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 |
| Hypervisor | RHEL XEN | KVM | KVM |
| 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” |