291 lines
7.5 KiB
Markdown
291 lines
7.5 KiB
Markdown
# OCI Bundle
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Since containerd consumes the OCI bundle format containers and configuration will have to be created
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on the machine that containerd is running on. The easiest way to do this is to download an image
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with docker and export it.
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## Setup
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First thing we need to do to create a bundle is setup the initial directory structure.
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Create a directory with a unique name. In this example we will create a redis container.
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We will create this container in a `/containers` directory.
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```bash
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mkdir redis
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```
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Inside the `redis` directory create another directory named `rootfs`
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```bash
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mkdir redis/rootfs
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```
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## Root Filesystem
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Now we need to populate the `rootfs` directory with the filesystem of a redis container. To do this we
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need to pull the redis image with docker and export its contents to the `rootfs` directory.
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```bash
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docker pull redis
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# create the container with a temp name so that we can export it
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docker create --name tempredis redis
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# export it into the rootfs directory
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docker export tempredis | tar -C redis/rootfs -xf -
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# remove the container now that we have exported
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docker rm tempredis
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```
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Now that we have the root filesystem populated we need to create the configs for the container.
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## Configs
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An easy way to get temp configs for the container bundle is to use the `runc`
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cli tool from the [runc](https://github.com/opencontainers/runc) repository.
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You need to `cd` into the `redis` directory and run the `runc spec` command. After doing this you
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should have two files created, `configs.json` and `runtime.json`. The directory structure should
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look like this:
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```
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/containers/redis
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├── config.json
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├── rootfs/
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└── runtime.json
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```
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## Edits
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We need to exit the config to add `redis-server` as the application to launch inside the container along with
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a few other settings. The resulting `config.json` should look like this:
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```json
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{
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"version": "0.2.0",
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"platform": {
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"os": "linux",
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"arch": "amd64"
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},
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"process": {
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"terminal": false,
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"user": {
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"uid": 1000,
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"gid": 1000
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},
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"args": [
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"redis-server", "--bind", "0.0.0.0"
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],
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"env": [
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"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
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"TERM=xterm"
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],
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"cwd": ""
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},
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"root": {
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"path": "rootfs",
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"readonly": false
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},
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"hostname": "shell",
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"mounts": [
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{"name": "proc", "path": "/proc"},
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{"name": "dev", "path": "/dev"},
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{"name": "devpts", "path": "/dev/pts"},
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{"name": "shm", "path": "/dev/shm"},
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{"name": "mqueue", "path": "/dev/mqueue"},
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{"name": "sysfs", "path": "/sys"}
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],
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"linux": {
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"capabilities": [
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"CAP_AUDIT_WRITE",
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"CAP_KILL",
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"CAP_NET_BIND_SERVICE"
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]
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}
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}
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```
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You will also want to edit the `runtime.json` file to remove the network namespace so that
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you can connect to the redis server on your system. The final result for the `runtime.json`
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file should look like this:
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```json
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{
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"mounts": {
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"dev": {
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"type": "tmpfs",
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"source": "tmpfs",
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"options": [
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"nosuid",
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"strictatime",
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"mode=755",
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"size=65536k"
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]
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},
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"devpts": {
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"type": "devpts",
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"source": "devpts",
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"options": [
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"nosuid",
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"noexec",
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"newinstance",
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"ptmxmode=0666",
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"mode=0620",
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"gid=5"
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]
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},
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"mqueue": {
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"type": "mqueue",
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"source": "mqueue",
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"options": [
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"nosuid",
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"noexec",
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"nodev"
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]
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},
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"proc": {
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"type": "proc",
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"source": "proc",
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"options": null
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},
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"shm": {
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"type": "tmpfs",
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"source": "shm",
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"options": [
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"nosuid",
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"noexec",
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"nodev",
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"mode=1777",
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"size=65536k"
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]
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},
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"sysfs": {
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"type": "sysfs",
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"source": "sysfs",
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"options": [
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"nosuid",
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"noexec",
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"nodev"
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]
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}
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},
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"linux": {
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"rlimits": [
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{
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"type": "RLIMIT_NOFILE",
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"hard": 1024,
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"soft": 1024
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}
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],
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"resources": {
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"disableOOMKiller": false,
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"memory": {
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"limit": 0,
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"reservation": 0,
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"swap": 0,
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"kernel": 0
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},
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"cpu": {
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"shares": 0,
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"quota": 0,
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"period": 0,
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"realtimeRuntime": 0,
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"realtimePeriod": 0,
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"cpus": "",
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"mems": ""
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},
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"pids": {
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"limit": 0
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},
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"blockIO": {
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"blkioWeight": 0,
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"blkioLeafWeight": 0,
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"blkioWeightDevice": null,
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"blkioThrottleReadBpsDevice": null,
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"blkioThrottleWriteBpsDevice": null,
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"blkioThrottleReadIOPSDevice": null,
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"blkioThrottleWriteIOPSDevice": null
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},
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"hugepageLimits": null,
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"network": {
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"classId": "",
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"priorities": null
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}
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},
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"namespaces": [
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{"type": "pid", "path": ""},
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{"type": "ipc", "path": ""},
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{"type": "uts", "path": ""},
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{"type": "mount", "path": ""}
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],
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"devices": [
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{
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"path": "/dev/null",
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"type": 99,
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"major": 1,
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"minor": 3,
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"permissions": "rwm",
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"fileMode": 438,
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"uid": 0,
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"gid": 0
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},
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{
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"path": "/dev/random",
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"type": 99,
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"major": 1,
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"minor": 8,
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"permissions": "rwm",
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"fileMode": 438,
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"uid": 0,
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"gid": 0
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},
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{
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"path": "/dev/full",
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"type": 99,
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"major": 1,
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"minor": 7,
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"permissions": "rwm",
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"fileMode": 438,
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"uid": 0,
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"gid": 0
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},
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{
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"path": "/dev/tty",
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"type": 99,
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"major": 5,
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"minor": 0,
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"permissions": "rwm",
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"fileMode": 438,
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"uid": 0,
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"gid": 0
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},
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{
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"path": "/dev/zero",
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"type": 99,
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"major": 1,
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"minor": 5,
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"permissions": "rwm",
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"fileMode": 438,
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"uid": 0,
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"gid": 0
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},
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{
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"path": "/dev/urandom",
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"type": 99,
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"major": 1,
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"minor": 9,
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"permissions": "rwm",
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"fileMode": 438,
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"uid": 0,
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"gid": 0
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}
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]
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}
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}
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```
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This is what you need to do to make a OCI compliant bundle for containerd to start.
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