Install PostgreSQL 13 on CentOS 8 / RHEL 8 / Oracle Linux 8

Both RHEL 8 and its derivatives include PostgreSQL 10 in their repositories. However, we already have available version 13. And it is recommended to install it because thanks to it, we can enjoy interesting news and improvements in the performance of the application. Important, if we are going to store large quantities of records.

So first, open a terminal session. Or if you are using a server connect to it using ssh.

:~$ ssh [your-user]@[your-host]

Then log in as the root user.

:~$ su
:~#

The best way to install PostgreSQL 13 on CentOS 8, RHEL 8 and Oracle Linux 8 is to add the official PostgreSQL refill. Not only is it easy, but also safe and the possibility to be always up to date.

To do this, run the following command:

:~# dnf install https://download.postgresql.org/pub/repos/yum/reporpms/EL-8-x86_64/pgdg-redhat-repo-latest.noarch.rpm

Then, disable the PostgreSQL module on CentOS 8.

:~# dnf module disable postgresql

Now, install PostgreSQL 13 on CentOS 8.

:~# dnf install postgresql13-server postgresql13

After that, let us configure it.

Configure PostgreSQL on CentOS / RHEL 8 / Oracle Linux 8

Initialize PostgreSQL database and start the service

After installing it, the first thing to do is to initialize the database. To achieve this, it is necessary to execute the following command:

:~# /usr/pgsql-13/bin/postgresql-13-setup initdb
Initializing database ... OK

With this, we will have already started the initial database. At this point, the PostgreSQL service is not enable, so you can’t use it yet. Then you have to do it.

:~# systemctl enable postgresql-13

Then, if you want PostgreSQL to start along with the system run this command:

:~# systemctl start postgresql-13

To check that everything is going well, check the status of the service:

:~# systemctl status postgresql-13

As you can see, everything’s fine.

Change the password to the “postgres” user and allow the remote connections

During the installation of PostgreSQL, a new user called postgres is created. The problem is that you do not define a password, so it makes you vulnerable. To avoid problems, it is convenient to create a password.

To do this, just use the Unix passwd command.

:~# passwd postgres

There you will have to enter the password twice. If both are effective, the final change will be made.

Now, we have to allow access to remote connections. The client must be installed on each of the systems that will access PostgreSQL. It will depend on each operating system.

Then, a good security measure is to specify the hosts that can access it. Of course, if the data will be served on the Internet, then it is necessary to allow all the accesses.

:~# nano /var/lib/pgsql/13/data/postgresql.conf

then searches for the listen_addresses line and places the hosts that can access it. If you allow any access, type ‘*’.

listen_addresses = '[host/IP_adress]'
or
listen_addresses = '*'

Then, restart PostgreSQL.

:~# systemctl restart postgresql-13

Finally, you have to open the port 5432 on the firewall to allow the connections.

:~# firewall-cmd --add-port=5432/tcp --permanent
success
:~# firewall-cmd --reload
success

Now, you can access to the PostgreSQL shell.

:~# su - postgres
:~# psql

Now, you can start to work.

Conclusion

PostgreSQL is one of the best there is for databases. Thanks to its community spirit, it is possible to find a lot of documentation about it. On the other hand, installing version 13 on CentOS 8, RHEL 8 and Oracle Linux 8 is quite simple as you have seen in this post.

Also, you can read how to install Postgresql on Ubuntu 18.04?

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The post How to install PostgreSQL 13 on CentOS 8 / RHEL 8 / Oracle Linux 8? appeared first on Linux Windows and android Tutorials.

Docker CLI working

Docker CLI operates as a client/server to communicate with the Docker engine upon creation of operations of a container. But it will raise issues when you have to start the Docker daemon before accessing Docekr CLI live. After it CLI sends API call to the Docker Engine to launch Open Contianer Initiative (OCI) runtime.

Difference between Docker and Podman

One of the main difference between Docker and Podman is that there is no daemon in the Podman. Upon applying any cgroup constraints you apply on the podman command containers will recieve those constraints directly. Moreover, advanced features of systemd can be utilized using this model.

Libpod

Libpod provides the library for those applications which are looking to use the Container Pod concept. It is also refereed as the Home of Podman.
So now lets proceed further

Step 1: Managing Container Images

Type the below command to download the container Images using Podman

$ podman pull ubuntu
$ podman pull centos
$ podman pull centos:8

Run the below command to list the downloaded images

$ podman  images
 REPOSITORY                 TAG      IMAGE ID       CREATED        SIZE
 docker.io/library/ubuntu   latest   3556258649b2   2 weeks ago    66.6 MB
 docker.io/library/alpine   latest   b7b28af77ffe   3 weeks ago    5.85 MB
 docker.io/library/debian   latest   00bf7fdd8baf   4 weeks ago    119 MB
 docker.io/library/centos   latest   9f38484d220f   4 months ago   209 MB

Follow the below syntax to remove the images

$ podman rmi <Type your Container Image ID here>
$ podman rmi 00bf7fdd8baf
 00bf7fdd8baf2ba6f0918e1f48415b2a4a1a616806e7cf32527a749dd2ce4b2c
 $ podman rmi docker.io/library/ubuntu
 3556258649b2ef23a41812be17377d32f568ed9f45150a26466d2ea26d926c32

Tagging Image

Check out the tag by running podman images command

podman tag  <Image ID> webserver

Step 2: Running Containers with Podman

Let’s print a message using simple container

[sabi@localhost ~]$ podman run --rm centos /bin /echo/ "Osradar"
Osradar

Use -d option to run the container in background

podman run -dt -p 8080:8080/tcp -e HTTPD_VAR_RUN=/var/run/httpd -e HTTPD_MAIN_CONF_D_PATH=/etc/httpd/conf.d \

                  -e HTTPD_MAIN_CONF_PATH=/etc/httpd/conf \

                  -e HTTPD_CONTAINER_SCRIPTS_PATH=/usr/share/container-scripts/httpd/ \

                  registry.fedoraproject.org/f29/httpd /usr/bin/run-httpd

It will return the contianer ID:

Trying to pull registry.fedoraproject.org/f29/httpd…Getting image source signatures
 Copying blob d77ff9f653ce done
 Copying blob aaf5ad2e1aa3 done
 Copying blob 7692efc5f81c done
 Copying config 25c76f9dcd done
 Writing manifest to image destination
 Storing signatures
 d2cdf0efb0ddc6e2ae52a5a0bdadababa6ee6cc2e1e49145c92a0474b089b664

To List the running containers, use the below command

$ podman ps
 CONTAINER ID  IMAGE                                        COMMAND               CREATED        STATUS            PORTS                   NAMES
 d2cdf0efb0dd  registry.fedoraproject.org/f29/httpd:latest  container-entrypo…  4 minutes ago  Up 4 minutes ago  0.0.0.0:8080->8080/tcp  cranky_borg
 To include stopped / exited containers, use:
 $ podman ps --all

For accessing a container shell use the option -it

podman run -it ubuntu bash
 root@d273c12899cd:/#
 root@d273c12899cd:/# apt update
  Get:1 http://archive.ubuntu.com/ubuntu bionic InRelease [242 kB]
  Get:2 http://security.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB]          
  Get:3 http://security.ubuntu.com/ubuntu bionic-security/universe amd64 Packages [717 kB]
  Get:4 http://archive.ubuntu.com/ubuntu bionic-updates InRelease [88.7 kB]        
  Get:5 http://security.ubuntu.com/ubuntu bionic-security/main amd64 Packages [535 kB]
  Get:6 http://archive.ubuntu.com/ubuntu bionic-backports InRelease [74.6 kB]

Step 3: Searching in Podman

podman search httpd

Inspect Containers

It will display the some basic info on containers & images identified by name or ID

podman inspect <image id>

For help run the below command

podman inspect --help

Step 4: Removing Containers

To remove the containers, list all running containers.

podman ps -a

Now type the command podman rm with the ID of container image to remove it.

podman rm <image id>

For removing all containers, type the following command.

Note it will remove all containers running and stopped.

podman rm $(podman ps -a -q)

Step 5: View the container’s logs

Here we will view the containers logs in different ways

View by latest category

podman logs --latest

View by mentioning container ID:

podman p
podman logs <image id>

For attaining real-time, use the below command

podman logs -f 
podman logs --follow=true --since 10m Container ID

You can also specify the number of lines in logs:

podman logs --tail 10 

Step 6: View the container’s pids

Type podman top to view container pids.

podman top <image id>

Output:

$ podman top d2cdf0efb0dd
 USER      PID   PPID   %CPU    ELAPSED            TTY     TIME   COMMAND
 default   1     0      0.000   29m22.496484247s   pts/0   0s     httpd -D FOREGROUND 
 default   22    1      0.000   29m21.496767511s   pts/0   0s     /usr/bin/coreutils --coreutils-prog-shebang=cat /usr/bin/cat 
 default   23    1      0.000   29m21.496866314s   pts/0   0s     /usr/bin/coreutils --coreutils-prog-shebang=cat /usr/bin/cat 
 default   24    1      0.000   29m21.497020539s   pts/0   0s     /usr/bin/coreutils --coreutils-prog-shebang=cat /usr/bin/cat 
 default   25    1      0.000   29m21.497127237s   pts/0   0s     /usr/bin/coreutils --coreutils-prog-shebang=cat /usr/bin/cat 
 default   26    1      0.000   29m21.49723933s    pts/0   0s     httpd -D FOREGROUND 
 default   27    1      0.000   29m21.497361006s   pts/0   0s     httpd -D FOREGROUND 
 default   28    1      0.000   29m21.497459891s   pts/0   0s     httpd -D FOREGROUND 
 default   29    1      0.000   29m21.497552695s   pts/0   0s     httpd -D FOREGROUND 

Step 7: Checkpointing the container

Checkpointing a container stops the container while writing the state of all processes in the container to disk. To do this you’ll requires CRIU 3.11 or later installed on the system.

See CRIU Installation guide here.

podman container checkpoint <container id>

Example:

podman container checkpoint d1hf0dbf0dd

It can later be restored and continue running exactly at the same point in time as the checkpoint.

podman container restore <container id>

Step 8: Migrate Container

Migrating the container contains 3 steps.

In first step, checkpoint the container on the source system.

podman container checkpoint <container id> -e /tmp/checkpoint.tar.gz

In Second Step copy it to the destination server.

scp /tmp/checkpoint.tar.gz :/tmp

Last step involve the restoration on the destination system.

Step 9: Manage Container pods with Podman

Podman pods are similar to the Kubernetes concept of Pods.

You can expose most of the interaction with pods through the podman pod command.

podman pod --help

Create a pod called web

podman pod create --name web

Below will creates a pod without the extra attributes available on:

podman pod create --help

Make sure pod is created

podman pod list

By default, the created pod will have a container called infra. The infra container holds the namespace associated with the pod to allow podman to connect to the containers to the pod. It is in sleep mode by default.

podman ps -a --pod

After creating pod, we can add a container to it.

podman run -dt --pod web alpine:latest top

You’ll see that the pod has two containers.

podman ps -a --pod
CONTAINER ID  IMAGE                            COMMAND  CREATED             STATUS                 PORTS  NAMES               POD
 36ccace2d653  docker.io/library/alpine:latest  top      About a minute ago  Up About a minute ago         zen_hugle           0f565b11e9cb
 44cca777d12f  k8s.gcr.io/pause:3.1                      28 minutes ago      Up 28 minutes ago             0f565b11e9cb-infra  0f565b11e9cb

You can also expose a port to the created container with root privileges.

sudo podman pod create -p 8080:80 --name web1
sudo podman run -dt --pod web1 -p  8080 nginx:latest

You need to publish as many port as will be used during the pod creation. This can't be changed after the creation.

So this is how we can run Docker Container using podman and libpod.

The post How To run Docker Containers using Podman and Libpod. appeared first on Linux Windows and android Tutorials.

Step 1: Install iscsi-initiator-utils on CentOS / RHEL 8.

sudo dnf -y install iscsi-initiator-utils

Step 2: Configure Initiator Name

Edit the file /etc/iscsi/initiatorname.iscsi/ and name it to match the target server name you’ve used.

sudo vi /etc/iscsi/initiatorname.iscsi

InitiatorName=iqn.2019-11.com.osradar:initiator01

Step 3: Configure Credentials

Open the following file to set up credential details.

sudo vi /etc/iscsi/iscsid.conf

Note: Use the credentials as you’ve done in setting up target so they match.

Uncomment "node.session.auth.authmethod=CHAP"
Uncomment "node.session.auth.username" and set username as "Initiator01"
Uncomment "node.session.auth.password" and set it as you've setup in previous setup.

Step 4: Testing iSCSI Target discovery

Run the following command to confirm that iSCSI can discover our installed iSCSI Target.

iscsiadm -m discovery -t sendtargets -p 172.17.52.184

Note: Use your iSCSI target server IP.

If the IP info and access details is displayed we can say the discovery is successful.

Step 5: Confirm Target’s status

Run the given command to check the status.

iscsiadm -m node -o show

# BEGIN RECORD 6.2.0.874-10  node.name = iqn.2019-11.osradar.com:target01  node.tpgt = 1  node.startup = automatic  node.leading_login = No  iface.hwaddress =   iface.ipaddress =   iface.iscsi_ifacename = default  iface.net_ifacename =   iface.gateway =   iface.subnet_mask =   iface.transport_name = tcp  iface.initiatorname =   iface.state =   iface.vlan_id = 0  iface.vlan_priority = 0  iface.vlan_state =   iface.iface_num = 0  iface.mtu = 0  

Step 6: Access iSCSI Target on CentOS / RHEL 8

Login to your account by typing this command , you will see a success message at the end.

iscsiadm -m node --login

Logging in to iface: default, target: iqn.2019-11.osradar.com:target01, portal: 172.17.255.109,3260 Login to [iface: default, target: , portal: 172.17.255.109,3260] 
 iqn.2019-11.osradar.com:target01 successful.

Make sure you’re logged into your iSCSI Target Server.

iscsiadm -m session -o show

tcp: [1] 172.17.255.109:3260,1 iqn.2019-11.osradar.com:target01 (non-flash)

Check disks if you’ve added Target’s disk

We’ve created backstore of 5GB space in our previous tutorial.

lsb1k

Format & mount the new disk to make it ready for use.

In this tutorial we’ll use fdisk to set up LVM type. You are free to use your desired one.

fdisk /dev/sdb

Confirm the new partition number.

lsb1k

Look at the new partition , we have sdb1 as seen below. Now, add a file system on the new partition.

 NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT  fd0               2:0    1    4K  0 disk  sda               8:0    0   20G  0 disk  ├─sda1            8:1    0  953M  0 part /boot  └─sda2            8:2    0 19.1G  0 part    ├─centos-root 253:0    0    6G  0 lvm  /    ├─centos-swap 253:1    0  956M  0 lvm  [SWAP]    ├─centos-home 253:2    0  7.5G  0 lvm  /home    └─centos-var  253:3    0  4.7G  0 lvm  /var  sdb               8:16   0    5G  0 disk  └─sdb1            8:17   0    5G  0 part ##sdb1 Added  sr0              11:0    1 1024M  0 rom 

Set file system on the partition

Here, we’ll use xfs. You can use any (ext3,ext4,Btrfs etc) to fit your case.

mkfs.xfs /dev/sdb1

Mount your partition and confirm

mount /dev/sdb1/mnt

df -TH

Congratulations! You’ve all done. If have any queries regarding this tutorial, you can ask in comments.

The post How To Configure iSCSI Initiator on CentOS / RHEL 8. appeared first on Linux Windows and android Tutorials.

OpenNMS is a free & open source highly configurable, scaleable, extensible and cross-platform network Monitoring and network management platform. It is built using Java.

Features:

• Device & Application Monitoring
• Event-driven Architecture.
• It supports the collection of performance from Industry standard agents via SNMP,JMX,WMI,NPRE,NSCLient++ & XMP simply through configuration.
• Provides easy integration to extend service polling, performance & data collection framework.
• Different modes like maual, detected or ReST API driven interfaces.

OpenNMS Requirements:

Operating System: Red Hat Enterprise Linux 8 or Centos 8.
Minimal Hardware: 2 CPU, 2 GB RAM, 20 GB Disk.

In this tutorial, we will learn how to install & setup the latest OpenNMS Horizon network service monitoring software in Centos / RHEL 8.

Step 1: Install Java & Setting Java_Home

yum install java-11-openjdk

Check installed version

java -version

Add this line to set Java Environment to all users at boot time.

export JAVA_HOME=/usr/lib/jvm/java-11

Step 2: Installing OpenNms Horizon

For installing OpenNMS Horizon, add the following yum repository & then import GPG key.

yum -y install https://yum.opennms.org/repofiles/opennms-repo-stable-rhel8.noarch.rpm
rpm --import https://yum.opennms.org/OPENNMS-GPG-KEY

Now, Install opennms meta package together alognwith all its built-in dependencies like jicmp6, opennms-webapp-jettty, postgresql and many more.

yum -y install opennms

Confirm that packages are successfully installed.

cd /opt/opennms

Step 3: Initializing & Setup PostgreSQL

Initialize the PostgreSQL database

postgresql-setup initdb

Start & enable PostgreSQL services and check status for confirmation.

systemctl start postgresql
systemctl enable postgresql
systemctl status postgresql

Switch to PostgreSQL user account to create access to PostgreSQL. After it create opennms database user with a password & create an opennms database.

su - postgres
createuser -P opennms
createdb -O opennms opennms 

Setup password for Postgres super user.

psq; -c "ALTER USER postgres WITH PASSWORD 'admin123';"
 exit

Modify the access policy for PostgreSQL in the /var/lib/pgsql/data/pg_hba.conf config file.

vi var/lib/pgsql/data/pg_hba.conf

Change the authentication method to md5 by finding given lines to allow OpenNMS Horizon accessing database over LAN with a MD5 hashed password.

host           all            all           127.0.0.1/32           md5
host           all            all           ::1/128                   md5

Reload postgresql to take effect of configuration.

systemctl reload postgresql

Now, configure the db access in OpenNMS Horizon by opening following file.

vim /opt/opennms/etc/opennms-datasources.xml. 

And set up Credentials.

Step 4: Initialize & Start OpenNMS Horizon

Now, you need to integrate the default version of JAVA with OpenNMS. Run the following command to detect environment and persist in the /opt/opennms/etc/java.conf file.

/opt/opennms/bin/runjava -s

On next step, you need to run the OpenNMS installer which will initialize the db and detect system libararies persisted in /opt/opennms/etc/libararies.properties.

/opt/opennms/bin/install -dis

Start OpenNMS service via systemd for the mean time, enable it to auto-start at system boot.

systemctl start opennms
systemctl enable opennms
systemctl status opennms

Allow 8990 port to access Web Console.

firewall-cmd --permanent --add-port=8980/tcp
 firewall-cmd --reload

Step 5: Access OpenNMS Web Console & Login

Go to your browser and type any of the following command to access the web console.

http://SERVER_IP:8980/opennms
 OR
 http://FDQN-OF-YOUR-SERVER:8980/opennms

Provide authentication details as default username admin & password admin.

This is not secure so you should change your password. To do so, go to main navigation menu on admin.

Under Account Self-Service, click Change Password”.
Enter the old, set new and click “Submit”. Afterwards, logout and login with your new user details for security.

That’s it You’ve done installing OpenNMS, if have any queries regarding this tutorial feel free to ask!

The post How to Install OpenNMS on Centos / RHEL 8. appeared first on Linux Windows and android Tutorials.

What is Zabbix?

Zabbix is quite a wonder. It is an open-source application that works under the client-server architecture. In other words, when installed on any server, it requires an agent to be installed on the client computers. In this way, the application will be able to monitor all the behavior of the nodes as well as the performance of the network.

On the other hand, the development of Zabbix is quite positive and constant, which makes it quite safe and functional. In addition to being quite mature in its development supports several database management systems including the popular MariaDB, MySQL, PostgreSQL or proprietary alternatives such as Oracle and IBM DB2.

In this post, we will install step by step the Zabbix server on CentOS 8 / RHEL 8 / Oracle Linux 8.

Install Zabbix on CentOS 8 / RHEL 8 / Oracle Linux 8

As expected, Zabbix has precompiled binaries available for RHEL 8 and derivatives. These are available from the official repository, but there are some prerequisites we must meet. One of them is that we need a web server running on our computer. Besides that, a database management system like MariaDB.

Install LAMP on CentOS 8 / RHEL 8 / Oracle Linux 8

In this case, we have a complete tutorial where you can install LAMP on CentOS 8 / RHEL 8 / Oracle Linux 8. There, step by step, you will be able to get a web server running as well as the database manager MariaDB.

Read, How to install LAMP on CentOS 8 / RHEL 8 / Oracle Linux 8?

Create the Zabbix user on MariaDB

Once the server is running correctly. It is necessary to create a new user and database for Zabbix. To do this, open the MySQL console and run:

:~# mysql -u root -p 
> CREATE DATABASE zabbixdb;
> GRANT ALL PRIVILEGES ON zabbixdb.* TO 'zabbixuser'@'localhost' IDENTIFIED BY 'zabbixpss';
> FLUSH PRIVILEGES;
> exit;

Install Zabbix on CentOS 8 / RHEL 8 / Oracle Linux 8 (I)

Then we can install Zabbix without problems. We will achieve this by using the official Zabbix repository for RHEL 8.

So as a root user, run the following command to add the GPG key from the repository:

:~# rpm --import http://repo.zabbix.com/RPM-GPG-KEY-ZABBIX

Then add the repository as such:

:~# rpm -ivh https://repo.zabbix.com/zabbix/4.0/rhel/8/x86_64/zabbix-release-4.0-2.el8.noarch.rpm

Then proceed to install the Zabbix packages.

:~# dnf install zabbix-server-mysql zabbix-web-mysql zabbix-agent zabbix-get zabbix-sender zabbix-java-gateway

If you want you can modify the PHP timezone on the Zabbix configuration file.

:~# nano /etc/httpd/conf.d/zabbix.conf

Uncomment the line date.timezone and add your timezone.

php_value date.timezone [TIMEZONE]

The next step is to load the initial Zabbix database.

:~# zcat /usr/share/doc/zabbix-server-mysql*/create.sql.gz | mysql -u zabbixuser -p zabbixdb

Then, it is necessary to specify the database parameters in the Zabbix configuration file.

:~# nano /etc/zabbix/zabbix_server.conf

In this file, you have to modify the following values

DBHost:localhost
DBName=[DB_name]
DBUser=[Mariadb_zabbix_user]
DBPassword=[Password]

Save the changes and close the file. The next step is to open the Zabbix ports in the Firewall so that it can run smoothly.

:~# firewall-cmd --permanent --add-port=10050/tcp
success
:~# firewall-cmd --permanent --add-port=10051/tcp
success
:~# firewall-cmd --reload
success

Finally, start the service. If you want Zabbix to run at system startup, you can add these commands:

:~# systemctl enable zabbix-server
:~# systemctl start zabbix-server
:~# systemctl restart httpd

Install Zabbix on CentOS 8 / RHEL 8 / Oracle Linux 8 (II)

The last thing we need to do before we have our Zabbix server running is to complete the installation using the web browser. Open it and go to http://your-server/ you will see this

Then, the installer will check the prerequisites.

Now, we have to set the parameters of the database that we have previously defined.

Then, set up some server details.

In the end, you will see the summary and the message that Zabbix has been successfully installed.

After finishing the process, you will see the login screen. Log in with admin as user and zabbix as password.

Finally, you will see the dashboard. And that is it.

Install the Zabbix agent on the nodes

In order for Zabbix to monitor correctly, it is necessary to install the agents in each of the nodes. Probably, they use different operating systems, so the installation can vary in each of them.

First, you have to add the Zabbix repository for each system. In case you use Ubuntu 18.04:

:~$ wget https://repo.zabbix.com/zabbix/4.0/ubuntu/pool/main/z/zabbix-release/zabbix-release_4.0-2+bionic_all.deb
:~$ sudo dpkg -i zabbix-release_4.0-2+bionic_all.deb
:~$ sudo apt update

Then, install Zabbix with the following command:

:~$ sudo apt install zabbix-agent

If you use CentOS 8, add the repository with this command:

:~# rpm -ivh https://repo.zabbix.com/zabbix/4.0/rhel/7/x86_64/zabbix-release-4.0-2.el7.noarch.rpm

Then, install the agent with the following command:

:~# yum install zabbix zabbix-agent

Finally, if you use Debian 9:

:~$ wget https://repo.zabbix.com/zabbix/4.0/debian/pool/main/z/zabbix-release/zabbix-release_4.0-2+stretch_all.deb
:~# dpkg -i zabbix-release_4.0-2+stretch_all.deb
:~# apt update

And you install it with the command:

:~$ apt install zabbix-agent

Conclusion

Zabbix is an important application in any network service. Thanks to it it is possible to do complete monitoring on the operation of the same one. It also verifies the state of the nodes. In this post, you have learned to install it on the server-side.

The post How to install Zabbix server on CentOS 8 / RHEL 8 / Oracle Linux 8 ? appeared first on Linux Windows and android Tutorials.

GlassFish is the reference implementation of Java EE and as such supports Enterprise JavaBeans, JPA, JavaServer Faces, JMS, RMI, JavaServer Pages, servlets, etc. This allows developers to create enterprise applications that are portable and scalable, and that integrate with legacy technologies. Optional components can also be installed for additional services.

Step 1: Install Some necessary packages

Install wget and unzip using below commands

dnf install -y wget unzip

Step 2: Install and Configure OpenJDK

dnf install -y java-1.8.0-openjdk

Set Java’s Home Environment

Run below command to find java path

update-alternatives --config java

Then copy that path and insert it into below file

Now Set Java’s Path in Your Environment using below command

vi .bash_profile

Now add below line in .bash_profile file

export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.222.b10-0.el8_0.x86_64/jre/bin/java

Refresh .bash_file to make changes using below command

source .bash_profile

Run below commands to see the Java path you set and the java version.

echo $JAVA_HOME
java -version

Step 3: Installing Glassfish 5.0 on RHEL/CENTOS 8

We will install Glassfish Full platform.

Create a user for Glassfish.

useradd -s /sbin/nologin glassfish

Download Glassfish 5.0

wget http://download.oracle.com/glassfish/5.0/release/glassfish-5.0.zip

Unzip glassfish-5.0.zip file.

unzip -d /opt/ glassfish-5.0.zip

Assign the ownership of /opt/glassfish5 directory to glassfish user which we have created above.

chown -R glassfish:glassfish /opt/glassfish5/

Step 4: Create a Glassfish Service on CentOS 8 / RHEL 8

Create systemd service (glassfish.service) for Glassfish server

vi /usr/lib/systemd/system/glassfish.service

Now add below script in this file

[Unit]
Description = GlassFish Server v5.0
After = syslog.target network.target

[Service]
User = glassfish
ExecStart = /usr/bin/java -jar /opt/glassfish5/glassfish/lib/client/appserver-cli.jar start-domain
ExecStop = /usr/bin/java -jar /opt/glassfish5/glassfish/lib/client/appserver-cli.jar stop-domain
ExecReload = /usr/bin/java -jar /opt/glassfish5/glassfish/lib/client/appserver-cli.jar restart-domain
Type = forking

[Install]
WantedBy = multi-user.target

Save changes and exit the file.

Start and enable glassfish services.

systemctl start glassfish.service
systemctl enable glassfish.service

Step 5: Add Glassfish ports in Firewall

firewall-cmd --add-port={4848,8080,8181}/tcp --permanent 
firewall-cmd --reload

Step 6: Setting up Glassfish Path

Now set Glassfish binaries PATH environment variable using below command

sed -i 's/^PATH=*/PATH=\/opt\/glassfish5\/bin:/g' ~/.bash_profile

Step 7: Set password for Glassfish and enable secure login

By default, Glassfish has no password using below command and set a password for the admin user, Press ENTER 2 times and then type new password

/opt/glassfish5/bin/asadmin --port 4848 change-admin-password

Glassfish Admin Console is running as a clear text HTTP service. Run the following command to enable secure administration console.

/opt/glassfish5/bin/asadmin --port 4848 enable-secure-admin

Now restart Glassfish

systemctl restart glassfish.service

Note: we may unable to access the Glassfish Admin Console after enabling the secure login due to older version of Grizzly module so we will update Grizzly using below commands to access Glassfish admin console.

cd /opt/glassfish5/glassfish/modules/endorsed

mv grizzly-npn-bootstrap.jar grizzly-npn-bootstrap.jar.1

wget https://search.maven.org/remotecontent?filepath=org/glassfish/grizzly/grizzly-npn-bootstrap/1.9/grizzly-npn-bootstrap-1.9.jar -O grizzly-npn-bootstrap.jar

chown glassfish:glassfish grizzly-npn-bootstrap.jar

systemctl restart glassfish.service

Step 8: Accessing Glassfish Server on CentOS / RHEL 8

Finally browse below URL to access Glassfish Admin Console, ignore the certificate warning or install it.

https://SERVER-IP-OR-DOMAIN-NAME:4848/

Then, type your login credentials to log in it.

So, this is the Glassfish Admin Console

So, you can read our post about Payara server which is another server.

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As time goes by, the versions of the programs that come in the repositories of the Linux distributions become old. Similarly, program developers often release new versions with new features or bug fixes and we miss them.

Git is a program with quite active development and that requires to be always updated to have news and security fixes. So it is better to do it. And the best way to do it is to compile the source code of the application yourself.

Let us get started.

The latest version of GIT on CentOS 8 / RHEL 8 / Oracle Linux 8

Open a terminal and log in as root user, in case you do not have sudo. Then, install all the tools to compile and build from the source code.

:~$ su
:~# dnf groupinstall "Development Tools"

Then, it is necessary to install some packages that will help us with the process.

:~# dnf install wget unzip curl

Now it is necessary to install some libraries necessary for Git compilation.

:~# dnf install curl-devel expat-devel gettext-devel openssl-devel zlib-devel perl-CPAN perl-devel

Now, we can start to download Git using wget.

:~# wget https://github.com/git/git/archive/v2.23.0.zip -O latestgit.zip

Then, unzip it. And access the folder.

:~# unzip latestgit.zip
:~# cd git-2.23.0/

After that, configure the source before starting the compilation.

:~# make configure
:~# ./configure --prefix=/usr/local

Then, run the make command.

:~# make all

Now, start the installation.

:~# make install

And that is it. Git is installed. If you want to check, you can use the Git command to display the current version.

:~# git --version

So, enjoy it.

Conclusion

Git is a pretty good version control system. It is one of the best. And by the way, if we combine it with a powerful Linux distribution like CentOS 8 or RHEL 8 or Oracle Linux 8, it is better used. Now that you know how to install its latest stable version, it’s time to make the most of it.

Also, you can learn to install Git on Debian 10? or Ubuntu 18.04.

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What is the EPEL repository?

The Extra Packages for Enterprise Linux (EPEL) is an unofficial repository that provides a variety of packages that are not in the official RHEL and derivative repositories. It is quite reliable and secure, so it is highly recommended to enable it if we need any packages available in this repository.

Keep in mind that Linux distirbutions such as RHEL and its derivatives, as well as Debian, Ubuntu and SUSE, incorporate packages tested by them. In this immense effort, there are many very good packages that cannot be added to the repositories.

For that reason, these repositories are born, to be able to install many extra packages without much effort… let us get to work.

Enable the EPEL repository on CentOS 8 / RHEL 8 / Oracle Linux 8

The EPEL project is fantastic. Not only because of the large number of packages available but also because of the ease of use. To add it, you have to download and install an RPM package that they put at our disposal.

So, open a terminal and upgrade the system.

:~$ sudo dnf update

This way we will have all the packages updated with the built-in security patches.

Now install the repository configuration package with the following command:

:~$ sudo dnf install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm

Then, check that everything is OK with the new repository. So, list all the enabled repository.

:~$ sudo dnf repolist -v

As you can see in the image, the repository was correctly added. That is to say, we will be able to use it.

You can see all available packages with the following command:

:~$ sudo dnf repository-packages epel list

The image above shows that there are many packages available to be installed thanks to the EPEL repository.

Conclusion

In conclusion, adding the EPEL repository is almost an obligation if we want to counter many extra packages for our distribution. On the other hand, EPEL is a safe, reliable and easy to enable repository. To be so simple, the benefits are many.

Also, you can read How to enable Sudo on Debian 10?

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Step 1: Install LAMP Stack

Elgg requires MySQL, PHP, and a web server. So we need to install LAMP stack before Elgg installation.

i: Install Apache webserver

dnf install httpd -y

Now start and enable apache service on boot.

systemctl start httpd

systemctl enable httpd

Adding apache ports in the firewall.

firewall-cmd --add-port={80/tcp,443/tcp} --permanent
firewall-cmd --reload

ii: Install PHP

dnf install php php-common php-pecl-apcu php-json php-cli php-pear php-pdo php-mysqlnd php-pgsql php-gd php-mbstring php-xml -y

iii: Install MYSQL

dnf install mysql-server -y

Start and enable MYSQL service on boot.

systemctl start mysqld
systemctl enable mysqld

Complete MYSQL installation

mysql_secure_installation

Set root password? [Y/n] Y 
New password: password
Re-enter new password: password
Remove anonymous users? [Y/n] Y 
Disallow root login remotely? [Y/n] Y
Remove test database and access to it? [Y/n] Y
Reload privilege tables now? [Y/n] Y

Step 2: Create a MySQL database for Elgg

Log in to the MySQL console using below command and type your password when asked.

mysql -u root -p

now create a new database

CREATE DATABASE elgg;

Now create a new MySQL user and grant it privileges on the created database. You can replace username and password with the username and password of your own choice.

CREATE USER 'database_user'@'localhost' IDENTIFIED BY 'user_password';
GRANT ALL PRIVILEGES ON database_name.* TO 'database_user'@'localhost';
FLUSH PRIVILEGES;

Exit the MySQL console.

exit

Step 3: Download and Install Elgg on CentOS 8 / RHEL 8

Download Elgg using below commands

cd /var/www/html
wget https://elgg.org/about/getelgg?forward=elgg-3.1.1.zip

Now Unzip the downloaded archive

unzip getelgg?forward=elgg-3.1.1.zip
mv ./elgg-3.1.1/* .
rm -rf getelgg?forward=elgg-3.1.1.zip
rm -rf elgg-3.1.1

Create a data directory for Elgg in /var/www/html directory

mkdir -p /var/www/html/data

Set the appropriate file permissions

chown -R apache:apache /var/www/html/
chmod -R 755 /var/www/html/

Step 4: Apache Configuration for Elgg

Create an Apache virtual hosts configuration file.

vi /etc/httpd/conf.d/vhost.conf

and place below lines in that file.

<VirtualHost *:80>
DocumentRoot /var/www/html/
<Directory /var/www/html/>
Options FollowSymlinks
AllowOverride All
Require all granted
</Directory>
ErrorLog /var/log/httpd/elgg_error.log
CustomLog /var/log/httpd/elgg_access.log combined
</VirtualHost>

Save changes and exit.

Restart Apache server.

systemctl restart httpd.service

Step 5: Install Elgg on CentOS 8 / RHEL 8 (using the web interface)

Finally, browse below URL to access

http://YOUR-SERVER-IP/
OR
http://YOUR-DOMAIN-NAME

Click Next and enter the Database and its user details.

Click Next and enter the required details.

Once again click Next button and create your Admin Account.

Finally, you will see below page, Click on “Go to Site” button and start your work.

So, that is it. Hope you like it.

Also, you can read How to create an Nginx Server block on CentOS 8 / RHEL 8 / Oracle Linux 8?

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A little bit of ArangoDB

ArangoDB is a NoSQL database manager. It is built in C++ and is open source. Its main feature is that it is multi-model. That is, it supports different data models such as (JSON), graphs and key-value.

On the other hand, ArangoDB has two versions. The first one is paid and offers support at different levels. The second is communitarian, ideal for small or educational projects.

If you want to manage a server instance easily, ArangoDB allows it through a nice and intuitive web interface. Besides this, it has connectors for many programming languages, so this should not be a limitation. Of course, it has installers for many Linux distributions.

So let us get to work.

Install ArangoDB on CentOS 8 / RHEL 8 / Oracle Linux 8

ArangoDB is an application that takes documentation very seriously. In fact, it is a very well documented application that makes it easy to work with. And the installation process is available to many systems through its repository.

So the first step to install ArangoDB on CentOS 8 / RHEL 8 / Oracle Linux 8 is to add the repository.

Open a terminal and run the following:

:~$ su
:~# cd /etc/yum.repos.d/

Then, import the GPG key to secure the repository addition.

:~# curl -OL https://download.arangodb.com/arangodb35/RPM/arangodb.repo

After this, you can install ArangoDB by typing the following command:

:~# dnf install arangodb3-3.5.0

Now that ArangoDB is installed, you have to do some configuration before using it.

Making some configuration before using ArangoDB on CentOS 8 / RHEL 8 / Oracle Linux 8

ArangoDB is already installed but does not have a key configured for the root user. As we know, this is vital because then, anyone can access the stored data.

So use the following command to set the password for the root user:

:~# arango_secure_installation

With this you can now enter the ArangoDB shell and start working:

:~# systemctl start arangodb3
:~# arangosh

One of the most outstanding potentials of ArangoDB is its web interface. Thanks to it, it is possible to administer the instance quickly and easily. In addition to visualizing the data in a better way.

So, open the file /etc/arangodb3/arangod.conf. At the beginning of the file, it changes the endpoint value and adds the IP address of the computer where ArangoDB is running. By default, it is configured for localhost. There you will also see the default port used by the application which is 8529.

:~# nano /etc/arangodb3/arangod.conf

This same process must be done in the file /etc/arangodb3/arangosh.conf.

:~# nano /etc/arangodb3/arangosh.conf

For all this to work, it is necessary to add the corresponding rules in the Firewall. Specifically, open port 8529. Then, restart ArangoDB.

:~# firewall-cmd --add-port=8529/tcp --permanent
success
:~# firewall-cmd --reload
success
:~# systemctl restart arangodb3

Now, you can access to the web interface using your web browser. Go to http://your-server:8529

Type your credentials and click on the Login button. You will have to select the database.

Finally, you will see the dashboard. And you can start to work.

And that is it.

Conclusion

ArangoDB is a very popular database manager and increasingly influential in the world of programming. It is frequently used in IoT technology as well as in mobile phones. As you could see, it is easy to install and thus saves us a lot of work.

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