* Autamatically populate resolv.conf when new DNS is acquired
@ 2018-06-26 16:11 john doe
2018-06-26 19:23 ` Automatically " Brian Inglis
2018-06-27 11:01 ` Autamatically " Andrey Repin
0 siblings, 2 replies; 6+ messages in thread
From: john doe @ 2018-06-26 16:11 UTC (permalink / raw)
To: cygwin
Hi,
In gnupg2 the use of dirmngr utility is required to interact with a
keyserver.
Dirmngr requires that '/etc/resolv.conf' be populated with my name servers.
That means that everytime the dns changes (new network ...) I need to
manually edit that file.
How can I let Cygwin update that file whenever the DNS is changed?
--
John Doe
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Automatically populate resolv.conf when new DNS is acquired
2018-06-26 16:11 Autamatically populate resolv.conf when new DNS is acquired john doe
@ 2018-06-26 19:23 ` Brian Inglis
2018-06-27 11:08 ` john doe
2018-06-27 11:01 ` Autamatically " Andrey Repin
1 sibling, 1 reply; 6+ messages in thread
From: Brian Inglis @ 2018-06-26 19:23 UTC (permalink / raw)
To: cygwin
[-- Attachment #1: Type: text/plain, Size: 1372 bytes --]
On 2018-06-26 04:33, john doe wrote:
> In gnupg2 the use of dirmngr utility is required to interact with a keyserver.
> Dirmngr requires that '/etc/resolv.conf' be populated with my name servers.
> That means that everytime the dns changes (new network ...) I need to manually
> edit that file.
> How can I let Cygwin update that file whenever the DNS is changed?
Attached an awk script to generate resolv.conf from Windows ipconfig /all
output, run from .cygwin_profile (sourced under Cygwin from login .bash_profile)
using the stanza below: it only replaces an existing writable /etc/resolv.conf
when the content changes - touch, chown, chmod /etc/resolv.conf to enable.
# update /etc/resolv.conf if changed
c=/etc/resolv.conf
test -w $c && \
i=$(/usr/bin/which -- ipconfig) && \
r=$(/usr/bin/which -- resolv.awk) && \
t=$(/bin/mktemp -t -- resolv.conf.$$.XXXXXXXX) && \
if $i /all | $r > $t; then
/usr/bin/cmp -s -- $t $c || \
/bin/cp -fv -- $t $c
/bin/rm -f -- $t
fi
unset c i r t
This could be used in a bash script run from a Windows scheduled task when a
relevant DHCP event occurs: you can find DHCP events by checking Windows Admin
Tools/Event Viewer/Window Logs/System/Filter Current Log/Event
Sources/Dhcp-Client,DHCPv6-Client, or a similar PowerShell script.
--
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
[-- Attachment #2: resolv.awk --]
[-- Type: text/plain, Size: 766 bytes --]
#!/usr/bin/awk -f
# resolv.awk - create Windows resolv.conf from ipconfig /all output
{ sub( /\r/, "", $NF) } # trim \r
# collect DNS domain suffixes
/D[Nn][Ss]\sSuffix[^:]*:\s\S/ { domain[$NF] = $NF }
# collect DNS search suffixes
/Search\sList[^:]*:\s\S/ { search[$NF] = $NF }
# collect DNS server IP addresses
/DNS\sServers[^:]*:\s\S/ { dns = 1 } # enable
dns && $NF ~ /^[0-9.]+$/ { nameserver[++ns] = $NF } # collect
dns && $NF !~ /^[0-9.]+$/ { dns = 0 } # disable
# output unique resolv.conf entries
END {
for (n = 1; n <= ns; ++n) { print "nameserver", nameserver[n] }
for (d in domain) { print "domain", domain[d] }
p = "search"
for (s in search) {
printf "%s %s", p, search[s]
p = ""
}
if (!p) { print p }
}
[-- Attachment #3: Type: text/plain, Size: 219 bytes --]
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Autamatically populate resolv.conf when new DNS is acquired
2018-06-26 16:11 Autamatically populate resolv.conf when new DNS is acquired john doe
2018-06-26 19:23 ` Automatically " Brian Inglis
@ 2018-06-27 11:01 ` Andrey Repin
2018-06-27 16:10 ` john doe
1 sibling, 1 reply; 6+ messages in thread
From: Andrey Repin @ 2018-06-27 11:01 UTC (permalink / raw)
To: john doe, cygwin
Greetings, john doe!
> In gnupg2 the use of dirmngr utility is required to interact with a
> keyserver.
> Dirmngr requires that '/etc/resolv.conf' be populated with my name servers.
Looks like an upstream bug. /etc/resolv.conf is not a required file for DNS
resolution.
> That means that everytime the dns changes (new network ...) I need to
> manually edit that file.
> How can I let Cygwin update that file whenever the DNS is changed?
--
With best regards,
Andrey Repin
Wednesday, June 27, 2018 10:44:06
Sorry for my terrible english...
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Automatically populate resolv.conf when new DNS is acquired
2018-06-26 19:23 ` Automatically " Brian Inglis
@ 2018-06-27 11:08 ` john doe
2018-06-28 4:40 ` Brian Inglis
0 siblings, 1 reply; 6+ messages in thread
From: john doe @ 2018-06-27 11:08 UTC (permalink / raw)
To: cygwin
Good morning Brian, bottom posting.
On 6/26/2018 4:18 PM, Brian Inglis wrote:
> On 2018-06-26 04:33, john doe wrote:
>> In gnupg2 the use of dirmngr utility is required to interact with a keyserver.
>> Dirmngr requires that '/etc/resolv.conf' be populated with my name servers.
>> That means that everytime the dns changes (new network ...) I need to manually
>> edit that file.
>> How can I let Cygwin update that file whenever the DNS is changed?
>
> Attached an awk script to generate resolv.conf from Windows ipconfig /all
> output, run from .cygwin_profile (sourced under Cygwin from login .bash_profile)
> using the stanza below: it only replaces an existing writable /etc/resolv.conf
> when the content changes - touch, chown, chmod /etc/resolv.conf to enable.
>
> # update /etc/resolv.conf if changed
> c=/etc/resolv.conf
> test -w $c && \
> i=$(/usr/bin/which -- ipconfig) && \
> r=$(/usr/bin/which -- resolv.awk) && \
> t=$(/bin/mktemp -t -- resolv.conf.$$.XXXXXXXX) && \
> if $i /all | $r > $t; then
> /usr/bin/cmp -s -- $t $c || \
> /bin/cp -fv -- $t $c
> /bin/rm -f -- $t
> fi
>
> unset c i r t
>
> This could be used in a bash script run from a Windows scheduled task when a
> relevant DHCP event occurs: you can find DHCP events by checking Windows Admin
> Tools/Event Viewer/Window Logs/System/Filter Current Log/Event
> Sources/Dhcp-Client,DHCPv6-Client, or a similar PowerShell script.
>
Thanks for the awk script and the explanation on how to use it! :)
By Windows Admin you mean "Windows Admin Center"?
I'm using Cygwin on a laptop (win 7 pro) and sadly, if I'm not
mistaking, "Windows Admin" is not available on non-server platform.
If I can't find a way to determine when my DNS changes I can clearly
emulate an hourly cron job by using "task scheduler".
Many thanks for the task scheduler hint and for your help.
--
John Doe
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Autamatically populate resolv.conf when new DNS is acquired
2018-06-27 11:01 ` Autamatically " Andrey Repin
@ 2018-06-27 16:10 ` john doe
0 siblings, 0 replies; 6+ messages in thread
From: john doe @ 2018-06-27 16:10 UTC (permalink / raw)
To: cygwin
On 6/27/2018 9:45 AM, Andrey Repin wrote:
> Greetings, john doe!
>
>> In gnupg2 the use of dirmngr utility is required to interact with a
>> keyserver.
>
>> Dirmngr requires that '/etc/resolv.conf' be populated with my name servers.
>
> Looks like an upstream bug. /etc/resolv.conf is not a required file for DNS
> resolution.
>
Yes, I have also contacted the dirmngr developer regarding that issue.
But I have to find a work around in the meantime! :)
--
John Doe
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Automatically populate resolv.conf when new DNS is acquired
2018-06-27 11:08 ` john doe
@ 2018-06-28 4:40 ` Brian Inglis
0 siblings, 0 replies; 6+ messages in thread
From: Brian Inglis @ 2018-06-28 4:40 UTC (permalink / raw)
To: cygwin
On 2018-06-27 03:31, john doe wrote:
> Good morning Brian, bottom posting.
> By Windows Admin you mean "Windows Admin Center"?
Line wrapped - Windows Admin Tools - on W10 - or search for event (log) viewer
> I'm using Cygwin on a laptop (win 7 pro) and sadly, if I'm not mistaking,
> "Windows Admin" is not available on non-server platform.
May be Administrative Tools on W7
> If I can't find a way to determine when my DNS changes I can clearly emulate
> an hourly cron job by using "task scheduler".
If you're using DHCP it could potentially change when your lease expires,
sometimes a couple of days, (depends on your router settings or ISP: my external
IP changes every few months, internal and DNS never) or if on WiFi, when you
connect to a new AP.
--
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
--
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^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-06-27 16:45 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-06-26 16:11 Autamatically populate resolv.conf when new DNS is acquired john doe
2018-06-26 19:23 ` Automatically " Brian Inglis
2018-06-27 11:08 ` john doe
2018-06-28 4:40 ` Brian Inglis
2018-06-27 11:01 ` Autamatically " Andrey Repin
2018-06-27 16:10 ` john doe
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