [service-name]

Stopping a service

$ systemctl stop [service-name]

Restarting a service

$ sudo systemctl restart [service-name]

To request the service to reload its configuration.

$ sudo systemctl reload [service-name]

Showing the current status of a service

$ sudo systemctl status [service-name]

To restart your Systemd.

$ sudo systemctl daemon-reload

List running services on the Ubuntu distribution

To get the list of the services on your system.

$ service --status-all

Conclusion

Through the article, you can use Linux list services as above. I hope will this your helpful. Thank you for reading the DevopsRoles page!

Linux

tar command examples in Linux

10/12/2018 HuuPV Leave a comment

In this tutorial, How do I use the tar command the compress and extract files and folders in Linux? Linux the essential for DevOps Roles.

The tar command in Linux is used for creating and manipulating tar archives, which are commonly used for bundling multiple files and directories into a single file. Here are a few examples of how to use the tar command.

The syntax tar command

tar [Options] your_tar_name.tar source_tar

Options

-c –create Create a new archive.
-x –extract Extract files from an archive.
-t –list List the contents of an archive.
-f –file=ARCHIVE Use archive file or directories ARCHIVE.
-v –verbose Verbosely list files processed.
-a –auto-compress Use archive suffix to determine the compression program.
-j –bzip2 Filter the archive through bzip2.
-J –xz Filter the archive through xz.
-z –gzip Filter the archive through gzip.

For example, tar command examples, compress a directory.

Creating an archive of a directory as command below

[huupv@huupv devopsroles]$ tar -cvf folder.tar folder

The archiving a folder compressed “gzip” you can use -z option.

[huupv@huupv devopsroles]$ tar -czf folder.tar.gz folder

You can compress the archive with “bzip2” by using -j option

[huupv@huupv devopsroles]$ tar -cjf folder.tar.bz2 folder

Or compress “xz” by using the -J option.

[huupv@huupv devopsroles]$ tar -cJf folder.tar.xz folder

For example, Extract a directory from an archive

To extract a directory from an archive in the current location

[huupv@huupv devopsroles]$ tar -xvf folder.tar

Or to extract a directory from an archive to a specific “your_folder”.

[huupv@huupv devopsroles]$ tar -xvf  folder.tar -C ./directory/your_folder

For example list archive content

Listing content as command below

[huupv@huupv devopsroles]$ tar -tvf folder.tar

For listing the content of a tar.gz archive

[huupv@huupv devopsroles]$ tar -tzvf folder.tar.gz

Compress and exclude one or multiple directories

This is my folder tree

[huupv@huupv devopsroles]$ tree tar-folder
tar-folder
├── folder1
├── folder2
└── folder3

3 directories, 0 files

You can exclude one or several folders “–exclude” option as the command below

[huupv@huupv devopsroles]$ tar --exclude='./tar-folder/folder1' --exclude='./tar-folder/folder3' -cvf my-archive.tar ./tar-folder

The screen output terminal

./tar-folder/
./tar-folder/folder2/

Conclusion

Through the article, you can use tar command examples in Linux as above. These are just a few examples of how to use the tar command in Linux. The tar command offers many other options and functionalities, so you can refer to the command’s manual (man tar) for more detailed information and usage examples. I hope will this your helpful. Thank you for reading the DevopsRoles page!

Linux

Linux System information and Hardware Information

10/09/2018 HuuPV Leave a comment

How to get System Information about CPU, Memory, Network, and Disk I/O on the Linux operating system. Linux the essential for DevOps Roles.

To obtain system and hardware information on a Linux system, you can use various commands and utilities. Here are a few commonly used ones.

Linux System information

CPU

You can use the mpstat command to get processor-related statistics.

[huupv@huupv devopsroles]$ mpstat 2 10

The screen output terminal:

Using the lscpu command to get CPU information

[huupv@huupv devopsroles]$ lscpu

The screen output terminal:

Find CPU model/speed information

[huupv@huupv devopsroles]$ cat /proc/cpuinfo

Count processor

[huupv@huupv devopsroles]$ grep -c processor /proc/cpuinfo

DISK

To get information about your disk in real-time with the iostat command

[huupv@huupv devopsroles]$ iostat -kx 2

NETWORK

To see your network services with the netstat command

The command as below

[huupv@huupv devopsroles]$ netstat -ntlp # Open TCP sockets
[huupv@huupv devopsroles]$ netstat -nulp # Open UDP sockets
[huupv@huupv devopsroles]$ netstat -nxlp # Open Unix sockets

LIST HARDWARE

You can report the exact memory configuration, Mainboard configuration, Firmware version, CPU version, and speed cache.

Using lshw command

[huupv@huupv devopsroles]$ sudo lshw

To show PCI info

[huupv@huupv devopsroles]$ lspci -tv

Getting USB info

[huupv@huupv devopsroles]$ lsusb -tv

Display BIOS Infomation

[huupv@huupv devopsroles]$ sudo dmidecode -q | less

How to read speed test on disk sda

[huupv@huupv devopsroles]$ sudo hdparm -tT /dev/sda

The screen output terminal:

[sudo] password for huupv:

/dev/sda:
Timing cached reads: 5668 MB in 2.00 seconds = 2837.23 MB/sec
Timing buffered disk reads: 110 MB in 3.08 seconds = 35.73 MB/sec

Using badblocks command test for an unreadable block on disk sda

[huupv@huupv devopsroles]$ badblocks -s /dev/sda

Process monitoring

List processes in a hierarchy

[huupv@huupv devopsroles]$ ps -e -o pid,args --forest

How to list processes “% CPU” usage

[huupv@huupv devopsroles]$ ps -e -o pcpu,cpu,nice,state,cputime,args --sort pcpu | sed '/^ 0.0 /d'

List processes mem (KB) usage

[huupv@huupv devopsroles]$ ps -e -orss=,args= | sort -b -k1,1n

Interactive monitoring

You can use the tool for dynamic monitoring

[huupv@huupv devopsroles]$ top
[huupv@huupv devopsroles]$ htop
[huupv@huupv devopsroles]$ atop
[huupv@huupv devopsroles]$ sudo iotop

Conclusion

Through the article, you can use Linux system information and hardware Information as above. These are just a few examples of commands you can use to obtain system and hardware information on Linux. Depending on your distribution and installed packages, there may be additional tools available. I hope will this your helpful. Thank you for reading the DevopsRoles page!

Linux

Linux check disk space

10/09/2018 HuuPV Leave a comment

In this tutorial, How do I check disk space on Linux distribution? Sometimes you find out which directory consumes how much disk space. I used the du command and the df command. Linux the essential for DevOps Roles.

To check the disk space on a Linux system, you can use the df command. Here’s how you can do it:

Investigate the folder for Disk Usage
Checking Disk Space

Linux check disk space

Investigate the folder for Disk Usage

du command summarizes disk usage and recursively for files and directories

The syntax,

du [option]

For example, Summarizing disk usage in the current directory

[huupv@huupv devopsroles]$ du -sh *

The summarizing includes hidden files

[huupv@huupv devopsroles]$ du -sh .[!.]* *

you can add total the output by adding the -c option

[huupv@huupv devopsroles]$ du -csh .[!.]* *

The screen output terminal:

Investigate root director will only show folders with more than 20GB for disk usage

[huupv@huupv devopsroles]$ sudo du --threshold=20G -ch /.[!.]* /*

Checking Disk Space

[huupv@huupv devopsroles]$ df -h

Conclusion

Thought the article, you can use Linux check disk space as above. I hope will this your helpful. Thank you for reading the DevopsRoles page!

Linux

Check Linux version

10/08/2018 HuuPV Leave a comment

In this tutorial, How do I check Linux version for Linux distribution? Linux the essential for DevOps Roles.

Check RHEL / CentOS / Fedora distribution

Look at the content of “/etc/redhat-release”

[huupv@huupv devopsroles]$ cat /etc/redhat-release

The screen output terminal:

Check systemd-based distribution

This method will work on a modern version of Linux distribution.

[huupv@huupv devopsroles]$ cat /etc/os-release

Check Debian-based distribution

Run command lsb_release -a

$ lsb_release -a

From the bash shell,

[huupv@huupv devopsroles]$ ( source /etc/os-release && echo "$PRETTY_NAME" )

The screen output terminal:

To check the Linux version on your system, you can use the uname command with the -a option. Open your terminal and type the following command:

[huupv@huupv devopsroles]$ uname -a

This will display information about your Linux kernel, including the version. The output will typically look like this:

For example: The screen output terminal

Linux huupv 4.18.11-200.fc28.x86_64 #1 SMP Sun Sep 30 15:31:40 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

Conclusion

Through the article, you can use the Check Linux version as above. I hope will this your helpful. Thank you for reading the DevopsRoles page!

RPM query installed packages

Conclusion

bad interpreter: /bin/sh^M: no such file or directory fixed

Conclusion

Introduction

Why Kill Processes in Linux?

How to View Running Processes

Using ps

Using top and htop

kill specific processes in Linux

Frequently Asked Questions (FAQ)

How do I kill a process without knowing its PID?

What’s the difference between kill and kill -9?

Is there any risk in using kill -9?

How can I kill processes that belong to another user?

Why is xkill not working on my Linux distribution?

External Resources

Conclusion

Introduction

SCP command example

Conclusion

Linux list services

Systemd service management

List running services on the Ubuntu distribution

Conclusion

The syntax tar command

For example, tar command examples, compress a directory.

For example list archive content

Compress and exclude one or multiple directories

Conclusion

Linux System information

CPU

DISK

NETWORK

LIST HARDWARE

Process monitoring

Conclusion

Linux check disk space

Conclusion

Check RHEL / CentOS / Fedora distribution

Check systemd-based distribution

Check Debian-based distribution

Conclusion

Devops Tutorial

Using `top` and `htop`

What’s the difference between `kill` and kill -9?