How to tranfer files between an Android tablet and Linux

I recently tried to connect an Android tablet to my Debian computer- and found the connection didn't work. Google told me the connection now uses MTP (older versions of Andoid, including my phone, used USB mass storage to connect) so I wondered if MTP was broken in Debian Jessie, but then I tried another tablet and it connected without a problem.

On the tablet that did connect, USB debugging was enabled, as well as MTP.

Now I certainly didn't enable USB debugging, because the menu option is hidden- you have to go to About tablet and tap Build number seven times which I didn't know about until just now, when I looked for the option and couldn't find it. (I discovered the information on greenbot.com.)

Nor did I enable MTP. (Go to Storage, tap the menu icon (three vertical square dots to the right), tap USB computer connection when it appears and tick Media device (MTP).

Enabling MTP on the tablet that wouldn't connect allowed it to connect. I also enabled USB debugging, which on this tablet wasn't hidden for some reason, although a subsequent test proved it wasn't necessary to connect.

However, on the second tablet, USB debugging is necessary.

Curious as both tablets run the same version of Android and are both from the same manufacture, although they are different models.

A useful reference from How-To Geek:

Android USB Connections Explained: MTP, PTP, and USB Mass Storage

Browse files on Android from Thunar

If you try to browse an Android device from Thunar in XFCE over Bluetooth, it will try to launch Nautilus, which of course isn't installed in XFCE.

The Arch Linux Wiki has a useful script to allow Thunar to browse files on Android over Bluetooth. The script uses obexftp, which must be installed.

obexftp must also be installed in Android. I've read that some Android devices have the service running, but mine didn't.

Bluetooth File Transfer and ES File Explorer File Manager both install the service.

To be honest, I didn't have much success browsing files. In particular, image files from the phone's camera took a long time to browse, and half way through the folder, Thunar would give the same thumbnail to every file.

But I thought I'd document what I did in case I need to come back to it, or in case somebody else finds it useful.

Freeing up memory on my Android phone

I've noticed on my Android phone (an Alcatel 990) that if I try to install too many apps, I get a message about the phone being low on internal memory.

I also noticed that if I update the system apps the memory warning appears constantly. I'd guessed that this was because the phone is storing the update and the original version- it's possible to uninstall updates for system apps.

I rooted the phone recently, and decided to see if I could free up some memory. The first thing I did was to delete some apps that are installed by the service provider but which I never use. Alcatel has a partition for system apps called /cutspack/apps (in addition to /system/apps), and it was simply a case of deleting the unwanted apps from there. (Android Forums.)

My guess about updates to system apps was confirmed when I found that updates are stored as user apps in data/apps while the original app remains in /cutspack/apps. bongizmo.com has the answer:

Q: Can I move system apps such as Gmail, Google Maps to SD card on a rooted phone?

A: Thanks to Dominique Tardif for this tip: “You have first to uninstall any updates to the system apps in question. Second, using a rooted file manager, delete the original apk from /system/app (android keeps the system app apart from the updates, the latter being at /data/apps). Once this is done, reboot and reinstall the app from the market. It will be installed as a user app and as such will be movable to the sd card. As an example, my gmail, facebook, maps etc. are all on my sd card now.” 

Having updated a few apps this way, I was surprised to find that I was getting the low on memory warning again. I managed to install partitions info lite,  and noticed that it was the /data partition that was almost full- there was plenty of room in /system and /cutspack.

But why was /data so full? The updated apps weren't there. I noticed that /data contained a huge folder called dalvik-cache. Android Forums said it was safe to delete, so I did. Free space in /data went from 10MB to 60MB. Dalvik-cache is a cache of optimised files, and I reckoned there were files in there for application I no longer had that were taking up space.

I rebooted the phone and it took a very long tome to boot. I was beginning to suspect I'd bricked the phone, but in the end it booted up. Free space was down to 50MB as the Dalvik-Cache had been regenerated with the necessary files.

With lots of free space on the system partition, but limited space on the user partition, I wondered if it was possible to install apps that won't be moved to the SD card to the system partitions: indeed it is. addictivetips has the answer- in essence to cut and past the app. I haven't noticed any problems with permissions.

A word of caution: delete or move the wrong system file and the phone could become unbootable. Follow these instructions at your own risk.

Add book cover in Aldiko

I love Aldiko. I read all of the Sherlock Holmes stories on it this summer on my mobile phone. Bump the text size up a bit and it's perfectly readable.

Today I tried to change the covers of some of the books in my collection, something I've done before, but I couldn't remember how to do it.

I finally figured out how I'd done it. This time I'm writing it down so I can remember.

Download a cover image. In Aldiko, long press on a book on the bookshelf. Select Details, long press and release on the book image in the pane that appears. Select Gallery, go to Downloads and choose the cover image. Select or crop as necessary.

Using the file browser to find the image didn't seem to work for me, although it may have been a glitch.

SuperOneClick in VirtualBox on Linux

My Android phone is out of warranty, so I thought I'd try rooting it. There are a few apps on it that I never use, and wanted to get rid of. SuperOneClick seems to be the easiest way to do it. It automates a process of hacking the phone that is also possible to do manually in Linux, as cYpherpunK describes. However, as I've recently installed Windows XP on VirtualBox, I decided to give SuperOneClick a go.

I couldn't get the program to work until today, when I noticed this error message at one point:

error: protocol fault (status 55 6e 61 62?!)

A post in the XDA Developers' forum gave me the answer: disabling USB 2 in VirtualBox settings allows SuperOneClick to work.

My phone (an Alcatel 990) seems to store apps in an unusual location, but I was able to remove the unwanted apps by deleting them in a root browser- I used Root Browser Lite.

I'm also trying out an ad-blocker app called AdAway which requires root. Blame the floating ads that making reading and navigating web pages so difficult, and are so difficult to avoid clicking by accident on a small screen.

Resize video for Android

A 32GB MicroSD card is now around £20, room enough for a large music collection and a few TV shows and movies. But although 32GB is a lot of space, why store a 300MB file that has a bigger size in pixels than the mobile device, and is not compatible with the stock Android video player, when you can store a 50MB file exactly customised for the screen size of your mobile device and plays on the stock player?
I was looking around for an application that would do this in Linux, but in the end found a command line application that does the job. I've lost the original link, so I'll just post the command, using an example file name, and screen dimensions for an Android phone. The frame rate is a bit low, but perfectly watchable. First install ffmpeg. Then in a Terminal, in the directory where the original file is, issue this command:

ffmpeg -i "TOS - S02E19 - The Immunity Syndrome.avi" -s 480x320 -vcodec mpeg4 -acodec aac -strict experimental -ac 1 -ar 16000 -r 15 -ab 32000 -aspect 3:2 "TOS - S02E19 - The Immunity Syndrome.mp4"

Gallery full of album art in Android?

The solution is simple: change all the cover.jpg or album jpg files to albumart.jpg and they won't appear in Android Gallery.
Of course, if you've bought a 32Gb SD card and filled it with hundreds of albums, this is going to be a bit of a chore. (That's not a lead up to a solution, just a bit of British sarcasm.)
While I'm on the subject of album art, if Android music player is showing the wrong thumbnail image for an album, because you have images for the back and inside of the CD in the music folder (and because the music player is not able to recognise that the image file labelled cover or album is the one it should use) delete image in the Android albumthumbs cache as described here.