borgbackup_on_android/README.md

# BorgBackup on Android
Forked from [ravenschade/borgbackup_on_android](https://github.com/ravenschade/borgbackup_on_android)
with modifications from [GAhlekzis](https://github.com/GAhlekzis/borgbackup_on_android).


## Introduction
This project provides build scripts to compile [BorgBackup](https://github.com/borgbackup/borg) and its dependencies on
Android. It uses  [Termux](https://termux.com/) as a lightweight environment.

You do not need root permission on your phone to use it. However, without root permissions the access to data of other
apps or system data is not possible, but you can still access your photos, videos.

If you have root permission on your device, you can use the "sudo" of Termux, [tsu](https://github.com/cswl/tsu), to
conveniently gain root permissions in Termux and backup your complete device.


## Building Borg
Install [Termux](https://f-droid.org/en/packages/com.termux/) from F-Droid, open it, and execute the following:
```bash
pkg install git
git clone https://git.caspervk.net/caspervk/borgbackup_on_android
cd borgbackup_on_android
bash build.sh
```
If virtualenv for Python does not work properly, set selinux to permissive (`tsudo /system/bin/setenforce 0`).

Warning messages like 
```
WARNING: linker: /data/data/com.termux/files/usr/lib/libacl.so.1.1.0: unused DT entry: type 0xf arg 0x449
```
are due to the Android linker. More details can be found [here](https://stackoverflow.com/questions/33206409/unused-dt-entry-type-0x1d-arg).

Tested with:
- Termux 0.56, 0.66
- Borg 1.0.12, 1.1.3, 1.2.0a5


## Configuration
Install [Tasker](https://play.google.com/store/apps/details?id=net.dinglisch.android.taskerm) and 
[Termux:Task](https://f-droid.org/packages/com.termux.tasker/) for Termux-Tasker integration.

Copy backup script to a folder where Termux:Task can find it
```bash
mkdir -p ~/.termux/tasker
cp backup.sh ~/.termux/tasker/backup.sh
```

Create a repository passphrase (and remember to back it up!!)
```bash
head -c 1024 /dev/urandom | base64 > /data/data/com.termux/files/home/borgbackup_on_android/borg-passphrase
```

Change `<server>` and `<port>` in `borg.sh` to correct values.

Generate keypair for root with empty password
```bash
tsudo ssh-keygen -t ed25519
tsudo cat 
```

Add ~/.ssh/id_ed25519.pub to authorized_users on server
```bash
command="mkdir -p ~/repos/phone; cd ~/repos/phone; borg serve --restrict-to-path ~/repos/phone",restrict ssh-ed25519 AAA..yX root@phone
```


## Known Issues
Borg starting at 1.1 requires the system call sync_file_range (see https://github.com/borgbackup/borg/pull/985 and
https://github.com/borgbackup/borg/issues/1961). The linux subsystem in Windows 10 and some older Android versions (for
example Lineage including 14.1) do not yet have this. Lineage 15.0 has this call and should work. I have added a test to
the build script that checks if sync_file_range is available. If it is not, then I apply a patch
(borg_sync_file_range.patch) that replaces this sync with conventional file syncs.