I want to install a complete Linux system on an external SSD so I can plug it into different computers and boot from it without relying on the internal drive. I previously installed Mint XFCE alongside Mint Cinnamon, but when I connected the SSD to a Windows computer, it was not recognized as bootable. While trying to fix it, I damaged both GRUB installations and had to start over.
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 computer would keep everything on the external drive, but Fedora also placed its bootloader on the computer's internal disk.
My current plan is to install Linux using a very inexpensive computer with its internal drives removed, ensuring the installer can only see the external SSD. Would that reliably create a self-contained installation? Once it is set up, could installing updates while the SSD is connected to another computer cause its bootloader or EFI files to be deleted or replaced? Are there other compatibility or boot issues I should expect when moving the SSD between different PCs?
2 Answers
Some Linux installers will automatically reuse an EFI System Partition they find on another drive, so your suspicion is reasonable. The safest approach is to disconnect or disable every other drive during installation. If the firmware supports it, disabling the internal drives in UEFI settings can work just as well as physically removing them.
If you install with the other drives attached, manually create an EFI System Partition on the external SSD and make sure it is the partition mounted at /boot/efi during installation. The installer’s exact wording varies, but selecting the target disk for the Linux installation alone is not always enough. You can also temporarily remove the boot/EFI flags from the internal EFI partition, then restore them afterward, though disconnecting the drives is less error-prone.
Afterward, check the firmware’s boot menu and select the external SSD’s own UEFI boot entry. Updates normally do not delete the external drive’s EFI files just because another computer has an internal operating system. The main risk is an installation that was originally configured to depend on the internal drive’s EFI partition, so verify that the external disk boots independently before relying on it.
A durable setup is one bootloader per drive, with each bootloader and EFI partition stored on that same drive. During installation, either remove the internal drives or disable them in firmware so the installer cannot place GRUB on the wrong disk. Then use the computer’s one-time BIOS/UEFI boot menu to choose the external SSD when you want to run it.
The SSD should not decide to delete its own bootloader simply because another computer has an EFI partition. The bigger issue is that different computers may use different boot modes, such as UEFI versus legacy BIOS, and Secure Boot or unusual hardware can also affect whether Linux starts. Installing in UEFI mode and keeping a suitable EFI partition on the external SSD gives you the best chance of portability, but you may still need to choose the drive manually in each computer’s boot menu.
That makes sense. I was choosing the target disk for the Linux partitions, but I probably missed the separate setting for which EFI partition should be mounted. I’ll make sure the external disk has its own EFI partition and test it with the other drives disconnected before using it elsewhere.