Re: cgd usage

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Wed, 4 Apr 2018 01:32:48 +0200
    From:        Thomas Klausner <tk%giga.or.at@localhost>
    Message-ID:  <20180403233248.swb2p7tiziks2aug@danbala>

  | Wouldn't it be better to check device availability before asking for
  | the passphrase?

Seems reasonable to me.  I am testing a modification now...
(While not all that hard, it isn't as trivial as it seems).

In the meantine, I find the appended script (next_avail) useful
rather than embedding cgdN type things in scripts, etc...

kre

#! /bin/sh

# Usage: next_avail cloner-type-disk
#	eg; next_avail vnd
#			(or cgd or raid ...)

next_avail ()
{
	local dev="$1"
	local N=$(( ${#dev} + 1 ))
	local unit units
	local nl='
'

	sysctl -n kern.drivers | tr ',' "$nl" | tr -d '][' |	
	    grep " ${dev}\$" >/dev/null 2>&1 || {
		echo >&2 "No ${dev} driver in booted kernel"
		return 1
	}

	units=$(
		sysctl -n hw.disknames				|
			tr ' ' '\012'			|
			grep '^'"${dev}"'[0-9]'			|
			sort -u -n -k 1.$N			)

	test -z "${units}" && {
		test -e "/dev/${dev}0a" || {
			echo >&2 "No ${dev}s available!"
			return 1
		}
		echo "${dev}0"
		return
	}

	N=0
	for unit in ${units}
	do
		if [ "${unit}" = "${dev}${N}" ]
		then
			N=$(( N + 1 ))
		else
			echo "${dev}${N}"
			return
		fi
	done

	test -e /dev/"${dev}${N}a" || {
		echo >&2 "All ${dev}s in use"
		return 1
	}

	echo "${dev}${N}"
}


for A
do
	next_avail "${A}"
done