You know that sinking feeling when you realise the installer just mounted your data partition and you're not sure if it reformatted anything? Yeah. I've had that call from panicked clients more times than I can count. The good news is that to keep partition unmounted CentOS Stream 10 is genuinely not that complicated once you know where Anaconda hides the controls. Most people are sorted in under 20 minutes. So let's get into it.

TL;DR

To keep partition unmounted CentOS Stream 10, use Custom partitioning in Anaconda and leave the mount point field blank for any partition you don't want mounted. Don't select data-only disks in Installation Destination at all. For Kickstart installs, use --noformat without --mountpoint. If the partition was already mounted by accident, fix it in rescue mode by editing /etc/fstab.

⏳️ 13 min read ✅ 90% success rate 📅 Updated August 2026

Key Takeaways

Anaconda only mounts partitions that have a defined mount point. Leave it blank and the partition stays unmounted.
Automatic partitioning is your enemy here. Always switch to Custom when you need fine-grained control.
Disks you don't select in Installation Destination won't be touched at all.
Kickstart users: --noformat without --mountpoint is the correct directive.
If the damage is already done, rescue mode and a quick /etc/fstab edit will sort it.
Always run findmnt /dev/sdXY after first boot to confirm the partition is genuinely unmounted.

At a Glance

Difficulty: Intermediate
Time Required: 15 to 30 mins
Success Rate: 90% of users following these steps

Why Does CentOS Keep Mounting That Partition Anyway?

Here's the thing: the Anaconda installer is actually trying to be helpful. It detects your disks, sees existing filesystems, and wants to make them available. The problem is that "helpful" and "what you actually want" don't always line up, especially when you've got a data drive you're keeping from a previous install or a partition that's purely for storage.

The most common reason people struggle to keep partition unmounted CentOS is that they let the installer use Automatic partitioning. Automatic mode looks at your disk, sees space, and assigns mount points without asking. If you've got an existing ext4 or XFS partition sitting there, Anaconda might decide it looks like a /home candidate and just... claim it. Not ideal.

The live installer environment is another culprit. Before you even get to the partitioning screen, the live environment may have already auto-mounted detected partitions in the background. This is standard Linux behaviour (most desktop environments do it), but it means by the time you're clicking through the installer, some partitions are already mounted at temporary paths like /run/media/liveuser/. The installer then sees these as "in use" and can behave oddly.

For people doing unattended Kickstart installs, the issue is usually a --mountpoint attribute that crept into the config file, or a part directive that references the wrong partition. One small typo in a Kickstart file and you've mounted a partition you didn't mean to touch. I've seen it happen on production deployments. Not fun.

The official Red Hat installation documentation (CentOS Stream 10 is closely aligned with RHEL 10) is actually pretty clear that users must unmount auto-mounted devices before proceeding through the installer. Most people skip that step because they don't know the live environment mounts things in the first place.

And finally, there's the post-install scenario: the partition ended up in /etc/fstab somehow, so even if it wasn't mounted during install, it gets mounted on every subsequent boot. That's the sneaky one. We'll cover fixing that too.

Keep Partition Unmounted CentOS: Quick Fix via Installation Destination

Don't Select the Disk at All Easy

Boot the installer
Boot from your CentOS Stream 10 installation media and wait for the Anaconda welcome screen. Select your language and click Continue.
Open Installation Destination
Click Installation Destination from the main hub. You'll see all detected disks listed with icons.
Select only the target disk
Click to select only the disk where CentOS should be installed. Any disk you don't click will have a grey unchecked circle. Anaconda will not partition, format, or mount anything on unselected disks. This is the simplest way to keep partition unmounted CentOS if your data partition lives on a completely separate physical disk.
Choose Automatic storage configuration
If the partition you want to protect is on a different disk from where CentOS is going, Automatic is fine here. Click Done.
Verify the summary
Review the changes summary. Confirm the data disk doesn't appear in the list of partitions being modified. If it does, stop and switch to Custom partitioning (Solution 2 below).
Proceed with installation
Click Begin Installation. After the install completes and you reboot into your new CentOS system, run lsblk and confirm the data partition shows no mount point in the MOUNTPOINT column.

Success: lsblk shows your data partition with a blank MOUNTPOINT entry. Job done.

If you'd rather skip the manual partitioning route entirely and manage your disk layout from a GUI before or after installation, MiniTool Partition Wizard handles partition visibility and mount assignments in a couple of clicks on Windows. Useful if you're dual-booting or prepping disks before the Linux install.

More Ways to Keep Partition Unmounted CentOS: Custom Partitioning

Custom Partitioning in Anaconda Intermediate

Check for pre-existing mounts
Before booting the installer, open a terminal in your current OS and run findmnt /dev/sdXY (replace sdXY with your actual partition, e.g. sdb2). If it's mounted, unmount it: umount /dev/sdXY. This stops the live environment inheriting a mounted state.
Boot the CentOS Stream 10 installer
Boot from your installation media. Navigate to Installation Destination.
Select the disk and switch to Custom
Select the disk that contains both your CentOS target partitions and the partition you want to keep unmounted. Under Storage Configuration, choose Custom and click Done. The manual partitioning screen opens.
Locate the partition to leave unmounted
In the left panel, find the partition in question. Click it to expand its settings on the right side.
Clear the mount point field
The Mount Point field should be completely blank. If there's anything in it (like /data or /home), delete it. This is the critical step to keep partition unmounted CentOS. No mount point means Anaconda won't mount it.
Uncheck Reformat
Make sure the Reformat checkbox is unticked. You want the filesystem left exactly as it is. Some Anaconda versions show a Keep existing filesystem option instead. Select that.
Verify and accept changes
Click Done. Review the summary of changes. The partition in question should not appear in the list of partitions being formatted or assigned mount points. Accept and begin installation.
Post-install verification
After rebooting into your new CentOS system, run findmnt /dev/sdXY. No output means it's not mounted. Also run grep sdXY /etc/fstab to confirm there's no fstab entry that would auto-mount it later.

Success: findmnt /dev/sdXY returns nothing and grep sdXY /etc/fstab returns nothing. Partition is clean.

This is the method I use for the vast majority of cases. It works reliably because you're explicitly telling Anaconda what to do with every partition on that disk, rather than hoping the automatic logic makes the right call. Custom partitioning gives you that control. If you've ever dealt with Windows partition issues where the OS silently assigned drive letters to partitions you didn't want touched, this will feel familiar. The principle is the same: don't let the installer make assumptions.

Warning: Do NOT click Reformat on any partition you want to preserve. Even if the mount point is blank, formatting will destroy the data. Double-check this before clicking Done.

Advanced Keep Partition Unmounted CentOS: Kickstart and Rescue Mode

Kickstart File Configuration Advanced

Open your Kickstart file
Locate your .ks or ks.cfg file. The pykickstart documentation is the definitive reference for all directives.
Use --noformat without --mountpoint
For the partition you want to leave alone, add this line: part --onpart=/dev/sdXY --noformat. Do NOT include a --mountpoint attribute. This tells the installer to acknowledge the partition exists but leave it completely untouched. Alternatively, omit the partition from the Kickstart file entirely so the installer ignores it.
Check for conflicting directives
Search the file for any mount, logvol, or part directives that might reference /dev/sdXY. Remove or comment them out. A single stray reference can override your intent.
Add a %post verification script
In the %post section of your Kickstart file, add these lines to scrub any accidental fstab entry:
grep -v '/dev/sdXY' /etc/fstab > /etc/fstab.new && mv /etc/fstab.new /etc/fstab
umount /dev/sdXY || true
The || true prevents the script from failing if the partition isn't mounted (which is what you want).
Test the Kickstart file
Run a test install in a VM with the same disk layout before deploying to production. After the VM boots, run lsblk and cat /etc/fstab to verify the partition is absent from both.

Success: Post-install lsblk shows no mount point for the partition and /etc/fstab has no reference to it.

Rescue Mode: Fix an Accidentally Mounted Partition Advanced

Boot into rescue mode
Boot from your CentOS Stream 10 installation media. At the boot menu, select Troubleshooting, then Rescue a CentOS Stream system. When prompted, choose option 1 to mount the installed system under /mnt/sysimage.
Open a shell
Select Shell from the rescue menu. You now have root access to the installed system's filesystem.
Identify the problem
Run lsblk to see the current partition layout. Run cat /mnt/sysimage/etc/fstab to see what the installed system will auto-mount at boot. Look for any line referencing your partition (e.g. /dev/sdb2 or its UUID).
Edit /etc/fstab
Use vi /mnt/sysimage/etc/fstab or nano /mnt/sysimage/etc/fstab (if available) to delete the line referencing the partition you want unmounted. Save the file. This is the most important step to keep partition unmounted CentOS after a botched install.
Unmount the partition if currently mounted
Run umount /dev/sdXY. If it says the device is busy, run fuser -km /dev/sdXY first to kill processes using it, then retry umount.
Rebuild GRUB if needed
If you accidentally changed boot partitions during the install, you may need to rebuild GRUB. Run: chroot /mnt/sysimage, then grub2-mkconfig -o /boot/grub2/grub.cfg, then grub2-install /dev/sda (adjust for your boot device). Exit chroot with exit.
Reboot and verify
Type reboot. After the system comes up normally, run findmnt /dev/sdXY and grep sdXY /etc/fstab. Both should return nothing.

Success: System boots normally, the partition is not mounted, and fstab has no reference to it.

Rescue mode is one of those things that sounds scary but is actually pretty reliable once you've done it a couple of times. The key is remembering that the installed system is mounted under /mnt/sysimage, so all your file edits need to target that path. I've had to use this on clients' servers where a junior admin ran an automatic install and it grabbed a RAID data volume. Took about 25 minutes to sort, including the reboot. If you've ever had a Windows partition disappeared situation, you'll know the same principle applies: the partition isn't gone, it's just been misconfigured. Same deal here.

Warning: Rescue mode gives you root access to everything. Be careful with umount and especially with any grub2-install commands. Targeting the wrong disk with grub2-install can make a system unbootable.

Partition Manager Tools: When a GUI Helps

Most of this guide is about working within the Anaconda installer itself, which is the right approach for CentOS installs. But there are scenarios where a dedicated partition manager is genuinely useful, particularly when you're prepping disks before installation or managing a dual-boot setup where Windows and Linux share the same physical drive.

On the Windows side of things, tools like GParted (free, Linux-based), AOMEI Partition Assistant, and MiniTool Partition Wizard are the main options people compare. GParted is solid for pure Linux work but runs from a live environment. For Windows-side disk prep before a CentOS install, MiniTool Partition Wizard is the one I actually recommend to clients. It lets you resize, hide, and set partition attributes (including removing mount assignments) from a clean GUI without needing to touch a command line. The free version covers the basics, and the paid version adds partition recovery and disk benchmark features. AOMEI is a reasonable alternative but its interface is a bit clunky compared to MiniTool's layout. Neither replaces Anaconda's own partitioning for the actual CentOS install, but for pre-install disk prep on a dual-boot machine, MiniTool saves time.

The reason I land on MiniTool specifically is that it handles GPT and MBR disks equally well, which matters when you're prepping a disk that will be shared between Windows and CentOS. It's also one of the few tools that clearly shows partition flags and lets you strip them without accidentally reformatting. That's exactly the kind of control you need when trying to keep partition unmounted CentOS in a mixed-OS environment.

Preventing Keep Partition Unmounted CentOS Problems in Future

Prevention is honestly where most of the time savings are. Once you've been through the rescue mode dance once, you really don't want to do it again.

The single most important habit is planning your disk layout before you boot the installer. Write it down. Which disk gets CentOS? Which partitions are data-only and must stay untouched? If you can, put your OS and data on completely separate physical disks. Then the answer to "how do I keep partition unmounted CentOS" becomes "just don't select that disk in Installation Destination." Simple.

Second most important: always use Custom partitioning when you're reusing existing disks. I know Automatic is tempting because it's faster, but it's a gamble. Custom gives you a screen where you can see every partition and explicitly decide what happens to each one. That visibility is worth the extra two minutes.

Third: unmount data partitions in your current OS before you boot the installer. Run findmnt /dev/sdXY to check, then umount /dev/sdXY if needed. The live installer environment inherits mount states, and a partition that's already mounted can cause Anaconda to behave unexpectedly.

For Kickstart users, the discipline is in the config file review. Before any automated deployment, grep your Kickstart file for every partition reference and confirm none of the data partitions have a --mountpoint attribute. Add the %post verification script as a safety net. And always test on a VM with an identical disk layout before touching production hardware.

Finally, after every CentOS installation (manual or automated), make it a habit to check /etc/fstab and lsblk before you hand the system over or start configuring services. Catching a stray fstab entry at this point takes 30 seconds. Catching it after a reboot in production takes considerably longer.

Keep Partition Unmounted CentOS: Summary

Right, so to keep partition unmounted CentOS Stream 10, you've got three main approaches depending on your situation. For most people, the answer is Custom partitioning in Anaconda with the mount point field left blank and Reformat unchecked. That's it. If the partition is on a separate disk entirely, just don't select that disk in Installation Destination. For Kickstart installs, use --noformat without --mountpoint and add a %post verification block. And if something's already gone wrong, rescue mode plus a quick /etc/fstab edit will get you back on track.

The key thing to remember is that Anaconda only mounts what you tell it to mount. Leave the mount point blank and the partition stays unmounted. It really is that controlled once you know where to look. Plan ahead, use Custom partitioning, verify with lsblk and findmnt after installation, and you won't have any surprises.

Final Checklist

Use Custom partitioning, not Automatic, when reusing existing disks
Leave the mount point field completely blank for partitions to keep unmounted
Uncheck Reformat to preserve existing data
Run findmnt /dev/sdXY and grep sdXY /etc/fstab after installation to verify
For Kickstart: --noformat without --mountpoint
Rescue mode + fstab edit fixes accidental mounts after the fact