A long time ago, when I tried something like that, I was stymied because the SSH server did not have permissions to write to any directory which the document readers etc. could see.

Is this sort of thing still a problem? How did you get around it?

I haven't used SimpleSSHD but I use Termux, which gives me a "normal" terminal (no root required).

Since Android 8 I've lost write access to general locations in the sd-card but I still have read access, as well as read+write on the internal storage.

It has an ssh server which can be nice if you want to edit some files on the phone remotely but that's not needed for rsync. I have a shortcut on the home screen which triggers a script that runs an rsync command for photos and other stuff I want to backup. Also use it to reverse-sync a folder from my NAS, want to send a file to the phone? But the file in that folder and run the script.

I think that you need to run the command "termux-setup-storage" to be able to r/w again:

https://wiki.termux.com/wiki/Termux-setup-storage

Thanks, doesn't work though. I have write access to the private directory for termux on the sdcard but nothing else (which unfortunately breaks my usage, I'll report it to them any day to see if a fix is possible).

This is the way Termux works so far, External storage: Storage on external SD cards. Each app has a private folder on the external SD card, and interchange between them needs to use a special API not yet available in Termux.

https://wiki.termux.com/wiki/Internal_and_external_storage

It worked fine in Android 7, when I updated to 8 my scripts started getting permission-denied errors on writes.

I don't see anything in that link that says that sdcard (outside private folder) is read-only.

The way I read "Each app has a private folder on the external SD card, and interchange between them needs to use a special API not yet available in Termux." is that I can't read another applications private folder, but I'm not trying to - I just want (write+delete) access to the publicly accessible parts of the sdcard (lots of other applications do this, and termux did in Android 7).

Well I have Android 7 and termux works in the way you described at first: I have write access to the private directory for termux on the sdcard but nothing else... other applications can access every DIR in sdclard due implements SAF: https://developer.android.com/guide/topics/providers/documen... and I think this what termux doc refers to.

It was never an issue for me. Giving the SimpleSSHD docs a quick glance, the app itself does not operate as root, although its packaged subcomponents like rsync optionally can depending on what shell you point them to.

My phone isn't rooted. Everything in /storage/emulated/0 backs up without issue. Obviously not a full system backup, but all my data none the less.

With regards to write permission, I've only ever issued any writes to my image folders to prune photos or screenshots older than xx days that have already been backed up. On that note, freeing up 20GB of space instantly with a single command is incredibly satisfying (compared to the MTP hell alternative).

If you only need a shell, adb does that, as well as blazing fast file transfer (for the standards of MTP).

For sure, although I think it isn't as well suited to being a remote daemon. With SimpleSSHD, all concerns are compartmentalized into an app, you get rsync out of the box plus a nice minimalist UI for monitoring. Then adb can be left disabled, and its configuration untouched.

If your phone is rooted, you can use e.g. Linux Deploy to install a full Linux distribution. Then, you can set up regular ol' OpenSSH, mount /sys and /data under the Linux chroot, and rsync as usual.

I use this method to rsync to btrfs snapshots (+ raw copies of non-filesystem partitions) to make daily incremental backups of the entire phone. (Restoring said backups is a bit more involved, but I verified it's doable.)

I'd backup to a more reliable filesystem than btrfs. In my experience you will eventually randomly lose data with btrfs. I have lost all trust in it.

Backups are by definition redundant, however, btrfs is still the only Linux filesystem with its featureset. Let me know when ZFS on Linux supports shrinking or cloning file ranges.

https://news.ycombinator.com/item?id=16494370

"raid" 1/0 and 10 are stable, others are not. Theoretically btrfs can protect against bit-rot where other fs's typically don't.

Theoretically that might be the goal. In my experience data melts away like butter on btrfs.

This is an Android problem that is sold as a feature by Google... still a problem on my version of Android (in Android 5.0 and later, an app can request the permission for reading/writing to a folder on the SD card though: https://metactrl.com/docs/sdcard-on-lollipop/ )

I use the Syncopoli app which can do this on a scheduled basis. It uses Dropbear internally and is also on F-Droid. You do need a SSH server but you can limit the wireless networks it syncs on, so it needn't be public.

Syncthing does an admirable job here as well (also available on F-droid).

Does syncthing work on SD cards yet?

Last I checked there were some Go/Android technical hurdles that prevented it from working.

Great idea, I'd grown too reliant on Google Photos and always hated that. I should set this up.

Is there an equivalent for iOS?

Lol

Let’s keep in mind the user story: “Being able to wirelessly perform an incremental backup of all your photos and data is life-changing”

The LOL is telling your Mom about DropbearSSH when this is now how iCloud Photos and Files just works. The equivalent goal is baked in.

You can still use cables or local WiFi via iTunes, but now all media and files sync over-the-air as files, along with an incremental backup of all state.

For the first time in last fall’s iPhone hardware upgrade, I didn’t use a wired backup/restore and every app’s and settings worked, along with device config. I’ve had an iPad Pro unexpectedly need replacing, no wired backup/restore needed. All my stuff syncs across all devices including desktop, all ambiently available.

The life changing part is confidence it’s working to the point of not having to think about it any more.

// Note: Photos and media end up as originals on Mac, along with all files. Those all backup in turn to Backblaze, for loss scenarios not covered by rsync style replication.

Everything in iCloud, including your encrypted messages, are easily accessible to Apple[0] and will be released without a fight, despite Apple's vaunted privacy stance. (Perhaps that social contract has some fine print if the CEO of your company looks at your files and decides you're guilty without wasting time with 'a jury of your peers' and all that nonsense.)

Android (with Google) offers the same functionality (AFAIK) as iCloud, but sometimes you just prefer that your private photos remain just that.

0. https://news.vice.com/en_us/article/xwm4ya/paul-manafort-may...

Any data you sync to a cloud provider is subject to subpoena by LEO.

tarsnap/cryptfs should really be SOP when uploading anything to cloud.

Despite how inappropriate this comment is its cynicism is appreciated. I like my iPhone but I miss Android for things like this.

That said, I think it might be possible but I think you might have to shim it and wouldn’t have direct access to the file system under the photos.

Thank you for your thoughtful contribution.

Open Terminal managed to sandbox a busybox like suite (grep, curl, gzip…). And a scripting language to boot.

rsync limited to the app's directory + shared folders such Photos, iCloud drive, etc would be pretty useful, even without full file system access.

iOS's restrictions are loosening up, vide Files.app

As an iOS user this is an appropriate response.

iLol :)

For non-jailbroken devices that wouldn't be possible in the same way, but an app could certainly implement SSH with libraries (photos, contacts, etc) exposed as a filesystem and interpret a set of commands (like rsync).

It's somewhat flaky, but you can also mount your phone as a local FS over USB debugging, requires a wired connection though: https://github.com/spion/adbfs-rootless

It's possible on most devices to use adb over the network. It's a separate toggle in the de developer settings as it exposes the adb port to all network interfaces (think WiFi, LTE, Bluetooth, etc.) Use `adb connect <ip>` to connect to your device over WiFi and you should be able to use this tool without having a wired connection to the phone.

What do you use to have rsync on your phone?

And did you have to root your phone to achieve any of this?

Also, is there a tool to use duckdns or similar to assign a hostname to your phone?

1) SimpleSSHD includes rsync.

2) No.

3) Haven't looked into dynamic DNS yet; only using the setup with local wifi currently.

I use acrosync, a rsync UI, pretty limited but works... I'm gonna try your sshd to see if it's better.

With Android now restricting background services, will this continue to work in the future?

Short answer: yes

Love it, works like a charm.

Since the phone's IP address can be expected to change, you can't really use that to choose the right key to present, or to verify the host fingerprint right?. How do you work around this?

You can set a static IP in your wireless settings.

Or ‘better’ fix an IP to your device MAC in your dhcp settings.

Usually not needed, since your router will usually try to assign a fixed address for already known devices.

What spockz said takes the words "usually" and "try" out of that. (-:

But means more work, with web interfaces of varying quality

What happens when the DHCP lease expires?

The router will try to reassign it, usually.

Not all routers support this. In fact at work we've got a router that seems to black-hole anything whose source or destination isn't in the DHCP table (TP-Link 480t+).

In the end I solved this by accessing this only while I'm tethered, that fixes the phone's IP address.

Too bad there doesn't seem to be an option to select keys according to host key instead of hostname or alias.