Compile Gargoyle for Netgear R6220

I recently got a Netgear R6220 router, an AC1200 dual-band router with very impressive specs. It was awarded the best router in 2016 and now in 2019, I still think it is a very good router. It has a 2 core Mediatek MT7621 (MIPS) processor with 128 MB RAM & 128 MB ROM i.e. ample space with some good processing power. Below you can see the impressive specs. BTW: I got this for almost 15 USD which was a steal!

root@OpenWrt:~# cat /proc/cpuinfo
system type             : MediaTek MT7621 ver:1 eco:3
machine                 : Netgear R6220
processor               : 0
cpu model               : MIPS 1004Kc V2.15
BogoMIPS                : 584.90
wait instruction        : yes
microsecond timers      : yes
tlb_entries             : 32
extra interrupt vector  : yes
hardware watchpoint     : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
isa                     : mips1 mips2 mips32r1 mips32r2
ASEs implemented        : mips16 dsp mt
shadow register sets    : 1
kscratch registers      : 0
package                 : 0
core                    : 0
VPE                     : 0
VCED exceptions         : not available
VCEI exceptions         : not available

processor               : 1
cpu model               : MIPS 1004Kc V2.15
BogoMIPS                : 584.90
wait instruction        : yes
microsecond timers      : yes
tlb_entries             : 32
extra interrupt vector  : yes
hardware watchpoint     : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
isa                     : mips1 mips2 mips32r1 mips32r2
ASEs implemented        : mips16 dsp mt
shadow register sets    : 1
kscratch registers      : 0
package                 : 0
core                    : 0
VPE                     : 1
VCED exceptions         : not available
VCEI exceptions         : not available
root@OpenWrt:~# cat /proc/meminfo
MemTotal:         124016 kB
MemFree:           67696 kB
MemAvailable:      50560 kB
Buffers:            2460 kB
Cached:            12820 kB
SwapCached:            0 kB
Active:            25640 kB
Inactive:           5116 kB
Active(anon):      18372 kB
Inactive(anon):      144 kB
Active(file):       7268 kB
Inactive(file):     4972 kB
Unevictable:           0 kB
Mlocked:               0 kB
HighTotal:             0 kB
HighFree:              0 kB
LowTotal:         124016 kB
LowFree:           67696 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:         15476 kB
Mapped:             2920 kB
Shmem:              3040 kB
Slab:               9628 kB
SReclaimable:       2636 kB
SUnreclaim:         6992 kB
KernelStack:         448 kB
PageTables:          336 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:       62008 kB
Committed_AS:      23588 kB
VmallocTotal:    1040376 kB
VmallocUsed:           0 kB
VmallocChunk:          0 kB

I am running OpenWRT on this router. You can use the OpenWRT information page to install OpenWRT over the stock FW.

Now OpenWRT is good but I miss some of the user-friendly features from Gargoyle FW, which is another open source FW based on OpenWRT. One of the best features is the Quota & throttling support in the UI. I can do all these things in OpenWRT but again, it is a lot of manual steps and I also want somebody like my wife to be able to manage the router as well if needed.

The current binaries available for the MT7621 does not have R6220 profile and also, it does not have the latest OpenWRT base. Hence the only option is to compile Gargoyle and create a working FW. Below are the steps for the same. The code below is self-documenting but do ask me your questions in comments as needed.

The original source is: I have a forked version available at: Start working on the master branch since that is up-to-date and being actively worked upon upstream.

git clone
cd gargoyle
git checkout master
make ramips.mt7621

If the compilation is successful, you should have the necessary binaries generated in: ramips-src/bin/targets/ramips/mt7621

Gargoyle R6220 Firmware Images

You might face error with obfsproxy-legacy which I faced. So I had to apply the patch to get it to compile. Now simply do a sysupgrade on your OpenWRT FW to enjoy Gargoyle. I will put another blog post if I find any instabilities.

More documentation on the same can be found at:

To Docker or to Vagrant

To Docker or to Vagrant, an eternal struggle for a dev-ops / smart people (like me!) who wants to automate stuff is a big life and death question! No seriously, I mean there are just 2 camps of people, one is hardcore docker supporters who want docker everywhere (without realizing that docker is not a full virtualization solution but uses Linux kernel’s namespaces and cgroups functionality. So what does it mean? Well for starters, anything that requires mounting operations inside the docker container, for instance, requires special privileged access and these have the possibility to change your actual host filesystem (eg: mounting filesystems inside the container will mount it indirectly on your host as well and rest is history. It is not just mount operations, simple things like socket access, changes to locale or local-gen will not work inside docker containers without passing special access privilege flags while running the docker container.

Vagrant is a straightforward configuration script for Virtual Box (VB) which is a full virtualization solution. So one basically installs an OS and does everything inside that container itself. Also, vagrant vbox files are easier to share (since it is a single file itself, unlike the layered approach in Docker). In any case, doing privileged operations in VB/Vagrant is more reassuring then doing the same on Docker. So even though I am a docker supporter, I also like vagrant because of the full virtualization support and next to impossibility to mess up with your host system.

Anyways, that’s that. So to Docker or to Vagrant is a personal choice depending on the use case one is trying to implement as well as the need for distribution (private or public). Cheers & send in your comments.

Update Anaconda Navigator

Everybody using Python would nowadays be using Anaconda instead. And if you aren’t, my recommendation is to use it. Why may you ask? Because with python comes a lot of packages and each such package comes with a host load of dependencies and it is difficult & time-consuming to resolve those dependencies manually. Also, anaconda allows one to create multiple environments (basically environment containers for package isolation). So let’s say you need package1 for some type of work and package2 for some other type of work. But package2 inherently depends on a different version of package1. Now if you have the same environment, you will have conflicts but creating different isolated environment containers helps the use case.

Anyways, just use it. Its simple and allows you to spend more time focussing on the business logic. Now then, once you have installed Anaconda and when you launch the Anaconda Navigator application, it will give you an upgrade dialog box showing that a new version is available. If you have installed it somewhere in “Program Files”, the auto-upgrade mechanism will not work. So instead of being frustrated or trying to install it somewhere else, go through the following steps.

1. Open the command prompt using “Run as Administrator” option from Windows Start Menu
2. Go to the location where conda.exe is installed. In my case, it was ” C:\Program Files (x86)\Microsoft Visual Studio\Shared\Anaconda3_64\Scripts ” (Yes, I got the anaconda installed with Visual Studio Community Edition :).
3. Execute the following code
conda.exe update --prefix "C:\Program Files (x86)\Microsoft Visual Studio\Shared\Anaconda3_64" anaconda-navigator

Now your anaconda-navigator will be upgraded and something similar to the following text will be seen.

Fetching package metadata .............
Solving package specifications: .

Package plan for installation in environment C:\Program Files (x86)\Microsoft Visual Studio\Shared\Anaconda3_64:

The following packages will be UPDATED:

anaconda: 5.0.0-py36hea9b2fc_0 --> custom-py36h363777c_0
anaconda-navigator: 1.6.8-py36h4b7dd57_0 --> 1.6.12-py36hdad2993_0
conda: 4.3.27-py36hcbae3bd_0 --> 4.4.7-py36_0
pycosat: 0.6.2-py36hf17546d_1 --> 0.6.3-py36h413d8a4_0

Proceed ([y]/n)? y

anaconda-custo 100% |###############################| Time: 0:00:00 131.17 kB/s
pycosat-0.6.3- 100% |###############################| Time: 0:00:00 662.27 kB/s
conda-4.4.7-py 100% |###############################| Time: 0:00:01 904.57 kB/s
anaconda-navig 100% |###############################| Time: 0:00:02 1.96 MB/s
DEBUG menuinst_win32:__init__(185): Menu: name: 'Anaconda${PY_VER} ${PLATFORM}', prefix: 'C:\Program Files (x86)\Microsoft Visual Studio\Shared\Anaconda3_64', env_name: 'None', mode: 'None', used_mode: 'system'
DEBUG menuinst_win32:__init__(185): Menu: name: 'Anaconda${PY_VER} ${PLATFORM}', prefix: 'C:\Program Files (x86)\Microsoft Visual Studio\Shared\Anaconda3_64', env_name: 'None', mode: 'None', used_mode: 'system'

Don’t worry about the DEBUG prints, it just says that I have run the command outside of a container environment. Now voila, your anaconda navigator is updated. As a bonus, you might also see a list of packages that are upgradeable in the UI. The UI, unfortunately, will now allow you to carry on the upgrades. Instead, just write the following in an environment window (a python window opened via the environment from anaconda-navigator)

conda update --all

If you run the command outside of an environment, the base/root environment will be updated. You can also use the –name argument to the command to give a specific environment name. Running it from inside a contained environment will only update the packages for that environment. To update the environment itself, you can use  conda env update . Check the conda documentation for the same.

So long people, ENJOY learning!

Remote control your Linux Workstation (Efficiently)

There are many different solutions to remote control your Linux workstation but most of them are not effective. For example, one can always ssh into the workstation and forward X. Well, this kind of works but has several drawbacks; the major one being that all the processes you started with your ssh session will be killed when you loose your SSH session. I call nohup, screen, etc. as bypass methods because they essentially try to give you a workaround solution instead of actually solving it. And if you are like me who keeps logging in and out and starting/stopping scripts, I am pretty sure you will forget to use those just like me and login after a good night sleep to find out that your compile script got terminated because you forgot to screen it! Also, SSH with X forwarding typically needs an X-Server on your host machine and can be a PIA to setup if you are on Windows. Yes, yes, we can all use MobaXTerm but hey, believe me, X-server is heavy in terms of resource usage on Windows. Also automatic file changes are not detected with that solution.

Next in the queue of nonviable solution is x2go. I haven’t been able to use it properly because the X-server on my windows machine keeps crashing whenever I have a different resolution than the one on the workstation. So that is a big failure. Then minors on the list are VNC, RDP, XRDP, etc. All have their drawbacks. For VNC, it is excruciatingly slow when I use it. Also the ability to dynamically change screen resolutions is tossed out of the window. Yes, I know about the geometry setups in .vncstartup but hey, I am in no mood to write down all the resolutions that I want to use in that file! It is NOT EFFICIENT. RDP and XRDP rarely if ever works and again is affected by the slowness.

So the last remaining option is to use NX from NoMachine. Both the NXServer and the NXClient are actually free for personal use. One needs to install the server on Linux (pretty simple with the deb file provided). And then use the NXClient on windows and it works like a charm. Of course again, the whole thing becomes mighty slow under the following conditions:
– Changing the resolution of the remote display to a different one than the monitor connected to
– Using a virtual display instead of the actual physical one

Now, there are multiple reasons to use virtual displays with the simplest being that I can turn off my monitor and still use NX. And the person sitting on the desk besides my Linux workstation does not see a ghost operating it. And yes, there is an option to turn off physical display when someone connects, but as soon as you logoff, the physical screen becomes active in its full form. And if you forget to lock the computer before disconnecting your NX client, the person besides you gets access to your screen and can start doing weird stuff on it. Believe me, I have a monkey friend who used to do that and one time, he simply shutdown the machine to annoy me and get me to commute the whole 25KM (he wanted to have lunch with me!). Besides that, as I wrote earlier, I want to keep changing the resolutions as I work. When I am editing stuff, I need lower resolution bigger fonts, when it is compiling/running scripts, I can go with the default 2K resolution.

Virtual displays are a great way to do this. So now you want to evaluate the terminal server from NX but don’t. Use the LTSP (Linux Terminal Server Project) which works amazingly well with the NX protocol. Just

sudo apt-get install ltsp-server-standalone

and you are off to go. Now you will have a virtual desktop that you can connect to (in fact as many as you want) without having to cough up the precious greens or settling for something low grade. You can always ssh and have NX running simultaneously. Best part with NX is that you can pickup from where you left off. Yes, now that is what I call efficient.

ENJOY your remoting Linux workstation from Windows and still being happy!

Tensorflow OOM error when running on GPU!

I know you are interested in #MachineLearning and your first instinct is to use #TensorFlow (of course since it is backed by #Google) and you will probably find a lot of support with queries. The best part is that the available #Docker container will help you experiment and it simply runs out of the box. Look at my article on getting started with Tensorflow. Soon you will get bored by the amazingly slow executing speeds on CPU and will be thirsty to run it on your GPU because:

1. GPU is faster at running multiple parallel threads
2. GPU is faster at doing matrix/multi-dimensional operations
3. Your GPU is simply idling when you are running model training/inference on your CPU
4. Your coffee can only last for 2 minutes in which GPU can finish processing your model whereas, with CPU you will need at least 10 coffees (not good for health)
5. Last and not the least, go and get yourself an NVIDIA GPU if you haven’t already to save yourself time and achieve efficiency

In any case, all experts & hobbyists alike train their models on GPUs. And boy they have powerful GPUs (Quadro P6000 (:drooling)). But hobbyists/poor engineers like me do not have access to those professional grade GPUs. Instead, we need to get away with low-end GeForce graphic cards. Nothing wrong with those though. They plan amazing games. But there are some problems when running ML algorithms like mnist_deep (a DNN based sample application) that allocates huge amount of memory in one go. The problem executing this on GPU with less than 4GB of GDDR5 is that the application simply causes an Out Of Memory (OOM) exception.

Though there is a way to use batch-size (i.e. allocate memory in small chunks). The Tensorflow team talks about it in the documentation but does not have a proper example that we can follow. So after some search and find operations, I was able to get hold of the code. Below is the modified that runs on all GPUs irrespective of the memory they have. One can further reduce the batch-size if the problem continues.

Line #166 and #167 were the original lines which were trying to create the dictionary with the whole set of data in memory causing OOMs. Line #168 to Line #179 is the replacement code that divides the data into batch-sizes of 50. Nothing strange there, we are simply taking smaller number of images and calculating the accuracy. Hope it is easier for you to get the solution and don’t have to run around like me. ENJOY!