I need to use c5 instance type in AWS and found this breaks my terraform automation. Unlike the t2 instances where each boot sequence provides consistent device names under /dev.
resource "aws_volume_attachment" "ebs_att" {
device_name = "/dev/xvdb"
volume_id = aws_ebs_volume.dev_build_data_dir.id
instance_id = aws_instance.dev_build.id
skip_destroy = "true"
}
creates that exact /dev/xvd(x) device on the ec2 instance. Easy to automate.
However on c5 instances using multiple (devices) terraform /dev/xvd(x) devices translates to /dev/nvme(x) and is not consistent across hosts or reboots. In my case I have multiple volumes I am trying to mount.
From the server side I dont see anything I can use for automation:
[root@ip-192-168-1-110 ~]# ls /dev/disk/by-id/
nvme-Amazon_Elastic_Block_Store_vol027ba08**********
nvme-Amazon_Elastic_Block_Store_vol085cd16**********
nvme-Amazon_Elastic_Block_Store_vol0a3b21f**********
nvme-Amazon_Elastic_Block_Store_vol0a3b21f**********-part1
nvme-Amazon_Elastic_Block_Store_vol0d2b239**********
nvme-nvme.1d0f-766f6c3032376261303865343732643164303632-416d617a6f6e20456c617374696320426c6f636b2053746f7265-00000001
nvme-nvme.1d0f-766f6c3038356364313630333864616665663835-416d617a6f6e20456c617374696320426c6f636b2053746f7265-00000001
nvme-nvme.1d0f-766f6c3061336232316661386434623862313138-416d617a6f6e20456c617374696320426c6f636b2053746f7265-00000001
nvme-nvme.1d0f-766f6c3061336232316661386434623862313138-416d617a6f6e20456c617374696320426c6f636b2053746f7265-00000001-part1
nvme-nvme.1d0f-766f6c3064326232333935336235656637356130-416d617a6f6e20456c617374696320426c6f636b2053746f7265-00000001
[root@ip-192-168-1-110 ~]# ls /dev/disk/by-
by-id/ by-path/ by-uuid/
[root@ip-192-168-1-110 ~]# ls /dev/disk/by-uuid/
1f140d37-9663-48db-b32d-6cf5859b958f 388a99ed-9486-4a46-aeb6-06eaf6c47675
387f3e88-33ce-4eb9-8a2d-6c9a9233a15e a6581468-80a8-4c54-bc5c-55842807ead6
[root@ip-192-168-1-110 ~]# ll /dev/disk/by-uuid/
total 0
lrwxrwxrwx 1 root root 13 Nov 9 20:10 1f140d37-9663-48db-b32d-6cf5859b958f -> ../../nvme3n1
lrwxrwxrwx 1 root root 13 Nov 9 20:10 387f3e88-33ce-4eb9-8a2d-6c9a9233a15e -> ../../nvme1n1
lrwxrwxrwx 1 root root 15 Nov 9 20:10 388a99ed-9486-4a46-aeb6-06eaf6c47675 -> ../../nvme0n1p1
lrwxrwxrwx 1 root root 13 Nov 9 20:13 a6581468-80a8-4c54-bc5c-55842807ead6 -> ../../nvme2n1
[root@ip-192-168-1-110 ~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
nvme0n1 259:0 0 8G 0 disk
└─nvme0n1p1 259:1 0 8G 0 part /
nvme1n1 259:2 0 150G 0 disk
nvme2n1 259:3 0 50G 0 disk
nvme3n1 259:4 0 8G 0 disk
Terraform code (for one volume resource):
resource "aws_volume_attachment" "ebs_att" {
device_name = "/dev/xvdb"
volume_id = aws_ebs_volume.dev_build_data_dir.id
instance_id = aws_instance.dev_build.id
skip_destroy = "true"
}
resource "aws_ebs_volume" "dev_build_data_dir" {
availability_zone = var.AvailabilityZone
size = var.EbsDataVolumeSize
}
User data script (for one volume resource):
#!/bin/bash
if ! file -s /dev/nvme1n1 | grep 'XFS' &> /dev/null; then
mkfs -t xfs /dev/nvme1n1
fi
if [ ! -d "/opt/home/user/data" ]; then
mkdir -p /opt/home/user/data
fi
volume_uuid_nvme1n1=$(blkid | grep nvme1n1 |cut -d'"' -f2)
if ! grep $volume_uuid_nvme1n1 /etc/fstab &> /dev/null; then
echo "UUID=$volume_uuid_nvme1n1 /opt/home/user/data xfs defaults,nofail 0 2" | tee -a /etc/fstab
fi
if grep $volume_uuid_nvme1n1 /etc/fstab &> /dev/null; then
mount -a
chown -R user:user /opt/home/user/data
fi
Using Terraform does anyone have any solutions that will allow me to programmatically identify volumes and mount them?
