Linux migration for business

CentOS Linux 8 stopped receiving updates at the end of 2021 and CentOS Linux 7 on 30 June 2024, so any server still running either has been piling up unpatched vulnerabilities for a while. The way out depends on whether you need vendor support with a service agreement: if you do, convert2rhel turns the server into RHEL without a reinstall; if community support plus ours is enough, AlmaLinux and Rocky Linux are compatible with RHEL and day-to-day work barely notices the change.

Converting does not change the major version. A converted CentOS 7 is still a 7, so the usual approach is to use the same maintenance window to move up to 9 with Leapp or ELevate, or to buy RHEL 7 extended support as a bridge while that upgrade is prepared.

Tools

convert2rhel, ELevate, Leapp and, from CentOS 8, migrate2rocky

Where it gets tricky

Third-party repositories such as EPEL, hand-compiled packages and kernel modules from other vendors: storage drivers, backup agents and antivirus.

RHEL 7 left maintenance in June 2024 and only gets critical fixes if you pay for Extended Life Cycle Support (ELS), which runs out on 31 May 2029, the same day RHEL 8 maintenance ends. Leapp upgrades a server in place, always one major version at a time, and before touching anything it produces a report of everything blocking the upgrade, which is the best measure of the work ahead.

Going from 7 to 9 means two jumps in a row. On servers carrying years of manual changes it is often cheaper to install a clean RHEL 9, automate the configuration with Ansible and move the data across, and that is what we propose when the Leapp report comes back long.

Tools

Leapp and its pre-upgrade report, Ansible, Satellite or Foreman for batch migrations

Where it gets tricky

Python 2 is gone, iptables gives way to nftables, RHEL 9 drops network-scripts and its crypto policy rejects SHA-1 signatures that some older certificates and applications still rely on.

Extended support for Windows Server 2016 ends on 12 January 2027, and before renewing licences it pays to check which servers could move to Linux. File servers go to Samba, IIS sites to Apache or Nginx, modern .NET applications (.NET Core and .NET 5 onwards) run on Linux without a rewrite, and SQL Server has had a Linux edition since 2017.

Active Directory can stay as it is, because Linux servers join the domain through SSSD and people keep logging in with the same account. Whatever cannot move, such as .NET Framework 4 applications or software that only exists for Windows, stays on Windows, and we say so in the inventory, before the project starts.

Tools

Samba, SSSD and realmd, .NET on Linux, SQL Server on Linux, Ansible

Where it gets tricky

Applications with COM or registry dependencies, third-party licences tied to Windows and scheduled tasks nobody ever documented.

Windows 10 reached end of support on 14 October 2025 and a good share of those machines fail the hardware requirements for Windows 11, so the alternative to scrapping them is giving them another system. Linux works well for administrative staff, front desks, classrooms and kiosks, where the job is browser, email and office software, and works badly for anyone who depends on complex Excel macros or design software that only exists for Windows.

That is why we always start with a small pilot group, measure incidents for a few weeks and only then roll out to everyone else.

Tools

Ubuntu LTS or Debian, LibreOffice, Ansible to deploy and maintain the machines

Where it gets tricky

VBA macros, peripherals whose drivers only exist for Windows and digital certificates, which work but have to be installed browser by browser.

Leaving UNIX does not mean replacing the hardware. RHEL, SUSE and Ubuntu run on IBM Power (as ppc64le), so an AIX shop can move workloads to Linux in another partition of the same server, which is what we do in Linux on IBM Power.

What is easy to miss is byte order: AIX and Solaris on SPARC store data as big-endian, while Linux, on x86 and on Power (ppc64le) alike, is little-endian, so even on the same machine the binary files an application writes itself may need converting. Data exported from a database, on the other hand, travels without trouble. And if you are heading the other way, moving Linux workloads to AIX, we cover that in migration to AIX.

Tools

Pacemaker in place of PowerHA, ReaR for system backups (the counterpart of mksysb), Ansible

Where it gets tricky

ksh scripts full of AIX-specific commands, different volume management and compiled applications whose source code is long gone.

Db2 on IBM i and on z/OS is not the same product as Db2 for Linux: the catalogue changes, part of the SQL changes and so does the way it is administered, and the data moves from EBCDIC to ASCII or Unicode along the way. That is why we treat these migrations as database projects, with performance tests under real load before cutover and the source system kept available until the new one has been stable for weeks.

After the move we carry on with Db2 technical support on Power and x86.

Tools

Db2 export and load, replication for short cutovers, tests under real load

Where it gets tricky

Character set conversion, RPG or COBOL programs that access the data directly and batch jobs with tight schedules.