Linux – How to make a dmsetup change permanent

datastoreiscsilinuxstorage-area-network

The full case is the following:

  • I attach a LUN from a SAN box (iscsi configuration has been done correctly)
  • As soon as I restart the open-iscsi daemon, the LUN is attached and its name appears under /dev/mapper is something like the following string: 360060e80104dac0004f349c800000001

Now I don't want to use this alphanumeric, I need a decent mnemonic. So, I use the dmsetup command as follows:
# dmsetup rename 360060e80104dac0004f349c800000001 datastore

and a datastore link to a dm device appears under /dev/mapper. Problem solved, until the next reboot. where the datastore mnemonic is gone and the above alphanumeric appears again under /dev/mapper.

How do I make this change permanent?

Best Answer

Consider referencing the LUN via /dev/disk/by-{id,path,uuid} instead of trying to rename WWN every time.

Or maybe you can make a udev(7) rule to create a static node under /dev representing your block device based on attributes related to your WWN. You can get all the attributes with udevadm(8). A good starting point would be ID_WWN_WITH_EXTENSION:

ENV{ID_WWN_WITH_EXTENSION}=="360060e80104dac0004f349c800000001", SYMLINK+="iscsi/datastore"

This creates a symlink at /dev/iscsi/datastore that points to your iscsi LUN.

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