Ttylinux

What you are searching for is called ttylinux.

Major components

• Kernel
• Glibc
• Iptables
• Dropbear (scp, ssh, sshd)
• GPM
• Bash
• Busybox
• E2fsprogs

Not maintained

The distribution was hosted at Ttylinux.net, and is currently not maintained.

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Latest ttylinux release is dated 2015.02 (updated 2015.03).

A good linux distro that I've fallen in love with (and also has no GUI) is MicroCore Linux. It also has an older brother TinyCore Linux that does have a GUI (a pretty crappy one though).

You could always try DSL (Damn Small Linux)

I don't think any of these explicitly come with busybox (I don't know of any distro that ships with it), but it shouldn't be too hard to install it afterwards. From what I understand your main concern is a small fast system with a decent shell.

"Alpine Linux is a security-oriented, lightweight Linux distribution based on musl libc and busybox."

The best most current distribution I can think of is Debian NetInst: http://www.debian.org/CD/netinst/

There are a number of small Linux distributions out there but this one I think will be among the best maintained. Another thing is, if you need to grow it to full size, it's a trivial operation.

Minimal Linux Live

https://github.com/ivandavidov/minimal

For a more interesting interactive system, this is a (mostly educational) small script that:

• downloads the source for the kernel and busybox
• compiles them
• generates a bootable 8Mb ISO with them

The ISO then leaves you in a minimal shell with busybox.

With QEMU you can easily boot into the system.

I have modified it to allow running it from the kernel source directory: https://github.com/cirosantilli/runlinux

Usage:

git clone https://github.com/ivandavidov/minimal
cd minimal/src
./build_minimal_linux_live.sh
# Wait.
# Install QEMU.
# minimal_linux_live.iso was generated
./qemu64.sh

and you will be left inside a QEMU Window with you new minimal system. Awesome.

Since it is small, this is a good option to read the source and understand what is going on.

Tested on Ubuntu 16.04.

Buildroot

https://buildroot.org/

Large set of Makefile scripts that manage:

• GCC cross compilation toolchain
• kernel compilation
• bootloader compilation
• generation of rootfs
• has tons of package download / build recipes in the source tree, including complex stuff like GTK. There is a dependency system.

Minimal example:

git clone git://git.buildroot.net/buildroot
cd buildroot
git checkout 2016.05
make qemu_x86_defconfig
# Can't use -jN, use `BR2_JLEVEL=2` instead.
BR2_JLEVEL=2 make
# Wait.
# cat board/qemu/x86_64/readme.txt
qemu-system-x86_64 -M pc -kernel output/images/bzImage -drive file=output/images/rootfs.ext2,if=virtio,format=raw -append root=/dev/vda -net nic,model=virtio -net user
# You are now in a shell with BusyBox utilities.

Professional stuff.

Alpine Linux

https://github.com/gliderlabs/docker-alpine

Embedded distribution with a package manager that offers precompiled binaries from a website.

Single executable rootfs

The absolute minimum system runs a single /init program as I've explained at https://superuser.com/a/991733/128124