When you choose "Erase disk and install Ubuntu" on a multi-partition drive, the installer wipes only the partition it targets — but any personal files stored inside that partition (including folders like Documents, Pictures, and Downloads that live under your home directory) are destroyed with it. Partitions you did not select, such as a separate data partition, are left untouched. The key is understanding which partition the installer is about to erase before you confirm.
Why the installer behaves this way
Ubuntu's installer offers two main paths on a disk that already contains a system:
- Erase disk and install Ubuntu — despite the name, when you have multiple partitions it may offer to erase just the selected partition (for example,
sda3) and install the new version there. Anything on that partition is gone: the operating system, the old home directory, and every file that had drifted into it. - Something else (manual partitioning) — you choose exactly which partition holds the new system and which ones are mounted but not formatted. This is the only path that guarantees your data partition survives.
The "upgrade" option some people mention only appears when the installer can detect an existing supported Ubuntu release and offers to preserve its installed packages. It is not always available, especially when jumping across many years of releases, so relying on it is a gamble.
Why personal files end up in the doomed partition
By default, Ubuntu puts everything under one root partition: the system, the applications, and your home directory with all its subfolders. If you have been using the machine for years, photos, downloads, and documents accumulate inside /home — which lives on the same partition as the OS. A clean reinstall of that partition therefore takes your personal files with it, even if the installer's summary only mentions "erasing the system."
How to check before you install
Before touching anything, boot the machine from a live USB (or any working system) and inspect the partitions:
lsblk -f
This lists every partition with its filesystem type and size. Identify which one holds the old Ubuntu installation (it will contain directories like usr and home when mounted) and which one holds your data. Then:
- Mount the old system partition and browse
/home. Copy anything you care about to the data partition or an external drive. - Mount the data partition and confirm its contents are intact and readable.
- Write down the device names and sizes — you will need them in the installer.
Only after a verified backup should you proceed. A backup is not a backup until you have opened a few files from it and confirmed they are readable.
Reinstalling without losing the data partition
At the installer's "Installation type" screen, choose Something else instead of the erase option. Then:
- Select the old system partition (e.g.,
sda3) and set it as the mount point/, with the "Format" box checked. This wipes only the OS. - Select the data partition (e.g.,
sda4) and set a mount point such as/mnt/data— but leave "Format" unchecked. This mounts it without erasing anything. - Set the boot/EFI partition appropriately if you have UEFI firmware.
After installation, the data partition is available at /mnt/data every boot. You can then move your personal folders onto it or link them from your new home directory.
Preventing the problem next time
The cleanest long-term fix is to separate system from data permanently:
- Create a dedicated
/homepartition, so reinstalls of the root partition never touch your files. When reinstalling, format/but mount the existing/homepartition without formatting. - Alternatively, keep a plain data partition and symlink or reconfigure your Documents, Pictures, and Downloads folders to point at it.
- Either way, treat "nothing critical in there" as a warning sign, not a comfort. Data you have not backed up is data you have decided to lose.
One caution: if you reuse an old /home partition across a major version jump, configuration files written by the old release may conflict with the new one. If you see odd behavior after login, create a fresh user account, or rename your old home directory and let the new system build a clean one, then copy your files back selectively.
Frequently Asked Questions
Will "Erase and install" delete my other partitions?
It deletes only the partition it names in the summary screen. Read that screen carefully — it tells you exactly which device will be wiped. If it says the whole disk, everything goes; if it names a single partition, the rest survives.
Why didn't I see an "Upgrade" option during the install?
The upgrade path appears only in certain conditions, such as a supported release being detected and no conflicting disk layout. Long jumps between versions and non-standard partitioning often hide it. Manual partitioning is the reliable route.
Can I recover files after the partition was wiped?
Sometimes. Stop using the partition immediately, boot from a live USB, and run a recovery tool such as testdisk or photorec. Every write to that partition reduces the chance of recovery, so act fast and recover to a different disk.
Is a separate /home partition still worth it?
Yes. It makes reinstalls trivially safe — you format the root partition, mount the existing home partition unformatted, and your files are waiting for you. It also simplifies backups, since you can back up one partition instead of carefully excluding system directories.
What if my old home partition has a different filesystem?
Ubuntu handles ext4, and can read NTFS and FAT partitions, but a separate home should be a Linux filesystem such as ext4. If your data partition is NTFS, mount it as extra storage rather than as /home, since Linux permissions do not work properly on NTFS.
Should I back up even if I plan to keep the data partition?
Always. Partitioning mistakes, installer misclicks, and failing disks are all easy to make and hard to undo. Copy the data partition to an external drive before any install — it takes minutes and removes all the risk.