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additional volume support in building

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Signed-off-by: Avi Deitcher <avi@deitcher.net>
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Avi Deitcher
2024-09-30 15:09:28 +03:00
parent e4d41061b6
commit 76f4802ccf
3 changed files with 125 additions and 11 deletions
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docs/yaml.md
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@@ -18,8 +18,17 @@ For private registries or private repositories on a registry credentials provide
## Sections
The configuration file is processed in the order `kernel`, `init`, `onboot`, `onshutdown`,
`services`, `files`, `volumes`. Each section adds files to the root file system. Sections may be omitted.
The configuration file is processed in the order:
1. `kernel`
1. `init`
1. `volumes`
1. `onboot`
1. `onshutdown`
1. `services`
1. `files`
Each section adds files to the root file system. Sections may be omitted.
Each container that is specified is allocated a unique `uid` and `gid` that it may use if it
wishes to run as an isolated user (or user namespace). Anywhere you specify a `uid` or `gid`
@@ -100,8 +109,13 @@ including those in `services`, `onboot` and `onshutdown`. The volumes are create
chosen by linuxkit at build-time. The volumes then can be referenced by other containers and
mounted into them.
Volumes normally are blank directories. If an image is provided, the contents of that image
will be used to populate the volume.
Volumes can be in one of several formats:
* Blank directory: This is the default, and is an empty directory that is created at build-time. It is an overlayfs mount, and can be shared among multiple containers.
* Image laid out as filesystem: The contents of the image are used to populate the volume. Default format when an image is provided.
* Image as OCI v1-layout: The image is used as an [OCI v1-layout](https://github.com/opencontainers/image-spec/blob/main/image-layout.md). Indicated by `format: oci`.
Examples of each are given later in this section.
The `volumes` section can declare a volume to be read-write or read-only. If the volume is read-write,
a volume that is mounted into a container can be mounted read-only or read-write. If the volume is read-only,
@@ -111,7 +125,36 @@ By default, volumes are created read-write, and are mounted read-write.
Volume names **must** be unique, and must contain only lower-case alphanumeric characters, hyphens, and
underscores.
Sample `volumes` section:
#### Samples of `volumes`
##### Empty directory
Yaml showing both read-only and read-write:
```yml
volumes:
- name: dira
readonly: true
- name: dirb
readonly: true
```
Contents:
```sh
$ cd dir && ls -la
drwxr-xr-x 19 root wheel 608 Sep 30 15:03 .
drwxrwxrwt 130 root wheel 4160 Sep 30 15:03 ..
```
In the above example:
* `dira` is empty and is read-only.
* `volb` is empty and is read-write.
##### Image directory
Yaml showing both read-only and read-write:
```yml
volumes:
@@ -120,8 +163,7 @@ volumes:
readonly: true
- name: volb
image: alpine:latest
readonly: false
- name: volc
format: filesystem # optional, as this is the default format
readonly: false
```
@@ -129,7 +171,56 @@ In the above example:
* `vola` is populated by the contents of `alpine:latest` and is read-only.
* `volb` is populated by the contents of `alpine:latest` and is read-write.
* `volc` is an empty volume and is read-write.
Contents:
```sh
$ cd dir && ls -la
drwxr-xr-x 19 root wheel 608 Sep 30 15:03 .
drwxrwxrwt 130 root wheel 4160 Sep 30 15:03 ..
drwxr-xr-x 84 root wheel 2688 Sep 6 14:34 bin
drwxr-xr-x 2 root wheel 64 Sep 6 14:34 dev
drwxr-xr-x 37 root wheel 1184 Sep 6 14:34 etc
drwxr-xr-x 2 root wheel 64 Sep 6 14:34 home
drwxr-xr-x 13 root wheel 416 Sep 6 14:34 lib
drwxr-xr-x 5 root wheel 160 Sep 6 14:34 media
drwxr-xr-x 2 root wheel 64 Sep 6 14:34 mnt
drwxr-xr-x 2 root wheel 64 Sep 6 14:34 opt
dr-xr-xr-x 2 root wheel 64 Sep 6 14:34 proc
drwx------ 2 root wheel 64 Sep 6 14:34 root
drwxr-xr-x 2 root wheel 64 Sep 6 14:34 run
drwxr-xr-x 63 root wheel 2016 Sep 6 14:34 sbin
drwxr-xr-x 2 root wheel 64 Sep 6 14:34 srv
drwxr-xr-x 2 root wheel 64 Sep 6 14:34 sys
drwxr-xr-x 2 root wheel 64 Sep 6 14:34 tmp
drwxr-xr-x 7 root wheel 224 Sep 6 14:34 usr
drwxr-xr-x 13 root wheel 416 Sep 6 14:34 var
```
##### Image OCI Layout
Yaml showing both read-only and read-write, and both all architectures and a limited subset:
```yml
volumes:
- name: volo
image: alpine:latest
format: oci
readonly: true
- name: volp
image: alpine:latest
readonly: false
format: oci
platforms:
- linux/amd64
```
In the above example:
* `volo` is populated by the contents of `alpine:latest` as an OCI v1-layout for all architectures and is read-only.
* `volb` is populated by the contents of `alpine:latest` as an OCI v1-layout just for linux/amd64 and is read-write.
##### Volumes in `services`
Sample usage of volumes in `services` section: