I attempted to install the following two guest OSes using Cockpit.
The host is RockyLinux 10.1.
・CentOS 6.6
・RockyLinux 9.6
Regarding the CD-ROM drive bus, CentOS 6.6 uses IDE, while RockyLinux 9.6 uses SATA.
I would like to know the reason for this. Is there a specific reason why this happens when the guest kernel is 2.6.x, for example?
*Please note that this text has been machine-translated from Japanese, so I apologize if it is difficult to understand.
I asked Google Gemini your question, and it gave me this answer, quoting below:
There has been a significant shift in how Linux distributions handle hardware virtualization and physical storage interfaces over the last decade.
In the world of Linux, this change reflects the evolution from legacy hardware standards to modern, high-speed interfaces. While both IDE and SATA serve the same purpose—connecting storage devices like CD-ROMs and Hard Drives to the motherboard—their architecture and performance capabilities are worlds apart.
The transition from CentOS 6 (released circa 2011) to Rocky Linux 9 (released in 2022) mirrors the industry-wide move away from the Parallel ATA (PATA/IDE) standard toward the Serial ATA (SATA) standard.
| Feature | IDE (Integrated Drive Electronics) | SATA (Serial AT Attachment) |
|---|---|---|
| Data Transfer | Parallel (multiple bits at once) | Serial (one bit at a time, but faster) |
| Cable Type | Wide, 40-pin ribbon cables | Thin, 7-pin data cables |
| Max Speed | ~133 MB/s | Up to 600 MB/s (SATA III) |
| Hot Swapping | Not supported | Supported |
| Standard Era | Dominant in the 1990s/early 2000s | Industry standard since mid-2000s |
Rocky Linux 10.1 further solidifies this transition by prioritizing modern bus types like SATA and, increasingly, VirtIO for virtualized environments.
The reason Rocky Linux 10.1 defaults to SATA for CD-ROMs and storage is due to the hardware abstraction layers in the 6.x series kernels.
| Feature | IDE (CentOS 6 Era) | SATA (Rocky 10.1 Era) |
|---|---|---|
| Kernel Driver | CONFIG_IDE (Legacy) |
libata / ahci (Standard) |
| Addressing | Master/Slave (HDA, HDB) | Serial Channel (SDA, SDB) |
| Architecture | Parallel (Bulky cables) | Serial (High-speed point-to-point) |
| Efficiency | High CPU overhead | Low overhead with NCQ support |
If you are setting up a Rocky 10.1 system today—especially on modern server hardware like a Dell PowerEdge—you will notice several functional changes:
Driver Deprecation: Rocky 10.1 uses a kernel that has essentially moved IDE support to the “obsolete” category. While it may still exist for extreme backwards compatibility, it is no longer tested or optimized.
Virtualization Defaults: In virt-manager or cockpit on a Rocky 10.1 host, creating a new virtual machine will automatically assign the CD-ROM to a SATA bus or a VirtIO-SCSI bus. Using the IDE bus in a VM configuration can lead to significantly slower boot times or the installer failing to “see” the ISO.
UEFI Compatibility: Modern systems running Rocky 10.1 almost exclusively use UEFI rather than Legacy BIOS. UEFI works natively and more reliably with SATA/AHCI controllers compared to the old IDE/Mapped controllers.
If you are troubleshooting a Rocky Linux 10.1 installation and the CD-ROM isn’t mounting, the first thing to check is the controller type in the BIOS or the VM settings. Ensuring it is set to AHCI/SATA (or VirtIO for performance) is mandatory for a stable 10.x environment.
What error did you get, what did it say on the screen?
No error messages are displayed.
I just want to know if “Cockpit” uses a specific criterion to choose between IDE and SATA based on the guest OS.
I again asked Google Gemini, and it provided the below, quoting:
As of early 2026, Rocky Linux 10.1 (and its upstream, RHEL 10) has significantly restricted legacy hardware support, making the use of an IDE CD-ROM bus technically challenging but not entirely impossible depending on your configuration.
Here is the breakdown of why this is a hurdle and how to handle it:
Rocky Linux 10.1 defaults to the Q35 machine type and the 6.12+ kernel.
The Problem: The Q35 chipset does not natively support the legacy IDE (PATA) controller. It is built entirely around SATA (AHCI) and PCIe.
The Support Status: While the underlying QEMU emulator still contains code for IDE, it is considered deprecated/legacy. In Rocky 10.1, many “legacy” drivers were removed from the kernel to reduce the attack surface and binary size.
If you have a guest like CentOS 6.6 that insists on an IDE bus to see its installation media, you have two options on a Rocky 10.1 host:
Switch to the i440FX Machine Type: Instead of the modern q35, you can manually set the VM to use the older pc-i440fx machine type (often listed as pc in virt-install or virsh). This virtual motherboard does include a legacy IDE controller.
SATA Emulation: Most guests that support IDE also support SATA if the AHCI driver is present. For CentOS 6.6, try setting the CD-ROM bus to SATA first. It is much more likely to work on a Rocky 10.1 host than a forced IDE bus.
I don’t use cockpit, so cannot offer definitive answer. However, the cockpit is just a frontend,
probably to libvirt, which itself is a frontend to KVM. That leads to questions:
Typically, one could hit the wall of “KVM would support, but the frontend does not offer as option”.
Here though the question is, if the front-end offers “Enter type of client” selection, then does it pass different set of options to the KVM based on that selection?
It probably can. No idea whether it does.
I’m quite sure that nobody in that chain does sniff the binary that you load as installer to auto-detect what it is/requires.
Rocky has what RHEL has, which is: Chapter 23. Feature support and limitations in RHEL 10 virtualization | Configuring and managing Linux virtual machines | Red Hat Enterprise Linux | 10 | Red Hat Documentation
There is a link to supported guests: Certified Hypervisors and Guest Operating Systems in Red Hat OpenStack Platform, Red Hat Virtualization, Red Hat OpenShift Virtualization and Red Hat Enterprise Linux with KVM - Red Hat Customer Portal
Apparently neither el9 nor el10 has support for CentOS 6 guests. One could use Rocky 8 host for that.