Walk through an enterprise Linux migration

1© 2017 Rogue Wave Software, Inc. All Rights Reserved.
How to migrate from Red Hat to CentOS successfully
Episode 2:
Walk through an enterprise
Linux migration
Richard Alloway
Greg Rogers

Presenters
Greg Rogers
Enterprise account executive
greg.rogers@roguewave.com
Richard Alloway
CentOS developer, technology support
richard.alloway@roguewave.com

Agenda
• Why migrate to CentOS?
• Migration walkthrough
• Getting packages
• Upgrading
• When things go wrong
• Migrating between different versions
• Q & A

Why migrate to CentOS?

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The only difference is branding
Red Hat
releases
(commercial paid)
Community repackaging
• Remove branding
• Remove links to Red Hat Network
• Recompile binaries
CentOS
source code
(free)
B i n a r y c o m p a t i b l e
Main project
(free)
Community Enterprise Operating System

Savings potential
Licensing Support+
$1.75M $2.97M
Based on sample scenario: 1,000 servers*
$0+
+
* Based on RHEL Virtual Datacenters with Smart Management, Premium Support
= Annual total
$4.72M=
Over 50% savings

Compare component costs
Item Red Hat SKU
($)
CentOS equivalent CentOS SKU
($)
Delta
OS license – server $TBD CentOS $0 TBD
OS license – virtual $TBD CentOS $0 TBD
High Availability Add-on $TBD Linux-HA $0 TBD
Load Balancer Add-on $TBD Linux-HA $0 TBD
Resilient Storage Add-on $TBD GFS + LVM $0 TBD
Satellite Capsule Server $TBD Katello $0 TBD
Directory server $TBD OpenLDAP $0 TBD
Certificate system $TBD pki-* packages $0 TBD
etc.

Migration walkthrough

High-level roadmap
1. Inventory your apps
2. Prioritize apps
YourApp1
Low risk
Low time to migrate
YourAppN
High risk
High time to migrate
…
3. Group similar & schedule migration timeline
1 4 5 7 … N
YourApp1 YourApp2
4. Execute migration
Install
Configure
Stage
Test
Final decision
Large OSS deployment
Reporting & metrics
Key internal expertise
Critical apps
Key infrastructure
Potential for large revenue
loss
Publicly-hosted SaaS
Prototyping & testing
Isolated systems
Unchanging configs
Not significant
Need for
fast response
Need for support

Business goals
What do we want to get out of migration?
• Same applications, databases, services, APIs, etc.
running the same way
• No downtime during migration
• Depends on applications
• For OS, depends on whether you need to reboot
• Less expensive support going forward

Migration consultation
Complimentary to all attendees
Reply "Yes" in the chat or email greg.rogers@roguewave.com
Leverage expertise & experience with successful migrations
• Assess readiness for a migration
• Develop a migration blueprint
• Determine potential ROI specific to your organization

Non-live (offline) migration steps
For both OS and applications:
1. Install
Considerations: Physical/virtual hardware allocation & costs when non-live; people-time (IT/DevOps)
2. Configure
Considerations: People-time (IT/DevOps/Dev) - dev involvement comes with opportunity cost
3. Stage
Considerations: Physical/virtual hardware allocation & costs when non-live; people-time (IT/DevOps)
4. Test
Considerations: Test data & workloads to reproduce production-like environment
5. Final decision
Considerations: Who/when to make a go or no-go decision

Live migration steps
For both the OS and non-Red Hat proprietary applications:
1. Create a fresh backup (of the entire system, if possible)
2. Remove Red Hat-specific OS packages
3. Manually download & install a minimal set of CentOS packages
4. Clean & rebuild package cache
5. Perform upgrade
This converts the actual system from RHEL to CentOS
6. Test
Considerations: Test functionality of migrated system
7. Final decision
Considerations: Approve migrated system or rollback via backups taken in step 1

Walkthrough environment
Migrate from RHEL 7.4 to CentOS 7.4
Start
• RHEL 7.4 VM inside VirtualBox
– From the Red Hat Ansible Core Engineering team
• No Red Hat subscription – simulates an expired license
Finish
• CentOS 7.4 VM with latest package updates
• Zero OS downtime
– Packages may be brought down/up by the package
manager

Walkthrough Demonstration

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Package change overview
• CentOS source code comes directly from Red Hat
• Same upstream parents
• Many RHEL packages are available from non-Red Hat sources
• Out of 600 packages, less than 20% were updated or replaced in
our demonstration
We are the official maintainer of CentOS on Azure:
Search for “Rogue Wave Software” on Azure Marketplace

When things go wrong
• Red Hat-specific code within apps
• Double-check before migration
• Move into containers that appear as a Red Hat system to the app
• Mitigation steps:
• Ensure system backups are made before migrating
• Test live migration on non-mission critical instances first
• Snapshot VM to be migrated
• Stand up a test instance
• Test live migration

Plan for support
Migration services
• Direct access to Tier 3/4 enterprise architects – no escalation path
necessary
• Expertise across all critical packages
• Help assess, plan, and execute
• Experience across different stacks, environments, and scales
• Support Red Hat and CentOS simultaneously during migration

Migration complete
What we did:
1. Remove Red Hat dependencies
2. Download & install RPMs
3. Clean up yum cache
4. Upgrade
5. Verify CentOS is running
6. (Reboot if necessary)

Reminder on maintaining production SLAs
Only migrate the OS!
• Identify risks accurately
• Follow the roadmap
• Stage and test before production push
Where possible, follow a live migration plan

Migrating between different
versions

Live migration within major versions is OK
RHEL 6.x to CentOS 6.x
OK!
OK!
RISKY!

RHEL 7.x to CentOS 7.4
Within major versions, use the same process except for…
1. Remove Red Hat dependencies
2. Download & install CentOS 7.x RPMs
3. Clean up yum cache
4. Upgrade
5. Verify CentOS 7.4 is running
6. (Reboot if necessary)
Migration between major versions: Use non-live (offline) migration

Watch the webinar

Q&A

Walk through an enterprise Linux migration

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