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Re: Automatically populate resolv.conf when new DNS is acquired
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
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
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.
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