# Linux Kernel Module Cheat

#### 7.4.3. BusyBox shell init environment

On top of the Linux kernel, the BusyBox `/bin/sh` shell will also define other variables.

We can explore the shenanigans that the shell adds on top of the Linux kernel with:

    ./run --kernel-cli 'init=/bin/sh'

From there we observe that:

    env

gives:

    SHLVL=1
    HOME=/
    TERM=linux
    PWD=/

therefore adding `SHLVL` and `PWD` to the default kernel exported variables.

Furthermore, to increase confusion, if you list all non-exported shell variables https://askubuntu.com/questions/275965/how-to-list-all-variables-names-and-their-current-values with:

    set

then it shows more variables, notably:

    PATH='/sbin:/usr/sbin:/bin:/usr/bin'

- BusyBox shell initrc files