Features:

• Ability to load and performance test many different applications/server/protocol types. like (FTP, SMTP, TCP, Apache etc)
• Generate Dynamic HTML report.
• Extract data in HTML, JSON , XML or any textual format formats.
• Portability and 100% Java purity.
• Multi-threading, testing and debugging.
• CLI mode (Command-line mode) to load test from any Java compatible OS.
• Caching and offline analysis/replaying of test results.

Install JAVA on CentOS 8 / RHEL 8

JMeter is compatible with Java version 8 or higher. so first, we have to install Java to run it normally.

dnf install java-11-openjdk-devel -y

Installation done, now you can verify Java version using below command:

java -version

Install Apache JMeter on CentOS 8 / RHEL 8

You can also download latest binary release from its website.

Download it using below command

cd
wget https://downloads.apache.org//jmeter/binaries/apache-jmeter-5.4.1.tgz
ls

Now unpack downloaded package

tar zxvf apache-jmeter-5.4.1.tgz
ls

Once its done there is no need to install it, just go to apache-jmeter-5.4.1/bin directory and run Jmeter using below commands.

cd apache-jmeter-5.4.1/bin/
./jmeter

Finally its done. Now you can start using JMeter to run load testing tool for analyzing and measuring the performance of a variety of services.

The post How to Install Apache JMeter on CentOS 8 / RHEL 8 appeared first on OS Grove.

kill is a command that is used in many operating systems to send signals to the running processes. In linux kill command is normally used to terminate running process. The kill command can be executed in many ways. In this very article we gonna cover basics of kill command so you gonna understand and then applies in your environment.

Before kill or terminate any process we must know its process ID (PID) or process name, so to find a process name we have two commands which can be run. First is “ps” command and the second it “top” command. in this artice we will use ps command to find a process ID and its name.

Find process using ps command

ps command used to check processes, the below command is used to list all running processes.

ps aux

a: Show processes for all users
u: Display the user who is using the process
x: Show all processes. (It shows the processes running in a GUI environment)

List specific process ID

If you want to search any specific process you can use any of following three Procedure.

Procedure 1:

ps -aux | grep process-name

We gonna check for vsftpd(FTP server) process

ps -aux | grep vsftpd

As you can see process ID of vsftpd in following image.

Procedure 2: Use pidof command

pidof vsftpd

Sample outputs:

17702

Procedure 3: Use pgrep command

pgrep vsftpd

All above Procedure gonna show you process ID’s of vsftpd process.

Kill Process

kill command used to terminate or kill running processes.

Procedure 1: Kill process by its process ID

Now I will kill one vsftpd process using its process ID.

kill -9 17702

now verify that PID is killed

pidof vsftpd

You can see in below image that process 17702 is no more exist.

Procedure 2: Kill process by its name

If you want to kill all the processes of a service you can use this method.

kill -9 vsftpd

OR

pkill vsftpd

Now verify that process is killed

pidof vsftpd

Now you will see that all processes of vsftpd will no more exist.

Kill all processes of a User

To show all running processes of a user, run below command

ps -fu user-name

Now you will get process ID’s of that user. E.g I show process ID’s of  user “osgrove” in above image

Now run below command to kill all processes of that user.
You need to make sure that you are going to use following command while your are login on a root user. On other hand if you run following command while working from a user then your session will be terminated.

kill -HUP process-ids

kill -HUP 46397 46406 46416 46417 46421 46476

Now when you run following command again there you gonna see no result of it.

ps -fu user-name

That’s about it.
Now you get enough idea that how to kill running processes in linux.

The post Use of Kill process in Linux appeared first on OS Grove.

There are two types of ACLs:

1- Access ACL
2- Default ACL

Access ACL

Access ACL are utilized to give assurance for a file system object.

Default ACL

Default ACL can only be applied to a directory. If files/folders placed under that directory won’t have a ACL set, they inherit the default ACL of their parent directory .
ACLs can be configured per user, per group, or per user not in the owning group of a file and also can be configured using UMASK.
Permissions must be defined in characters r,w and x in ACLs.
ACLs are set and removed using setfacl, with either the -m or -x options, respectively.

Configure Access ACL:

Setting ACL on a folder for users.

First we gonna create multiple users “zack” and “zeeshan“

useradd zack
useradd zeeshan

Then, create a example directory which we gonna use for ACL.

mkdir exampledir
ls -lh

Then set Access ACL on that directory

setfacl -R -m u:zack:rwx exampledir
setfacl -R -m u:zeeshan:r-x exampledir

Setfacl Command to set ACL
-R recursively for directory.
-m to add or modify acl.
u used for user.
rwx permissions read, write and execute.

Now run following command

ls -lh

Now we will see a plus (+) sign along with permissions section of exampledir folder. It shows that ACL is set on that file/folder.

List configured ACL

Command to see configured ACLs is getfacl

getfacl exampledir

Now user zack has full permissions on testdir he can create, modify files/folder in exampledir.
But user zeeshan has limited permissions on testdir he cannot create files/folder in exampledir.

Set acl on a folder for a group

First create a group “admin” then, create a new directory.

groupadd admin
mkdir newexampledir
ls -lh

Now set ACL on created directory.

setfacl -R -m g:admin:rwx newexampledir

g It is used to set ACL on group

Now all the member of “admin” group will have rwx permissions on newexampledir folder.

getfacl newexampledir

Set acl on a folder for a group and a user.
Always keep in mind users have high priority then groups in ACL.

Create a group “support“

groupadd support

Then, create two users and assign them “support” group

useradd razee -g support
useradd zaheer -g support

Now, create a exmp folder

mkdir exmp 
 ls -lh 

set ACL for “support” group and “razee” user

 setfacl -R -m g:support:rwx exmp
 setfacl -R -m u:razee:r-x exmp
 getfacl test

In above scenario both users razee and zaheer are member of support group.
but user razee is also have separate acl for it. (It means user razee acl has high priority over group acl).
zaheer has full access on exmp folder, e.g. he can make files/folders in that folder.
But razee cannot create files/folders in exmp folder because he do not has full w(write) permission.

Set ACL for others

we will set it on exmp folder.
Let’s for instance azam is other user. It means he is not the owner nor the member of that “exmp” folder’s group.

useradd azam
setfacl -R -m o:r-x exmp
getfacl exmp

Now user azam has read and execute permissions on exmp folder. It means it can read all files folders under exmp folder.

Assign full permissions to user “azam”

setfacl -R -m o:rwx exmp
getfacl exmp

Now user azam has full permissions on exmp folder. It means it can read, write, modify files folders under exmp folder.

Remove all Permission from user “azam“

setfacl -R -m o:--- exmp
getfacl exmp

Now user azam has no permissions on exmp folder. It means it cannot go to exmp folder.

To remove single/desired ACL from a file/folder.
we will remove ACL of user zack from exampledir folder.

setfacl -R -x u:zack exmp
getfacl exmp

x it is used to remove ACL

To remove all the ACLs from a file/folder:
we will remove ACLS from exmp folder

setfacl -R -b exmp
getfacl exmp

-b used to remove all ACLs

Default ACL

The default ACL is a specific type of permissions assigned to a directory, default ACL doesn’t change the permissions of the directory itself, but specified permission in that ACL will set by default on all the folders which will be created inside of it for specified user, group and other users.
We can say the default ACL permissions on parent directory inherit by subdirectories.

We will set default ACL for user zeeshan.

mkdir exampledir1
setfacl -m d:u:zeeshan:rx exampledir1
getfacl exampledir1

d it used to set default ACL.

Now each directory created under test directory will have default permission of rx for user zeeshan.

Now we will set default ACL for group admin.

setfacl -m d:g:admin:rwx exampledir1
getfacl exampledir1

We will set default ACL for other

setfacl -m d:o:--- exampledir1
getfacl exampledir1

That’s about it.

The post How to configure Acl in Linux appeared first on OS Grove.

Run top command and it will show the following

top

PID: Shows each task unique process id.
PR: shows task priority
SHR: Represents the amount of shared memory used by a task.
VIRT: Total virtual memory.
USER: User name or owner of task.
%CPU: Represents the CPU usage.
TIME+: CPU Time
SHR: display Shared Memory in kb used by a task.
NI: Shows a Nice Value of task. A Negative nice value means higher priority, and positive Nice value means lower priority.
%MEM: Shows the Memory usage of task.

press “q” on your keyboard to quite from top.

Highlight Running Process in Top

When you execute top command press “z” key to highlight running processes.

Show Path of Processes

Make sure press “c” after running top command and it will show the path of processes.

Kill running process

After running Top command you can see all processes along with their process ID (PID)

If you want to kill a process,
simply run “Top” command to find your specific process ID,
Press “k” and then type your PID number
and press “enter” key to kill it.

Renice a Process

Renice is used to change a process priority.
By simply running a “top” command you can find your specific process ID.

I will renice the priority of PID 22.
Use this command “renice -n -10 p22” to change the priority of the process. You can select your own PID.
You gonna see the Old priority and new one.

That’s about it.

The post Use of Top Command in Linux appeared first on OS Grove.

Prerequisites

The instructions assume that you are logged in as root user and JAVA is installed on machine because JAVA is necessary for it.

Step 1 Install JAVA

As JAVA is Necessary for Maven so, we need to install Java OpenJDK on CentOS 8 and RHEL 8 using below command.

dnf install java-11-openjdk -y

Once the installation done. You can verify Java installation using below command.

java -version 

Step 2: Download and Install Apache Maven

You can download latest binary release from maven download page

Install wget tool

dnf install wget -y

Then go to /usr/local/ directory and download maven.

cd /usr/local/
wget https://downloads.apache.org/maven/maven-3/3.6.3/binaries/apache-maven-3.6.3-bin.tar.gz

Now, extract the compressed file and rename “apache-maven-3.6.3” directory to “maven”

tar -xvf apache-maven-3.6.3-bin.tar.gz
mv apache-maven-3.6.3 maven

Finally it has been installed and you can start using it. but, its environment is not configured but we will do that in next step.

Step 3: Configure Environment for Apache Maven

Now we are going to setup Apache Maven Environment so all users on the machine can use it.

Go to /etc/profile/ directory and create maven.sh file.

cd /etc/profile.d/
vi maven.sh

Now paste below script content in this file

## Apache Maven Environment Variables ##
export M2_HOME=/usr/local/maven
export PATH=${M2_HOME}/bin:${PATH}

Save changes to file and exit.

Make the script file executable and load the environment variable using below commands.

chmod +x /etc/profile.d/maven.sh
source /etc/profile.d/maven.sh

Finally verify Maven installation and its version using below command.

mvn --version

If everything is successful you will see below output.

That’s it. The latest version of Maven is now installed on your CentOS system.

You can also learn, how to monitor your Linux machine using SAR commands by clicking here

The post How to Install Apache Maven on CentOS 8 and RHEL 8 appeared first on OS Grove.

fdisk command

fdisk is a command-line utility that provides disk partitioning functions. It is used to create, modify or delete the partitions on the linux systems. Use following command to list all hard disks and their partitions.

fdisk -l

Small (–l) switch Used to list hard disks partitions

you can see sample output in below image.

df command

df (disk free) is a Unix command used to display the amount of available disk space for file systems. It shows File System, Disk Space Usage and mount point of partitions.

df

to see in human readable form then run following command

df -h

You can see disk partitions, disk sizes, amount of space used and available and mount point of the partition in sample image.

Parted

Parted is another popular commad line utility which allows you to manage hard disks partitions. In this article we will use parted command to see all available hardisks with their size, avaialble and used space of hard disks and created partitions on the hard disks.

Use following command to list hard disks and their partitions on the system

parted -l

sfdisk

Lets check one more command which we use to list partitions and hard drives. It’s quite similar to fdisk command. It shows both physical and logical (virtual) volumes, It provides “summary” of physical volumes, partitions information with the start and end cylinders, total blocks, size and File systems.

sfdisk -l

That’s about it.

The post How to Get Hard Disk and Partition Information in Linux appeared first on OS Grove.

Copy a file

First we gonna create a file “example.txt” and a directory “test” using following commands.

touch example.txt
mkdir test
ls

Now, in the following command we gonna copy a file “example.txt” to the “test” directory.

cp example.txt test

now use following command to check whether example.txt file is copied into test directory.

ls test

Copy multiple files

So in this example we gonna copy multiple files into a directory. Let assume we have many files with .txt extension and all we want to copy them in a directory “test” simply use following command.

cp *.txt test
ls test

* Asterisk means all files matching with .txt extension.

To Copy a Directory

Now we will copy a directory into another directory.
Note: Always use -R (capital R) option whenever you copy a directory so, that complete data having in this directory will also be copied.

We are copying example directory to the test directory.

ls
cp -R example test

Now verify example directory is copied into test directory.

ls test

That’s about it.

The post How to copy Folder/File using cp command in Linux appeared first on OS Grove.

Vim/Vi used to edit or modify a text files in CLI (Command Line Interface). It is most popular and people’s choice text editor in Linux. We gonna discuss its usage and option.

Most often Vim is started to edit a single file with the following command. Vim is nothing but improved version of vi command. We can also use vi command for same purpose. You can use according to your choice.

vim file

If you specify an existing file, then the editor open it for you to edit. Otherwise, you can create a new one.

vim [file_new] or [file_existing]

Vim or Vi has two Modes:

Insert mode press i to insert. We can insert/add text in the file using insert mode.
Command mode for operations the like saving, exiting from a file etc .

I am gonna use test1.txt file for vim command also you can edit any file. Run following command and you gonna get into normal mode.

vim test1.txt

Now if you want to edit your file, you need to go on insert mode. Press “i” for insert mode and now you can add text in the file. It is especially useful for editing programs.

After adding your text, Press “escape” key to switch back to normal mode.
Now save and exit file by typing : x OR :wq and press “enter” key.

You can play around with the arrow keys by using the vim movement keys, as follows.

• h left
• j down
• k up
• l right

Vim commands for Escape/Normal mode.

• :w save changes to file.
• :wq save and exit from file.
• : x save and exit from file.
• :q! Exit without saving.
• i is used to insert.
• o cursor will move to next line to insert.
• x Delete the character the cursor is on.
• yy Copy current line.
• Ctrl+b Go back one page.
• Ctrl+f Go forward one page.
• p past copied line or text.
• y4 Copy multiple lines. 4 is the number of lines we want to copy.
• /stringname to search desired text. String name is the text we want to search.
• n go to next searched string.
• shft+n go to previous searched string.
• :%s/oldstring/newstring/g Replace old text with new text.
• :9 to go line no. 9
• Shift+x Delete the character before the cursor.
• dd Delete the current line, also used for delete.
• Shift+d Delete everything from the cursor to the end of the line.
• u Undo a line you just deleted.
• Shift+u Undo all changes to the current line.
• gg To go on the top of file.
• shft+g To go to the end of file.

That’s about it.You can get a handful of experience on vim by using above commands.

The post How to edit/modify files with Vim and Vi command appeared first on OS Grove.

In this article we will install SAR and use it to monitor server.

Run below command to install SAR on CentOS, RHEL, Fedora

yum install -y sysstat

If you want to install it on Ubuntu run following command

sudo apt-get install sysstat

Start and enable SAR service on system boot.

systemctl start sysstat.service
systemctl enable sysstat.service
systemctl status sysstat.service

SAR reports are saved in /var/log/sa directory. A script “sa1” logs sar output into sysstat binary log file format, and translate it into human readable format in “sar1″ file.

Each and every sar report saved with current date. E.g if today is 10th the sar report will save as sa10 in binary file and sar10 in human readable file.

So you can use below command to see all sar files.

ls /var/log/sa

Run below command to see system statistics.

sar

There are many sar commands but some useful commands are given below.

You can check Server’s average load history using below command.

sar -q

So if you want to see Memory statistics use following command.

sar -R

Command to see CPU utilization statistics.

sar -u

List Memory utilization statistics using -r switch with sar command

sar -r

Check I/O and transfer rate statistics.

sar -b

Mounted Filesystems statistics.

sar -F

Check Swap space utilization statistics using following command.

sar -S

Kernel table statistics.

sar -v

Paging statistics.

sar -B

TTY device statistics.

sar -y

That’s it, hope you like this article. You can add sar in your administration tools to manage and monitor your server activities.

The post How to use SAR Command in Linux appeared first on OS Grove.

Cat Syntax

cat [OPTION] [FILE]

View a file Content

While using following command it will display content of /etc/selinux/config file

cat /etc/selinux/config

View multiple file content

If you want to see multiple files content, simply type following command

cat newfile1 newfile2 newfile3

and it’s gonna list content of all three files respectivily.

Create a File with Cat Command

cat > test1

After that, you can put your desired text into the file and press CTRL+d to exit from file. Redirection Operator “>” used to add text.

Now you gonna see the added text in a test file using following command.

cat test1

Note: If you already have an existing file then you add text in it while using Redirection Opertor “>” it’s gonna overwrite previous content with new one in doing so, you gonna lose your old data. Check following command for a referance.

In above scenario we have created a test file and added some text in it.

Now we gonna add more text in a test file.

cat > test1

After adding text, press CTRL+D to make changes and exit.

Now check “test” file again and you will see that previous text has removed and new text taken its place.

cat test1

Append text in a file

Now if you want to add more text in a file without losing existing content use redirection operator “>>” in a command.

cat >> test1

Now see its content and you will see data is appended instead of overwritten.

cat test1

Copy multiple files content in a single file.

If you want to copy multiple files data in a single file, simply use following command

cat test1 test2 > test3

That’s about it, you get an idea how to use cat command in many ways. See manual using command “man cat” for more information.

The post Use of Cat Command in Linux appeared first on OS Grove.