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.
In this tutorial, I am using the cut command in Linux to remove sections from each line of files.
The cut the command is used to extract specific sections (columns) from lines of input text or files in Linux and Unix systems. It is particularly useful for working with delimited data.
What does cut command mean?
cut – remove sections from each line of files
Syntax
cut OPTION... [FILE]...
On the man page, the description it
cut – remove sections from each line of files.
man cut – More details information about the cut command.
cut command in Linux with an example
I have created a file cut_command.txt as below
[vagrant@DevopsRoles ~]$ cat cut_command.txt
HuuPV, My website DevopsRoles.com and HuuPhan.com.SN:199x.
Devops Roles.
Hello world. xxx.
For delimiter-separated fields. The default delimiter is the tab character.
cut command in Linux is a simple command in Linux. It is used to remove sections from each line of files.
These are just a few examples of how you can use the cut command. It offers various options and functionalities for extracting specific sections from text or files. You can refer to the cut man page (man cut) for more details and additional options.
In this tutorial, we’ll explore how to use the fmt command in Linux to neatly format text in files, set optimal column widths, and standardize spacing. This guide aims to enhance your text processing skills on Linux using practical examples of the fmt command. Let’s dive into the capabilities of the fmt command in Linux.
What does the fmt command mean?
fmt – a straightforward command used as an optimal text formatter.
Syntax
fmt [-WIDTH] [OPTION]... [FILE]...
In the manual page, the fmt command is described as a simple and optimal text formatting Linux. For more detailed information about the fmt command, you can refer to the man fmt section in the manual.
fmt command in Linux with an example
By default, fmt sets the column width at 75.
I have created a file fmt_command.txt
[vagrant@DevopsRoles ~]$ cat fmt_command.txt
HuuPV, My website DevopsRoles.com and HuuPhan.com.SN:199x.
Devops Roles.
Hello world. xxx.
fmt with no options
[vagrant@DevopsRoles ~]$ fmt fmt_command.txt
HuuPV, My website DevopsRoles.com and HuuPhan.com.SN:199x. Devops Roles.
Hello world. xxx.
How to change the width of formatting.
[vagrant@DevopsRoles ~]$ fmt --width 20 fmt_command.txt
HuuPV, My website
DevopsRoles.com and
HuuPhan.com.SN:199x.
Devops Roles.
Hello world. xxx.
with -u option uses one space between words and two spaces after sentences for formatting.
[vagrant@DevopsRoles ~]$ fmt -u fmt_command.txt
HuuPV, My website DevopsRoles.com and HuuPhan.com.SN:199x. Devops Roles.
Hello world. xxx.
Formatting Multiple Files
You can also format multiple files simultaneously. Simply list the files as arguments:
fmt file1.txt file2.txt file3.txt
fmt will process each file and output the formatted text for all of them.
Splitting Long Lines
If you need to split long lines without breaking words, use the -s or --split-only option:
fmt -s myfile.txt
This option splits lines at spaces, ensuring words are not cut off.
Advanced Formatting Options
The fmt command offers several advanced options for more precise text formatting:
-c or --crown-margin: Preserve the indentation of the first two lines.
-t or --tagged-paragraph: Format the text as tagged paragraphs, maintaining a hanging indentation.
-g or --goal: Set the goal width for formatting. This is the preferred width, while the -w option sets the maximum width.
Frequently Asked Questions
What is the default width for the fmt command?
The default width is 75 characters. You can change it using the -w or --width option.
Can fmt handle multiple files at once?
Yes, you can list multiple files as arguments and fmt will format each of them.
How can I preserve indentation with fmt?
Use the -u or --uniform-spacing option to keep the original indentation intact.
What is the difference between the -w and -g options?
The -w option sets the maximum line width, while the -g option sets the goal width, which is the preferred width for formatting.
Can fmt split long lines without breaking words?
Yes, use the -s or --split-only option to split lines at spaces without cutting off words.
Conclusion
The fmt command is a straightforward Linux utility that helps format text files, set column width commands, and ensure uniform spacing. It simplifies text editing tasks, making it a valuable tool for developers and system administrators alike. Thank you for reading this guide on the DevopsRoles page!
By understanding and utilizing the various options and features of fmt, you can efficiently format text files to meet your specific requirements. Experiment with the examples provided in this guide and explore the full potential of the fmt command in your Linux environment.
Good morning, I am working and changing the ownership folder of my home, but I cannot run chown command. It is Error “Invalid argument”. This is indeed an NFS4 issue. The error chown Invalid argument as following below:
[root@Client ~]# chown -R huupv:huupv /home/huupv
chown: changing ownership of `huupv/.bashrc': Invalid argument
chown: changing ownership of `huupv': Invalid argument
[root@DevopsRoles ~]# cat /etc/exports
The Content in file exports
#Data Volume Share
/mnt/data 192.168.1.12(rw,sync,no_root_squash,no_subtree_check)
Solve Problem
From the Client, we will umount and mount as below
[root@Client ~]# umount /mnt/data # if umount is busy then you need run umount -lf /mnt/data
[root@Client ~]# mount -t nfs -o vers=3 192.168.1.13:/mnt/data /mnt/data
[root@Client ~]# chown -R huupv:huupv /home/huupv
You have solved the problem “chown Invalid argument centos” Thank you for reading the DevopsRoles page!
In this tutorial, How to run Spring Boot Application as a service in Linux. Spring boot preferred deployment method via an executable jar file that contains tomcat inside.
Spring Boot application as a service
Spring Boot and Systemd
Create new file “/etc/systemd/system/myapp.service” as a service to start on reboot.
In this tutorial, How to install Gradle on CentOS. Gradle is a free and Open Source that helps your build, automate and deliver better software, faster.
Prerequisites
Server instance : CentOS 7
A sudo user.
Your System update
Login into the sudo user and run the following commands to update your system.
This tutorial is a Step-by-Step Guide to Redis Install and Configure. Now, let’s go Redis Install and Configure.
Dive into the efficient world of Redis with this detailed guide on installation and configuration on Linux systems. Whether you’re setting up Redis for the first time or optimizing an existing installation, this tutorial offers clear, step-by-step instructions to get Redis up and running smoothly on your server.
Redis
It is an Open Source.
In-memory data structure store.
Used as Database.
Cache and message broker.
Redis is a key-value pair cache and store
Redis is perfect for storing sessions. All operations are performed in memory, so reading and writing will be fast
$ cd /opt
$ wget http://download.redis.io/releases/redis-5.0.5.tar.gz
$ sudo tar zxvf redis-5.0.5.tar.gz
$ cd redis-5.0.5
Install Redis
$ sudo make test
$ sudo make
$ sudo make install
If the following error is in make test command as below.
You need tcl 8.5 or newer in order to run the Redis test
make[1]: *** [test] Error 1
make[1]: Leaving directory `/opt/redis-5.0.5/src'
make: *** [test] Error 2
You need to install tcl
$ sudo yum install -y tcl
Again install Redis
$ sudo make test
Error
Executing test client: couldn’t execute “src/redis-benchmark”: no such file or directory.
Then perform the following steps
$ sudo make distclean
$ sudo make
$ sudo make install
For more advanced details the “redis.conf” file configuration item is described as follows:
When the client is idle for a long time, close the connection
timeout 300
Specify the logging level. Redis supports four levels: debug, verbose, notice, and warning. The default is verbose.
loglevel verbose
Set the number of databases, the default database is 0, you can use the “select DBID from v$database;” command to specify the database ID on the connection
databases 16
Set the IP address and port of the master service when the machine is slav service. When Redis starts, it will automatically synchronize data from the master.
slaveof <masterip> <masterport>
When the master service is password protected, the slav service connects to the master password.
masterauth <master-password>
Set the Redis connection password. If the connection password is configured, the client needs to provide the password through the AUTH command when connecting to Redis. The default is off.
requirepass abc
Set the maximum number of client connections at the same time. The default is unlimited.
maxclients 128
Specify the maximum memory limit of Redis. Redis will load the data into the memory at startup. After the maximum memory is reached, Redis will first try to clear the expired or expired Key. When this method is processed, the maximum memory setting is still reached. The write operation will no longer be possible, but the read operation will still be possible. Redis’ new VM mechanism will store the Key in memory and the value will be stored in the swap area.
maxmemory <bytes>
You can use the same configuration file between multiple Redis instances on the same host, and each instance has its own specific configuration file.
include /path/to/local.conf
Conclusion
Successfully installing and configuring Redis enhances your application’s performance by providing rapid data access. This guide aims to equip you with the knowledge to seamlessly integrate Redis into your system, ensuring optimal setup for a robust data management solution. Thank you for reading the DevopsRoles page!
The sed command is a stream editor for filtering and transforming text. In this tutorial, How to sed command in Linux with Examples.
The sed command-Line in Linux, which stands for “stream editor,” is a powerful text processing tool used for performing various text manipulations and transformations. It reads input line by line, applies specified operations, and outputs the result. Here are a few examples of how to use the sed command line:
Syntax
sed [OPTION]... {script-only-if-no-other-script} [input-file]...
On the man page, the describes it
sed – modifies lines from the specified File parameter according to an edit script and writes them to standard output.
man sed – More details information about the sed command.
The sed command in Linux with Examples
For example, the file sed_test.txt as below
[huupv@DevopsRoles vagrant]$ cat sed_test.txt
# /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help
driftfile /var/lib/ntp/ntp.drift
# Enable this if you want statistics to be logged.
#statsdir /var/log/ntpstats/
statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable
# Specify one or more NTP servers.
# Use servers from the NTP Pool Project. Approved by Ubuntu Technical Board
# on 2011-02-08 (LP: #104525). See http://www.pool.ntp.org/join.html for
# more information.
pool 0.ubuntu.pool.ntp.org iburst
pool 1.ubuntu.pool.ntp.org iburst
pool 2.ubuntu.pool.ntp.org iburst
pool 3.ubuntu.pool.ntp.org iburst
Append line
$ sed '/^pool 3/ a server ntp.devopsroes.com' sed_test.txt
Insert line
It will be added lines before the matching line.
$ sed '/^pool 3/i server ntp.devopsroles.com' sed_test.txt
Delete line
used d to delete matching lines. \s is escaped for regular expressions.
$ sed ' /^pool\s[0-9]\.ubuntu/d' sed_test.txt
How to write multi-line
There are two ways, use {} or other files.
Use {}
$ sed ' {
/^pool 0/i server ntp.devopsroles.com
/^pool\s[0-9]/d
} ' ./sed_test.txt
create a ntp.sed file and read with the -f option.
The content ntp.sed file.
/^$/d
/^\s*#/d
/^pool 0/ i server ntp.devopsroles.com prefer
/^pool\s[0-9]\.ubuntu/d
Explain the above line.
/^$/d - Delete blank lines.
/^\s*#/d - Delete the line following # after any space including 0 (Delete comment line of #)
As a result
$ sed -f ntp.sed sed_test.txt
The backup file before changing the original file has been modified.
$ sed -i.bak -f ntp.sed ntp.conf
Print specific lines from a file
sed -n '2,5p' input_file
Delete lines matching a pattern
sed '/pattern/d' input_file
Append text after a specific line
sed '/pattern/a\new_line' input_file
Conclusion
sed Linux is a simple command in Linux. It uses the number of lines of files. These are just a few examples of how to use the sed command in Linux.
The sed command offers a wide range of text manipulation capabilities, including search and replace, insertions, deletions, and more. Thank you for reading the DevopsRoles page!
In today’s DevOps-driven world, Kubernetes has become an essential tool for managing containerized applications at scale. However, setting up a full Kubernetes cluster can be complex and resource-intensive. How to Minikube Build local Kubernetes.
Minikube is a lightweight Kubernetes implementation that creates a local, single-node Kubernetes cluster for development and testing. In this guide, we’ll walk you through everything you need to know to build a local Kubernetes environment using Minikube, from basic setup to advanced configurations. In this tutorial, How to use Minikube Build local Kubernetes environment.
Why Use Minikube?
Ease of Use: Minikube simplifies the process of setting up a Kubernetes cluster.
Local Development: Ideal for local development and testing.
Resource Efficient: Requires fewer resources compared to a full-scale Kubernetes cluster.
Feature-Rich: Supports most Kubernetes features and add-ons.
Prerequisites
Before you start, ensure you have the following:
A computer with at least 2GB of RAM and 20GB of free disk space.
A hypervisor like VirtualBox, VMware, Hyper-V, or KVM.
kubectl, the Kubernetes command-line tool, was installed.
Minikube installed.
My Virtual Machine has installed Docker. Reference: Link here
$ sudo kubectl run hello-minikube --image=k8s.gcr.io/echoserver:1.4 --port=808
To verify node and pod
$ sudo kubectl get nodes
$ sudo kubectl get pods
Instances run on nodes as Docker containers. Displays a list of deployments.
$ sudo kubectl get deployments
Creating service
You use "--type=NodePort" option. Open the service on the IP of each node to the static port (NordPort). A ClusterIP Service routed by the NodePort Service is automatically created. You can access the NordPort Service from outside the cluster by requesting :
Minikube started with the "--vm-driver=none" option, it can only be accessed from the host OS using the proxy. Therefore, change the proxy settings so that they can be accessed from outside the host OS (browser).
$ sudo kubectl get nodes
$ sudo kubectl get pods
$ sudo kubectl get services
$ sudo kubectl get deployments
Stop minikube and delete the cluster
$ sudo minikube stop
$ minikube delete
Conclusion
Minikube is an excellent tool for developers who want to learn and experiment with Kubernetes without the complexity of setting up a full-scale cluster. By following this guide, you can easily set up a local Kubernetes environment using Minikube, deploy applications, and explore advanced features. Whether you’re a beginner or an experienced developer, Minikube provides a convenient and efficient way to work with Kubernetes on your local machine.
In this tutorial, How to install Minikube kubernetes to configure a single Node Cluster within a VM. How do I Configure Kubernetes which is a Docker Container system?
A Hypervisor supported by Minikube. In this example, Install KVM Hypervisor. You can use other Hypervisors such as VirtualBox, VMware Fusion v.v.
#show status
[root@DevopsRoles ~]# minikube status
[root@DevopsRoles ~]# minikube service list
[root@DevopsRoles ~]# minikube docker-env
[root@DevopsRoles ~]# kubectl cluster-info
[root@DevopsRoles ~]# kubectl get nodes
[root@DevopsRoles ~]# virsh list
[root@DevopsRoles ~]# minikube ssh # possible to access with SSH to the VM
[root@DevopsRoles ~]# minikube stop # to stop minikube, do like follows
[root@DevopsRoles ~]# minikube delete # to remove minikube, do like follows
[root@DevopsRoles ~]# virsh list --all
Conclusion
Thought the article, How to install “Minikube Kubernetes on Centos” as above. I hope will this your helpful. Thank you for reading the DevopsRoles page!
