UDEV SCSI Rules Configuration for ASM in Oracle Linux 5, 6 and 7

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UDEVSCSI Rules Configuration for ASM in Oracle Linux 5, 6 and 7

For Oracle Automatic Storage Manager (ASM) touse disks, it needs to be able to identify the devices consistently and forthem to have the correct ownership and permissions. In Linux you can use ASMLibto manage these tasks, but it is seen as an additional layer of complexity andhas never really gained any popularity. Instead, many people use the Linuxdevice manager "udev" to perform these tasks. This article presents abrief overview of setting up udev rules with respect to disks for use with ASMin Oracle 11g. The examples are all done using Oracle Linux 5, 6 and 7, so theywill be consistent with RHEL and CentOS 5, 6 and 7.

Background
Identify the Disks (/sbin/scsi_id)
Make SCSI Devices Trusted
Create UDEV Rules File
Load Updated Block Device Partitions (/sbin/partprobe)
Test Rules (udevtest)
Restart UDEV Service
Check Ownership and Permissions

Background

Essentially, what udev does is apply rulesdefined in files in the "/etc/udev/rules.d" directory to the devicenodes listed in the "/dev" directory. The rules can be defined in avariety of ways, but what we need to do is identify the device and say what wewant udev to do with it.

In this case I know all my disk devices arenamed "/dev/sd?1", where the "?" represents a letter froma-d, so I can identify the devices of interest using the following ruleparameters.

KERNEL=="sd?1",BUS=="scsi"

I want to tie each specific device to analias, so it is always identified the same way, regardless of the device nameLinux assigns it. So I need to be able to test each device that matches theprevious pattern to see if it is the disk I am interested in. Each disk has aunique SCSI ID, so I can place a test into the rule, telling it how to performthe test, and the result it should return for a positive match. The followingrule parameters explain how to test the device and what result constitutes amatch in Oracle Linux 5.

PROGRAM=="/sbin/scsi_id -g -u -s/block/$parent", RESULT=="SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_"

The scsi_id command works a little differently in Oracle Linux 6, sofor that the following test works better.

PROGRAM=="/sbin/scsi_id -g -u -d/dev/$parent", RESULT=="SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_"

The scsi_id command is located in a different place in Oracle Linux7, so for that the following test is correct.

PROGRAM=="/usr/lib/udev/scsi_id -g -u -d/dev/$parent", RESULT=="SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_"

Once we have identified the specific deviceof interest, we need to indicate what actions should be performed on it. Thefollowing parameters specify an alias, the ownership and the permissions forthe device.

NAME="asm-disk1",OWNER="oracle", GROUP="dba", MODE="0660"

So the whole rule for each disk will looksomething like this in Oracle Linux 5.

KERNEL=="sd?1",BUS=="scsi", PROGRAM=="/sbin/scsi_id -g -u -s/block/$parent",RESULT=="SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_",NAME="asm-disk1", OWNER="oracle", GROUP="dba",MODE="0660"

Or this in Oracle Linux 6.

KERNEL=="sd?1", BUS=="scsi",PROGRAM=="/sbin/scsi_id -g -u -d /dev/$parent",RESULT=="SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_",NAME="asm-disk1", OWNER="oracle", GROUP="dba",MODE="0660"

Or this in Oracle Linux 7.

KERNEL=="sd?1",SUBSYSTEM=="block", PROGRAM=="/usr/lib/udev/scsi_id -g -u -d/dev/$parent",RESULT=="SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_",SYMLINK+="asm-disk1", OWNER="oracle",GROUP="dba", MODE="0660"

This means that the device pointing to thepartition "sd*1" on the disk with the SCSI ID of"SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_" will always be called"/dev/asm-disk1", regardless of the letter "?" Linuxassigns when the device is discovered. In addition, the device will have thecorrect ownership and permissions for ASM.

There are a number of wildcards and matchingpatterns that can be used if you don't want to write device-specific rules.

Now we know roughly what we are trying toachieve, we will look at each step necessary for setting up the disks for ASMto use.

Identifythe Disks (/sbin/scsi_id)

We are going to write device-specific rules,so we need to be able to identify each device consistently, irrespective of theorder in which Linux discovers it. To do this we are going to use the SCSI IDfor each disk (not the partition), which we get using the scsi_id command. The "-s" option makes the pathsrelative to the "/sys" directory. For Oracle Linux 5, use thefollowing command.

# /sbin/scsi_id -g -u -s /block/sdb

SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_

# /sbin/scsi_id -g -u -s /block/sdc

SATA_VBOX_HARDDISK_VB46dec7e0-192e8000_

# /sbin/scsi_id -g -u -s /block/sdd

SATA_VBOX_HARDDISK_VBce8c63bb-ac67a172_

# /sbin/scsi_id -g -u -s /block/sde

SATA_VBOX_HARDDISK_VB7437a3b7-95b199cd_

The "-s" is not available in OracleLinux 6, so you must use the following syntax.

# /sbin/scsi_id -g -u -d /dev/sdb

SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_

# /sbin/scsi_id -g -u -d /dev/sdc

SATA_VBOX_HARDDISK_VB46dec7e0-192e8000_

# /sbin/scsi_id -g -u -d /dev/sdd

SATA_VBOX_HARDDISK_VBce8c63bb-ac67a172_

# /sbin/scsi_id -g -u -d /dev/sde

SATA_VBOX_HARDDISK_VB7437a3b7-95b199cd_

The location of the scsi_id command has changed in Oracle Linux 7, so you must usethe following syntax.

# /usr/lib/udev/scsi_id -g -u -d /dev/sdb

SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_

# /usr/lib/udev/scsi_id -g -u -d /dev/sdc

SATA_VBOX_HARDDISK_VB46dec7e0-192e8000_

# /usr/lib/udev/scsi_id -g -u -d /dev/sdd

SATA_VBOX_HARDDISK_VBce8c63bb-ac67a172_

# /usr/lib/udev/scsi_id -g -u -d /dev/sde

SATA_VBOX_HARDDISK_VB7437a3b7-95b199cd_

Make SCSIDevices Trusted

Add the following to the"/etc/scsi_id.config" file to configure SCSI devices as trusted.Create the file if it doesn't already exist.

options=-g

CreateUDEV Rules File

Create the"/etc/udev/rules.d/99-oracle-asmdevices.rules" file.

# vi /etc/udev/rules.d/99-oracle-asmdevices.rules

The file should contain the following linesfor Oracle Linux 5. The PROGRAM parameter must match the command you used to retrieve theSCSI ID, and the RESULT parameter must match the value returned from your disks.

KERNEL=="sd?1", BUS=="scsi",PROGRAM=="/sbin/scsi_id -g -u -s /block/$parent",RESULT=="SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_",NAME="asm-disk1", OWNER="oracle", GROUP="dba",MODE="0660"

KERNEL=="sd?1",BUS=="scsi", PROGRAM=="/sbin/scsi_id -g -u -s/block/$parent", RESULT=="SATA_VBOX_HARDDISK_VB46dec7e0-192e8000_",NAME="asm-disk2", OWNER="oracle", GROUP="dba",MODE="0660"

KERNEL=="sd?1",BUS=="scsi", PROGRAM=="/sbin/scsi_id -g -u -s/block/$parent",RESULT=="SATA_VBOX_HARDDISK_VBce8c63bb-ac67a172_",NAME="asm-disk3", OWNER="oracle", GROUP="dba",MODE="0660"

KERNEL=="sd?1",BUS=="scsi", PROGRAM=="/sbin/scsi_id -g -u -s/block/$parent",RESULT=="SATA_VBOX_HARDDISK_VB7437a3b7-95b199cd_",NAME="asm-disk4", OWNER="oracle", GROUP="dba",MODE="0660"

The equivalent for Oracle Linux 6 is shownbelow.

KERNEL=="sd?1",BUS=="scsi", PROGRAM=="/sbin/scsi_id -g -u -d/dev/$parent",RESULT=="SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_",NAME="asm-disk1", OWNER="oracle", GROUP="dba",MODE="0660"

KERNEL=="sd?1",BUS=="scsi", PROGRAM=="/sbin/scsi_id -g -u -d/dev/$parent",RESULT=="SATA_VBOX_HARDDISK_VB46dec7e0-192e8000_",NAME="asm-disk2", OWNER="oracle", GROUP="dba",MODE="0660"

KERNEL=="sd?1",BUS=="scsi", PROGRAM=="/sbin/scsi_id -g -u -d/dev/$parent", RESULT=="SATA_VBOX_HARDDISK_VBce8c63bb-ac67a172_",NAME="asm-disk3", OWNER="oracle", GROUP="dba",MODE="0660"

KERNEL=="sd?1",BUS=="scsi", PROGRAM=="/sbin/scsi_id -g -u -d/dev/$parent",RESULT=="SATA_VBOX_HARDDISK_VB7437a3b7-95b199cd_",NAME="asm-disk4", OWNER="oracle", GROUP="dba",MODE="0660"

The equivalent for Oracle Linux 7 is shownbelow.

KERNEL=="sd?1",SUBSYSTEM=="block", PROGRAM=="/usr/lib/udev/scsi_id -g -u -d/dev/$parent",RESULT=="SATA_VBOX_HARDDISK_VB46dec7e0-192e8000_",SYMLINK+="asm-disk2", OWNER="oracle", GROUP="dba",MODE="0660"

KERNEL=="sd?1",SUBSYSTEM=="block", PROGRAM=="/usr/lib/udev/scsi_id -g -u -d/dev/$parent", RESULT=="SATA_VBOX_HARDDISK_VBce8c63bb-ac67a172",SYMLINK+="asm-disk3", OWNER="oracle",GROUP="dba", MODE="0660"

KERNEL=="sd?1",SUBSYSTEM=="block", PROGRAM=="/usr/lib/udev/scsi_id -g -u -d/dev/$parent", RESULT=="SATA_VBOX_HARDDISK_VB7437a3b7-95b199cd_",SYMLINK+="asm-disk4", OWNER="oracle",GROUP="dba", MODE="0660"

LoadUpdated Block Device Partitions (/sbin/partprobe)

Load updated block device partition tables.

# /sbin/partprobe /dev/sdb1

# /sbin/partprobe /dev/sdc1

# /sbin/partprobe /dev/sdd1

# /sbin/partprobe /dev/sde1

Test Rules(udevtest)

Test the rules are working as expected.

# #OL5

# udevtest /block/sdb/sdb1

# udevtest /block/sdc/sdc1

# udevtest /block/sdd/sdd1

# udevtest /block/sde/sde1

# #OL6 and OL7

# udevadm test /block/sdb/sdb1

# udevadm test /block/sdc/sdc1

# udevadm test /block/sdd/sdd1

# udevadm test /block/sde/sde1

The output from the first disk should looksomething like this.

# udevtest /block/sdb/sdb1

main: looking at device '/block/sdb/sdb1'from subsystem 'block'

udev_rules_get_name: add symlink'disk/by-id/scsi-SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3-part1'

udev_rules_get_name: add symlink'disk/by-path/pci-0000:00:0d.0-scsi-1:0:0:0-part1'

run_program: '/lib/udev/vol_id --export/dev/.tmp-8-17'

run_program: '/lib/udev/vol_id' returned withstatus 4

run_program: '/sbin/scsi_id -g -u -s/block/sdb/sdb1'

run_program: '/sbin/scsi_id' (stdout)'SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3_'

run_program: '/sbin/scsi_id' returned withstatus 0

udev_rules_get_name: rule applied, 'sdb1'becomes 'asm-disk1'

udev_device_event: device '/block/sdb/sdb1'already in database, validate currently present symlinks

udev_node_add: creating device node'/dev/asm-disk1', major = '8', minor = '17', mode = '0660', uid = '1100', gid ='1200'

udev_node_add: creating symlink'/dev/disk/by-id/scsi-SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3-part1' to'../../asm-disk1'

udev_node_add: creating symlink'/dev/disk/by-path/pci-0000:00:0d.0-scsi-1:0:0:0-part1' to '../../asm-disk1'

main: run: 'socket:/org/kernel/dm/multipath_event'

main: run: 'socket:/org/kernel/udev/monitor'

main: run: '/lib/udev/udev_run_devd'

main: run:'socket:/org/freedesktop/hal/udev_event'

main: run: '/sbin/pam_console_apply/dev/asm-disk1 /dev/disk/by-id/scsi-SATA_VBOX_HARDDISK_VBd306dbe0-df3367e3-part1/dev/disk/by-path/pci-0000:00:0d.0-scsi-1:0:0:0-part1'

RestartUDEV Service

Restart the UDEV service.

# #OL5

# /sbin/udevcontrol reload_rules

# #OL6 and OL7

# udevadm control --reload-rules

# #OL5 and OL6 : Not needed for OL7

# /sbin/start_udev

CheckOwnership and Permissions

Check the disks are now available with the"asm-disk*" alias and the correct ownership and permissions.

# cd /dev

# ls -al asm-disk*