Some new-user questions

[peedee8tch]

Hi, I’m new to open source, terminal etc, after discovering Linux 12 months ago. I’ve managed to muddle through, without disaster, and now looking at options to back-up my android phone to my Linux/Win11 laptop. I recently discovered your app and, after some trial and error, seem to have it running. I like it. Simple but solid, although I'm wondering if I can speed up/simplify the routine. I'm guessing (??) hooks are one way of doing that but I'm not confident enough to try that approach yet. Anyway, three short questions and two observations.
Qu 1. Am I correct thinking that Open Android Backup only provides for a full backup, with no option for incremental versions? I can live with this but wanting to check that I’m not missing something obvious. 
Qu 2. One way to speed up the process would be to modify what gets backed up each time. The initial on screen set-up routine lists what is to be backed up – Apps, Storage, Contacts/SMS/Calls – and appears to offer a choice of those components for backup, but I can't figure out how to de-select, if that is actually what is intended here. Arrows move the red highlight but what then? 
Qu 3. Does it matter where the bundle is saved? I have it sitting in the desktop folder for now.
Ob 1. Just before the 7-Zip process starts there are two prompts, to enter and then re-enter a password. I've been entering a carefully saved password at this point for a few weeks but just a few days ago I forgot to add the password but the process started running anyway after I pressed Enter. No harm done it seems as the archive was successfully created, but is this ok?
Ob 2. Immediately after 7-Zip starts, another prompt “Enter password (will not be echoed):” appears but the process carries on regardless. Again, no harm done as the archive was  created, but is this ok too? 
Thanks.

[mrrfv]

Hi, and welcome to Linux!

Am I correct thinking that Open Android Backup only provides for a full backup, with no option for incremental versions?

For the most part, yes. Open Android Backup simply creates a full .7z archive of your data.
However, advanced users can use the discouraged_disable_archive environment variable (set to any value) to instead get a raw folder containing the backup files, without encryption or compression. Theoretically, you could combine this with a deduplicating backup tool like Borg or Restic.

I can't figure out how to de-select, if that is actually what is intended here. Arrows move the red highlight but what then?

You use the space key to select or de-select items, Tab to switch between the list and buttons, and Enter/Return to confirm.
If you'd like to get into the technical details, the manual for whiptail - the program used to show the dialog you're seeing - explains everything in great detail.

Does it matter where the bundle is saved?

No, it doesn't matter. You can always download a fresh one from GitHub if needed; the bundle and backup archive and independent of each other. You can even open the archive in 7-Zip and manually copy all your files if this project disappears one day for some reason (albeit still going strong since 2022).

I forgot to add the password but the process started running anyway after I pressed Enter. No harm done it seems as the archive was successfully created, but is this ok?

I haven't checked this, but I think your backup must have been created either without a password, or with a blank password. Therefore, if you get a password prompt while restoring, pressing Enter should let you continue.

Immediately after 7-Zip starts, another prompt “Enter password (will not be echoed):” appears but the process carries on regardless. [...] is this ok too?

Yes, this is a side effect of the specific way Open Android Backup handles your password: it's the script that prompts you for the password, not 7-Zip, as a workaround for a small security problem present in some distros (issue #142). The password is then safely passed to 7-Zip in a way that isn't visible on screen.

[peedee8tch]

Thanks for the quick and helpful response. I'll double-check that password thing and let you know the results.

[peedee8tch]

Belatedly, I've double-checked that issue with the "forgotten" password (Ob1 in my original and your second last para in response). 

I checked my previous archives and found that those I knew were created with my saved password opened without issue. The archive where I forget to enter the password wouldn't open at all. Not with my saved password and not with a simple Enter at the prompt (my attempt to replicate the "forgotten" password incident).  Note that I wasn't trying to restore the archive; just opening it in the file manager. 

I also did a couple of quick tests backing up only SMS/call logs/contacts and entering random "passwords" at the prompt, like: 1) "abc", 2) a spacebar space and 3) Enter. The first two opened the archive without issue when I entered them at the password prompt in file manager but a simple (or in my case, forgetful) Enter was rejected.

What I learnt from this: 1) Even if you forget to enter a password, like I did, an archive will be created but it won't be possible to open it or, I presume, restore it, although I didn't try that; and 2) Whatever is entered at the password prompt - my Keepass password, "abc" or a space - will work when you come to open it later, but a simple Enter won't work.

Related but separate, I was originallly imagining that the password needs to be the same for every archive (as might be required for an incremental backup or a sequence of differential backups) but because the app creates full backups, each archive is self-contained so any entered password will work for the archive in question.

That might all seem obvious but it's helped me understand the app better.

Thanks again for assistance.