Why stop at 100kB? What's the smallest possible, runnable docker image we can make?
hello.asm
hello.asm
; Define variables in the data section
SECTION .DATA
hello: db 'Hello world!',10
helloLen: equ $-hello
; Code goes in the text section
SECTION .TEXT
GLOBAL _start
_start:
mov eax,4 ; 'write' system call = 4
mov ebx,1 ; file descriptor 1 = STDOUT
mov ecx,hello ; string to write
mov edx,helloLen ; length of string to write
int 80h ; call the kernel
; Terminate program
mov eax,1 ; 'exit' system call
mov ebx,0 ; exit with error code 0
int 80h ; call the kernel
Makefile
hello.o: hello.asm
nasm -f elf64 $< -o $@
hello: hello.o
ld $< -o $@
The Dockerfile
FROM alpine:latest as builder
WORKDIR /build
RUN apk update && \
apk add nasm make binutils
COPY . ./
RUN make hello
FROM scratch
WORKDIR /
COPY --from=builder /build/hello .
CMD ["/hello"]
Basically the same as before, just new apk deps for nasm.
Only 980 Bytes!
docker images |grep tiny-hello|awk '{print $8}'
952B
What's Next?
We'll build a more workable REST API that guts 99% out of a typical docker image.
This was a shorter example, since it's principally the same as the last .
➡️ Until then, can you beat 980-bytes?
Many thanks to my friend and devops expert Philippe and this hello world assembler for encouraging me to go smaller.
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