Linux discovery

Discovery and Service Mapping applications use probes and patterns to discover and map information about Linux computers and servers. The information is populated in the CMDB. Discovering some of these resources may require updating to the latest version of the Discovery and Service Mapping Patterns application from the ServiceNow Store.

Supportability details

The Linux server pattern can discover only English-based Linux.

• Supported Linux operating systems

  For IPv4 discovery:

  • Red Hat
  • Oracle
  • Fedora
  • Debian
  • SUSE
  • CentOS
  • Ubuntu
  • Rocky Linux
  • AlmaLinux OS
  • Debian GNU/Linux
  • VMware Photon OS
  • Amazon Linux
  • Alpine Linux (starting from Visibility Content version 6.30.0)* * Operating System and OS Version only

  For IPv6 discovery:

  • CentOS 7

  • Ubuntu 20 The following operating systems or devices haven’t been verified for IPv6 discovery:

  • Red Hat cluster

  • Oracle Clusterware
  • Linux Pacemaker cluster
  • Network storage

Classifier, probes, and pattern

*These probes aren't active on the classifier, as Discovery uses patterns by default for these discoveries.

^These probes remain active by default, even when Discovery uses pattern discovery.

To use patterns, verify that the correct pattern is specified in the horizontal pattern probe on the classifier. See Add the Horizontal Pattern probe to a classifier for instructions.

Request new or enhanced Patterns on the ServiceNow® Store

Visit the ServiceNow Store to view all the available updates and for information about submitting requests to the store. For cumulative release notes information for all released apps, see the ServiceNow Store version history release notes.

Requirements for Linux discovery

Before running a discovery, you must verify that all the required configurations are complete.

• Verify the plugins installation and activation
  • Plugins or applications installed with ITOM Visibility
  • Install Discovery and Service Mapping Patterns
  • Install Visibility Content

• Verify the required credentials configuration

  Configure the credentials by the required SSH permissions. Discovering sensitive Linux data may require a user with appropriate sudo privileges to run the sudo commands. To configure the required sudo privileges, modify the /etc/sudoers file to include the commands that Discovery needs. For /etc/sudoers line examples for each command, see SSH commands requiring a privileged user during probe-based discovery.

  For more information about the commands that require a user with elevated rights, refer to the following documents.

  • Commands that require root privileges for Discovery, Orchestration, and Integration Hub.

  • For a list of privileged commands that you need for Discovery and Service Mapping, see Service Mapping commands requiring a privileged user. This list includes commands that require elevated rights to discover and map Unix-based hosts in your organization.

  • MID Server privileged commands

  • View Patterns commands through the Discovery Patterns module
  • Validate commands used in pattern-based discovery SSH private key credentials are preferable over SSH password credentials for security reasons.

• Verify the MID Server configuration

  For detailed information, see:

  • Test MID Server connectivity
  • MID Server properties
  • Verify the configuration of the discovery schedule

  For information on creating a discovery schedule, see Schedule a horizontal discovery.

  Defining IP ranges ensures that only the specified network adapters and their primary IP addresses are used during Linux discovery. You can configure Quick Ranges by entering comma-separated IPv4 address ranges or single IPv6 address.

  Alternatively, you can use the network_adapter_exclusion_list property to limit Linux discovery to specific network adapters and their primary IP addresses. For more information, see Omit network adapter secondary IP addresses in Linux discovery.

• (Optional) Populate Virtual Machine Object field in Hardware [cmdb_ci_hardware] table

  Starting with Discovery and Service Mapping Patterns version 1.30.2, you can improve query performance by populating the Virtual Machine Object field in the Hardware [cmdb_ci_hardware] table. For more information, see Improved query performance with direct field population in CI tables.

• Set the preferred IP address version for network adapter discovery

  Starting with Visibility Content version 6.32.0, if your network adapters support both IPv4 and IPv6, the IPv4 address is populated by default in the IP address [ip_address] field on the Network Adapter [cmdb_ci_network_adapter] table. To control which IP version is populated, see Set the preferred IP version for network adapter discovery.

Data collected

The Linux classifier triggers probes that perform the discovery. Several probes are launched during the discovery. See the classifier for a list of the trigger probes.

Note: See the knowledge article KB0687582 for information on model_id and manufacturer.

* The value in the disk_space field is an aggregation of the total capacity (to include used space) for all non-removable disks, including both directly attached and SAN storage.

** Starting with Visibility Content version 6.32.0, for network adapters that support both IPv4 and IPv6, the IPv4 address is populated by default. Before this release, the populated value was selected randomly. To control which IP version is populated, see Set the preferred IP version for network adapter discovery.

Note: Make sure to define unique serial numbers for the RAMs on the Linux server.

Discovery also identifies and classifies information about Linux KVM. Discovery identifies Linux kernel-based virtual machines (KVM) when the process classifier detects libvirtd running on a Linux server. The classification triggers the creation of a cmdb_ci_kvm record and launches the SSH Command probes to explore the Linux server with virsh, lbvert utility, and virtual machine configuration data.

Discovery creates a [cmdb_ci_kvm_instance] record for each virtual machine on the server, and then matches the [cmdb_ci_kvm_instance] record to a corresponding [cmdb_ci_computer] record using the MAC addresses of installed network adapters.

Related topics

Linux discovery fails with "Cannot connect, status is SSH_CONNECTION_FAILURE. Could not agree on signature algorithm Client (KB1425502)

Linux discovery fails in Unix Classification with the error - Name of unclassified CI is 'servername' (KB0860486)

Linux discovery error "rbash: PATH: readonly variable Exit status: 1" (KB0866860)