Command merge-docker-save repacks output of the docker save command called for a single image to a tar stream with merged content of all image layers.
Command docker save outputs docker-specific tar stream:
$ docker save alpine:latest | tar tv |head
drwxr-xr-x 0/0 0 2017-09-13 14:32 030cf30aac0be224d6b7e02ca2b7cadf1d078bf90ef1e9656ff54a924a5f163a/
-rw-r--r-- 0/0 3 2017-09-13 14:32 030cf30aac0be224d6b7e02ca2b7cadf1d078bf90ef1e9656ff54a924a5f163a/VERSION
-rw-r--r-- 0/0 1184 2017-09-13 14:32 030cf30aac0be224d6b7e02ca2b7cadf1d078bf90ef1e9656ff54a924a5f163a/json
-rw-r--r-- 0/0 4220928 2017-09-13 14:32 030cf30aac0be224d6b7e02ca2b7cadf1d078bf90ef1e9656ff54a924a5f163a/layer.tar
-rw-r--r-- 0/0 1512 2017-09-13 14:32 76da55c8019d7a47c347c0dceb7a6591144d232a7dd616242a367b8bed18ecbc.json
-rw-r--r-- 0/0 202 1970-01-01 00:00 manifest.json
-rw-r--r-- 0/0 89 1970-01-01 00:00 repositories
Command merge-docker-save transforms this output to produce tar stream with container filesystem:
$ docker save alpine:latest | merge-docker-save | tar tv |head
drwxr-xr-x 0/0 0 2017-06-25 17:52 bin/
lrwxrwxrwx 0/0 0 2017-06-25 17:52 bin/ash -> /bin/busybox
lrwxrwxrwx 0/0 0 2017-06-25 17:52 bin/base64 -> /bin/busybox
lrwxrwxrwx 0/0 0 2017-06-25 17:52 bin/bbconfig -> /bin/busybox
-rwxr-xr-x 0/0 825504 2017-06-11 06:38 bin/busybox
lrwxrwxrwx 0/0 0 2017-06-25 17:52 bin/cat -> /bin/busybox
lrwxrwxrwx 0/0 0 2017-06-25 17:52 bin/catv -> /bin/busybox
lrwxrwxrwx 0/0 0 2017-06-25 17:52 bin/chgrp -> /bin/busybox
lrwxrwxrwx 0/0 0 2017-06-25 17:52 bin/chmod -> /bin/busybox
lrwxrwxrwx 0/0 0 2017-06-25 17:52 bin/chown -> /bin/busybox
Known limits
Command only supports docker save output for a single image, i.e. piping docker save alpine:latest works, but docker save alpine may not if it outputs multiple images.
This tool uses system default directory to store temporary files, which can be overridden by setting $TMPDIR environment.