Getting '/dev/sdx: Can't open blockdev' messages in logs

Solution Verified - Updated -


  • Getting /dev/sdx: Can't open blockdev messages in logs

    register_make_request(mms,7731): OK. kdev=8:2, mq=1.
    snumbdctl_open(mms,19633): OK s=000000005xxxxxxx
    session_init(mms,19633): OK. kdev=fc:1, len=8388608 sect=512 s=000000005xxxxxxx pgrp=(64865).
    snumbd_open_blk(systemd-udevd,19635): Disable access (868,64865,64865)...
    snumbdctl_release(mms,19633): OK s=000000005xxxxxxx
    /dev/sdad: Can't open blockdev
    /dev/sdag: Can't open blockdev
    /dev/sdar: Can't open blockdev


  • Red Hat Enterprise Linux 8.4
  • Acronis Snapshot kernel API (snapapi26.ko)
  • Acronis User Mode Block Device (snumbd26.ko)

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