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D.5. Linux

The probes in this section monitor essential aspects of your Linux systems, from CPU usage to virtual memory. Apply them to mission-critical systems to obtain warnings prior to failure.
Unlike other probe groups, which may or may not require the Red Hat Network Monitoring Daemon, every Linux probe requires that the rhnmd daemon be running on the monitored system.

D.5.1. Linux::CPU Usage

The Linux::CPU Usage probe monitors the CPU utilization on a system and collects the following metric:
  • CPU Percent Used — The five-second average of the percent of CPU usage at probe execution.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to run this probe.

Table D.15. Linux::CPU Usage settings

Field Value
Timeout* 15
Critical Maximum CPU Percent Used
Warning Maximum CPU Percent Used

D.5.2. Linux::Disk IO Throughput

The Linux::Disk IO Throughput probe monitors a given disk and collects the following metric:
  • Read Rate — The amount of data that is read in kilobytes per second.
  • Write Rate — The amount of data that is written in kilobytes per second.
To obtain the value for the required Disk number or disk name field, run iostat on the system to be monitored and see what name has been assigned to the disk you desire. The default value of 0 usually provides statistics from the first hard drive connected directly to the system.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe. Also, the Disk number or disk name parameter must match the format visible when the iostat command is run. If the format is not identical, the configured probe enters an UNKNOWN state.

Table D.16. Linux::Disk IO Throughput settings

Field Value
Disk number or disk name* 0
Timeout* 15
Critical Maximum KB read/second
Warning Maximum KB read/second
Warning Minimum KB read/second
Critical Minimum KB read/second
Critical Maximum KB written/second
Warning Maximum KB written/second
Warning Minimum KB written/second
Critical Minimum KB written/second

D.5.3. Linux::Disk Usage

The Linux::Disk Usage probe monitors the disk space on a specific file system and collects the following metrics:
  • File System Used — The percentage of the file system currently in use.
  • Space Used — The amount of the file system in megabytes currently in use.
  • Space Available — The amount of the file system in megabytes currently available.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.17. Linux::Disk Usage settings

Field Value
File system* /dev/hda1
Timeout* 15
Critical Maximum File System Percent Used
Warning Maximum File System Percent Used
Critical Maximum Space Used
Warning Maximum Space Used
Warning Minimum Space Available
Critical Minimum Space Available

D.5.4. Linux::Inodes

The Linux::Inodes probe monitors the specified file system and collects the following metric:
  • Inodes — The percentage of inodes currently in use.
An inode is a data structure that holds information about files in a Linux file system. There is an inode for each file, and a file is uniquely identified by the file system on which it resides and its inode number on that system.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.18. Linux::Inodes settings

Field Value
File system* /
Timeout* 15
Critical Maximum Inodes Percent Used
Warning Maximum Inodes Percent Used

D.5.5. Linux::Interface Traffic

The Linux::Interface Traffic probe measures the amount of traffic into and out of the specified interface (such as eth0) and collects the following metrics:
  • Input Rate — The traffic in bytes per second going into the specified interface.
  • Output Rate — The traffic in bytes per second going out of the specified interface.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.19. Linux::Interface Traffic settings

Field Value
Interface*
Timeout* 30
Critical Maximum Input Rate
Warning Maximum Input Rate
Warning Minimum Input Rate
Critical Minimum Input Rate
Critical Maximum Output Rate
Warning Maximum Output Rate
Warning Minimum Output Rate
Critical Minimum Output Rate

D.5.6. Linux::Load

The Linux::Load probe monitors the CPU of a system and collects the following metric:
  • Load — The average load on the system CPU over various periods.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.20. Linux::Load settings

Field Value
Timeout* 15
Critical CPU Load 1-minute average
Warning CPU Load 1-minute average
Critical CPU Load 5-minute average
Warning CPU Load 5-minute average
Critical CPU Load 15-minute average
Warning CPU Load 15-minute average

D.5.7. Linux::Memory Usage

The Linux::Memory Usage probe monitors the memory on a system and collects the following metric:
  • RAM Free — The amount of free random access memory (RAM) in megabytes on a system.
You can also include the reclaimable memory in this metric by entering yes or no in the Include reclaimable memory field.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.21. Linux::Memory Usage settings

Field Value
Include reclaimable memory no
Timeout* 15
Warning Maximum RAM Free
Critical Maximum RAM Free

D.5.8. Linux::Process Counts by State

The Linux::Process Counts by State probe identifies the number of processes in the following states:
  • Blocked — A process that has been switched to the waiting queue and whose state has been switched to waiting.
  • Defunct — A process that has terminated (either because it has been killed by a signal or because it has called exit()) and whose parent process has not yet received notification of its termination by executing some form of the wait() system call.
  • Stopped — A process that has been stopped before its execution could be completed.
  • Sleeping — A process that is in the Interruptible sleep state and that can later be reintroduced into memory, resuming execution where it left off.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.22. Linux::Process Counts by State settings

Field Value
Timeout* 15
Critical Maximum Blocked Processes
Warning Maximum Blocked Processes
Critical Maximum Defunct Processes
Warning Maximum Defunct Processes
Critical Maximum Stopped Processes
Warning Maximum Stopped Processes
Critical Maximum Sleeping Processes
Warning Maximum Sleeping Processes
Critical Maximum Child Processes
Warning Maximum Child Processes

D.5.9. Linux::Process Count Total

The Linux::Process Count Total probe monitors a system and collects the following metric:
  • Process Count — The total number of processes currently running on the system.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.23. Linux::Process Count Total settings

Field Value
Timeout* 15
Critical Maximum Process Count
Warning Maximum Process Count

D.5.10. Linux::Process Health

The Linux::Process Health probe monitors user-specified processes and collects the following metrics:
  • CPU Usage — The CPU usage rate for a given process in milliseconds per second. This metric reports the time column of ps output, which is the cumulative CPU time used by the process. This makes the metric independent of probe interval, allows sane thresholds to be set, and generates usable graphs (i.e. a sudden spike in CPU usage shows up as a spike in the graph).
  • Child Process Groups — The number of child processes spawned from the specified parent process. A child process inherits most of its attributes, such as open files, from its parent.
  • Threads — The number of running threads for a given process. A thread is the basic unit of CPU utilization, and consists of a program counter, a register set, and a stack space. A thread is also called a lightweight process.
  • Physical Memory Used — The amount of physical memory (or RAM) in kilobytes used by the specified process.
  • Virtual Memory Used — The amount of virtual memory in kilobytes used by the specified process, or the size of the process in real memory plus swap.
Specify the process by its command name or process ID. (PID). Entering a PID overrides the entry of a command name. If no command name or PID is entered, the error Command not found is displayed and the probe will be set to a CRITICAL state.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.24. Linux::Process Health settings

Field Value
Command Name
Process ID (PID) file
Timeout* 15
Critical Maximum CPU Usage
Warning Maximum CPU Usage
Critical Maximum Child Process Groups
Warning Maximum Child Process Groups
Critical Maximum Threads
Warning Maximum Threads
Critical Maximum Physical Memory Used
Warning Maximum Physical Memory Used
Critical Maximum Virtual Memory Used
Warning Maximum Virtual Memory Used

D.5.11. Linux::Process Running

The Linux::Process Running probe verifies that the specified process is functioning properly. It counts either processes or process groups, depending on whether the Count process groups checkbox is selected.
By default, the checkbox is selected, thereby indicating that the probe should count the number of process group leaders independent of the number of children. This allows you, for example, to verify that two instances of the Apache Web server are running regardless of the (dynamic) number of child processes. If it is not selected, the probe conducts a straightforward count of the number of processes (children and leaders) matching the specified process.
Specify the process by its command name or process ID. (PID). Entering a PID overrides the entry of a command name. If no command name or PID is entered, the error Command not found is displayed and the probe enters a CRITICAL state.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.25. Linux::Process Running settings

Field Value
Command name
PID file
Count process groups (checked)
Timeout* 15
Critical Maximum Number Running
Critical Minimum Number Running

D.5.12. Linux::Swap Usage

The Linux::Swap Usage probe monitors the swap partitions running on a system and reports the following metric:
  • Swap Free — The percent of swap memory currently free.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.26. Linux::Swap Usage settings

Field Value
Timeout* 15
Warning Minimum Swap Free
Critical Minimum Swap Free

D.5.13. Linux::TCP Connections by State

The Linux::TCP Connections by State probe identifies the total number of TCP connections, as well as the quantity of each in the following states:
  • TIME_WAIT — The socket is waiting after close for remote shutdown transmission so it may handle packets still in the network.
  • CLOSE_WAIT — The remote side has been shut down and is now waiting for the socket to close.
  • FIN_WAIT — The socket is closed, and the connection is now shutting down.
  • ESTABLISHED — The socket has a connection established.
  • SYN_RCVD — The connection request has been received from the network.
This probe can be helpful in finding and isolating network traffic to specific IP addresses or examining network connections into the monitored system.
The filter parameters for the probe let you narrow the probe's scope. This probe uses the netstat -ant command to retrieve data. The Local IP address and Local port parameters use values in the Local Address column of the output; the Remote IP address and Remote port parameters use values in the Foreign Address column of the output for reporting.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.27. Linux::TCP Connections by State settings

Field Value
Local IP address filter pattern list
Local port number filter
Remote IP address filter pattern list
Remote port number filter
Timeout* 15
Critical Maximum Total Connections
Warning Maximum Total Connections
Critical Maximum TIME_WAIT Connections
Warning Maximum TIME_WAIT Connections
Critical Maximum CLOSE_WAIT Connections
Warning Maximum CLOSE_WAIT Connections
Critical Maximum FIN_WAIT Connections
Warning Maximum FIN_WAIT Connections
Critical Maximum ESTABLISHED Connections
Warning Maximum ESTABLISHED Connections
Critical Maximum SYN_RCVD Connections
Warning Maximum SYN_RCVD Connections

D.5.14. Linux::Users

The Linux::Users probe monitors the users of a system and reports the following metric:
  • Users — The number of users currently logged in.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.28. Linux::Users settings

Field Value
Timeout* 15
Critical Maximum Users
Warning Maximum Users

D.5.15. Linux::Virtual Memory

The Linux::Virtual Memory probe monitors the total system memory and collects the following metric:
  • Virtual Memory — The percent of total system memory - random access memory (RAM) plus swap - that is free.
Requirements — The Red Hat Network Monitoring Daemon (rhnmd) must be running on the monitored system to execute this probe.

Table D.29. Linux::Virtual Memory settings

Field Value
Timeout* 15
Warning Minimum Virtual Memory Free
Critical Minimum Virtual Memory Free