/lib/udev/rules.d/65-drbd.rules is in drbd8-utils 2:8.4.4-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | # This file contains the rules to create named DRBD devices.
# DO NOT WRAP THIS LINE
#
# old udev does not understand some of it,
# and would end up skipping only some lines, not the full rule.
# which can cause all sort of trouble with strange-named device nodes
# for completely unrelated devices,
# resulting in unusable network lookback, etc.
#
# in case this is "accidentally" installed on a system with old udev,
# having it as one single line avoids those problems.
#
# DO NOT WRAP THIS LINE
SUBSYSTEM=="block", KERNEL=="drbd*", IMPORT{program}="/sbin/drbdadm sh-udev minor-%m", NAME="$env{DEVICE}", SYMLINK="drbd/by-res/$env{RESOURCE} drbd/by-disk/$env{DISK}"
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