Mocker Linux Distro Experiment

This project creates a custom bare linux distro environment using linux namespaces.

The bare linux environment is created by mocker.c, which similar to Docker. It uses linux namespaces to create new PID/mount/UTS namespaces that containerize a child instance from rootfs/. Mocker accomplishes this through linux syscalls and filesystem manipulation to create an environment akin to a fresh linux boot with no utilities or files. It uses rootfs/usr/sbin/init as the primary entrypoint into this environment.

Inside rootfs is the init, getty, login, and shell executables that are the backbone of the distro. Init handles creating the getty processes for each tty in the system (only 1 in this case). Getty handles claiming control of a tty and passing it to login. Login handles reading a username/password and enabling a user environment for secure system login. Shell, obviously, works as the main interface for creating and running processes and performing system functions.

Custom Shell Utilities

(NOTE: Some utilities have options not listed here)

• echo <message> - Print message to STDOUT
• env - Print all environment variables
• pwd - Print the current working directory
• sleep <t> - Sleep for t seconds
• cat [file] - Open a file and read it to STDOUT
• mv <src> <dst> - Move a file or directory from src to dst
• cp <src> <dst> - Copy a file or directory from src to dst
• rm <src> - Remove a file or directory
• ls [dir] - List a directory's contents
• mkdir <dir> - Create a new directory
• kill <pid> - Send SIGTERM (or another signal) to a process
• sudo <cmd...> - Run a command as superuser (root)
• su [login] - Switch to another user
• adduser <login> - Create a new user
• gpasswd <user> <group> - Add or remove a user to a group
• whoami - Prints the current user
• segfault - Intentionally create a SIGSEGV condition
• shutdown - Send SIGTERM to init to end container

Compile & Run

To compile rootfs:

make rootfs

To compile mocker:

make mocker

To start the container:

make run

Using the Container

The default (and only) login for the container is root with no password:

login: root
password: 
/# echo hello world
hello world
/#

To exit the container, you can use the shutdown command:

login: root
password: 
/# shutdown

To create a new account and login as that account:

login: root
password:
/# adduser jacob
password: helloworld
confirm password: helloworld
/# gpasswd -a jacob sudo
/# exit
login: jacob
password: helloworld
/home/jacob# whoami
uid=1000 (jacob)
/home/jacob# shutdown
(shutdown: must be run as root)
/home/jacob# sudo shutdown