Whiteout entries for files from parent image lost by squashing

Using 1.0.0rc5:

If you attempt to remove a file which was in the parent image then squash back to the parent image, the relevant white-outs are lost and the files come back.

Trivial example:

# cat Dockerfile 
FROM rhel7
RUN rm -rvf /etc/cron*/*
RUN rm -rvf /etc/logrotate*/*

# docker build --no-cache -t squash-test ./
Sending build context to Docker daemon 2.048 kB
Step 1 : FROM rhel7
 ---> c453594215e4
Step 2 : RUN rm -rvf /etc/cron*/*
 ---> Running in e73dc03cd23b
removed '/etc/cron.daily/0yum-daily.cron'
removed '/etc/cron.daily/rhsmd'
removed '/etc/cron.hourly/0yum-hourly.cron'
 ---> 56b59574af25
Removing intermediate container e73dc03cd23b
Step 3 : RUN rm -rvf /etc/logrotate*/*
 ---> Running in b307623d18e9
removed '/etc/logrotate.d/subscription-manager'
removed '/etc/logrotate.d/yum'
 ---> c4b59cb23cc6
Removing intermediate container b307623d18e9
Successfully built c4b59cb23cc6

# docker-squash -f rhel7 -t squash-test:squashed squash-test
2016-05-31 09:55:32,130 root         INFO     docker-squash version 1.0.0rc5, Docker 78ee77d/1.9.1, API 1.21...
2016-05-31 09:55:32,131 root         INFO     Using v1 image format
2016-05-31 09:55:32,140 root         INFO     Old image has 3 layers
2016-05-31 09:55:32,143 root         INFO     Checking if squashing is necessary...
2016-05-31 09:55:32,143 root         INFO     Attempting to squash last 2 layers...
2016-05-31 09:55:32,143 root         INFO     Saving image c4b59cb23cc602d0f11ddf31dda32c17d02793fed6197c42dd812669b108c4c8 to /tmp/docker-squash-HYqT55/old/image.tar file...
2016-05-31 09:55:42,532 root         INFO     Image saved!
2016-05-31 09:55:42,533 root         INFO     Unpacking /tmp/docker-squash-HYqT55/old/image.tar tar file to /tmp/docker-squash-HYqT55/old directory
2016-05-31 09:55:42,995 root         INFO     Archive unpacked!
2016-05-31 09:55:43,041 root         INFO     Squashing image 'squash-test'...
2016-05-31 09:55:43,042 root         INFO     Starting squashing...
2016-05-31 09:55:43,042 root         INFO     Squashing file '/tmp/docker-squash-HYqT55/old/c4b59cb23cc602d0f11ddf31dda32c17d02793fed6197c42dd812669b108c4c8/layer.tar'...
2016-05-31 09:55:43,043 root         INFO     Squashing file '/tmp/docker-squash-HYqT55/old/56b59574af2578b0757055151f1655e6ae3d1fd89115870ce2f68e866ad2a5f3/layer.tar'...
2016-05-31 09:55:44,037 root         INFO     Squashing finished!
2016-05-31 09:55:44,038 root         INFO     New squashed image ID is b69cec34b4ddf09a80e04921e0a9dcfde0adff65aeb1c665f8a496ff900f10f5
2016-05-31 09:55:46,689 root         INFO     Image registered in Docker daemon as squash-test:squashed
2016-05-31 09:55:46,731 root         INFO     Done

# docker run -t -i --rm=true squash-test
[root@3fb0f5b1e8fd /]# ls /etc/cron.*
/etc/cron.daily:

/etc/cron.hourly:

# docker run -t -i --rm=true squash-test:squashed 
[root@7ccd53847399 /]# ls /etc/cron.*
/etc/cron.daily:
0yum-daily.cron  rhsmd

/etc/cron.hourly:
0yum-hourly.cron

[goldmann]

After long try and fail, I do have a hacky way to fix this. Working now to make it suitable for a PR.

[goldmann]

I’ve tried your example and this is what I got:

➜  docker-squash git:(whiteout-fix) ✗ docker run -it --rm squash-test:latest
[root@88be14492a5c /]# ls /etc/cron.* 
/etc/cron.daily:

/etc/cron.hourly:
[root@88be14492a5c /]# exit
➜  docker-squash git:(whiteout-fix) ✗ docker run -it --rm squash-test:squashed
[root@0ce648fba616 /]# ls /etc/cron.* 
/etc/cron.daily:

/etc/cron.hourly:

For me it looks the same 😃