Re: [Astlinux-devel] When does DNS come up ?

[David K. <da...@ke...>]

Thanks Lonnie, that explains what I was seeing.  I have implemented the
background trick you suggest.

Thanks
David

On Sat, Dec 19, 2020 at 10:13 AM Lonnie Abelbeck <li...@lo...>
wrote:

>
> > On Dec 19, 2020, at 7:54 AM, David Kerr <da...@ke...> wrote:
> >
> > Can anyone tell me when DNS comes up during the boot process?  I am
> doing a host lookup within my firewall custom rules script $(host -t A
> $fqdn) and it appears to get no IP address when the firewall is setup
> during boot, but works fine if I do a firewall restart after the system has
> booted up.
> >
> > Thanks
>
> Hi David,
>
> The order of the startup "Snn*" script symlinks are:
>
> pbx3 ~ # cd /etc/runlevels/default/
>
> pbx3 ~ # ls -l S*
> ...
> lrwxrwxrwx    1 root     root            20 Dec 16 21:34 S03network ->
> ../../init.d/network
> lrwxrwxrwx    1 root     root            19 Dec 16 21:34 S04elocal ->
> ../../init.d/elocal
> lrwxrwxrwx    1 root     root            21 Dec 16 21:34 S05watchdog ->
> ../../init.d/watchdog
> lrwxrwxrwx    1 root     root            22 Dec 16 21:34 S06lmsensors ->
> ../../init.d/lmsensors
> lrwxrwxrwx    1 root     root            19 Dec 16 21:34 S08msmtpd ->
> ../../init.d/msmtpd
> lrwxrwxrwx    1 root     root            18 Dec 16 21:34 S09crond ->
> ../../init.d/crond
> lrwxrwxrwx    1 root     root            21 Dec 16 21:34 S10iptables ->
> ../../init.d/iptables
> lrwxrwxrwx    1 root     root            23 Dec 16 21:34 S11netsyslogd ->
> ../../init.d/netsyslogd
> lrwxrwxrwx    1 root     root            18 Dec 16 21:34 S11snmpd ->
> ../../init.d/snmpd
> lrwxrwxrwx    1 root     root            23 Dec 16 21:34 S12keepalived ->
> ../../init.d/keepalived
> lrwxrwxrwx    1 root     root            21 Dec 16 21:34 S18dnscrypt ->
> ../../init.d/dnscrypt
> lrwxrwxrwx    1 root     root            20 Dec 16 21:34 S18unbound ->
> ../../init.d/unbound
> lrwxrwxrwx    1 root     root            20 Dec 16 21:34 S20dnsmasq ->
> ../../init.d/dnsmasq
> ...
>
> So the firewall starts at S10, and DNS starts at S20.
>
> If you want to keep the $(host -t A $fqdn) in the firewall custom-rules,
> you could spawn a background sub-shell, something like:
>
> https://github.com/astlinux-project/astlinux/blob/c3ff8beba28533487c65d77e9ec2d54dd9facc3b/package/openssh/sshd.init#L144
>
> Off the top of my head , untested...
> --
> fqdn="example.com"
> (
>   cnt=6
>   while [ $cnt -gt 0 ]; do
>     cnt=$((cnt - 1))
>     sleep 10
>
>     A="$(host -t A $fqdn | sed -n -r -e 's#^.* has address
> ([0-9.]+)$#\1#p')"
>     if [ -n "$A" ]; then
>       ## use $A example ##
>       echo "$A" > /tmp/test
>       exit
>     fi
>   done
> ) >/dev/null 2>&1 &
> --
>
> Adjust the retry 'cnt' and sleep delay to your liking.
>
> Lonnie
>
>
>
>
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