dockerTools: Fix layer redundancy.

When building an image with multiple layers, files
already included in an underlying layer are supposed to
be excluded from the current layer. However, some subtleties
in the way filepaths are compared seem to be blocking this.

Specifically:
* tar generates relative filepaths with directories ending in '/'
* find generates absolute filepaths with no trailing slashes on directories

That is, paths extracted from the underlying tarball look like:
    nix/store/.../foobar/
whereas the layer being generated uses paths like:
    /nix/store/.../foobar

This patch modifies the output of "tar -t" to match the latter format.
This commit is contained in:
Tom Boettcher 2016-09-23 16:10:47 -05:00
parent 124f25bc7d
commit 1e8b69c35e

View file

@ -1,5 +1,5 @@
{ stdenv, lib, callPackage, runCommand, writeReferencesToFile, writeText, vmTools, writeScript
, docker, shadow, utillinux, coreutils, jshon, e2fsprogs, go, pigz }:
, docker, shadow, utillinux, coreutils, jshon, e2fsprogs, go, pigz, findutils }:
# WARNING: this API is unstable and may be subject to backwards-incompatible changes in the future.
@ -249,7 +249,7 @@ EOF
then mkPureLayer { inherit baseJson contents extraCommands; }
else mkRootLayer { inherit baseJson fromImage fromImageName fromImageTag contents runAsRoot diskSize extraCommands; });
result = runCommand "${baseName}.tar.gz" {
buildInputs = [ jshon pigz ];
buildInputs = [ jshon pigz coreutils findutils ];
imageName = name;
imageTag = tag;
@ -261,6 +261,18 @@ EOF
buildArgs = args;
};
} ''
# Print tar contents:
# 1: Interpreted as relative to the root directory
# 2: With no trailing slashes on directories
# This is useful for ensuring that the output matches the values generated by the "find" command
ls_tar() {
for f in $(tar -tf $1 | xargs realpath -ms --relative-to=.); do
if [ "$f" != "." ]; then
echo "/$f"
fi
done
}
mkdir image
touch baseFiles
if [ -n "$fromImage" ]; then
@ -276,7 +288,7 @@ EOF
parentID=$(jshon -e $fromImageName -e $fromImageTag -u < image/repositories)
for l in image/*/layer.tar; do
tar -tf $l >> baseFiles
ls_tar $l >> baseFiles
done
fi
@ -297,8 +309,7 @@ EOF
fi
echo Adding layer
tar -tf temp/layer.tar >> baseFiles
sed 's/^\.//' -i baseFiles
ls_tar temp/layer.tar >> baseFiles
comm <(sort -u baseFiles) <(sort -u layerFiles) -1 -3 > newFiles
tar -rpf temp/layer.tar --mtime=0 --no-recursion --files-from newFiles 2>/dev/null || true