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[wip] implement persistent storage for services
Signed-off-by: Serge Hallyn <[email protected]>
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# Storage for targes | ||
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Following is an example manifest.yaml showing how to specify storage | ||
for targets: | ||
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``` | ||
storage: | ||
- label: zot-data | ||
persistent: true | ||
nsgroup: "zot" | ||
size: 30G | ||
- label: zot-config | ||
persistent: true | ||
nsgroup: "zot" | ||
size: 1G | ||
- label: zot-tmp | ||
persistent: false | ||
nsgroup: "zot" | ||
size: 1G | ||
- label: nginx-data | ||
persistent: true | ||
nsgroup: "zot" | ||
size: 1G | ||
targets: | ||
- service_name: zot | ||
source: docker://zothub.io/machine/bootkit/demo-zot:0.0.4-squashfs | ||
version: 1.0.0 | ||
nsgroup: zot | ||
storage: | ||
- dest: /zot | ||
label: zot-data | ||
- dest: /etc/zot | ||
label: zot-config | ||
- dest: /tmp | ||
label: zot-tmp | ||
- service_name: nginx | ||
source: docker://zothub.io/machine/bootkit/demo-nginx:0.0.4-squashfs | ||
version: 1.0.0 | ||
nsgroup: zot | ||
storage: | ||
- dest: /data/zot | ||
label: zot-data | ||
- dest: /var/lib/www | ||
label: nginx-data | ||
``` | ||
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When a target starts up, its rootfs is an overlay of a writeable tmpfs | ||
over the source OCI image (which itself is an overlay of dmverity-protected | ||
squashfs images). The writeable overlays are all in a shared partition | ||
mounted at /scratch-writes. In order to provide persistent storage | ||
across boots, shared storage between containers, or a larger private | ||
ephemeral storage which does not risk filling up /scratch-writes, | ||
extra storage can be requested. | ||
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In the above example, four additional storage volumes are requested. The | ||
30G volume called zot-data will be persistent, so its contents will be | ||
saved across boots. In contrast, zot-tmp is not persistent, so its contents | ||
will be deleted across reboots. All four are in the 'nsgroup zot', which | ||
both of the targets, zot and nginx, run in. The nsgroup is a named | ||
user namespace mapping, so uid 0 will be represented by the same host | ||
uid (for instance 100000) for all. | ||
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Note that if nginx were not placed into nsgroup 'zot', it would still | ||
be able to mount zot-data, however all files would appear as | ||
owned by nobody:nogroup, and nginx would get the world access rights. | ||
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Each target now has an optional storage section, where it can | ||
specify which volumes it should mount, and where. | ||
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On boot, the machine will first create the storage volumes, and uid-shift | ||
them if needed. If a non-persistent volume already exists, it will be | ||
deleted and recreated. | ||
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All storage volumes are created as ext4 filesystems. |
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