To test mail server I need an MX record in DNS server, it always with a delay because DNS cache, I need to make it faster. Is there a way make an MX record locally like A record by etc/hosts file?
Thanks, this works.
echo "10.10.10.1 mail.example.com" | sudo tee --append /etc/hosts > /dev/null
echo "disable_dns_lookups = yes" | sudo tee --append /etc/postfix/main.cf > /dev/null
systemctl restart postfix
i'm managing to use postfix on a proxmox server to delivery the mail to a local mail server on a vm , with a different ip address from the dns mx record, i've found very useful this article,
http://www.readonlymaio.org/rom/2018/01/16/force-postfix-to-search-mx-records-in-etc-hosts-file/
he leds me to disable the dns lookup in postfix to force it to use the hosts A record !!
it works
in the hosts
X.X.X.X example.com
Edit the /etc/postfix/main.cf file and add this line:
disable_dns_lookups = yes
after, restart postfix
Related
I need to programmatically set DNS servers of the host on their active network interfaces (Wi-fi, ethernet, etc) on both Windows, MacOS and as a bonus Linux.
I want to avoid having to manually update/pollute /etc/hosts for my Kubernetes services I am running on my ingress.
Currently, my process is to manually set the DNS server for each person in my team running our app
The problem with this is that it's a manual process, and I am having trouble trying to automate it because the outputs are weirdly formatted and hard to parse. This means I am unable to know which is the proper network interface to use.
Essentially, what needs to be done is the following (on both platforms)
Get the active networks name
Set the DNS servers for the active network to 127.0.0.1 & 8.8.4.4
What is being done manually currently
MacOS:
networksetup -setdnsservers Wi-Fi 127.0.0.1 8.8.8.8
sudo killall -HUP mDNSResponder
127.0.0.1 is the local DNS server running on node that serves the A record for the service
8.8.8.8 is Google's Public DNS Server
Currently, I am assuming the user on MacOS is using the "Wi-Fi" network, but i'd like to determine this programatically
Windows
As administrator:
netsh interface show interface
Locate the network connection for which you want the DNS server changed (eg: WiFi).
netsh interface ipv4 add dns "WiFi" 127.0.0.1 index=1
netsh interface ipv4 add dns "WiFi" 8.8.8.8 index=2
ipconfig /flushdns
On macOS, I don't think this will do what you want. When you configure multiple DNS servers on macOS, the system resolver doesn't try them in order, it just fires off requests semi-randomly between the available servers. This means it'll sometimes send off requests for your private servers to the public (Google) server, get told there's no such domain, and stop there. Or it'll send requests for pubic sites to the localhost DNS, and if that doesn't respond properly decide that site doesn't work. Basically, the macOS resolver doesn't do failover.
Are your private servers under a non-standard TLD or something like that? If so, you might be able to do the job by adding a file under /etc/resolver/ to redirect queries for that TLD to the private DNS server.
Anyway, in case it is useful, here's a way to detect the primary (active) network interface and set its DNS servers in macOS:
#!/bin/bash
interfaceDevice=$(netstat -rn | awk '($1 == "default") {print $6; exit}')
if [[ -z "$interfaceDevice" ]]; then
echo "Unable to get primary network interface device" >&2
exit 1
fi
interfaceName=$(networksetup -listallhardwareports | grep -B1 "Device: $interfaceDevice\$" | sed -n 's/^Hardware Port: //p')
if [[ -z "$interfaceName" ]]; then
echo "Unable to get primary network interface name" >&2
exit 1
fi
networksetup -setdnsservers "$interfaceName" 127.0.0.1 8.8.8.8
I've got a very strange problem.
There's a cron job on the server to run a script daily:
wget -O /dev/null --timeout=300 --tries=1 "http://website.com/script"
It was all working well since about two weeks ago, I started receiving errors:
--2016-07-13 09:45:01-- http://website.com/script
Resolving website.com (website.com)... 11.22.33.44
Connecting to website.com (website.com)|11.22.33.44|:80... failed: Connection timed out.
Giving up.
These are some information for this question:
The cron job is on the same server of http://website.com hosted.
I can access the script (http://website.com/script) correctly from browser on my desktop.
The server is CentOS 7, with WHM and cPanel installed.
Anyone know what could be the issue? or how do I suppose to identify the issue?
Thanks
If the issue still is unresolved..
You could try running wget in debug mode to see if you get some more info.
wget -dv -O /dev/null --timeout=300 --tries=1 "http://website.com/script"
Also, confirm if the resolved IP "11.22.33.44" belongs to one of the servers NIC's.
ip a s (ip address show) or
ifconfig -a
If the IP is not listed, It could be that the ip "11.22.33.44" is a public facing address of the company's firewall. And that the FW is directing requests on port 80 from the outside/internet (where you're browser is) to that specific server. And the Firewall/Nat/Proxy, could be configured to not allow requests coming from inside the network, reaching the external IP of the firewall and getting back in.
If this is the case, you could try changing you're wget using the internal ip address, something like: (still using -dv for debugging, remove after)
wget -dv -O /dev/null --timeout=300 --tries=1 --header="Host: website.com" http://127.0.0.1/script
Note1: the --header="Host: website.com" will tell you're webserver what site you wanna reach
Note2: maybe you'll have to change the IP: 127.0.0.1 (localhost address) to one of the server's NIC addresses.
If the website is up try a different command.
*/10 * * * * /usr/bin/wget -q -O temp.txt http://website.com/script
Try adding -H
wget -H -O /dev/null --timeout=300 --tries=1 "http://website.com/script"
My isp provides dynamic ip addresses.I have forwarded my port to an raspberry pi and accessing it through ssh and also using it as web server.but the problem is that ip changes every 3-4 days is there any way or script so that i can be informed or updated with new ip address.
Thank You.
You can write a script like:
============
#!/bin/bash
OUT=$(wget http://checkip.dyndns.org/ -O - -o /dev/null | cut -d: -f 2 | cut -d\< -f 1)
echo $OUT > /root/ipfile
============
Set a cron to execute this every 3h or something and configure your mta to send the file /root/ipfile to your email address ( that too you can use a cron ). mutt can be a useful tool to attach the file and do the email delivery.
I don't know how to search for this and that is why I asked for it (all my searches did not reveal any relevant information).
I have a Fedora 18 server that looks like this:
[root#dhcp-192-168-5-100 ~]#
I want to change that to:
[root#server1 ~]#
Currently, this machine is set to get IP through DHCP, but that is not the IP address of the machine and that is why I need to change the CLI to something more relevant.
Thank you
you can type "hostname HOSTNAME" where HOSTNAME is the new name you want. The next time you log in / connect via ssh, that's what you'll see.
Edit /etc/sysconfig/network and change/add HOSTNAME variable like so HOSTNAME=server1.domain.com After restart it should have server1.
Edit /etc/hosts and add server1 and server1.domain.com to 127.0.0.1 line, so it will look like: 127.0.0.1 localhost.localdomain localhost server1 server1.domain.com
More about network file you can read here:
https://docs.fedoraproject.org/en-US/Fedora/15/html/Deployment_Guide/ch-The_sysconfig_Directory.html#s2-sysconfig-network
Just found this and this is described pretty good.
[root#dhcp-192-168-5-100 ~]# hostname MYHOSTNAME
Change hostname in Feodora
Add "yournewhostname" into /etc/sysconfig/network in the HOSTNAME
field..
Add "yournewhostname" into /etc/hosts for 127.0.0.1
echo "yournewhostname" > /proc/sys/kernel/hostname or service hostname
IMPORTANT: logout and log back in.
For changing static ip address, i set the contents of /etc/network/interfaces to
auto lo
iface lo inet loopback
allow-hotplug eth0
iface eth0 inet static
address <newaddress>
netmask <netmask>
gateway <gateway>
dns-nameservers <dns1> <dns2>
then do ifdown eth0 && ifup eth0
For changing the hostname, i do the following actions
execute hostname <newname>
set contents of /etc/hostname to <newname>
replace <oldname> with <newname> in /etc/hosts
Issues
Both ip address and host name changes don't take effect.
If I change the ip address and ping the hostname, it still resolves to the oldaddress
If I change the hostname and ping the new hostname, it cannot resolve to an ip
If I change the hostname and ping the old hostname, it is still available and resolved the current ip address.
I restart the machine and it still behaves the same way.
What am I missing?
Could the parent network play any role in this?
Also note that my machine thinks the hostname is updated after I change it.
I think this is not actually a problem and this behavior is explained by arp caching.
The ARP tool manipulates or displays the kernel's IPv4 network neighbour and this includes in some way your host as well.
The arp command has many switches you can work on as, for example, the following command:
arp -n
This command prints out the list of arp cache entries.
Unfortunately there is no command to flush it hence, you have 2 options.
Option 1: You wait for the cache to update (won't take long)
Option 2: You run the following very basic script and you see:
#!/bin/sh
for i in `awk -F ' ' '{ if ( $1 ~ /[0-9{1,3}].[0-9{1,3}].[0-9{1,3}].[0-9{1,3}]/ ) print $1 }' /proc/net/arp` ;
do
arp -d $i
done
The script is not mine, I have reported the only I usually run which was taken originally from this well done example:
http://www.lainoox.com/display-add-flush-arpcache-linux-arp/
I hope this helps in some way.
Changing /etc/hostname will have the affect of changing the hostname displayed on your terminal, welcome messages, in your logs and anywhere else the system uses hostname. These are all vanity changes.
Channging /etc/hosts will change your local host-name resolution (i.e. translating an ip address to a hostname and vise versa) Anything DNS does not resolv or anything you want to override locally. By default, the local files override network resolution. This is determined in /etc/nsswitch which says to use local files first then then dns for host resolution.
The important thing to keep in mind here is that these changes will not affect how othesr on a network would determine this host's ip address or name, which of course is handled through DNS or maybe their local /etc/hosts file(s).
yeah resolv.conf is for dns. as is which handles NAMES and anything that has to do with the internet. Such as ping. dns resolvc locally weather you have server or not thus the hostname / ect hosts which ALSO handle dns. your resolv.conf will update from your isp when you connect or you can change it by hand / set some thing more dynamic on a bridged interface