RHEL Linux 6 versus 7

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Welcome
Red Hat Enterprise Linux 7, based on versions of the Linux kernel greater than 3.10, has important differences with RHEL 6.
Some differences between Red Hat Enterprise Linux 6 and Linux 7 are:
- hostname definition
- system startup
- file systems and file system check
- network time synchronization
- network interface bonding/teaming
- default firewall

Hostname Definition
Hostnames are now defined in /etc/hostname instead of the /etc/sysconfig/network file.

System Startup
RHEL 7 uses GRUB 2, which supports additional firmware types and can boot more file systems.

Run levels are called targets in RHEL 7. For example, instead of runlevel 0 RHEL 7 uses
runlevel0.target -> poweroff.target

Services in RHEL 7 are started with systemd. RHEL 6 uses service and chkconfig

File Systems And File System Check
RHEL 7 puts the following under under /usr instead of under / (root directory).
/bin
/sbin
/lib
/lib64
 

RHEL 7 uses XFS instead of EXT4. The file system check, xfs_repair, does not run automatically at boot. In RHEL 6, e2fsck runs at boot time. Also, xfs_repair checks for a larger list of possible issues. The command is also different since xfs_repair takes mount points as arguments.

Network Time Synchronization
RHEL 7’s chrony has better performance than ntpd. (Note that many organizations use third-party replacements for ntpd with RHEL 6).

Network Interface Bonding/Teaming
In RHEL 7, bonding of network interfaces is called teaming.

The configuration file is:
/etc/sysconfig/network-scripts/ifcfg-team0
New settings include:
DEVICE=team0
DEVICETYPE=team

Firewall
RHEL 7 uses firewalld by default instead of iptables.