Reinstalling can mean erasing everything, reformatting the partition, loosing all data and installing Ubuntu with a brand new /home/user directory. This is the common result when doing a google search.

This answer is about reinstalling Ubuntu and keeping /home/user directory. The following is from: Ubuntu Reinstallation

Ubuntu Reinstallation

Introduction

Sometimes reinstalling is the quickest way to solve a problem, for example if an upgrade failed or if your graphics driver is broken. When reinstalling, you’re most likely want to preserve two things:

• /home folder with your files and settings
• Entries in boot menu (if you have multiple OS installed)

How To Reinstall Ubuntu

Since Hardy it is possible to reinstall Ubuntu without losing the content of the /home folder (the folder that contains program settings, internet bookmarks, emails and all your documents, music, videos and other user files). This can be done even if /home is not on a separate partition (which is the case by default if you did not manually separate it when installing Ubuntu originally). This tutorial can also be used to upgrade Ubuntu (eg 11.04 -> 12.04 from a 12.04 live-CD).

Before doing anything

This operation should not damage your documents but, for security, backup your documents and settings (including /home hidden files) on external disk or DVDs. (eg via CloneZilla) Note: Some special applications settings may be in system folders, eg LAMP, see below in the thread.

Run the Ubuntu installer

• Run the UbuntuInstaller
• Follow the prompts until the “Installation type” (or “Allocate disk space”) menu
• Choose the right option as described below:

Choose the right option

There are two possibilities - choose the one that fits what the installer is showing:

• If an “Upgrade 1X.XX to 1Y.YY” option is available (like in the screenshot below), choose it.

• Or, if the above option is not available, choose manual partitioning (“Something-else” option), then select Ubuntu system partition, set its mount point as “/”. Be sure to keep the same format type, the same size, and untick the “Format” checkbox or all data on “/” will be deleted!. Also set other partitions (/boot, /home… see DiskSpace) if needed.

Then finish the installation process. (this may take several hours, like a normal install)

After reinstalling

After reinstalling, user accounts must be re-created with the same login and password.

See also

1. Discussion on the forum

Create a Live USB

• How to Create a Bootable Linux USB Flash Drive, the Easy Way