Difference between RHEL6, RHEL7 and RHEL8

Below table would list out the major differences between Red Hat Enterprise Linux 6, 7 and  8.

RHEL 6RHEL 7RHEL 8
Kernel Version – 2.6.32-71Kernel Version – 3.10.0-123Kernet Version – 4.18
Legacy GRUBGRUB 2 GRUB 2
Runlevels:
runlevel 0
runlevel 1
runlevel 2
runlevel 3
runlevel 4
runlevel 5
runlevel 6
Runlevels:
runlevel0.target -> poweroff.target
runlevel1.target -> rescue.target
runlevel2.target -> multi-user.target
runlevel3.target -> multi-user.target
runlevel4.target -> multi-user.target
runlevel5.target -> graphical.target
runlevel6.target -> reboot.target
Runlevels:
runlevel0.target -> poweroff.target
runlevel1.target -> rescue.target
runlevel2.target -> multi-user.target
runlevel3.target -> multi-user.target
runlevel4.target -> multi-user.target
runlevel5.target -> graphical.target
runlevel6.target -> reboot.target
How to check runlevel?
runlevel
How to check runlevel?
systemctl get-default
How to check runlevel?
systemctl get-default
How to change runlevel?
init [runlevel]
How to change runlevel?
systemctl isolate [Name.target]
How to change runlevel?
systemctl isolate [Name.target]
How to configure runlevel by default?
/etc/inittab
How to configure runlevel by default?
systemctl set-default [Name.target]
How to configure runlevel by default?
systemctl set-default [Name.target]
Kdump is enabled by default and will run without any problems if the system has too much RAM.Kdump is enabled by default and will run without any problems if the system has too much RAM (up to 3 TB).Kdump is enabled by default and will run without any problems if the system has too much RAM.
UID Allocation:

0-499
UID Allocation:

0-999
UID Allocation:

0-999 UIDs are reserved for system and application users.
Max Supported Single File & Filesystem Size:

EXT4= 16TB

EXT4= 16TB
Max Supported Single File & Filesystem Size:

XFS= 500TB

XFS= 500TB
Max Supported Single File & Filesystem Size:

XFS= 500TB

XFS= 1024TB
Service Manager:
service command
Service Manager:
systemctl command
Service Manager:
systemctl command
Enable service on startup:
chkconfig
Enable service on startup:
systemctl command
Enable service on startup:
systemctl command
ntpIt supports Chrony and ntpOnly Chrony (faster time sync and useful for the systems which are not online all the time)
RgmanagerPacemakerPacemaker
Gnome 2Gnome 3Gnome 3.28
Default Database:
MySQL
Default Database:
MariaDB
Default Database:
MySQL 8.0, MariaDB 10.3, PostgreSQL 10 and 9.6, and Redis 5.0
IptablesFirewalld, it uses Iptables framework in the backendFirewalld, it uses nftables framework in the backend
Python 2.0Python 2.7.5Python 3
PHP 5.3 PHP 5.4PHP 7.2
Default File System:
EXT4
Default File System:
XFS
Default File System:
XFS
File System Check:
e2fsck
File System Check:
xfs_repair
File System Check:
xfs_repair
File System Extend:
resize2fs
File System Extend:
xfs_growfs
File System Extend:
xfs_growfs
First Process:
init (PID 1)
First Process:
systemd (PID 1)
First Process:
systemd (PID 1)
Hostname file:

It’s defined in /etc/sysconfig/network file
Hostname file:

/etc/hostname
Hostname file:

/etc/hostname
For logging it has rsyslogrsyslog and journalrsyslog and journal
Required disk space (minimum):

1GB minimum, 5GB recommended
Required disk space (minimum):

10GB minimum, 20GB recommended
Required disk space (minimum):

10GB minimum, 20GB recommended
Can we upgrade it?

Yes, RHEL 6.10 to RHEL 7.7
Can we upgrade it?

Yes, RHEL 7.7 to RHEL 8
Can we upgrade it?

Yes
virt-managervirt-managercockpit
32-Bit and 64-BitOnly 64-BitOnly 64-Bit
Need to enable mount options manuallyBy default user_xattr and acl mount options are enabledBy default user_xattr and acl mount options are enabled
Default Repositories:

Repo ID: rhel-6-server-rpms

Repo Name: Red Hat Enterprise Linux 6 Server (RPMs)
Default Repositories:

Repo ID: rhel-7-server-rpms

Repo Name: Red Hat Enterprise Linux 7 Server (RPMs)
Default Repositories:

Repo ID: rhel-8-for-x86_64-appstream-rpms

Repo Name: Red Hat Enterprise Linux 8 for x86_64 – AppStream (RPMs)

Repo ID: rhel-8-for-x86_64-baseos-rpms

Repo Name: Red Hat Enterprise Linux 8 for x86_64 – BaseOS (RPMs)
Only YUMBy default only YUM and DNF can be installed from the Extra repoBy default both YUM and DNF are installed
Maximum RAM Supported:

12TB on x86_64 architecture

Maximum RAM Supported:

12 TB on x86_64 architecture
Maximum RAM Supported:

24 TB on x86_64 architecture

 

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