Why does an external HD which is an alternate startup disc on 2019 iMac ask for password on an internal encrypted Macintosh HD apfs volume?
I have successfully eliminated the password prompt from user accounts on my Macintosh HD using fstab, but does not seem to work on the external drive when it is the startup disc.
Any way to eliminate the prompt when starting from the external HD?
Thanks
MacBook Pro (2017 – 2020)
It isn’t a user-account prompt you can bypass with fstab, it’s macOS unlocking the internal APFS volume at the firmware and kernel level because FileVault ties the internal disk’s encryption keys to the Secure Enclave and the boot chain, not to whichever volume you boot from.
When you start from an external disk, macOS still mounts the internal encrypted APFS container early in boot for things like iCloud data, Preboot, recovery metadata, and system services, so it must be unlocked, and that prompt is coming from FileVault, not loginwindow. fstab can skip mounting or suppress login prompts, but it cannot auto-unlock a FileVault volume from another startup disk. On T2-era Macs especially, Apple explicitly prevents this for security reasons.
The only ways to eliminate the prompt are to fully disable FileVault on the internal disk, physically remove or erase the internal volume, or accept the password entry, there’s no supported or reliable workaround that keeps the internal disk encrypted and still avoids the prompt when booting externally.
It isn’t a user-account prompt you can bypass with fstab, it’s macOS unlocking the internal APFS volume at the firmware and kernel level because FileVault ties the internal disk’s encryption keys to the Secure Enclave and the boot chain, not to whichever volume you boot from.
When you start from an external disk, macOS still mounts the internal encrypted APFS container early in boot for things like iCloud data, Preboot, recovery metadata, and system services, so it must be unlocked, and that prompt is coming from FileVault, not loginwindow. fstab can skip mounting or suppress login prompts, but it cannot auto-unlock a FileVault volume from another startup disk. On T2-era Macs especially, Apple explicitly prevents this for security reasons.
The only ways to eliminate the prompt are to fully disable FileVault on the internal disk, physically remove or erase the internal volume, or accept the password entry, there’s no supported or reliable workaround that keeps the internal disk encrypted and still avoids the prompt when booting externally.
External disk prompts for internal encrypted HD volume password
