DISK INIT error: open device failed

On modern and secure operating systems, everything is secured with permissions and never production services are started using a high privileged accounts. That is good, as the systems are better secured and even one compromised service will not cause failing the entire server or application. On the other hand administering such a good secured system can become nightmare, because you will ever and ever receive error messages, when the permissions are not set correctly.

Let's look at following example. You want to create a new raw device for SAP Sybase databases:

disk init name='BetaDataDev', physname ='/dev/sdb1', size=5120
disk init name='BetaLogDev', physname ='/dev/sdb2', size=2560

When starting the command following error is shown:

DISK INIT encountered an error while attempting to open/create the physical file for device '/deb/sdb1'. Consult the Adaptive Server error log for more details. For the cluster edition, check the error log of each instance.

So let's look into the error log:

tail /opt/sap/SAP-16_0/install/SAP01.log

What can be found there?

00:0006:00000:00026:2017/03/19 10:47:47.73 kernel  basis_dsizecheck: attempt to open device '/dev/sdb1' failed, system error is: Permission denied

What does it mean? Sybase is running on the system on some specific account. This account does not have access to the device file /dev/sdb1. Let's change the permission, for example changing the owner of the device:

chown sap /dev/sdb1
chown sap /dev/sdb2

Well, it is time to retry the creation of devices:

disk init name='BetaDataDev', physname ='/dev/sdb1', size=5120
disk init name='BetaLogDev', physname ='/dev/sdb2', size=2560

Now the operation should succeed, and in the error log something similar should be recorded:

00:0006:00000:00026:2017/03/19 11:02:52.01 kernel  Initializing virtual device 7, '/dev/sdb1' with dsync 'off'.

00:0006:00000:00026:2017/03/19 11:02:52.01 kernel  Virtual device 7 started using asynchronous 

00:0006:00000:00026:2017/03/19 11:04:12.19 kernel  Initializing virtual device 8, '/dev/sdb2' with dsync 'off'.

00:0006:00000:00026:2017/03/19 11:04:12.19 kernel  Virtual device 8 started using asynchronous (with DIRECTIO) i/o.