50 lines
779 B
Bash
Executable File
50 lines
779 B
Bash
Executable File
#!/bin/sh
|
|
|
|
resolve() {
|
|
local domain="$1"
|
|
local server="$2"
|
|
|
|
if [ -x "$(command -v dig)" ]; then
|
|
if [ -z "$server" ]; then
|
|
dig +short "$domain"
|
|
else
|
|
dig +short "@$server" "$domain"
|
|
fi
|
|
return $?
|
|
fi
|
|
|
|
if [ -x "$(command -v drill)" ]; then
|
|
if [ -z "$server" ]; then
|
|
drill "$domain" | grep "^$domain." | cut -d$'\t' -f5
|
|
else
|
|
drill "@$server" "$domain" | grep "^$domain." |\
|
|
cut -d$'\t' -f5
|
|
fi
|
|
return $?
|
|
fi
|
|
exit 1
|
|
}
|
|
|
|
try_update() {
|
|
while read ip; do
|
|
if ntpdate -bu "$ip"; then
|
|
return 0
|
|
fi
|
|
done
|
|
|
|
return 1
|
|
}
|
|
|
|
pool="pool.ntp.org"
|
|
dns="1.1.1.1"
|
|
|
|
# try default DNS server first
|
|
resolve "$pool" "" | try_update
|
|
[ $? -eq 0 ] && exit 0
|
|
|
|
# try fallback public dns server
|
|
ping -q -c 1 "$dns" || exit 1
|
|
|
|
resolve "$pool" "$dns" | try_update
|
|
exit $?
|