user42318: Bitcoin Wallet for Android allows you to back up your wallet.  It asks for a password when doing so.
After much faffing, I finally managed to.. dum, dum, dum! .. copy the file to the SD card, and then I removed the SD card and mounted on a Linux system.
According to this question, the way to decrypt it is 
$ openssl enc -d -aes-256-cbc -a -in bitcoin-wallet-backup-2016-09-30

but I get:
enter aes-256-cbc decryption password:
error reading input file

when doing so.  This is an extremely poor error message from openssl.  I have confirmed that the file is readable using other utilities.

user423: The best way to restore a backup file is always to use the same app used for creating the backup. In other words, install the app again, then use Options > Safety > Restore wallet.

42318: <p>Bitcoin Wallet for Android allows you to back up your wallet.  It asks for a password when doing so.</p>

<p>After much faffing, I finally managed to.. dum, dum, dum! .. copy the file to the SD card, and then I removed the SD card and mounted on a Linux system.</p>

<p>According to <a href="https://bitcoin.stackexchange.com/questions/17176/how-to-decode-private-key-from-android-bitcoin-wallet">this question</a>, the way to decrypt it is </p>

<pre><code>$ openssl enc -d -aes-256-cbc -a -in bitcoin-wallet-backup-2016-09-30
</code></pre>

<p>but I get:</p>

<pre><code>enter aes-256-cbc decryption password:
error reading input file
</code></pre>

<p>when doing so.  This is an extremely poor error message from openssl.  I have confirmed that the file is readable using other utilities.</p>
 423: <p>The best way to restore a backup file is always to use the same app used for creating the backup. In other words, install the app again, then use Options > Safety > Restore wallet.</p>
