I want to install a complete, bootable Linux system on an external SSD so it can start on different computers without relying on the internal drive. I previously installed Linux Mint Xfce alongside Mint Cinnamon, but when I connected the SSD to a Windows PC, it was not recognized as bootable. While trying to repair the setup, I ended up breaking both GRUB installations.
I suspect the installer reused the existing computer's EFI partition instead of creating and using one on the external SSD. I then tried Fedora, hoping that installing it from the Windows machine would keep everything on the external drive, but Fedora also placed its GRUB files on the computer's internal drive.
My current plan is to install Linux using an inexpensive computer with its internal drives removed, ensuring the installer has no choice but to use the external SSD. Is that a reliable approach? Once the installation is complete, could the SSD later damage or remove its own bootloader when connected to another computer with an existing EFI partition or operating system? Are there any other compatibility or maintenance issues I should expect when moving the external Linux installation between different PCs?
3 Answers
The most dependable arrangement is one independent bootloader per drive, rather than having the internal drive’s GRUB manage every operating system. Install Linux, its EFI partition, and its bootloader entirely on the external SSD. When using it on another computer, open that computer’s firmware boot menu and choose the SSD. The installation should work across many UEFI PCs, although hardware differences may require driver adjustments, and Secure Boot or firmware settings can sometimes prevent it from starting.
A bootloader already installed on another drive will not normally delete the bootloader on your external SSD. The main problem is that the installer may place or update its files on the wrong EFI partition if that partition is mounted. After installation, each drive can have its own EFI partition and bootloader. You can then select the external SSD from the computer’s UEFI boot menu. Normal Linux updates should not remove the external drive’s boot files, provided the system is booted from and configured to use the SSD’s own EFI partition.
Some Linux installers will automatically reuse an EFI System Partition they find on an internal drive. To keep the installation self-contained, create an EFI partition on the external SSD and explicitly mount it at /boot/efi during the installation. Make sure the internal EFI partition is not mounted. If the installer still tries to use the wrong one, temporarily disable the other drives in the firmware settings, remove their boot flags, or disconnect them during installation. Installing with the other drives physically removed is generally the safest option.
That makes sense. I may have been selecting the correct root drive but missing the separate option that tells the installer exactly which EFI partition to use. If the SSD is installed correctly, should normal updates be safe when another computer’s internal drive is present?