Why can't I see my backup when I reboot from TWRP into Android?

[AC Question]

TWRP Nandroid backup to Ext SD & OTG

I have just started using TWRP to create a Nandroid backup. Backups can be created successfully to internal memory, SD card or OTG USB and I can see all backup files using the File Manager in TWRP when the backup completes. Problem is that when I reboot from TWRP into Android, the backups are not present on the SD card and OTG USB, backup only survives if made to internal memory.

Going back into TWRP File Manager, and the backups are not available if made to SD card or OTG USB. They really have been deleted.

Why?

 

[Harv91]

Re: TWRP Nandroid backup to Ext SD & OTG

I have found out the answer to my own question so positng it here in case it helps someone else.

When using TWRP to create a Nandroid backup to the SD card or OTG USB stick, you MUST manually unmount the target using the Mount options in TWRP. Selecting Reboot without doing this loses the backup files.

This seems wrong, surely TWRP should unmount automatically before rebooting

 

[Red falcon]

Re: TWRP Nandroid backup to Ext SD & OTG

Hi so did you succeed in saving backup to extsd?

 

[Rukbat]

Re: TWRP Nandroid backup to Ext SD & OTG

you MUST manually unmount the target using the Mount options in TWRP. Selecting Reboot without doing this loses the backup files.

The phone evidently has a delayed write. When you look at the SD card or OTG you see the files already written to it and the files queued to be written to it. See in them doesn't mean that they've been physically written yet.

This seems wrong, surely TWRP should unmount automatically before rebooting

All cellphones tell you to unmount external cards manually before removing them if the phone is still on. It's not just TWRP, it's any writes to the card. Rebooting may or may not flush the buffer. (I may try it when I have my phone on and a spare card to write a large file to.) But always assume that it won't.