Difference between RHEL 5, RHEL 6, and RHEL 7.

Today we will look at the between RHEL5, 6 and 7 version or you can say CentOS 5, 6 and 7 versions.

I have gone through multiple sites, however not able to find a single website where most of the differences among these three exists at one place.

(same) tag is used to specify there is no major change in this feature between RHEL5 and RHEL 6, or CentOS 5 & CentOS 6.

Features RHEL 5 RHEL 6 RHEL 7
Kernel Version 2.6.18 2.6.32 3.10.x
Filesystem EXT3 EXT4 XFS
OS Boot Time (same) 40 Sec 20 Sec
GRUB (same) GRUB 0.97 GRUB 2
Processor Arch (same) 32 & 64 Bit 64 Bit Only
Network Management command (same) system-config-network nmtui
/etc/sysconfig/ network_file /etc/hostname
First Process (same) Init systemd
Runlevel (same) runlevel 0 runlevel0.target -> poweroff.target
runlevel 1 runlevel1.target -> rescue.target
runlevel 2 runlevel2.target -> multi-user.target
runlevel 3 runlevel3.target -> multi-user.target
runlevel 4 runlevel4.target -> multi-user.target
runlevel 5 runlevel5.target -> graphical.target
runlevel 6 runlevel6.target -> reboot.target
“/etc/inittab” /etc/systemd/system/default.target
Hostname (same) hostname variable was defined in the “/etc/sysconfig/network” hostname variable is defined in “/etc/hostname” file.
UID Assignment (same) Default UID assigned to users would start from 500. UIDs assigned starting from 1000.
Filestructure change (same) /bin, /sbin, /lib, and /lib64 are usually under / /bin, /sbin, /lib, and /lib64 are now nested under /usr.
Kdump Support (same) Kdump doesn’t work properly with large RAM based systems. RHEL7 supports kdump on large memory based systems up to 3 TB
Service Management (same) service and chkcnfig commands were used. In RHEL 7, the systemctl command replaces service and chkconfig.
– Start Service : “service nfs start” OR “/etc/init.d/nfs start” – Start Service : “systemctl start nfs-server.service”.
– Enable Service : To start with specific runlevel : “chkconfig –level 3 5 nfs on” – Enable Service : To enable the service (example: nfs service ) to start automatically on boot : “systemctl enable nfs-server.service”.
Firewall (same) Iptables firewalld : built-in configuration is located under the “/usr/lib/firewalld” directory.
customization is from /etc/firewalld directory
Network Bonding (same) Bonding Team driver
/etc/sysconfig/network-scripts/ifcfg-bond0 /etc/sysconfig/network-scripts/ifcfg-team0
NTP Daemon (same) NTPD Chrony Suite
NFS Version NFS3 NFS4 NFS 4.1
Cluster Software (same) Rgmanager Pacemaker
GUI Interface (same) Far better GNOME 2 GNOME 3, and KDE 4.10
Load Balancer (same) Keepalived and HAProxy Piranha
Default Database (same) MySQL MariaDB
Temporary File Management (same) tmpwatch systemd-tmpfiles
Security Selinux Selinux Svirt module introduced New Selinux container security and performance boost up.
IP Protocol Support IPv4 IPv4 and IPv6 IPv4 and IPv6
Filesystem Difference
Max File Size 2 TB 16 TB(for 64 bit) or 8TB(32-bit) 500TB
Filesystem Scan (same) FSCK XFS_REPAIR
Resizing FS (same) “resize2fs” “xfs_growfs”

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