Mounting AWS EBS into CoreOS - amazon-ec2

Question

I have launched an EC2 instance with 100Gb EBS as https://coreos.com/os/docs/latest/booting-on-ec2.html docs.
#cloud-config
coreos:
units:
- name: media-ephemeral.mount
command: start
content: |
[Mount]
What=/dev/xvdb
Where=/media/ephemeral
Type=ext4
- name: format-ephemeral.service
command: start
content: |
[Unit]
Description=Formats the ephemeral drive
[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/usr/sbin/wipefs -f /dev/xvdb
ExecStart=/usr/sbin/mkfs.btrfs -f /dev/xvdb
- name: var-lib-docker.mount
command: start
content: |
[Unit]
Description=Mount ephemeral to /var/lib/docker
Requires=format-ephemeral.service
After=format-ephemeral.service
Before=docker.service
[Mount]
What=/dev/xvdb
Where=/var/lib/docker
Type=btrfs
if i run the above, the EBS is mounted correctly, but on system reboot, the volume is is not persistent
using
storage:
filesystems:
- name: ephemeral1
mount:
device: /dev/xvdb
format: ext4
wipe_filesystem: true
systemd:
units:
- name: media-ephemeral.mount
enable: true
contents: |
[Unit]
Before=local-fs.target
[Mount]
What=/dev/xvdb
Where=/media/ephemeral
Type=ext4
[Install]
WantedBy=local-fs.target
- name: var-lib-docker.mount
enable: true
contents: |
[Unit]
Description=Mount ephemeral to /var/lib/docker
Before=local-fs.target
[Mount]
What=/dev/xvdb
Where=/var/lib/docker
Type=ext4
[Install]
WantedBy=local-fs.target
- name: docker.service
dropins:
- name: 10-wait-docker.conf
contents: |
[Unit]
After=var-lib-docker.mount
Requires=var-lib-docker.mount
as per docs, i get
core#ip-10-1-2-188 ~ $ sudo /usr/bin/coreos-cloudinit --from-file storage1.conf
2019/01/15 17:09:28 Checking availability of "local-file"
2019/01/15 17:09:28 Fetching user-data from datasource of type "local-file"
2019/01/15 17:09:28 line 2: warning: unrecognized key "storage"
2019/01/15 17:09:28 line 9: warning: unrecognized key "systemd"
2019/01/15 17:09:28 Fetching meta-data from datasource of type "local-file"
2019/01/15 17:09:28 Parsing user-data as cloud-config
2019/01/15 17:09:28 Merging cloud-config from meta-data and user-data
2019/01/15 17:09:28 Updated /etc/environment
2019/01/15 17:09:28 Ensuring runtime unit file "etcd.service" is unmasked
2019/01/15 17:09:28 Ensuring runtime unit file "etcd2.service" is unmasked
2019/01/15 17:09:28 Ensuring runtime unit file "fleet.service" is unmasked
2019/01/15 17:09:28 Ensuring runtime unit file "locksmithd.service" is unmasked
core#ip-10-1-2-188 ~ $ cat /etc/os-release
NAME="Container Linux by CoreOS"
ID=coreos
VERSION=1967.3.0
VERSION_ID=1967.3.0
BUILD_ID=2019-01-08-0044
PRETTY_NAME="Container Linux by CoreOS 1967.3.0 (Rhyolite)"
ANSI_COLOR="38;5;75"
HOME_URL="https://coreos.com/"
BUG_REPORT_URL="https://issues.coreos.com"
COREOS_BOARD="amd64-usr"
What is the correct way to mount the EBS volume on CoreOS?
Any advice is much appreciated

Answer 1

It looks like you missed a step. [cloud-configs have been deprecated for quite some time now. You correctly converted that cloud-config into a container linux config (CLC) file, but missed using config transpiler (CT) to then render an ignition sequence. You can check this by running your config through the online validator. After running that CLC config through the config transpiler I get the following, which validates correctly:
{
"ignition": {
"config": {},
"timeouts": {},
"version": "2.1.0"
},
"networkd": {},
"passwd": {},
"storage": {
"filesystems": [
{
"mount": {
"device": "/dev/xvdb",
"format": "ext4",
"wipeFilesystem": true
},
"name": "ephemeral1"
}
]
},
"systemd": {
"units": [
{
"contents": "[Unit]\nBefore=local-fs.target\n[Mount]\nWhat=/dev/xvdb\nWhere=/media/ephemeral\nType=ext4\n[Install]\nWantedBy=local-fs.target\n",
"enable": true,
"name": "media-ephemeral.mount"
},
{
"contents": "[Unit]\nDescription=Mount ephemeral to /var/lib/docker\nBefore=local-fs.target\n[Mount]\nWhat=/dev/xvdb\nWhere=/var/lib/docker\nType=ext4\n[Install]\nWantedBy=local-fs.target\n",
"enable": true,
"name": "var-lib-docker.mount"
},
{
"dropins": [
{
"contents": "[Unit]\nAfter=var-lib-docker.mount\nRequires=var-lib-docker.mount\n",
"name": "10-wait-docker.conf"
}
],
"name": "docker.service"
}
]
}
}
Additionally, it's important to note that there are other differences as well between ignition and coreos-cloud-init. The most important of which is that ignition only runs once. Thus, for things like wiping the contents of that ephemeral disk, you should not expect wipe_filesystem: true to be run every single boot.
Try booting the machine with this config instead. You should get the expected results.