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 requires updating 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
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

Classifier Probes Pattern
Linux

(Unix classification)
  • Horizontal discovery probe: Launches patterns
  • Linux - Installed Software^
  • Unix - ADM^
  • Linux - Identity*
  • Linux - CPU*
  • Linux - Distribution*
  • Linux - Find FQDN*
  • Linux - Memory*
  • Linux - Memory Modules*
  • Linux - Network ARP Tables*
  • Linux - Storage*
  • Linux - Amazon EC2*
  • Unix - OS Uptime*
  • UNIX - OS Filesystems*
  • UNIX - Find FQDN*
  • Unix - ADM Enhanced*
 Linux Server

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

SSH private key credentials are preferable over SSH password credentials for security reasons.

Verify the MID Server configuration
For detailed information, see:
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.

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.
Label Table Name Field Name Source
Operating System cmdb_ci_linux_server os uname -a
OS Version cmdb_ci_computer os_version uname -a or cat /etc/*release
Short description cmdb_ci_linux_server short_description uname -a
Name cmdb_ci_linux_server name DNS, NBT
Hostname cmdb_ci_linux_server host_name DNS, NBT
DNS domain cmdb_ci_linux_server dns_domain DNS
Start date cmdb_ci_linux_server start_date uptime
Manufacturer cmdb_ci_computer manufacturer dmidecode
Serial number cmdb_ci_computer serial_number dmidecode
CPU type cmdb_ci_linux_server cpu_type /proc/cpuinfo
CPU speed (MHz) cmdb_ci_linux_server cpu_speed /proc/cpuinfo
CPU count cmdb_ci_linux_server cpu_count /proc/cpuinfo
CPU core count cmdb_ci_computer cpu_core_count /proc/cpuinfo
CPU core thread cmdb_ci_computer cpu_core_thread /proc/cpuinfo
CPU manufacturer cmdb_ci_linux_server cpu_manufacturer /proc/cpuinfo
Model number cmdb_ci_computer model_number dmidecode
Model ID cmdb_ci_computer model_id dmidecode
RAM (MB) cmdb_ci_linux_server ram meminfo
Disk space (GB)* cmdb_ci_linux_server disk_space /proc/ide, /proc/scsi, /var/log/dmesg
Type cmdb_ci_disk type /proc/ide, /proc/scsi, /var/log/dmesg
Model ID cmdb_ci_disk model_id /proc/ide, /proc/scsi, /var/log/dmesg
Disk space (GB) cmdb_ci_disk disk_space /proc/ide, /proc/scsi, /var/log/dmesg
Name cmdb_ci_disk name /proc/ide, /proc/scsi, /var/log/dmesg
Name cmdb_ci_file_system name df
Capacity (MB) cmdb_ci_file_system capacity df
Free Space Bytes (MB) cmdb_ci_file_system free_space_bytes df
Mount point cmdb_ci_file_system mount_point df
Name cmdb_running_process name ps
Command cmdb_running_process command ps
Type cmdb_running_process type ps
PID cmdb_running_process pid ps
Parameters cmdb_running_process parameters ps
Name cmdb_ci_network_adapter name ifconfig or ip address show
IP address cmdb_ci_network_adapter ip_address ifconfig or ip address show
MAC address cmdb_ci_network_adapter mac_address ifconfig or ip address show
Netmask cmdb_ci_network_adapter netmask ifconfig or ip address show
Default gateway cmdb_ci_hardware default_gateway route
* 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.
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.

Table 1. Tables used by Discovery on Linux KVM
Table name Extends Description Source
cmdb_ci_kvm cmdb_ci_vm A hypervisor that manages kernel-based virtual machines (KVMs) Process classifier detects libvirtd running on Linux servers
cmdb_ci_kvm_vm_instance cmdb_ci_vm_instance A virtual machine instance on this hypervisor virsh list-all and dumpxml command
cmdb_ci_kvm_object cmdb_ci_vm_object An object connected to a virtual machine instance <network>, <storage pool>, and <storage volume> elements from the dumpxml command
cmdb_kvm_device Not applicable A device connected to a virtual machine instance <devices> element from the dumpxml command
Table 2. Data collected by Discovery on Linux KVM
Label Table name Field name Source
Linux Host cmdb_ci_kvm linux_host Reference to the cmdb_ci_linux_server that is running this virtual machine
Details cmdb_ci_kvm details_xml dumpxml
Object ID cmdb_ci_kvm_vm_instance object_id virsh dumpxml
State cmdb_ci_kvm_vm_instance state virsh list-all
CPUs cmdb_ci_kvm_vm_instance cpus virsh dumpxml
Memory cmdb_ci_kvm_vm_instance memory virsh dumpxml
Disks cmdb_ci_kvm_vm_instance disks virsh dumpxml
Disks size cmdb_ci_kvm_vm_instance disks_size virsh domblkinfo
Network adapters cmdb_ci_kvm_vm_instance nics virsh dumpxml
Name cmdb_ci_kvm_vm_instance name virsh dumpxml
Short description cmdb_ci_kvm_vm_instance short_description virsh desc
Details cmdb_ci_kvm_object details_xml XML element from dumpxml
KVM instance cmdb_kvm_device kvm_instance Reference to cmdb_ci_kvm_instance
Device cmdb_kvm_device device disk, controller, interface, and so on
Type cmdb_kvm_device type depends on the device
Details cmdb_kvm_device details_xml XML element from dumpxml
Table 3. Data collected by Discovery on KVM Relationship
Relationship Parent table Child table
Registered On::Has Registered KVM [cmdb_ci_kvm] KVM Virtual Machine instance [cmdb_ci_kvm_vm_instance]
Provided By::Provides KVM [cmdb_ci_kvm] Network [cmdb_ci_kvm_network]
Defines resource for::Gets resources from KVM [cmdb_ci_kvm] Storage Pool [cmdb_ci_kvm_storage_pool]
Connected By::Connects KVM Virtual Machine instance [cmdb_ci_kvm_vm_instance] Network [cmdb_ci_kvm_network]
Instantiated By::Instantiates KVM Virtual Machine instance [cmdb_ci_kvm_vm_instance] Computer [cmdb_ci_computer]
Virtualized By::Virtualizes Computer [cmdb_ci_computer] KVM [cmdb_ci_kvm]
Provides storage for::Stored on Storage Pool [cmdb_ci_kvm_storage_pool] KVM Virtual Machine instance [cmdb_ci_kvm_vm_instance]

Helpful resources

Some ServiceNow resources that can provide you with helpful information are:
Support