## Motivatation

- modern CMake is required for building a lot of new software
- CMake is dependency for many packages (e.g. ROS related)
- we don't want to remove CMake (which would remove packages that depend on it)
- we want safe procedure to update CMake that can be reversed easily 

## Current version in OS

Check current version

```bash
apt-cache policy cmake
```

## Build CMake 3.20

```bash
# get and build CMake
wget https://github.com/Kitware/CMake/releases/download/v3.20.0/cmake-3.20.0.tar.gz
tar -zvxf cmake-3.20.0.tar.gz
cd cmake-3.20.0
./bootstrap
make -j8
```

## Install as package

So that we can easily remove it later

```bash
sudo apt-get install checkinstall
# this will take more time than you expect
sudo checkinstall --pkgname=cmake --pkgversion="3.20-custom" --default
# reset shell cache for tools paths
hash -r
```

## Verify installation

```bash
apt-cache policy cmake
```

```bash
cmake --version
```

```bash
which cmake
```

## Uninstall

This step *only* if you want to revert back

- we don't want to remove cmake
- this could cause removal of packages that depend on it (e.g. ROS)
- instead we switch back to previous version

```bash
# idenitfy version of interest
apt-cache policy cmake
# switch to different version (from policy above)
apt-get install cmake=VERSION
```