62 lines
1.6 KiB
Bash
Executable File
62 lines
1.6 KiB
Bash
Executable File
#!/bin/bash
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# Emulate genhostid(1) available on RHEL/CENTOS, for use on distros
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# which do not provide that utility.
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#
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# Usage:
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# zgenhostid
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# zgenhostid <value>
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#
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# If /etc/hostid already exists and is size > 0, the script exits immediately
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# and changes nothing. Unlike genhostid, this generates an error message.
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#
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# The first form generates a random hostid and stores it in /etc/hostid.
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# The second form checks that the provided value is between 0x1 and 0xFFFFFFFF
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# and if so, stores it in /etc/hostid. This form is not supported by
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# genhostid(1).
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hostid_file=/etc/hostid
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function usage {
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echo "$0 [value]"
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echo "If $hostid_file is not present, store a hostid in it." >&2
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echo "The optional value must be an 8-digit hex number between" >&2
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echo "1 and 2^32-1. If no value is provided, a random one will" >&2
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echo "be generated. The value must be unique among your systems." >&2
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}
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# hostid(1) ignores contents of /etc/hostid if size < 4 bytes. It would
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# be better if this checked size >= 4 bytes but it the method must be
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# widely portable.
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if [ -s $hostid_file ]; then
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echo "$hostid_file already exists. No change made." >&2
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exit 1
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fi
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if [ -n "$1" ]; then
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host_id=$1
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else
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# $RANDOM goes from 0..32k-1
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number=$((((RANDOM % 4) * 32768 + RANDOM) * 32768 + RANDOM))
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host_id=$(printf "%08x" $number)
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fi
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if egrep -o '^0{8}$' <<< $host_id >/dev/null 2>&1; then
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usage
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exit 2
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fi
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if ! egrep -o '^[a-fA-F0-9]{8}$' <<< $host_id >/dev/null 2>&1; then
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usage
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exit 3
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fi
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a=${host_id:6:2}
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b=${host_id:4:2}
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c=${host_id:2:2}
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d=${host_id:0:2}
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echo -ne \\x$a\\x$b\\x$c\\x$d > $hostid_file
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exit 0
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