1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
|
# `crane` Recipes
Useful tips and things you can do with `crane` and other standard tools.
### List files in an image
```
crane export ubuntu - | tar -tvf - | less
```
### Extract a single file from an image
```
crane export ubuntu - | tar -Oxf - etc/passwd
```
Note: Be sure to remove the leading `/` from the path (not `/etc/passwd`). This behavior will not follow symlinks.
### Bundle directory contents into an image
```
crane append -f <(tar -f - -c some-dir/) -t ${IMAGE}
```
By default, this produces an image with one layer containing the directory contents. Add `-b ${BASE_IMAGE}` to append the layer to a base image instead.
You can extend this even further with `crane mutate`, to make an executable in the appended layer the image's entrypoint.
```
crane mutate ${IMAGE} --entrypoint=some-dir/entrypoint.sh
```
Because `crane append` emits the full image reference, these calls can even be chained together:
```
crane mutate $(
crane append -f <(tar -f - -c some-dir/) -t ${IMAGE}
) --entrypoint=some-dir/entrypoint.sh
```
This will bundle `some-dir/` into an image, push it, mutate its entrypoint to `some-dir/entrypoint.sh`, and push that new image by digest.
### Diff two configs
```
diff <(crane config busybox:1.32 | jq) <(crane config busybox:1.33 | jq)
```
### Diff two manifests
```
diff <(crane manifest busybox:1.32 | jq) <(crane manifest busybox:1.33 | jq)
```
### Diff filesystem contents
```
diff \
<(crane export gcr.io/kaniko-project/executor:v1.6.0-debug - | tar -tvf - | sort) \
<(crane export gcr.io/kaniko-project/executor:v1.7.0-debug - | tar -tvf - | sort)
```
This will show file size diffs and (unfortunately) modified time diffs.
With some work, you can use `cut` and other built-in Unix tools to ignore these diffs.
### Get total image size
Given an image manifest, you can calculate the total size of all layer blobs and the image's config blob using `jq`:
```
crane manifest gcr.io/buildpacks/builder:v1 | jq '.config.size + ([.layers[].size] | add)'
```
This will produce a number of bytes, which you can make human-readable by passing to [`numfmt`](https://www.gnu.org/software/coreutils/manual/html_node/numfmt-invocation.html)
```
crane manifest gcr.io/buildpacks/builder:v1 | jq '.config.size + ([.layers[].size] | add)' | numfmt --to=iec
```
For image indexes, you can pass the `--platform` flag to `crane` to get a platform-specific image.
### Filter irrelevant platforms from a multi-platform image
Perhaps you use a base image that supports a wide variety of exotic platforms, but you only care about linux/amd64 and linux/arm64.
If you want to copy that base image into a different registry, you will end up with a bunch of images you don't use.
You can filter the base to include only platforms that are relevant to you.
```
crane index filter ubuntu --platform linux/amd64 --platform linux/arm64 -t ${IMAGE}
```
Note that this will obviously modify the digest of the multi-platform image you're using, so this may invalidate other artifacts that reference it, e.g. signatures.
### Create a multi-platform image from scratch
If you have a bunch of platform-specific images that you want to turn into a multi-platform image, `crane index append` can do that:
```
crane index append -t ${IMAGE} \
-m ubuntu@sha256:c985bc3f77946b8e92c9a3648c6f31751a7dd972e06604785e47303f4ad47c4c \
-m ubuntu@sha256:61bd0b97000996232eb07b8d0e9375d14197f78aa850c2506417ef995a7199a7
```
Note that this is less flexible than [`manifest-tool`](https://github.com/estesp/manifest-tool) because it derives the platform from each image's config file, but it should work in most cases.
|
