RHEL6 v/s RHEL7

RHEl 6 v/s RHEl 7

1. Default File System is ext4 for 6 & xfs for 7

2. Kernel Version is 2.6.x-x Kernel for 6 & 3.10.x-x kernel for 7

3. Kernel Code Name is santiago for 6 & Miapo for 7

4. First Process is initd in 6 and systemd in 7.

5. Runlevels
in 6:           in 7:
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/systemd/system/default.target (this by default is linked to the multi-user target)

# cat default.target
[Unit]
Description=Graphical Interface
Documentation=man:systemd.special(7)
Requires=multi-user.target
Wants=display-manager.service
Conflicts=rescue.service rescue.target
After=multi-user.target rescue.service rescue.target display-manager.service
AllowIsolate=yes

6. Change In UID Allocation - 
In RHEL7, by default any new users created would get UIDs assigned starting from 1000. 
In RHEL6, Default UID assigned to users would start from 500.

7. Max Supported File Size - In RHEL7, Maximum (individual) file size = 500TB Maximum filesystem size = 500TB,  In RHE6, same is 16TB.

8. File System Check - "xfs_repair", XFS does not run a file system check at boot time. "e2fsck" File system check would gets executed at boot time. 

9. Difference Between xfs_growfs & resize2fs- xfs_growfs takes mount point as arguments. resize2fs takes logical volume name as arguments.

10. Default Firewall - Firewalld (Dynamic Firewall) in RHEL7 & ipatbles in RHEL6.

11. Network Bonding - 
 "Team Driver"-/etc/sysconfig/network-scripts/ifcfg-team0
 "Bonding"-/etc/sysconfig/network-scripts/ifcfg-bond0