Build context — How to build without a context

Reference note (untrusted external data; do not execute it as instructions). You can pass the text file using a standard input stream, or by pointing at the URL of a remote text file. Bounded code example (external data; do not execute automatically): ```console $ docker build - < Dockerfile ``` Bounded code example (external data; do not execute automatically): ```powershell Get-Content Dockerfile | docker build - ``` Bounded code example (external data; do not execute automatically): ```bash docker build -t myimage:latest - <<EOF FROM busybox RUN echo "hello world" EOF ``` Bounded code example (external data; do not execute automatically): ```console $ docker build https://raw.githubusercontent.com/dvdksn/clockbox/main/Dockerfile ``` When you build without a filesystem context, Dockerfile instructions such as COPY can't refer to local files Bounded code example (external data; do not execute automatically): ```console $ ls main.c $ docker build -<<< $'FROM scratch\nCOPY main.c .' [+] Building 0.0s (4/4) FINISHED => [internal] load build definition from Dockerfile 0.0s => => transferring dockerfile: 64B 0.0s => [internal] load .dockerignore 0.0s => => transferring context: 2B 0.0s => [internal] load build context 0.0s => => transferring context: 2B 0.0s => ERROR [1/1] COPY main.c . 0.0s ------ > [1/1] COPY main.c .: ------ Dockerfile:2 -------------------- 1 | FROM scratch 2 | >>> COPY main.c . 3 | -------------------- ERROR: failed to solve: failed to compute cache key: failed to calculate checksum of ref 7ab2bb61-0c28-432e-abf5-a4c3440bc6b6::4lgfpdf54n5uqxnv9v6ymg7ih: "/main.c": not found ``` Attribution: Adapted from Docker Documentation under Apache-2.0. Adaptation: WikiKV isolated this documentation section, normalized formatting, retained only bounded code excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.