Privileged SSH commands for probe-based discovery

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  • Updated July 31, 2025
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    Summary of Privileged SSH commands for probe-based discovery

    This document outlines the privileged SSH commands used by ServiceNow Discovery probes during horizontal discovery to gather system information. These commands require elevated privileges and are executed via SSH with a user account (commonly namedDisco). Proper configuration of sudo permissions is essential to enable these commands without requiring password prompts, especially since private key authentication does not support sudo password entry.

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    It is critical for ServiceNow customers to configure the sudoers file appropriately, using the NOPASSWD option for specific commands, ensuring smooth and secure probe execution.

    Key Points for Implementation

    • Sudo configuration: Add NOPASSWD entries in the sudoers file for each privileged command needed by the Discovery probes, e.g., disco ALL=(root) NOPASSWD:/usr/sbin/dmidecode.
    • SSH key authentication: Use SSH keys or certificates for authentication and avoid sending passwords over the connection.
    • Host key validation: MID Servers do not validate SSH host keys, so limit sensitive data exchanged over SSH to reduce risk from potential man-in-the-middle attacks.
    • Disco user substitution: Replace the example username Disco with your actual user configured on the target systems.

    Privileged Commands by Operating System

    The commands required vary by OS, and each must be enabled with sudo permissions:

    • HP-UX: adb for CPU speed and memory info.
    • Linux: Includes dmidecode (hardware info), fdisk -l (disk info), and multipath -ll (MPIO device mappings).
    • Linux and Solaris: dmsetup to examine low-level volumes.
    • All UNIX versions: Commands such as lsof, netstat, ss to identify process and connection relationships; oratab for Oracle configurations.
    • Solaris specific: Commands like iscsiadm (iSCSI info), fcinfo (WWPNs), prtvtoc (disk partitions), ps and pgrep for process info, and pfiles for socket details. Note the requirement to manually install the /usr/ucb/ps command on Solaris 11 systems.

    Practical Recommendations for ServiceNow Customers

    • Ensure all required privileged commands are listed with exact paths in your sudoers file and are allowed without password prompts.
    • Test SSH key-based authentication for the Disco user to confirm privileged commands run successfully during Discovery.
    • Be aware that commands requiring sudo will fail if the sudoers file is not configured with NOPASSWD for those commands.
    • Review non-privileged commands separately to complete your Discovery configuration.
    • Refer to Service Mapping documentation for commands specific to top-down discovery if applicable.

    These tables display the SSH commands run by Discovery probes during horizontal discovery. These SSH commands require elevated privileges to run.

    Operating system commands requiring elevated rights

    These examples assume that the user name is Disco. Substitute the actual user name and verify that the paths for the commands match the paths on the system.
    Note:
    Sudo commands don’t work with private key credentials, because there’s no password to supply to the sudo command. A solution is to add the NOPASSWD option to the sudo configuration. For example, you might enter: disco ALL=(root) NOPASSWD:/usr/sbin/dmidecode,/usr/sbin/lsof,/sbin/ifconfig.

    For information on commands that don’t require elevated rights, see Non-privileged SSH commands during probe-based discovery.

    For information on commands used by Service Mapping during the top-down discovery, see Service Mapping commands requiring a privileged user and Service Mapping commands not requiring a privileged user.

    SSH key not validated

    When the MID Server connects to a system, the MID Server doesn’t perform host key validation against that system and so treats it as untrusted. If an attacker performs a man-in-the-middle attack and redirects the traffic to a malicious SSH service, the attacker can intercept or modify any data sent over the connection.

    Therefore, limit any sensitive information exchanged between the MID Server and the target SSH server. Only use keys or certificates for SSH authentication, and avoid sending system credentials. Configure NOPASSWD in the sudoers file for the required privileged commands.

    Table 1. HP-UX
    Command Purpose
    adb Gathers CPU speed and memory.

    /etc/sudoers line example: Disco ALL=(root) /usr/bin/adb
    Table 2. All Linux
    Command Purpose
    dmidecode Gathers several pieces of information about the hardware, including the serial number embedded within the motherboard.

    /etc/sudoers line example: Disco ALL=(root) /sbin/dmidecode
    fdisk Gathers the disks and size information on the system.

    /etc/sudoers line example: Disco ALL=(root) /usr/bin/fdisk -l
    multipath Gathers device mappings for MultiPath Input Output (MPIO).

    /etc/sudoers line example: Disco ALL=(root) /usr/bin/multipath -ll
    Table 3. Linux and Solaris
    Command Purpose
    dmsetup Examines a low-level volume.

    /etc/sudoers line example

    • Disco ALL=(root) /usr/bin/dmsetup table *
    • Disco ALL=(root) /usr/bin/dmsetup ls
    Table 4. All UNIX versions
    Command Purpose
    lsof Determines the relationship between processes and the connections being made to the system.

    /etc/sudoers line example: Disco ALL=(root) /sbin/lsof
    oratab Grants read access to the oratab file for locating the Oracle Home and pfile.
    netstat Determines the relationship between processes and the connections being made to the system.

    /etc/sudoers line example: Disco ALL=(root) /bin/netstat
    ss Determines the relationship between processes and the connections being made to the system.

    /etc/sudoers line example: Disco ALL=(root) /sbin/ss
    Table 5. Solaris
    Command Purpose
    iscsiadm Gets iSCSI qualified names (IQNs).

    /etc/sudoers line example: ${sudo:iscsiadm list target -S}
    fcinfo Gets World Wide Port Names (WWPNs) for ports.

    /etc/sudoers line example: ${sudo:fcinfo remote-port -sl -p $port}
    prtvtoc Reports information about disk partitions.

    /etc/sudoers line example: Disco ALL=(root) /usr/bin/prtvtoc
    /usr/bin/ps Lists running process. As an alternative to running with root access, add a proc_owner role.sola.

    /etc/sudoers line example: Disco ALL=(root) /usr/bin/ps
    /usr/ucb/ps Lists running process. As an alternative to running with root access, add a proc_owner role.

    The use of the /usr/ucb/ps command is deprecated as of Solaris 11. Because Discovery requires the use of this command for all Solaris versions, you must install the ucb utility manually on Solaris 11 systems. For instructions, see KB0564262.

    /etc/sudoers line example: Disco ALL=(root) /usr/ucb/ps
    pgrep Gets list of process IDs (PIDs) with socket information.

    /etc/sudoers line example: Disco ALL=(root) /usr/bin/pgrep
    pfiles For each PID, gets and processes the output for S_IFSOCK.

    /etc/sudoers line example: Disco ALL=(root) /usr/bin/pfiles