Java is incredibly popular on servers, and if you plan on using RHEL 8 / CentOS 8, you'll need to install it. There are a couple of ways to install Java on RHEL, both from the open source OpenJDK packages and directly from Oracle.

• How to Install OpenJDK 8
• How to Install OpenJDK 11
• How to Install Oracle Java 8 JRE
• How to Install Oracle Java 8 JDK
• How to Switch Java Versions

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• How to check default boot target
• How to manually switch between different targets
• How to set default boot to multi-user target
• How to set default boot to graphical target

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• How to login as a regular user or root
• How to switch user in multiuser target

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• What are symbolic (soft) links
• What are hard links
• How to create a symbolic link
• How to create a hard link
• How to remove link

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Understand and use essential tools

• Access a shell prompt and issue commands with correct syntax
• Use input-output redirection (>, >>, |, 2>, etc.)
• Use grep and regular expressions to analyze text
• Access remote systems using SSH
• Log in and switch users in multiuser targets
• Archive, compress, unpack, and uncompress files using tar, star, gzip, and bzip2
• Create and edit text files
• Create, delete, copy, and move files and directories
• Create hard and soft links
• List, set, and change standard ugo/rwx permissions
• Locate, read, and use system documentation including man, info, and files in /usr/share/doc

Operate running systems

• Boot, reboot, and shut down a system normally
• Boot systems into different targets manually
• Interrupt the boot process in order to gain access to a system
• Identify CPU/memory intensive processes and kill processes
• Adjust process scheduling
• Locate and interpret system log files and journals
• Preserve system journals
• Start, stop, and check the status of network services
• Securely transfer files between systems

Configure local storage

• List, create, delete partitions on MBR and GPT disks
• Create and remove physical volumes
• Assign physical volumes to volume groups
• Create and delete logical volumes
• Configure systems to mount file systems at boot by universally unique ID (UUID) or label
• Add new partitions and logical volumes, and swap to a system non-destructively

Create and configure file systems

• Create, mount, unmount, and use vfat, ext4, and xfs file systems
• Mount and unmount network file systems using NFS
• Extend existing logical volumes
• Create and configure set-GID directories for collaboration
• Configure disk compression
• Manage layered storage
• Diagnose and correct file permission problems

Deploy, configure, and maintain systems

• Schedule tasks using at and cron
• Start and stop services and configure services to start automatically at boot
• Configure systems to boot into a specific target automatically
• Configure time service clients
• Install and update software packages from Red Hat Network, a remote repository, or from the local file system
• Work with package module streams
• Modify the system bootloader

Manage basic networking

• Configure IPv4 and IPv6 addresses
• Configure hostname resolution
• Configure network services to start automatically at boot
• Restrict network access using firewall-cmd/firewall

Manage users and groups

• Create, delete, and modify local user accounts
• Change passwords and adjust password aging for local user accounts
• Create, delete, and modify local groups and group memberships
• Configure superuser access

Manage security

• Configure firewall settings using firewall-cmd/firewalld
• Configure key-based authentication for SSH
• Set enforcing and permissive modes for SELinux
• List and identify SELinux file and process context
• Restore default file contexts
• Use boolean settings to modify system SELinux settings
• Diagnose and address routine SELinux policy violations