# Drop ballast... How I reduced the size of minectl 🗺

Looking at the current state of `minectl 🗺`, I think it reached now a good level in terms of features and functionalities. So it is time for me, to open the next big chapter: 

**Getting `minectl 🗺` CI ready.**

![image.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1628629005216/4A85oOwjM.png)


Before I could start with this, I wanted to be really sure that I did everything during the development and creation phase of the actual `minectl 🗺` binary.

So the first thing, what comes in to my mind was to verify the size of the binary.

To be honest, I don't want that the filesize of `minectl 🗺` becomes an issue, and users have to wait longer then necessary.

Having to wait to download an unreasonable sized binary (+container) is not really a good thing.

So let's have a look into the raw binary size of `minectl 🗺`:

```bash
➜  minectl git:(main) ✗ go build .                              
➜  minectl git:(main) ✗ ls -lah minectl 
-rwxr-xr-x  1 dirien  staff    58M Aug 10 22:50 minectl
➜  minectl git:(main) ✗ 
```
![image.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1628630017604/iFVU2_Yfh.png)

A quick look on the entropy graph (made with [binwalk](https://github.com/ReFirmLabs/binwalk)) reveals that we have potential to compress the binary further down.

![graph1.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1628630884874/EmeJV49MR.png)

Short explanation of the entropy graph:

>An entropy graph (to evaluate the amount of disorder) can be useful to detect the parts of the file that get close to random data.
>
>It will allow to detect the parts that have been encrypted/compressed and the parts that appear to be left untouched.

Okay, time to drop some ballast.

## Golang home remedies

Let us strip the binary from the debugging information. To do this we can use the -s and -w linker flags.

```bash
➜  minectl git:(main) ✗ go build -ldflags="-s -w" .
➜  minectl git:(main) ✗ ls -lah minectl 
-rwxr-xr-x  1 dirien  staff    48M Aug 10 23:33 minectl
➜  minectl git:(main) ✗ 
``` 
With this little action we nearly reduce the size to **82%** of the initial size. Quick look in the new entropy graph:

![minectl.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1628631665232/NcthAyHIU.png)

We can see that we lost a big chunk of padding.

We can to better than this! Open the stage for [UPX](https://github.com/upx/upx)

## UPX - The Ultimate Packer for eXecutables

`upx` is an advanced executable file compressor. `upx` will typically reduce the file size of programs by around 50%-70%, thus reducing disk space, network load times, download times and other distribution and storage costs.

So let us see what `upx` can do for us. Running `upx`, in vanilla mode, gives us following results:

```bash
➜  minectl git:(main) ✗ upx minectl
                       Ultimate Packer for eXecutables
                          Copyright (C) 1996 - 2020
UPX 3.96        Markus Oberhumer, Laszlo Molnar & John Reiser   Jan 23rd 2020

        File size         Ratio      Format      Name
   --------------------   ------   -----------   -----------
  50085008 ->  12988432   25.93%   macho/amd64   minectl                       

Packed 1 file.
➜  minectl git:(main) ✗ ls -lah minectl
-rwxr-xr-x  1 dirien  staff    12M Aug 10 23:33 minectl
```
So with the `-s and -w` flag  and `upx`, we reduced the size to **20%** of the initial binary. Reducing the overall size to nice 12M.

The new entropy graph looks like this:

![graph-upx.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1628634022500/j6l-cHyHa.png)

Can we squeeze more out of our `minectl 🗺` binary? Let us try to run `upx` in brute mode. This takes a little more time, but hey if it helps I can wait on my production build.

![image.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1628632848681/Nfem4ZENd.png)

```bash
➜  minectl git:(main) ✗ upx --brute minectl
                       Ultimate Packer for eXecutables
                          Copyright (C) 1996 - 2020
UPX 3.96        Markus Oberhumer, Laszlo Molnar & John Reiser   Jan 23rd 2020

        File size         Ratio      Format      Name
   --------------------   ------   -----------   -----------
  50085008 ->   8732688   17.44%   macho/amd64   minectl                       

Packed 1 file.
➜  minectl git:(main) ✗ ls -lah minectl
-rwxr-xr-x  1 dirien  staff   8.3M Aug 10 23:50 minectl
```
8.3M is the binary size, which is whopping **13%** of the initial binary.

Our entropy graph  is now very boring:

![graph-brute.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1628634269499/3O_gEw7PK.png)

The downside: decompression is not free, and we will get some overhead when starting the `minectl 🗺`. We're talking here in `ms`. I think that this is in a totally acceptable area.

## Connect the dots

### GoReleaser

![24697112.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1628634662583/5vfaTeppD.png)

As I am using [`goreleaser`](https://goreleaser.com/) for building my binaries and container image, I can easily add the `upx` call into the .goreleaser.yml:

```yaml
builds:
  -
...
    hooks:
      post:
       - upx --brute "{{ .Path }}"
```
### Container Build

To avoid bloating the container up, now we spent some time to reduce it. I am going to use an alpine base image for my container.

```dockerfile
FROM alpine:3.14.1
COPY minectl \
	/usr/bin/minectl
ENTRYPOINT ["/usr/bin/`minectl`"]
```

Thats it. With a relative low effort, we achieved our goal to reduce the size of `minectl 🗺`.

![image.png](https://cdn.hashnode.com/res/hashnode/image/upload/v1628636334169/_DYE5frdo.png)


#### Credits
- https://www.esticastresearch.com/wp-content/uploads/2018/07/Automotive-Robotics-Market.jpg
- https://goreleaser.com/
- https://embeddedbits.org/reverse-engineering-router-firmware-with-binwalk/