Network name resolution error

Introduction

The «Temporary failure in name resolution» error occurs when the system cannot translate a website name into an IP address. While the error sometimes appears due to a lost internet connection, there are multiple reasons why it may show up on your system.

This tutorial will guide you through troubleshooting and fixing the «Temporary failure in name resolution» error.

Prerequisites

• Sudo or root privileges
• A working internet connection

The error appears when a user attempts to communicate with a website using a command such as ping:

ping phoenixnap.com

The system cannot communicate with the DNS server and returns the error.

The most common cause of this error are the resolv.conf network configuration file and a misconfigured firewall. The steps to fix the error in both cases are given below.

Method 1: Badly Configured resolv.conf File

resolv.conf is a file for configuring DNS servers on Linux systems.

To start, open the file in a text editor such as nano.

sudo nano /etc/resolv.conf

Make sure the resolv.conf file contains at least one nameserver. The lines listing nameservers should look like this:

nameserver 8.8.8.8

If you do not have a nameserver listed in the file, add at least one. 8.8.8.8 and 8.8.4.4 are the popular nameservers owned by Google, but you can add any functional DNS server to this list.

Save the file and exit.

Then, restart the DNS resolver service.

sudo systemctl restart systemd-resolved.service

If successful, the command above returns no output. Test that your new nameservers are correctly configured by pinging a website:

ping phoenixnap.com

If you see the ping command transmitting and receiving data, your DNS server is working properly.

Misconfigured Permissions

If your resolv.conf file contains valid DNS servers, but the error persists, it may be due to misconfigured file permissions. Change ownership of the file to the root user with the following command:

sudo chown root:root /etc/resolv.conf

Modify the user permissions to allow everybody on the system to read the file:

sudo chmod 644 /etc/resolv.conf

Ping a website again.

ping phoenixnap.com

If wrong file permissions caused the error, the commands above successfully resolve it.

Method 2: Firewall Restrictions

Another reason for the «Temporary failure in name resolution» error may be a firewall blocking one or both of the following ports:

• port 43, used for whois lookup
• port 53, used for domain name resolution

Open the ports in UFW Firewall

Type the following command to allow traffic on port 43 using UFW firewall:

sudo ufw allow 43/tcp

UFW confirms the rule is successfully updated.

Repeat the command for port 53.

sudo ufw allow 53/tcp

Reload UFW with the following command:

sudo ufw reload

The output confirms the operation was successful.

Open the ports in firewalld

Some Linux distributions such as CentOS use firewalld as their default firewall. The syntax to open port 43 in firewalld is:

sudo firewall-cmd --add-port=43/tcp --permanent

firewalld outputs the word success.

Repeat the command for port 53.

sudo firewall-cmd --add-port=53/tcp --permanent

Reload the firewall.

sudo firewall-cmd --reload

Test the connection by pinging a website.

ping phoenixnap.com

Conclusion

This article provided ways to troubleshoot and fix the «Temporary failure in name resolution» error on Linux. To learn more about diagnosing DNS-related problems, read How to Use Linux dig Command.

When performed by the Discovery Wizard or PowerShell cmdlets, the discovery of UNIX and Linux agents in Operations Manager typically involves three activities:

1. Agent deployment
2. Certificate signing
3. Discovery of the agent

Agent deployment and certificate signing are performed using ssh, but these steps can also be performed

manually.  The final agent discovery is performed using a WS-Management query to the deployed agent. The discovery process may fail due to configuration issues, credential or privilege problems, or network and name resolution problems.

This document describes common errors that may be encountered during the discovery process, with potential causes and resolution steps.

Certificate Errors/Certificate Signing Errors

Signed certificate verification operation was not successful

Error Description

Possible Causes

• The agent certificate’s CN value does not match the provided or resolved Fully-Qualified Domain name

Resolutions

• For certificate CN failures, confirm that that agent host’s hostname and domain name match the Fully-Qualified Domain Name resolved through DNS.  More information can be found
  here.

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The SSL certificate could not be checked for revocation

Error Description

Possible Causes

• The certificate has been signed by an untrusted authority, when multiple Management Servers are members of the Resource Pool used for discovery, but certificate trust has not been configured between the Management Servers.

Resolutions

• Confirm that all Management Servers in the Resource Pool used for Discovery trust each other server’s certificate. More information can be found
  here.

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Certificate signing operation was not successful

Possible Causes

• The user account specified for discovery has insufficient privileges to perform file operations involved in signing
• Sudo elevation privileges for the user account specified for discovery was not correctly configured

Resolutions

• Inspect the StdErr output in the error details to identify the cause of the failure
• Verify sudo privilege configuration for the account used for certificate signing 

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Network/Name Resolution Errors

The target address is not resolvable

Error Description

Failed to resolve IP address 192.168.25.25 to name

Possible Causes

• An IP Address for the host was entered for discovery, but is not resolvable to name in DNS (reverse lookup)

Resolutions

• Correct name resolution (DNS) configuration for reverse lookup

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Failed to resolve name

Error Description

Failed to resolve name lxbad.test.com to IP address 

Possible Causes

• An FQDN for the host was entered for discovery but is not resolvable to IP Address in DNS (forward lookup)

Resolution

• Correct name resolution (DNS) configuration for forward lookup

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DNS configuration: forward DNS resolution does not match reverse DNS resolution

Error Description

The provided hostname host1 resolved to the IP address of 10.137.216.102. The hostname lx1.contoso.com returned by reverse lookup of the IP address 10.137.216.102 did not match the provided hostname. Verify the DNS configuration and try the request again.


Possible Causes 

• Forward and reverse DNS lookups do not match

Resolutions

• Correct name resolution (DNS) configuration for forward and/or reverse lookup

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The target address is unreachable

Error Description 

The WinRM client cannot complete the operation within the time specified. Check if the machine name is valid and is reachable over the network and firewall exception for Windows Remote Management service is enabled.


Possible Causes 

• The host is unreachable due to incorrect name resolution, network outage, or host outage
• A network or host-based firewall is blocking TCP port 1270 connectivity to the target host

Resolutions

• Verify that Management Server can ping the agent host by Fully-Qualified Domain Name
• Verify that no network firewalls or host firewall is blocking TCP port 1270

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SSH Connectivity Errors

SSH connection error

Error Description

Failed during SSH discovery. Exit code: -1073479162

Exception Message:An exception (-1073479162) caused the SSH command to fail - No connection could be made because the target machine actively refused it.


Possible Causes 

• The ssh daemon is not running on the target system
• A network or host-based firewall is preventing ssh connections on TCP port 22

Resolutions

• Verify that the ssh daemon is running
• Verity that no network firewalls or host firewall is blocking TCP port 22

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Failed
during SSH discovery (Exit code: -1073479118)

Error Description

Failed during SSH discovery. Exit code: -1073479118

Exception Message:An exception (-1073479118) caused the SSH command to fail - Server sent disconnect message: type 2 (protocol error : Too many authentication failures for root)


Possible Causes 

• The user account specified for discovery is not permitted to login via ssh.
• The user account specified for discovery was input with an invalid username or password

Resolutions

• Verify that the user is permitted to login via ssh
• Verify the input credentials and that the user is defined on the target host

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Failed during SSH discovery. Exit code: 1

Error Description

Failed during SSH discovery. Exit code: 1

Exception Message:

Possible Causes

• Sudo elevation was selected in the user credential input, but the requiretty option was not disabled for the user in sudoers.

Resolutions

• Edit the sudoers file on the target host (using the visudo command) and add the following line, replacing “” with the name of the user account specified for discovery:

  Defaults: !requiretty

  More information is available
  here.

Invalid SU password

Error Description

Possible Causes

• Su elevation was selected in the user credential input, but an invalid root password was provided for su elevation

Resolutions

• Verify the password input for root in the Elevation configuration dialog

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Failed during SSH discovery. Exit code: -2147221248

Error Description

Failed during SSH discovery. Exit code: -2147221248

Standard Error: Could not chdir to home directory /home/username: No such file or directory


Possible Causes

• The user account specified for discovery does not have a home directory

Resolutions

• Verify that the user has a home directory at: /home/ and that the user is able to write to this directory

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Failed during SSH discovery. Exit code: -2147221248

Error Description

Failed during SSH discovery. Exit code: -2147221248

Exception Message:Operation timed out 

Possible Causes

• Sudo elevation was selected in the user credential input, but the user account specified for discovery is not correctly configured to use passwordless sudo elevation or the required sudo elevation privileges were not granted for the user account used in
  discovery.

Resolutions

• Review sudo elevation configuration documentation and verify user configuration for sudo. Note that passwordless sudo must be configured.

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WSMan Connectivity Errors

Invalid credentials

Error Description

The agent responded to the request but the WSMan connection failed due to :  Access is Denied.


Possible Causes

• The agent is installed, and the agent certificate has been signed, but the user credential provided for agent verification is invalid.
• The user account specified for discovery was configured to authenticate with an ssh key, but the user credential provided for agent verification is invalid.

Resolutions

• Verify that the username and password for agent verification were input correctly and that the user is a valid user on the target host.

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The target address is unreachable

Error Description

WSMan Only Discovery failed for 192.168.1.30

Possible Causes

• The Discovery Type option was set to “Only computers with an installed agent and signed certificate,” the target host has the agent installed, but the target host certificate has not been signed.  In order to use the WSMan-only “Only computers with an installed
  agent and signed certificate” option, the agent must be installed and the certificate manually signed.
• The Discovery Type option was set to  “Only computers with an installed agent and signed certificate,” but the target host does not have the UNIX/Linux agent currently installed.
• The Discovery Type option was set to  “Only computers with an installed agent and signed certificate,” but the UNIX/Linux agent is not currently running.
• The Discovery Type option was set to  “Only computers with an installed agent and signed certificate,” but the target host is unreachable, a network or host-based firewall is preventing connectivity, or the UNIX/Linux agent is currently down.

Resolutions

• Manually sign the certificate
• Verify that the UNIX/Linux agent has been installed
• Change the option to “Discover all computers” to allow the Discovery Wizard to perform the certificate signing
• Verify that the UNIX/Linux agent is running and that the target host is reachable
• Verify that no network firewalls or host firewall are preventing access on TCP port 1270 

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Other Errors

Agent deployment operation was not successful

Error Description

The task cannot be executed against the object(s) because the target of the task does not match any of the classes of the object.


Possible Causes

• In a System Center 2012 – Operations Manager management group, the UNIX/Linux management packs imported are Operations Manager 2007 R2 versions.

Resolutions

• Import the System Center 2012 versions of the UNIX/Linux operating system management packs. 

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No actions are available

Error Description

The agent is installed and the computer is already being monitored by Operations Manager.


Possible Causes

• The target host has already been discovered in this Management Group

Resolution

• No action is required.  Agent upgrade or migration to an alternate resource pool can be performed from the UNIX/Linux Servers view in the Administration pane of the Operations Console

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Platform not supported

Error Description

Failed to find a matching supported agent instance in the imported management packs.

Import the Management Pack(s) for this platform in order to discover this computer.


Possible Causes

• The target host is running an unsupported operating system.
• The correct management pack for the target host’s operating system has not been imported.
• The correct management pack for the operating system has recently been imported, and has not yet fully loaded.

Resolutions

• Confirm that the target host is running a supported operating system. 
• Import the management pack for the target host’s operating system and version
• If the management pack was just imported, it may still be loading.  Wait a few minutes and rerun discovery.

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Pool Not Initialized

Error Description

Unable to enumerate Installable agent types.  The associated resource pool may still be initializing. If you had selected a newly created resource pool, please wait a few minutes before using it.

Possible Causes

• The Resource Pool used in discovery is not healthy (a majority of member servers are offline).
• The Resource Pool used in discovery was recently created but has not fully initialized.

Resolutions

• If the Resource Pool used in discovery was recently created, retry the discovery after several minutes to allow the pool to initialize.
• Otherwise, check the Operations Manager Event Log on the servers that are members of the Resource Pool used for discovery for indications of problems.

< en-US, Linux, Operations Manager 2012, System Center 2012, Unix, OpsMgr 2012, SCOM 2012 >

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Unable to copy new agent to this computer

Error Description

Possible Causes

• Latest verified occurrence: 7.5.1038.0
• File agent version mismatch between database and agent repository

Resolutions

• Try to update the failed agents again. Usually, the list of failed will get shorter and shorter during every update iteration
• Verify that the failed ones are all failing because of this issue. Otherwise, you’ve to apply other troubleshooting steps.
• Restart the Health Service on all members of your Linux Resource Pool or other Pool for managing UnixLinux machines. Check %ProgramFiles%Microsoft System Center 2012 R2Operations ManagerServerAgentManagementUnixAgentsDownloadedKits folder if file
  names are correct. Remember to close and re-open Discovery Wizard.

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See Also

• Manually installing and troubleshooting Operations Manager 2012 R2 Linux/UNIX Agents

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Sometimes when you try to ping a website, update a system or perform any task that requires an active internet connection, you may get the error message ‘temporary failure in name resolution’ on your terminal.

For example, when you try to ping a website, you might bump into the error shown:

[email protected]:~$ ping google.com
ping: tecmint.com: Temporary failure in name resolution

This is usually a name resolution error and shows that your DNS server cannot resolve the domain names into their respective IP addresses. This can present a grave challenge as you will not be able to update, upgrade, or even install any software packages on your Linux system.

In this article, we will look at some of the causes of the ‘temporary failure in name resolution‘ error and solutions to this issue.

1. Missing or Wrongly Configured resolv.conf File

The /etc/resolv.conf file is the resolver configuration file in Linux systems. It contains the DNS entries that help your Linux system to resolve domain names into IP addresses.

If this file is not present or is there but you are still having the name resolution error, create one and append the Google public DNS server as shown

nameserver 8.8.8.8

Save the changes and restart the systemd-resolved service as shown.

$ sudo systemctl restart systemd-resolved.service

It’s also prudent to check the status of the resolver and ensure that it is active and running as expected:

$ sudo systemctl status systemd-resolved.service

Then try pinging any website and the issue should be sorted out.

[email protected]:~$ ping google.com

2. Firewall Restrictions

If the first solution did not work for you, firewall restrictions could be preventing you from successfully performing DNS queries. Check your firewall and confirm if port 53 (used for DNS – Domain Name Resolution ) and port 43 (used for whois lookup) are open. If the ports are blocked, open them as follows:

For UFW firewall (Ubuntu / Debian and Mint)

To open ports 53 & 43 on the UFW firewall run the commands below:

$ sudo ufw allow 53/tcp
$ sudo ufw allow 43/tcp
$ sudo ufw reload

For firewalld (RHEL / CentOS / Fedora)

For Redhat based systems such as CentOS, invoke the commands below:

$ sudo firewall-cmd --add-port=53/tcp --permanent
$ sudo firewall-cmd --add-port=43/tcp --permanent
$ sudo firewall-cmd --reload

It’s our hope that you now have an idea about the ‘temporary failure in name resolution‘ error and how you can go about fixing it in a few simple steps. As always, your feedback is much appreciated.

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Иногда, когда вы пытаетесь проверить связь с веб-сайтом, обновить систему или выполнить какую-либо задачу, требующую активного подключения к Интернету, вы можете получить сообщение об ошибке “temporary failure in name resolution” на вашем терминале.

Например, когда вы пытаетесь проверить связь с веб-сайтом, вы можете столкнуться с указанной ошибкой:

ping itisgood.ru
ping: itisgood.ru: Temporary failure in name resolution

Обычно это ошибка разрешения имен, которая показывает, что ваш DNS-сервер не может преобразовать доменные имена в соответствующие IP-адреса.

Это может стать серьезной проблемой, поскольку вы не сможете обновлять или даже устанавливать какие-либо программные пакеты в вашей системе Linux.

В этой статье мы рассмотрим некоторые из причин ошибки «temporary failure in name resolution» и решения этой проблемы.

1. Отсутствующий или неправильно настроенный файл resolv.conf

Файл /etc/resolv.conf – это файл конфигурации резолвера в системах Linux.

Он содержит записи DNS, которые помогают вашей системе Linux преобразовывать доменные имена в IP-адреса.

Если этот файл отсутствует или существует, но ошибка разрешения имени все еще возникает, создайте его и добавьте общедоступный DNS-сервер Google, как показано далее:

nameserver 8.8.8.8

Сохраните изменения и перезапустите службу systemd-resolved, как показано.

$ sudo systemctl restart systemd-resolved.service

$ sudo systemctl status systemd-resolved.service

ping google.com

$ sudo ufw allow 53/tcp
$ sudo ufw allow 43/tcp
$ sudo ufw reload

$ sudo firewall-cmd --add-port=53/tcp --permanent
$ sudo firewall-cmd --add-port=43/tcp --permanent
$ sudo firewall-cmd --reload