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Nameserver resolvconf Ubuntu

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Ubuntu uses the nameserver resolvconf program to configure local DNS resolution. The resolvconf package includes a simple database and a runtime for dynamically modifying nameserver information.

Nameserver resolvconf Ubuntu

Ubuntu nameserver resolvconf NetworkManager

Typically, the program resolvconf runs through a network interface to push routines such as ifup, ifdown, NetworkManager, dhclient, and pppd, or local nameservers such as dnsmasq to update the DNS information.

If static IP addresses and DNS records are used on a host, the resolvconf package should be deactivated under Ubuntu, so that the DNS configuration from the dnsmasq daemon is not automatically made, the configuration that has been edited in /etc/resolv.conf and /etc/network/interfaces will otherwise be overwritten by the resolvconf program.

Disable nameserver resolvconf

$ resolvconf --disable-updates

Disable Ubuntu resolvconf from boot level and quit the program.

$ systemctl disable systemd-resolved.service
$ service systemd-resolved stop

Customize the Network Manager with default DNS.

$ vi /etc/NetworkManager/NetworkManager.conf
..
dns=default
..

Remove the symlink resolv.conf under /etc.

$ rm /etc/resolv.conf

Edit resolv.conf

and create a new resolv.conf file with the nameservers. in this example, it’s Google Public DNS.

  On a local network or ADS the internal nameservers should be used.

$ vi /etc/resolv.conf

nameserver 8.8.8.8
nameserver 8.8.4.4

Delete the resolv.conf file of the systemd configuration program.

$ rm /etc/systemd/resolved.conf

change the configuration.

$ service network-manager restart

nameservers can also be defined in the interface configuration.

$ vi /etc/network/interfaces

auto lo
iface lo inet loopback

auto ens160
iface ens160 inet static
  address 10.10.0.8
  gateway 10.10.0.1
  netmask 255.255.255.0
  network 10.10.0.0
  broadcast 10.10.0.255
  dns-nameservers 8.8.8.8 8.8.4.4
  dns-search my.local

The interface name (ens160) may differ and must correspond to that of the respective host.

  The /etc/resolv.conf file should not be missing.

Now enable the new network settings it will be read into memory.

$ /etc/init.d/networking restart

Troubleshooting using DNS

Many network issues are due to incorrect DNS or incorrect configuration of resolver. In a home network there is often no internal DNS, whereby the router or the firewall can be used as a nameserver, such as the Linksys or Netgear router. Basically, it should be ensured that the firewall used has a DNS cache, with semi-professional firewalls such as the FortiGate that not every model provide such a cache. For open source-based firewalls most provide a cache through DNS forwarder or dnsmasq.

After open up a command prompt will changes to the nameservers in Windows, the DNS cache should be reset.

C:\> ipconfig /flushdns

For Linux, the DNS cache can be reset out from terminal, with one of the following commands, depending on which service is installed.

$ sudo /etc/init.d/nscd restart
$ service nscd restart
$ service nscd reload
$ sudo /etc/init.d/dnsmasq restart
$ service dnsmasq restart
$ rndc reload

In the Mac OS X terminal as root.

$ lookupd -flushcache

If there is no internal DNS in the local network, the name servers of the Internet provider can be used, or may the Cloudflare public DNS.

1.1.1.1 1.0.0.1

Example of a nameserver querying its provider on Windows.

C:\> nslookup -type=ns green.ch
Server: dns1.agrinet.ch
Address: 81.221.250.11

Non-authoritative response:
green.ch nameserver = dns2.agrinet.ch
green.ch nameserver = dns1.agrinet.ch

dns1.agrinet.ch internet address = 81.221.250.11

Example nameserver lookup query on Linux.

$ host -t ns green.ch
green.ch name server dns1.agrinet.ch.
green.ch name server dns2.agrinet.ch.

host dns1.agrinet.ch & host dns2.agrinet.ch
dns1.agrinet.ch has address 81.221.250.11
dns2.agrinet.ch has address 81.221.252.11
dns2.agrinet.ch has IPv6 address 2a01:2a8:2001:252::11

A ping -n1 resolves addresses to host names with parameters –a and –4 for IPv4 address.

C:\> ping -4 -n 1 -a www.google.com

Ping runs for www.google.com with [216.58.201.4]32 bytes of data:
Response from 216.58.201.4: Bytes=32 Time=32ms TTL=50

Ping statistics for 216.58.201.4:
    Packages: Sent = 1, Receive = 1, Lost = 0
    (0% loss),
Approx. times in millisec.:
    Minimum = 32ms, Maximum = 32ms, Mean = 32ms

Show the current DNS nameservers available use systemd resolver.

$ systemd-resolve --status

Set-Clipboard, Get-Clipboard in PowerShell, How to use

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How to use Set-Clipboard and Get-Clipboard in PowerShell

Set-Clipboard in PowerShell

PowerShell provide a cmdlet for use the clipboard, advanced applications are allowed, from PowerShell save multible items to the clipboard to use later, it is possible to append content to already pasted items in the clipboard.

Use Set-Clipboard in PowerShell

Use the PowerShell cmdlet Set-Clipboard to copy a text to the clipboard.

Set-Clipboard "but this to clipboard.."

Use Get-Clipboard in PowerShell

Use the text you just copied can be retrieved with Get-Clipboard.

Get-Clipboard

Use Set-Clipboard with -Append copy a text to the existing one.

Write-Output "append something to" | Set-Clipboard -Append
Get-Clipboard

This the query again with Get-Clipboard.

Delete clipboard content

The following command deletes the contents on the clipboard.

Write-Host "delete items in clipboard.." $null | clip

Retrieve files and folders from Clipboard

And there is even more to go, if you want to retrieve files and folders that are to be copied from the clipboard, the following command gives the output.

Get-Clipboard -Format FileDropList
PowerShell Get-Clipboard -Format FileDropList

It is also useful to copy the text content of files directly without opening the file to clipboard, such as scripts or source code.

Use Get-Content with clipboard

Get-Content copies the content of test.bat to the clipboard.

Get-Content test.bat | clip

Compare-Object compares the content and copies it to the clipboard.

Compare-Object $(Get-Content c:\temp\test.bat) $(Get-Content c:\temp\test1.bat) | clip

The default of Compare-Object is not case sensitive, use the parameter -CaseSensitive to distinguish small and capital letters.

Help with examples for use can be found with Get-Help.

Get-Help Set Clipboard -Detailed
Get-Help Get Clipboard -Detailed

Remarks

Commonly, in Windows the text or content is copied to the clipboard by pressing the “CTRL+C” shortcut key. However, in PowerShell, the text can also be copied to the clipboard using the “Set-Clipboard” cmdlet. This cmdlet sets the content to the clipboard. Moreover, the copied cmdlets can be pasted too in PowerShell using the “Get-Clipboard” cmdlet.

The following post will elaborate on the method to copy the content to the clipboard.
Using PowerShell Copy to Clipboard Function

As described earlier, the copy to clipboard function in PowerShell sets the text or content to the clipboard. The command used for that purpose is the “Set-Clipboard”. Examples explaining the procedure to copy the text to the clipboard are explained.