New RHEL 7 Vs 6


This page would list out some of the major differences between RHEL 7 and 6 variants and key features in RHEL 7 . This is not a complete list. To know more one would visit the links that I've pasted below and check further.









FeaturesRHEL 7RHEL 6
Default File SystemXFSEXT4
Kernel Version3.10.x-x kernel2.6.x-x Kernel
Kernel Code NameMaipoSantiago
General Availability Date of First Major Release2014-06-09 (Kernel Version 3.10.0-123)2010-11-09 (Kernel Version 2.6.32-71)
First Processsystemd (process ID 1)init (process ID 1)
Runlevelrunlevels are called as "targets" as shown below:

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

/etc/systemd/system/default.target (this by default is linked to the multi-user target)
Traditional runlevels defined :

runlevel 0
runlevel 1
runlevel 2
runlevel 3
runlevel 4
runlevel 5
runlevel 6

and the default runlevel would be defined in /etc/inittab file.
/etc/inittab
Host Name ChangeIn Red Hat Enterprise Linux 7, as part of the move to the new init system (systemd), the hostname variable is defined in /etc/hostname.In Red Hat Enterprise Linux 6, the hostname variable was defined in the /etc/sysconfig/network configuration file.
Change In UID AllocationBy default any new users created would get UIDs assigned starting from 1000.

This could be changed in /etc/login.defs if required.
Default UID assigned to users would start from 500.


This could be changed in /etc/login.defs if required.
Max Supported File SizeMaximum (individual) file size = 500TB
Maximum filesystem size = 500TB

(This maximum file size is only on 64-bit machines. Red Hat Enterprise Linux does not support XFS on 32-bit machines.)
Maximum (individual) file size = 16TB
Maximum filesystem size = 16TB

(This maximum file size is based on a 64-bit machine. On a 32-bit machine, the maximum files size is 8TB.)
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.
Differences Between xfs_repair & e2fsck
"xfs_repair"

- Inode and inode blockmap (addressing) checks.
- Inode allocation map checks.
- Inode size checks.
- Directory checks.
- Pathname checks.
- Link count checks.
- Freemap checks.
- Super block checks.

"e2fsck"

- Inode, block, and size checks.

- Directory structure checks.

- Directory connectivity checks.

- Reference count checks.

- Group summary info checks.
Difference Between xfs_growfs & resize2fs"xfs_growfs"

xfs_growfs takes mount point as arguments.
"resize2fs"

resize2fs takes logical volume name as arguments.
Change In File System Structure/bin, /sbin, /lib, and /lib64 are now nested under /usr./bin, /sbin, /lib, and /lib64 are usually under /
Boot LoaderGRUB 2
Supports GPT, additional firmware types, including BIOS, EFI and OpenFirmwar. Ability to boot on various file systems (xfs, ext4, ntfs, hfs+, raid, etc)
GRUB 0.97
KDUMPRHEL7 supports kdump on large memory based systems up to 3 TBKdump doesn’t work properly with large RAM based systems.
System & Service Manager"Systemd"

systemd is a system and service manager for Linux, and replaces SysV and Upstart used in previous releases of Red Hat Enterprise Linux. systemd is compatible with SysV and Linux Standard Base init scripts.
Upstart
Enable/Start ServiceFor RHEL 7, the systemctl command replaces service and chkconfig.

- Start Service : "systemctl start nfs-server.service".

- Enable Service : To enable the service (example: nfs service ) to start automatically on boot : "systemctl enable nfs-server.service".

Although one can still use the service and chkconfig commands to start/stop and enable/disable services, respectively, they
are not 100% compatible with the RHEL 7 systemctl command (according to redhat).
Using "service" command and "chkconfig" commands.

- Start Service : "service start nfs" OR "/etc/init.d/nfs start"

- Enable Service : To start with specific runlevel : "chkconfig --level 3 5 nfs on"
Default Firewall"Firewalld (Dynamic Firewall)"

The built-in configuration is located under the /usr/lib/firewalld directory. The configuration that you can customize is under the /etc/firewalld directory. It is not possible to use Firewalld and Iptables at the same time. But it is still possible to disable Firewalld and use Iptables as before.
Iptables
Network Bonding"Team Driver"

-/etc/sysconfig/network-scripts/ifcfg-team0
- DEVICE=”team0”
- DEVICETYPE=”Team”
"Bonding"

-/etc/sysconfig/network-scripts/ifcfg-bond0
- DEVICE=”bond0”
Network Time SynchronizationUsing Chrony suite (faster time sync compared with ntpd)Using ntpd
NFSNFS4.1
NFSv2 is no longer supported. Red Hat Enterprise Linux 7 supports NFSv3, NFSv4.0, and NVSv4.1 clients.
NFS4
Cluster Resource ManagerPacemakerRgmanager
Load Balancer TechnologyKeepalived and HAProxyPiranha
Desktop/GUI InterfaceGNOME3 and KDE 4.10GNOME2
Default DatabaseMariaDB is the default implementation of MySQL in Red Hat Enterprise Linux 7MySQL
Managing Temporary FilesRHEL 7 uses systemd-tmpfiles (more structured, and configurable, method to manage tmp files and directories).Using "tmpwatch"



RHEL 7 Extras
Introduction of DockerDocker is an open source project that automates the deployment of applications inside Linux Containers, and provides the capability to package an application with its runtime dependencies into a container.
Device Hotplug RemovedWhile RHEL 5/6 has device hotplug support (udev rule that runs the ifup script for newly created devices), it has been disabled for RHEL 7 since it can result in race conditions when initializing newly found.
No 32 Bit ISO ImageNo 32 bit ISO for download. Red Hat Enterprise Linux 7 will only provide 64-bit ISO's, thus allowing only a 64-bit operating environment. RHEL 7 will not natively support 32-bit hardware.
MemAvailable Added to meminfoA new entry to the /proc/meminfo file has been introduced to provide the MemAvailable field. MemAvailable provides an estimate of how much memory is available for starting new applications, without swapping. However, unlike the data provided by the Cache or Free fields, MemAvailable takes into account page cache and also that not all reclaimable memory slabs will be reclaimable due to items being in use.
New Ruby and Python VersionsRed Hat Enterprise Linux 7 provides the latest Ruby version, 2.0.0 and Python 2.7.5.
OpenJDK7 Made DefaultRed Hat Enterprise Linux 7 features OpenJDK7 as the default Java Development Kit (JDK) and Java 7 as the default Java version.
More Powerful NetworkManager
NetworkManager has been significantly enhanced to configure and monitor all the networking features for enterprise class servers and for desktop applications.

For the enterprise data centers, NetworkManager can be used for tasks such as basic networking configuration, network teaming, configuring virtual LANs, bridges, bonds, IPv6, VPNs, assigning interfaces to firewall zones, and others. For desktop servers it can manage wired and wireless networks and VPNs.
Support for 40 Gigabit NICsRed Hat Enterprise Linux 7 supports 40 Gigabit network interface controllers (NICs) from multiple hardware partners. This provides support for 40 Gigabit Ethernet link speeds enabling faster network communication for applications and systems. Note that the ethtool utility will report interface link speeds up to 40Gb data rates.
No RHN ClassicRHN Classic is not supported in RHEL7. Older versions supported different subscription management method being used. Red Hat Subcription Management is the only one used by RHEL 7.
OpenSSH - Multiple Required AuthenticationsRed Hat Enterprise Linux 7 supports multiple required authentications in SSH protocol version 2 using the AuthenticationMethods option. This option lists one or more comma-separated lists of authentication method names. Successful completion of all the methods in any list is required for authentication to complete.
Minimum Disk Space for Installation of RHEL7Red Hat Enterprise Linux 7 now requires at least 1 GB of disk space to install. However, Red Hat recommends a minimum of 5 GB of disk space for all supported architectures.
Implementation of tmpfs file systemRed Hat Enterprise Linux 7 offers the ability to use /tmp as a mount point for a temporary file storage system (tmpfs).

When enabled, this temporary storage appears as a mounted file system, but stores its content in volatile memory instead of on a persistent storage device. No files in /tmp are stored on the hard drive except when memory is low, in which case swap space is used. This means that the contents of /tmp are not persisted across a reboot.
New Logging FrameworkRed Hat Enterprise Linux 7 introduces a new logging daemon, journald, as part of the move to systemd.

journald captures the following types of message for all services:

- syslog messages
- kernel messages
- initial RAM disk and early boot messages
- messages sent to standard output and standard error output.
Changes to mount optionsUnlike ext3 and ext4, the XFS file system enables the user_xattr and acl mount options by default. Ext3 and ext4 file systems do not enable these attributes by default.

Another Interesting blog on RHEL 7: http://www.certdepot.net/rhel7-quick-recipes/
 

……………..…………. *all these details are collected from Redhat Offical site. This may not be widespread, but it is my effort to make a user-friendly sheet with a few main points.

30 comments:

Anonymous said...

Thanks for good effort

ADMIN PRAVAS MISHRA said...

Thanks for the useful information.

Anonymous said...

Thanks for this useful details... I am sure it will come handy soon enough. Kudos...

Anonymous said...

Thanks a lot.. Really great effort.

Linux Admin said...

Thanks Mr. Murthy for sharing this details. Very helpful to identify major differences.

Anonymous said...

Hi

Thanks a lot. Great article.

Another difference is the new commands for net: ip addr versus ifconfig, ip route versus route, ...

Toni

Sadashiva Murthy said...

Thanks Toni. Yes, there are a lot of changes, new features, options introduced in RHEL7, as I noticed one such good one is the command auto-fill which auto-populates commands by typing a few characters and then pressing tab key (once/twice).

pawandeep kushwaha said...

Really Appreciate your Efforts for RHEL 6 And RHEL7 Difference.
And Also Very good Web Designing and Creativity As Well (Specially Embed code fro Fish TANK).

Keep it Up Sadashiva Murthy

Vishal Badgujar said...

Sadashiva Murthy, Document is very neat, simple and good collection of important differences. Please keep on posting further blogs.
Thank you again.

Anonymous said...

Thanks sir...

Sadashiva Murthy said...

Thanks Pawndeep, Vishal and everyone... :)

K A KARTHIK said...

Dear Sadashiva, Thanks for the great information.... Looking forward for many more informations like this..

Nasimuddin Ansari said...

httpd 2.2 v/s 2.6

inayat husain said...

Hello Mr. Murthy,

I want to know For 3.10 based kernels, what is the maximum LV size ??

Sadashiva Murthy said...

maximum device size with LVM is 8 exabytes on 64 bit CPU as per "LVM Guide" of rhel 7.

Anonymous said...

The mount command seems to behave differently in RHEL 7 when compared to RHEL 6. I found that entries that were marked as noauto in fstab are listed in RHEL 6 mount command but not so in RHEL 7. Any idea what we need to run to get these entries also in RHEL 7?

Thanks
rajesh

Sadashiva Murthy said...

The man page of 'mount' says this.....

noauto Can only be mounted explicitly (i.e., the -a option will not cause the filesystem to be mounted).

There is no change in either rhel versions.

Anonymous said...

Thanks a lot!

christian jerick Go said...

Thought-provoking blog post . For what it's worth , if someone need to merge PDF files , my business partner encountered a service here altomerge.com.

Anonymous said...

when i run yum update -y after updating all the packages. System is getting error at grub and not booting from then. Any solution for this issue.

Anonymous said...

Very, very useful. Bookmarked :)

Thank you.

Sadashiva Murthy said...

generally for an issue as such when system fails to boot up after kernel/system update would be because of missing boot driver/module from intramfs disk otherwise, mismatch of root file system disk. Make sure to re-create ramdisk after upgrade.. this would help.

Unknown said...

Hello Sadashiv,

Thanks for the summary.

Can you tell me if there are any compiler modifications from rhel 6 to rhel7?

Thanks in advance.

Sadashiva Murthy said...

I see that the primary compiler packages in RHEL 7.x is gcc 4.8.x compared to gcc 4.4.x of RHEL 6.x.

Check out these links for more details:

http://developers.redhat.com/blog/2014/08/11/whats-new-in-gcc-for-red-hat-enterprise-linux-7/


https://access.redhat.com/solutions/19458

abbas said...

Good Articles, Useful one

Anonymous said...

You did awesome job Sadash. It was a real and quick updates in a flash. I would suggest you to keep update this page as one point reference for RHEL7.

Vaazhthukkal.

vinayangadi said...

Nice article
Thanks for sharing the informative blog.

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Editor said...

Wonderful Post.

I found one more post :- Difference between RHEL6 and RHEL7

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