Friday, August 23, 2019

Main Differences Between RHEL & SLES

Red Hat Enterprise Linux (RHEL)SUSE Linux Enterprise Server (SLES)
Owned ByRed Hat
Red Hat, Inc is an American MNC with head office in Raleigh, North Carolina (USA). It was founded in March 26th 1993. Now, it has been acquired by IBM.
It is a German based software MNC, founded in 1992 and headquarter located at Nuremberg, Germany.

Company Logo*                                                
Founders of the companyBob Young & Marc EwingRoland Dyroff, Thomas Fehr, Hubert Mantel & Burchard Steinbild
How was the name decided?Red Hat got its name from founder Marc Ewing who wore a red Cornell University lacrosse hat, given to him by his grandfather, while attending Carnegie Mellon University.                  S.u.S.E → SUSE
Their name at founding was "S.u.S.E" and it was chosen as a German acronym for "Software und System-Entwicklung", meaning "Software and systems development". 

Later the company name was shortened to "SuSE" in October 1998, and in 2003 capitalized to "SUSE".
Upstream* Fedora & CentOS Stream

Fedora is built by the community ( for the benefit of the community and sponsored primarily by Red Hat. 

CentOS Stream will live in-between Fedora and RHEL, providing  a clearer vision of what the next version of RHEL would be.
                 OpenSUSE Leap
This is being maintained by OpenSUSE project. The openSUSE Project is a community project to create, promote, improve and document the openSUSE Linux distribution. 

OpenSUSE Tumbleweed is the development version and Leap is the stable release.
Product Support Lifecycle*
10 years + ELS

RHEL 5/6/7 does gets support for 10 years in Full Support, Maintenance Support 1 & Maintenance Support 2 Phases followed by an Extended Life Phase.

For RHEL 5/6 there is add-on subscription called Extended Life-cycle Support (ELS) which could be purchased to get support behind Maintenance Support 2 Phase.

Red Hat has simplified the support policy with the release of RHEL8. It is supported under 3 phases here: Full Support (5 years), Maintenance Support (5 years) & Extended Life Phase (2 years).
10 years + 3 years (extended support)
SUSE Linux Enterprise Server 11/12/15 got 13-year life cycle support, with 10 years of General Support and 3 years of Extended Support. 

Long Term Service Pack Support (LTSS) can extend the support duration for service packs. This can purchased as an additional 12 to 36 months in twelve month increments. This means that total of 3 to 5 years of support would be provided on Service Pack.

SUSE Linux Enterprise 10 or 9 might have 10 years life cycle support. 

*Major releases are published every four years. Service packs are published every 12-14 months.
Customer Support & Subscription Types *(license)
Red Hat offers supports to its customers in 3 types subscription basis:

- Self Support Subscription
- Standard Support Subscription
- Premium Support Subscription

Self Support is only for non-production and development systems which doesn't get technical support from Red Hat. It is available only for physical setup.

Standard & Premium does provide technical support via phone and web. Standard provides support only during standard business hours, however, Premium customers would get 24 x 7 support coverage with 1 hour response time for Sev 1 cases & 2 hours for Sev 2 cases.
SUSE Offers Support Subscription in two modes:

- Standard Subscription:

It provides 12 x 5 support coverage with 2 hours response time for Severity 1 cases & 4 hours for Severity 2 cases. For Severity 3/4 cases it would be 'Next Bus Day' response.

- Priority Subscription:

It provides 24 x 7 support coverage with 1 hour response time for Severity 1 & 2 hours for Severity 2 cases. For Severity 3 the response time would be 4 hours & 'Next Business Day' response time for Severity 4 cases.
Subscription Cost*
Red Hat Enterprise Linux Server, Standard (Physical or Virtual Nodes) :
- US$349 (Self-Support)
- US$799 (Standard Support)
- US$1,299 (Premium Support)

Red Hat Enterprise Linux for Virtual Datacenters (provides unlimited guest deployments) :
- US$2,499 (Standard Support)
- US$3,999 (Premium Support)
SUSE Linux Enterprise Server, x86 & x86-64, 1-2 Sockets or 1-2 Virtual Machines:
- US$799 (Standard Subscription)
- US$1,499 (Priority Subscription)

SUSE Linux Enterprise Server, x86 & x86-64, 1-2 Sockets with Unlimited Virtual Machines:
- US$1,499 (Standard Subscription)
- US$2,998 (Priority Subscription)
Main Functional/Technical Differences
First Enterprise Release, Date & Kernel VersionRHEL 2.1 GA, 2002-03-23 & 2.4.9-e.3SuSE Linux Enterprise Server, October 31, 2000 for S/390
Latest Enterprise Release, Date & Kernel Version*RHEL 8 GA, 2019-05-07 &
SLES15 SP1, Aug-07-2019 &
How to check for release version?
There is a dedicated file which
maintenance the release version details which is
"/etc/redhat-release". Also, there is "/etc/os-release" file which is uniquely used in most distros which can provided release details.
In SLES11, there is "/etc/SuSE-release" which provides the release details, however, in SLES12/15 this has been deprecated and there is only "/etc/os-release" which provides this details.
Default File System*
   - EXT3 in RHEL5
   - EXT4 in RHEL6
   - XFS in RHEL7/8

XFS is a robust and mature 64-bit journaling file system that supports very large files and file systems on a single host. It is the default file system in Red Hat Enterprise Linux 7/8.

The BTRFS file system has been removed in Red Hat Enterprise Linux 8.
   - EXT3 in SLES11
   - BTRFS in SLES12/15

With SUSE Linux Enterprise 12, BTRFS is the default file system for the operating system and XFS is the default for all other use cases.
Package/Software Management- Using 'yum', 'rpm' and DNF (in RHEL8 on-wards) commands & using PackageKit or by Satellite interface as well. The 'dnf' command is the advanced version of 'yum' command.- Using 'zypper', 'rpm', 'yast' commands. Also, using Yast2 utility & SUSE Manager as well.

Zypper is a command line package manager for installing, updating and removing packages. It also manages repositories. Yast is another nice utility which could do everything inside a SUSE box.
Behaviour Change of useradd Command

The 'CREATE_HOME' parameter by default is set to 'yes' in the file "/etc/login.defs" which creates users home directory when executed locally. 

Example: The command "# useradd test" when executed as root or root privileged user would create a local user by name test with home directory as '/home/test'.

The 'CREATE_HOME' is set to 'no' in the file "/etc/login.defs", hence, when using 'useradd' command need to use '-m' to create local user along with home directory.

Example: The command "# useradd -m test" when executed as root or root privileged user would create a local user by name test with home directory as '/home/test'.
Kernel Firewall Implementation - RHEL8/7 uses firewalld

This daemon (service) comes from ‘firewalld’ package which is installed by default in ‘base’ installation mode, however, not in ‘minimal’ mode. By default, rules are active on default zone which is 'public zone'.

- RHEL6 and earlier version uses iptables

In earlier RHEL6.x version there is ‘iptables’ being used which is a well-known netfilter program.
- SLES15 uses firewalld

In default installation mode, firewalld is active, enabled and configured to be active in public zone which blocks all incoming traffic by default.

- SLES12 uses SuSEFirewall2

SuSEFirewall2 is active and the network interfaces are configured to be in the External Zone which blocks incoming traffic in default installation setup.
Graphical User InterfaceThe default display server is Wayland used by Gnome Display Manager in RHEL 8.X.Org server is the default display server in RHEL 7 (GNOME3 & KDE 4.10). GNOME2 is used in RHEL6/5 versions.SUSE Linux Enterprise Server includes the server and the GNOME desktop. The server is the de facto standard for implementing the X11 protocol.
Upgrade Paths*- From RHEL6 to RHEL7

Yes, Red Hat officially supports upgrade from latest minor release of RHEL6 to RHEL7. For further details visit the below web link:

- From RHEL7 to RHEL8

Upgrade from RHEL7 to RHEL8 is also supported. Only on Server variant & Intel 64 architecture. There are other limitations and pre-requisites to be met, so for further details visit the below web link:

- Upgrade from RHEL5.x is not officially supported.
- Upgrade from SLES11 to SLES12

Only offline upgrade from SLES11SP4 to SLES12SP4. For further details, please visit:

- Upgrade from SLES12 to SLES15

Upgrading from SLES12SP3 or SLES12SP4 is only supported via an offline upgrade. SLES12SP3 can be upgraded to SLES15 & SLES12SP4 can be upgraded to SLES15SP1.

- Upgrade from SLES10 and older versions is not officially supported.

- Also, there is a direct upgrade path from SLES11SP4 to SLES15.

For further details, please refer:
System Management (Life Cycle,
Patch & Asset Management….)
                    Red Hat Satellite

Red Hat Satellite is a system management solution that enables you to deploy, configure, and maintain systems across physical, virtual, and cloud environments. Satellite provides provisioning, remote management and monitoring of multiple Red Hat Enterprise Linux deployments with a single, centralized tool. 

Red Hat Satellite Server synchronizes the content from Red Hat Customer Portal, and provides functionality including fine-grained life cycle management, user and group role-based access control, integrated subscription management, as well as advanced GUI, CLI, and API access.
                      SUSE Manager

SUSE Manager is an infrastructure management solution for software-defined IT environment. It is designed to help enterprise DevOps and IT Operations teams to reduce complexity and regain control of IT and IoT assets, increase efficiency while meeting security policies and optimize operations with automation to reduce costs.

SUSE Manager provides complete control and visibility into IT resources and life cycles, from asset management to redeployment. 
Updates, Severity Level & TypesIn Red Hat, updates are released in 3 levels:

Red Hat Security Advisory (RHSA): All critical and must be installed vulnerability updates.

Red Hat Bugfix Adivisory (RHBA): RHBA advisories always contain one or more bug fixes, may contain enhancements, but do not contain security fixes. 

Red Hat Enhancement Advisory (RHEA): RHEA advisories contain one or more enhancements or new features, and they do not contain bug fixes or security fixes.
SUSE provides updates with different relevance levels:

Security Updates: Fix severe security hazards and should always be installed.

Recommended UpdatesFix issues that could compromise your computer.

Optional UpdatesFix non-security relevant issues or provide enhancements.
Live Kernel Patching
Using kpatch

*Starting with RHEL 7.7 (GA Aug 6 2019), and coming soon to RHEL 8 and RHEL 7.6, live kernel patches will be available on the Red Hat Content Delivery Network(CDN) and can be installed via the yum command. Live kernel patching capability is implemented as a kernel module (kmod) that is delivered as an RPM.

*This is not supported on RHEL6/5 versions.
Using Kernel Live Patching (KLP) in SLES15
KLP is a live patching technology for runtime patching of the Linux kernel, without stopping the kernel. This maximizes system uptime, and thus system availability, which is important for mission-critical systems. By enabling dynamic patching of the kernel, the technology also encourages users to install critical security updates without deferring them to a scheduled downtime.

Using Kgraft in SLES12

kGraft is a live patching technology for runtime patching of the Linux kernel, without stopping the kernel. *This is not supported in SLES11.

Control No. of Kernels Available Automatically
Using installonly_limit parameter

In RHEL, it is defined using the "installonly_limit" parameter set in '/etc/yum.conf' or '/etc/dnf/dnf.conf' (in RHEL8) file as shown below:


The above line makes sure that the system always keeps latest (running) kernel along with its immediate predecessors. Hence, any older kernels would be removed automatically. 
Using multiversion.kernels parameter

In SLES, the number of kernels to keep in the system is automatically decided by the parameter “multiversion.kernels" which is set in the file '/etc/zypp/zypp.conf' as shown below:

multiversion.kernels = latest,latest-1,running

When system is rebooted after the installation of a new kernel, the system will keep 3 kernels: the current kernel (configured as latest,running), latest-1 and its currently running one. 

Generating System Config/Report

Complete system configuration and log details could be collected in one archived & compressed file which could be used later as a reference or base line for configuration file comparison or could be sent to support team for analysis.  The package to which this command belongs to is "sos".
Using Supportconfig

Same amount of data that gets generated when using SOSREPORT would be done by this command in SUSE systems. This command belongs to the "supportutils" package. 
Automated System Installation

Using kickstart

All required parameters for installation could be provided using an answer file (which is called kickstart file) that is used to deploy systems automatically without manual intervention. 

Using AutoYaST

AutoYaST is a system for unattended mass deployment of SUSE Linux Enterprise Server systems.    
These comparisons are based on Server Enterprise versions of Red Hat & SUSE.
*as of now data, at the time of writing this blog page. This could change down the line.


Girish said...

Nicely explained differences between two major unix distributions. Very informative for each unix user. Please keep it up ...

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