Udev Rules for AWS EBS Volumes

AWS EBS volumes could be used as ASM disks. When ASMLib or AFD is not used, udev rules must be used to set the correct permissions on the EBS block volumes. It's generally good practice to use a unique identifier (UUID) to identify the partitions that require permission being set. It's not a guarantee that partitions or the blocks will be attached to the server in the same order and getting the same name.
Depending on the tool/option used a unique identifier may not be always available. For example the default dos partition table type created using fdisk would not generate any unique ID.

Model: Xen Virtual Block Device (xvd)
Disk /dev/xvdb: 268GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number  Start   End    Size   Type     File system  Flags
 1      1049kB  268GB  268GB  primary  ext4

udevadm info --query=property /dev/xvdd1
DEVNAME=/dev/xvdd1
DEVPATH=/devices/vbd-51760/block/xvdd/xvdd1
DEVTYPE=partition
ID_PART_ENTRY_DISK=202:48
ID_PART_ENTRY_NUMBER=1
ID_PART_ENTRY_OFFSET=2048
ID_PART_ENTRY_SCHEME=dos
ID_PART_ENTRY_SIZE=209713152
ID_PART_ENTRY_TYPE=0x83
ID_PART_TABLE_TYPE=dos
MAJOR=202
MINOR=49
SUBSYSTEM=block
TAGS=:systemd:
USEC_INITIALIZED=634695673

On the other-hand if the partition table type was GPT, this could generate several unique IDs which could be used in the udev rule to identify the partition.

fdisk /dev/sdd

Command (m for help): g
Building a new GPT disklabel (GUID: EC7F1589-8BD2-4C94-8F8F-D22013D40406)


Command (m for help): n
Partition number (1-128, default 1):
First sector (2048-20971486, default 2048):
Last sector, +sectors or +size{K,M,G,T,P} (2048-20971486, default 20971486):
Created partition 1


Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

 fdisk -l /dev/sdd
WARNING: fdisk GPT support is currently new, and therefore in an experimental phase. Use at your own discretion.

Disk /dev/sdd: 10.7 GB, 10737418240 bytes, 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: gpt
Disk identifier: EC7F1589-8BD2-4C94-8F8F-D22013D40406


#         Start          End    Size  Type            Name
 1         2048     20971486     10G  Linux filesyste

udevadm info --query=property /dev/sdd1
...
ID_PART_ENTRY_DISK=8:48
ID_PART_ENTRY_NUMBER=1
ID_PART_ENTRY_OFFSET=2048
ID_PART_ENTRY_SCHEME=gpt
ID_PART_ENTRY_SIZE=20969439
ID_PART_ENTRY_TYPE=0fc63daf-8483-4772-8e79-3d69d8477de4
ID_PART_ENTRY_UUID=573dded4-21f1-48ce-925f-e02c5d94dace
ID_PART_TABLE_TYPE=gpt
ID_PATH=pci-0000:00:0d.0-ata-4.0
ID_PATH_TAG=pci-0000_00_0d_0-ata-4_0
...
SUBSYSTEM=block
TAGS=:systemd:

The partition UUID could be found out using blkid as well.

blkid /dev/sdd1
/dev/sdd1: PARTLABEL="data" PARTUUID="573dded4-21f1-48ce-925f-e02c5d94dace"

The ID_PART_ENTRY_UUID could be used in the udev rule.

KERNEL=="sd?1",ENV{ID_PART_ENTRY_UUID}=="573dded4-21f1-48ce-925f-e02c5d94dace", SYMLINK+="oracleasm/cgdata1", OWNER="oracle", GROUP="asmadmin", MODE="0660"

Similar to fdisk with g (gpt) option, parted could be used to achieve the same.

parted /dev/xvdd
GNU Parted 3.1
Using /dev/xvdd
Welcome to GNU Parted! Type 'help' to view a list of commands.
(parted) mktable gpt
Warning: The existing disk label on /dev/xvdd will be destroyed and all data on this disk will be lost. Do you want to continue?
Yes/No? yes
(parted) mkpart data 0% 100%

(parted) print all
Model: Xen Virtual Block Device (xvd)
Disk /dev/xvdd: 107GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start   End    Size   File system  Name  Flags
 1      1049kB  107GB  107GB               data

udevadm info --query=property /dev/xvdd1
DEVLINKS=/dev/disk/by-partlabel/data /dev/disk/by-partuuid/5a081ffa-56e2-467b-82a9-16e3a4f441bd
DEVNAME=/dev/xvdd1
DEVPATH=/devices/vbd-51760/block/xvdd/xvdd1
DEVTYPE=partition
ID_PART_ENTRY_DISK=202:48
ID_PART_ENTRY_NAME=data
ID_PART_ENTRY_NUMBER=1
ID_PART_ENTRY_OFFSET=2048
ID_PART_ENTRY_SCHEME=gpt
ID_PART_ENTRY_SIZE=209711104
ID_PART_ENTRY_TYPE=ebd0a0a2-b9e5-4433-87c0-68b6b72699c7
ID_PART_ENTRY_UUID=5a081ffa-56e2-467b-82a9-16e3a4f441bd
ID_PART_TABLE_TYPE=gpt
MAJOR=202
MINOR=49
SUBSYSTEM=block
TAGS=:systemd:
USEC_INITIALIZED=685327395