About Device Path Persistence
Understand device path persistence for Oracle Automatic Storage Management (Oracle ASM).
By default, the device file naming scheme udev
dynamically
creates device file names when the server is started, and assigns ownership of them to
root. If udev
applies default settings, then it changes Oracle device
file names and owners for the disks, making the disks inaccessible when the server is
restarted. For example, a voting disk on a device named /dev/sdd
owned by the user grid
may be on a device named
/dev/sdf
owned by root after restarting the server.
If you use Oracle ASMFD, then you do not have to ensure permissions and
device path persistence in udev
.
If you do not use Oracle ASMFD, then you must create a custom rules file.
Linux vendors customize their udev
configurations and use different
orders for reading rules files. For example, on some Linux distributions when
udev
is started, it sequentially carries out rules (configuration
directives) defined in rules files. These files are in the path
/etc/udev/rules.d/
. Rules files are read in lexical order. For example,
rules in the file 10-wacom.rules
are parsed and carried out before
rules in the rules file 90-ib.rules
.
When specifying the device information in the udev
rules
file, ensure that the OWNER, GROUP, and MODE are specified before all other
characteristics in the order shown. For example, to include the characteristic ACTION on
the UDEV line, specify ACTION after OWNER, GROUP, and MODE.
Where rules files describe the same devices, on the supported Linux kernel versions, the last file read is the one that is applied.
Parent topic: Configuring Storage Device Path Persistence Manually