How to create an external drive in Ubuntu

Here is a detailed, step-by-step tutorial on the different ways to create or use an external drive with Ubuntu.

By “external drive” I mean using an external HDD/SSD or USB stick as a bootable Ubuntu system, not just a data disk.

Overview & Considerations

Before diving into steps, here are key points and which method you might choose:

Many guides agree that installing Ubuntu to an external HDD/SSD is nearly the same as internal, except you must be careful where bootloader (GRUB/EFI) is installed (not overwriting internal disk’s).
Also, the --removable installation for GRUB is useful to ensure EFI boot is isolated to the external drive and doesn’t mess with internal system.

Requirements / What You Need

1. Ubuntu ISO — download from Ubuntu’s official site (e.g. Desktop edition).

2. A USB / external drive (HDD or SSD works) — make sure you have backups because partitions will be changed.

3. A USB stick / live media to bootstrap the install (unless using advanced direct-ISO methods).

4. A computer that supports booting from external USB devices.

5. Familiarity with partitioning tools like GParted, and careful with drive identifiers like /dev/sdb, /dev/sdc, etc.

Method A: Live USB (no persistence)

This is the simplest. It allows you to boot Ubuntu from a USB stick, but changes (installed packages, files) are lost after shutdown.

Steps

1. Use a utility like Startup Disk Creator (on Ubuntu), Etcher, Rufus, or UNetbootin to flash the ISO to a USB stick as a live USB.

   • Ubuntu includes Startup Disk Creator.

   • UNetbootin is cross-platform and supports live USB creation.

2. Boot your computer selecting USB as boot device.

3. Choose “Try Ubuntu” (or similar) instead of installing.

This method is great for testing, rescue, or temporary use, but not for persistent day-to-day use.

Method B: Persistent Live USB

This is like Live USB but with a provision to save data across reboots.

Steps & Notes

• When using tools like Rufus, you can allocate a “persistent partition” size.

• Some tools (Ventoy, mkusb) support persistence in more flexible ways.

• But note: persistence has limits (e.g. how much space; performance is slower; system upgrades may break).

This is often a middle ground between “throwaway live USB” and full install.

Method C: Full Ubuntu Install on External Drive

This gives you a full-fledged Ubuntu environment on the external drive, which you can boot from any (compatible) PC.

Detailed Step-by-Step

Below is a recommended workflow:

1. Boot from Live USB and “Try Ubuntu”

• Use your live USB (from previous methods) to boot into Ubuntu’s “live session” (Try Ubuntu mode).

• Connect your target external drive.

2. Open GParted and Prepare Partitions

• Launch GParted (installed by default or via sudo apt install gparted).

• In the top-right, choose the external drive (e.g. /dev/sdb, not your internal /dev/sda).

• If needed, unmount any mounted partitions on that drive.

• Delete existing partitions (if any) — be absolutely sure you're working on the external drive.

• Create a new partition table, e.g. GPT or MS-DOS (MBR) depending on your system’s need.

• Create at least:

  1. EFI System Partition (ESP) — ~100-300 MB, FAT32, with flags boot, esp (for UEFI systems)

  2. Root partition / — ext4, occupying the bulk of the remaining space

  3. Optionally swap partition (size depends on RAM and whether you want hibernation)

  4. Optionally separate /home or other partitions as you like

• Apply the operations in GParted.

3. Launch Ubuntu Installer and Use “Something Else”

• From the live session, run the Ubuntu installer.

• When asked Installation Type, select Something Else (manual partitioning).

• In the partitioning dialog:

  • Choose the ext4 partition you made, set it to mount as /, and check “Format”.

  • Assign swap partition (if using).

  • Set the bootloader installation location (this is critical!) to your external drive (e.g. /dev/sdb), not the internal drive.

  • The installer might try to default to your internal drive for EFI; override carefully.

• Proceed with installation (user, timezone, etc.).

4. After Installation: Reinstall GRUB in “Removable” Mode (Optional but Safer)

To make the external drive more portable (i.e. it doesn’t depend on a specific internal disk), you can reinstall GRUB using the --removable option. This helps ensure that the EFI boot files live fully on the external drive.

For example, after booting from the external drive:

sudo grub-install --removable sudo update-grub 

Alternatively, do this from a chroot environment pointed to your external drive.

5. Boot from External Drive

• Reboot your computer, enter BIOS/UEFI boot menu, and choose your external drive.

• If everything was set up correctly, Ubuntu should boot from the external drive.

• You can test on different machines (if hardware support is good).

Advanced / Alternative Methods & Tips

• Some guides recommend disconnecting internal drives during install so there's no chance of accidentally touching them.

• If you can’t disable internal drive, be super careful with partition/bootloader selection.

• Using the --removable GRUB install is often cited as best practice for fully portable external Ubuntu.

• There are guides for doing Ubuntu install to external drive without using a live USB, by mounting ISO directly, etc.

• Beware that Ubuntu installer sometimes ignores your manual ESP selection and writes to internal disk; always double-check.

• You may need to tweak /etc/fstab to ensure correct mounting of partitions when booting on different systems.

Example Walkthrough (UEFI Scenario)

Here’s an example scenario:

1. You have a Windows laptop that supports UEFI boot.

2. You prepare a live USB and boot “Try Ubuntu”.

3. You plug in an external SSD.

4. In GParted, you identify it as /dev/sdb, wipe it, create GPT table.

5. Create partitions:

   • /dev/sdb1 ~200 MB, FAT32, flags boot, esp

   • /dev/sdb2 ext4, size ~200 GB → mount as /

   • /dev/sdb3 swap, e.g. 8 GB

6. Run Ubuntu installer “Something Else”:

   • Set /dev/sdb2 to mount /

   • Set swap

   • Bootloader installation target: /dev/sdb

7. Complete installation.

8. Boot into the new Ubuntu on external SSD.

9. In terminal: sudo grub-install --removable & sudo update-grub.

10. Reboot, pick the external drive in BIOS/UEFI, and Ubuntu boots.

Troubleshooting & Tips

• Wrong drive selected accidentally → you might overwrite your system. Always double-check drive names.

• Ubuntu boots but problems with bootloader → check EFI partition mount, reinstall GRUB.

• Slowness → external USB may be slower; use USB 3.0 / SSD for better performance.

• Hardware differences → external installation may have drivers missing for some machines.

• Secure Boot / UEFI firmware issues → you may need to disable secure boot or enroll keys.