Asus Transformer Pad Infinity
Debian on Android

If I had a working sshfs command, the way to use it is:

sshfs jimc@jacinth.jfcarter.net:/home/jimc /system/media/jimc -o allow_root -o allow_others
fusermount -u /system/media/jimc #To unmount

To avoid long delays in the editor and file manager, I should mount the specific subdirectory containing the files I want to work on, rather than the entire home directory. Or I should reorganize the home directory so it and any subdirectory have only a limited number of files that the file manager will have to stat, or which have to be shown on the editor's file selection listbox.

So where am I going to get a working sshfs command? I already decided that SSHFSDroid was too alpha level to be considered. On the web there are a lot of forum posts that tell you how to use sshfs to mount directories from your Android device onto a remote machine like a desktop PC -- the opposite of what I want to do. If your hammer isn't working, use a bigger hammer. Or if the cockroach won't die, nuke it.

There are a number of packages on the Android Market (Play Store) that will install real GNU/Linux on your Android device. They generally operate as a chroot environment. However, one of them stands out: Debian Kit by Sven-Ola Tuecke. Its special feature is that it imports the Android host environment into the chroot, so each realm can affect the other: specifically, a sshfs mount done by Debian can be used by Android.

See the instructions in the above link; but the basic idea is:

• You create a big file on a SD card: minimum 512Mb, max 2047Mb due to an addressing limit of the loop device. You can also use a raw partition or a directory, but this is advanced usage which I will skip the first time around.

• The provided script formats it, populates it with the Debian installer, and starts downloading and installing packages. You can choose from among Debian Squeeze (6.0), Ubuntu Lucid Lynx (10.04), or Ubuntu Precise Pangolin (12.04); the Ubuntu choices are Long Term Support releases. I'm 99% sure that once you get something installed you can upgrade to the latest release. For other distros that have ARMv7, like OpenSuSE, you can probably get them on one way or another, but it's not officially supported.

• You run the deb command (script) which will start the OS and give you a shell, which you can exit from if you only need daemons. When done, stop the daemons (I think it's deb k), then deb u to unmount everything.

• It should take about 30 minutes to download and install Debian, with a reasonable Internet connection.

Installing Debian Kit

My experience installing Debian Kit:

• I installed Debian Kit from the Android Market (Play Store) rather than downloading the shar archive from his repo. I already had VX ConnectBot.

• On CyanogenMod-10.1 based on Android-4.2.x Super Jelly Bean, /sdcard and /storage/sdcard0 are symlinks to /storage/emulated/legacy upon which there is a FUSE mount, emulating a FAT filesystem, whose underlying directory is /data/media/0. /data itself is /dev/block/mmcblk0p8 (ext4). I'm going to try to direct the loop file to this underlying directory rather than going through FUSE.

• I started the Kit app. On the initial page I have all the prerequisites: compatible architecture, enough RAM, ext2/3/4 support, loop device, loadable modules, /data/local avoids noexec, and su works. The next step is to hit the download icon (arrow pointing down in upper right corner). You get a directory of the repo, from which you should download debian-kit-1.5.shar. To fake out some browsers it allegedly has a mime-type of jpeg; it's probably safest to use ES Image Browser to (fail to) open it. Back out and follow the instructions in the web page; you're picking up with step 4.

• The shar file ended up in /sdcard/Download/debian-kit-1.5.shar (note case, though FAT should be case insensitive). It executed and populated /data/local/deb. It continues and asks for the 2-byte code for the size of the image file and the OS version. Because I want a custom location for the image file, I just hit return, to make it exit. Next step: manual installation with mk-debian.

• To get the options for mk-debian, read the script and locate the usage() function. Or just exec mk-debian -h. My parameters: (-h as the last parameter tells it to do a sanity check and print usage.) We don't have to do export CUSTOM_ROM=true during installation, and not during execution either unless problems are noted with uncoordinated /etc between Android and Debian. CyanogenMod does not have a /lib symlink.

  /data/local/deb/mk-debian -d squeeze -s 2047 -i /data/media/0/debian.img -h

  On Android you can't do |& tee logfile; that's a bash-ism. Instead do 2>&1 | tee logfile.

  If there are no complaints, remove the -h and let 'er rip. Just creating the image file took 3 mins, after which it was quickly formatted. Then it downloaded (but did not yet install) a lot of basic-looking packages. This took 9 mins. Now it extracts packages, taking only 1 minute. Total 13 minutes. I did get the symlink for /system/bin/deb.

• Now you execute deb. (Don't redirect to a log file because fsck won't like it.) This is where it unpacks (installs) the packages. It also has to configure most of the packages. Finished in about 8 mins. It finishes by execing bash.

• Next step is to do online updates: apt-get update; apt-get upgrade; apt-get install andromize . Update means to get package lists (from 28 places, took 4 mins). Upgrade means to actually install new packages (3 packages, took 1 min). Andromize installs some android-specific configuration (plus 2 dependencies, took 1 min.)

• Basic installation is finished. Exit from the shell, then do deb u to shut down Debian and unmount the loop device, bind mounts, etc. If something cannot be unmounted, do deb k to kill Debian processes that might be sitting on a partition, then re-do deb u.

• After you upgrade Android, un-shar debian-kit.$VERS.shar (if you deleted the install dir), run /data/local/deb/mk-debian -u (re-creates the symlink from /system/bin/deb), then deb c to clean up symlinks that point to files that no longer exist.

• Slightly more than basic installation:

  • Install stuff that jimc considers basic: less …
  • apt-get clean: Toss installed package files in /var/cache/apt/archives.
  • addgroup --gid 550 maint: Pre-create my proper primary group.
  • adduser --uid 500 --ingroup maint jimc: Create a user login for myself, replicating the numeric UID and GID used on the fileserver, for maximum resistance to screwups.
  • adduser jimc sudo: Add myself to the sudo group; give myself the privilege to run a root shell using sudo with no arguments.
  • There is a lot of cool stuff that I could install including andromize-lxde which includes LXDE and Xrdp. But I'm going to defer that until after my trip.
  • Running the real OpenSSH in Debian is very attractive and a lot of people with Debian-Kit do this, but again I'm deferring it.

Testing sshfs

The point of this performance was to get sshfs. See this post on XDA-Developers by robert1968 (2013-02-09). The success story:

• Having installed Debian, all you have to do (as root on Debian) is apt-get install sshfs, then use the command at the beginning of this section to mount whatever you want.

  With dependencies, total of 31 packages, 60Mb uncompressed. Including perl, which was apparently not considered to be basic. I'm also going to want to install ssh-askpass (and 5 dependencies).

• Exact procedure to mount something, from a cold Debian (having already installed sshfs):

  • Start your terminal emulator; for me it's VX ConnectBot.
  • Start a local shell (this is automatic on Jack Palevich's Terminal Emulator).
  • su #To become root. If the su app doesn't remember you, tell it to let you on.
  • deb #Starts Debian, including fsck i.e. file system check. You're now in a root shell.
  • sshfs jimc@jacinth.jfcarter.net:/tmp/jimc.junk /system/media/jimc -o allow_root -o nonempty
  • And it works!

  About the arguments to sshfs:

  • jimc@ -- You run this as root, so you have to specify the remote user explicitly (unless it's root).
  • jacinth.jfcarter.net -- Android in general, and this Debian in particular, does not honor DHCP option domain-search, so you need to give a FQDN even if the host is on the local net.
  • :/tmp/jimc.junk -- This is a directory for transient log files and downloads, very suitable for possibly destructive testing.
  • /system/media/jimc -- This mount point was already created.
  • -o nonempty -- It turns out that without this option sshfs refuses to mount on a nonempty directory. I put a README file in there, which may be anally retentive.
  • -o allow_other -- To allow other users, like the user owning your editor or file manager, to access the directory. I'm not sure who the non-other is -- the mounter (root) or the remote owner -- but allow_other lets root use the files.

• This is now working! Both ES File Manager and Jota+ have read-write access to files in the mounted directory.

• A few little details:

  • I haven't set the timezone so dates are in UTC.

  • I created on Debian my loginID and primary group same as on the host with the files including the numerical values. All files that remotely are owned by me are reported by Debian to be owned by me by name and group, and a file created on Debian by root ends up owned by me:group (mode 644) on both Debian and the file server. If the mode is changed on Debian, e.g. 600, it stays changed; nonetheless the remote mode is not honored on Debian and various Android users have read-write access due to -o allow_other.

  • A very useful addition will be a SSH key agent.

  • Also useful will be a script to do the mounting.

  • According to robert1968's post, when you do deb u it will unmount sshfs, but I feel safer doing it explicitly with:

    fusermount -u /system/media/jimc

• The holy grail: this sucker can do Kerberos! How can I make that useful?

Installing a Real Desktop Environment

It is now 2014-05-26 and my goals have changed a bit: I want to use my tablet as a desktop replacement machine. The killer that keeps native Android from this service is that the window manager wants only one full screen window at a time. So I need a different window manager. The sub-goals in this phase are:

• Expand the Debian installation to include the XFCE or LXCE desktop environments. A standalone window manager like FVWM or Ratpoison could also be considered.
• Use the big partition on the 32Gb SD card. This means I'm going to reinstall Debian.
• Test for automatic startup and shutdown and improve as needed. This means, if the machine is rebooted, it should not hork the filesystem.
• Install jimc's locally written Perl and TCL/Tk apps.

Particularly desired local and global apps are:

• OpenSSH running as server
• SSH key agent (ssh-agent), preferably started at login
• Kerberos client service, preferably started at login
• Teddy text editor
• Pinger (Gangping) app
• Backup-host and the scripts it calls
• Speedsha (speed test benchmark)
• Clonedir to sync the home directory
• gpgview, depends on gpg
• Pidgin instant message app

A log of the installation procedure:

• See Sven-Ola's documentation for details.

• To uninstall the previous version: /data/local/deb/uninstall
  It removes /data/local/{deb,mnt} and that's all.

• To find your partition, if not auto mounted by Android vold, look in (ls) /dev/block. You will find mmcblk0* for the internal SD card, and in my case, mmcblk1 and mmcblk1p1 for the external card. Where is mmcblk1p2? Do:
  busybox fdisk -l /dev/block/mmcblk1
  This is on CyanogenMod-10.2. The documentation implies that some distros (likely rooted carriers' ROMs) lack the fdisk subcommand; I know that carriers rarely if ever include busybox itself.

• Well, isn't that cute! It's all one ext4 partition. /dev/block/vold/179:49 is mounted on /mnt/fuse/sdcard1 (ext4) with nosuid nodev noexec etc. This is not going to fly. I'm going to need to repartition the card, which has to be done on another machine. I want to keep the existing content, currently only 175Mb, but I will allow 2Gb for things like photo downloads.

• Now we have /dev/block/mmcblk1{,p1,p2}; however, vold did not mount either of them, hiss, boo!

• Next try: make the first one fat32 with a partition type of 0c, and leave the second one type 83 (Linux data) but with no filesystem on it. Now /dev/block/vold/179:49 is mounted on /storage/sdcard1 . /dev/block/vold/179:50 exists but has no filesystem on it. This is what will be used.

• In http://sven-ola.dyndns.org/repo/ as of 2014-05-27 you have a choice of debian-kit-1.5.shar dated 2013-02-26 or debian-kit-1.6-testing.shar dated 2014-05-13. Obviously I'm taking the latter. cd /data/local/tmp; wget http://sven-ola.dyndns.org/repo/debian-kit-1-5.shar

• Executing as root on Mica, sh /data/local/tmp/debian-kit-1.5.shar

  • Unpack to /data/local/deb? Answer Y
  • When it asks for autorun parameters, press enter (no parameters), and it will exit.

• /data/local/deb/mk-debian -i /dev/block/vold/179:50 -L mica-32-2 -h
  Default filesystem type is ext4. Default distro is Debian Squeeze.

  • Format (e)xisting device… Answer e. Does it.
  • It downloads basic packages and stores them somewhere.
  • When it has all the packages, it extracts (installs) them.
  • Look in /data/local/deb/debian-kit-*.html for documentation.
  • Type deb (/system/bin/deb symlink) for the second stage of installation.

• deb did these steps:

  • Ran fsck
  • Mounted the partition on /data/local/mnt
  • Installed and configured the packages previously downloaded
  • Installation was done in two batches.
  • Dropped you into Debian's bash.

• Recommended next steps, which I did:

  • apt-get update -- downloads package lists and copies to database.
  • apt-get upgrade -- will upgrade only 2 packages.
  • apt-get install locales
  • dpkg-reconfigure locales -- Use down-arrow to scroll down to your locale(s): for me, en_US.UTF8. Press space to select it/them. Then press enter to generate the locale. Then select which is to be the system default.
  • When finished, either restart the system (like Windows), or do: export LANG=en_US.UTF-8 . Re-executing the command: now the line drawing characters are right. Use tab twice to skip to the Cancel button.
  • dpkg-reconfigure tzdata -- to set the timezone. First level: US; second level: Pacific. It's a ncurses app and LANG needs to be set, else the line drawing characters all come out as @ signs.
  • apt-get andromize -- (Find out exactly what this does.)
  • So far we've used 406Mb, 2.67Gb available, 2.86Gb total.

• Installing additional packages by apt-get install $pkg; you can do several in one execution:

  • less
  • sudo -- I generally don't like sudo but a lot of the documentation is written assuming it's available.
  • openssh-server
  • andromize-lxde (with dependencies). We're getting iceweasel and libgstreamer0.10-0 and zenity. Downloading 146Mb, installed size 420Mb.