10 tools to Monitor Linux Server Resource Usage and Statistics

Introduction

Monitoring Linux Server resources is an important aspect of system administration that lets you track the general server performance and ensure system reliability. To monitor server resources, you can use built-in system utility tools, or install secondary tools to view real-time resource usage and performance statistics.

Linux Server CPU, GPU, memory, and storage devices are some of the major system resources that require constant monitoring. If any important resource fails or performs beyond the allowed capacity, it can directly affect the server performance and lead to system application failures.

This article explains how to monitor Linux Server resource usage and display performance statistics using utility tools to keep track of the general system performance.

Prerequisites

Before you begin:

• Deploy a Vultr Linux server to test the monitoring tools.
• Access the server using SSH as a non-root user with sudo privileges.
• Update the server to install secondary tools.

Monitor Server CPU, GPU, Storage and Memory Usage

NVIDIA-SMI

NVIDIA Management Interface (nvidia-smi) is a cross-platform command line utility that monitors attached GPU devices, VRAM usage,and performance statistics on a GPU-powered Linux Server. By default, nvidia-smi is available as part of the NVIDIA GPU drivers package. You can use the tool to display GPU information in XML or plain test formats.

• Run the nvidia-smi command to monitor your server GPU usage

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  $ nvidia-smi

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• To periodically update nvidia-smi to view real-time performance and usage information, use the watch utility. For example, run the following command to refresh the nvidia-smi output every 5 seconds.

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  $ watch -n 5 nvidia-smi

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  Press Ctrl + C to stop the watch process.

For more information about the nvidia-smi utility, visit the official documentation.

DF (Disk Free)

Disk Free (DF) is a built-in Linux utility that allows you to monitor the server disk space usage and attached storage device data directories. Using the tool, you can monitor the available file system directories, used space, free space, and mounting locations for each storage device attached to your server.

1. Run the df command to view your server disk usage information.

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   $ df

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   Your output should look like the one below:

   Filesystem     1K-blocks     Used Available Use% Mounted on
   udev             4039772        0   4039772   0% /dev
   tmpfs             812544      712    811832   1% /run
   /dev/vda2      176646024 12074588 156985756   8% /
   tmpfs            4062704        0   4062704   0% /dev/shm
   tmpfs               5120        0      5120   0% /run/lock
   /dev/vda1         523244    11848    511396   3% /boot/efi
   tmpfs             812540        0    812540   0% /run/user/0

2. df displays disk usage in Kilobits. To view data in a human-readable form of Kilobytes, Megabytes, and Gigabytes, use the -h option.

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   $ df -h

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   Output:

   Filesystem      Size  Used Avail Use% Mounted on
   udev            3.9G     0  3.9G   0% /dev
   tmpfs           794M  712K  793M   1% /run
   /dev/vda2       169G   12G  150G   8% /
   tmpfs           3.9G     0  3.9G   0% /dev/shm
   tmpfs           5.0M     0  5.0M   0% /run/lock
   /dev/vda1       511M   12M  500M   3% /boot/efi
   tmpfs           794M     0  794M   0% /run/user/0

3. To view information about a specific device volume, specify the filesystem path. For example, view the main system volume /dev/vda2 with the filesystem type T and human readable h options.

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   $ df -Th /dev/vda1

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   Output:

   Filesystem     Type  Size  Used Avail Use% Mounted on
   /dev/vda2      ext4  169G   12G  150G   8% /

   The df command output includes the following sections:

   • Filesystem: Displays the storage device name on the server filesystem. Usually, the main server storage volume uses the /dev/vda2 virtual disk ID while the boot volume uses /dev/vda1. Additional volumes such as /dev/vda3, /dev/vda4 may represent secondary partitions or volumes such as Vultr Block Storage.
   • 1K-blocks: Displays the volume total size on the file system in 1-kilobyte blocks.
   • Type: Displays the volume filesystem format.
   • Size: The Total size of the storage volume in Megabytes or Gigabytes.
   • Used: Displays the amount of used space on the storage volume.
   • Available: Displays the unused space available on the storage volume.
   • Use Percentage (Use%): Displays the percentage of used space on the storage volume on a scale of 100%.
   • Mounted on: Displays the volume mounting directory on the Linux filesystem. For example, / represents the root Linux server directory where all system files are stored. Files written to a mount directory are added to the storage volume.

4. For more information and storage monitoring options, view the df manual page.

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   $ man df

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Free

free is a built-in utility that displays information about the server memory usage. It's part of the default procps utilities package and allows you to view available and used memory on the server. This includes the default system memory (RAM) and SWAP memory borrowed from the disk. Run the free command together with your desired memory measurement value to view the active usage statistics.

1. By default, the free command without any option displays memory usage in Kibibytes.

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   $ free

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   Your output should look like the one below:

                  total        used        free      shared  buff/cache   available
   Mem:         8125412      814608     5234968         724     2395824     7310804
   Swap:        8388604           0     8388604

   To modify your memory measurement value, use any of the following options:

   • -b: Bytes
   • -k: Kibibytes
   • -m: Mebibytes
   • -g: Gibibytes
   • --kilo: Kilobytes
   • --mega: Megabytes
   • --giga: Gigabytes

2. To generate a more readable output, apply the human-readable option -h to display the server memory usage in Megabytes.

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   $ free -h

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   Output:

                  total        used        free      shared  buff/cache   available
   Mem:            7934         791        5136           0        2319        7143
   Swap:           8191           0        8191

   Below are the command sections:

   • Mem: The main Linux server memory (RAM)
   • Swap: Swap memory
   • Total: The total memory size
   • Used: Displays the amount of used memory
   • Free: Displays the amount of free unused memory
   • Available: Displays the amount of memory available to run system applications without switching to swap memory.

3. To monitor the server memory usage in real-time, use the watch command to continuously update the usage statistics. For example, run the following command to update the memory usage statistics every after 3 seconds.

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   $ watch -n 3 free -h

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4. To view detailed information about swap memory. Use the swapon command.

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   $ swapon

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   Your output should look like the one below:

   NAME      TYPE SIZE USED PRIO
   /swapfile file   8G   0B   -2

5. For more information, and free utility memory usage options, view the command manual page.

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   $ man free

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Top

Top is a built-in command-line utility that displays real-time information about the server resources and processes. It offers a dynamic interface that includes the system information, CPU usage, memory usage, and actively running server processes or threads. Within the top interface, you can monitor and kill any server processes to optimize the system performance.

1. By default, top is available in the default procps-ng system package. In case of any errors or unavailability, install the package using the default system package manager.

   • Debian/Ubuntu:

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     $ sudo apt-get install procps

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   • CentOS/Rocky Linux/ RHEL-based systems

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     $ sudo dnf install procps-ng

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2. To use the tool, run the top command.

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   $ top

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   Your output should look like the one below:

   top - 11:45:02 up 1 day, 13:55,  1 user,  load average: 1.93, 1.85, 1.85
   Tasks: 129 total,   1 running, 128 sleeping,   0 stopped,   0 zombie
   %Cpu(s): 41.9 us,  0.7 sy,  0.0 ni, 57.2 id,  0.0 wa,  0.0 hi,  0.3 si,  0.0 st
   MiB Mem :   7935.0 total,   5111.6 free,    812.8 used,   2323.1 buff/cache    
   MiB Swap:   8192.0 total,   8192.0 free,      0.0 used.   7122.2 avail Mem
   
       PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND                                                                      
   
      2731 root      20   0  792044 169828  15124 S 168.7   2.1     64,31 ffmpeg                                                                        
       911 root      20   0  799768 123128     40 S   4.3   1.5  71:21.02 obs-studio                                                                      
     33660 nginx     20   0 1269972  64124  31556 S   0.7   0.8   5:08.51 nginx                                                                        
        21 root      20   0       0      0      0 S   0.3   0.0   0:06.73 ksoftirqd/1                                                                  
     42893 root      20   0   11612   5524   3360 R   0.3   0.1   0:01.98 top                                                                          
         1 root      20   0  168792  13532   9268 S   0.0   0.2   0:05.17 systemd                                                                      
         2 root      20   0       0      0      0 S   0.0   0.0   0:00.03 kthreadd

   The top interface is divided into the following sections:

   • System Information: Displays real-time system information with the time, uptime, number of logged in Linux users, and load averages.
   • Tasks: Displays the total number of running tasks, active, stopped, and dormant processes on the server.
   • CPU Usage: Displays the CPU usage percentages including the time spent on system processes and the average Input/Output (I/O) processing time.
   • Memory Usage: Displays the server memory usage statistics including used and available memory.
   • System Processes: Displays all running processes available on the server. Within the section, each header represents a specific value as described below:
     • PID: The unique process id of each task on the server.
     • PR: The system process priority, a lower number represents a higher priority.
     • VIRT: Total virtual memory in use by a process.
     • USER: The system user that owns the running process.
     • %CPU: The percentage of CPU usage occupied by the process.
     • SHR: Represents the process Shared Memory size in Kilobytes.
     • NI: The process niceness value. A negative value represents a higher process priority while a lower priority uses a positive value.
     • %MEM: Displays the memory usage percentage occupied by the process.
     • RES: Displays the amount of resident memory used by the process in Kilobytes.
     • TIME+: Shows the process CPU execution time.
     • COMMAND: The server command under which the process runs.

   Press Q to exit the top interface.

3. To limit the top output to strictly display processes started by a user, apply the -u option together with the target username. For example, linuxuser.

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   $ top -u linuxuser

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   Output:

   top - 22:00:09 up 15 min,  2 users,  load average: 0.00, 0.01, 0.00
   Tasks: 125 total,   1 running, 124 sleeping,   0 stopped,   0 zombie
   %Cpu(s):  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
   MiB Mem :    951.5 total,     68.8 free,    205.4 used,    677.3 buff/cache
   MiB Swap:   2400.0 total,   2392.2 free,      7.8 used.    596.2 avail Mem
   
   
       PID USER          PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND                                                              
      3074 linuxuser  20   0    8732   4496   3788 S   0.0   0.5   0:00.02 bash                                                                
      4469 linuxuser  20   0   10500   4076   3488 R   0.0   0.4   0:00.01 top

4. To kill an active process on the server, press k, enter the Process ID to stop, and press Enter to end the process thread.

5. For more information and command options, view the top command manual page.

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   $ man top

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VmStat

Virtual Memory Statistics (VmStat) is a built-in utility that displays real-time information about the system memory, virtual memory, paging, and CPU activity. It's an important tool that allows you to constantly monitor your Linux server performance, identify memory-related issues, and analyze how running processes utilize the available system resources.

1. By default VmStat is part of the Linux procps-ng package, to use the tool, run the vmstat command.

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   $ vmstat

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   Output:

   procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
   r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
   0  0  19824  71196  13852 631596    0    6   435  1008   78  207  1  1 98  0  0

   Below is what the vmstat information categories represent:

   • procs: Process information about actively running processes.
   • memory: Server memory usage statistics.
   • swap: Available Swap memory usage processes.
   • io: Input and Output information that includes blocks sent in and out to the server storage devices.
   • system: System-related statistics including interrupts and the number of context switches per second.
   • cpu: CPU usage statistics with the average processing time in each space.

2. To update the VmStat output after a specific time, include the time range as a command option. For example, update the output after every 2 seconds.

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   $ vmstat 2

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3. To display a specific number of monitoring reports, include the count interval value as an option. For example, to update the monitoring information every 2 seconds and generate only 10 reports, run the following command.

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   $ vmstat 2 10

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4. To view a summary of the server memory and CPU usage statistics, use the -s option.

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   $ vmstat -s

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   Output:

      974344 K total memory
      257164 K used memory
      337900 K active memory
      353560 K inactive memory
       71196 K free memory
       14060 K buffer memory
      631924 K swap cache
     2457596 K total swap
       19824 K used swap
     2437772 K free swap
        3618 non-nice user cpu ticks
         407 nice user cpu ticks
        2706 system cpu ticks
      376208 idle cpu ticks
         222 IO-wait cpu ticks
           0 IRQ cpu ticks
          43 softirq cpu ticks
           2 stolen cpu ticks
     1484613 pages paged in
     3451429 pages paged out
         340 pages swapped in
        5331 pages swapped out
      281987 interrupts
      734623 CPU context switches
   1697060650 boot time
        6384 forks

5. To view server disk statistics, use the -d option.

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   $ vmstat -d

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   Output:

   disk- ------------reads------------ ------------writes----------- -----IO------
          total merged sectors      ms  total merged sectors      ms    cur    sec
   loop0     67      0    2486       8      0      0       0       0      0      0
   loop1   1203      0   90584      86      0      0       0       0      0      3
   loop2    222      0    4720      17      0      0       0       0      0      0
   loop3    635      0   47156      29      0      0       0       0      0      1
   loop4     26      0      68       0      0      0       0       0      0      0
   loop5      0      0       0       0      0      0       0       0      0      0
   loop6      0      0       0       0      0      0       0       0      0      0
   loop7      0      0       0       0      0      0       0       0      0      0
   vda    29546   6331 2824453    6052  13387  17304 9419714   18500      0     23
   sr0        4      0       1       0      0      0       0       0      0      0

6. To further optimize your VmStat monitoring output, view the command manual page and use any of the following options.

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   $ man vmstat

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   The available options include:

   • -a: Views the active server memory statistics and displays active and inactive memory pages.
   • -m: Displays information about the server Kernel slab cache memory usage.
   • -n: Shows column headers only once instead of every update interval.
   • -s: Displays a summary of memory usage, CPU and I/O statistics.
   • -d: Displays disk I/O statistics including read and write operations to storage devices.
   • -S: Sets the memory size display units. For example, vmstat -S M displays the memory values in Megabytes.
   • -t: Includes a timestamp on each output line.

Monitor System Processes

PS

Process Status (PS) is a built-in command line utility that displays information about actively running processes on your Linux server. Using the tool, you can view processes started by all users, a specific Linux user, or system daemons. In addition, you can filter the listed information using the grep utility to search for specific processes on the server.

1. Run the ps command to view actively running processes in your terminal session.

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   $ ps

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   Output:

      PID TTY          TIME CMD
   162611 pts/0    00:00:00 bash
   166207 pts/0    00:00:00 ps

2. To view all actively running processes on the server across all terminal sessions, use the aux option.

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   $ ps aux

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   Output:

   root       18112  0.0  0.0   2472    76 ?        S<   Nov20   0:06 /usr/sbin/atopacctd
   monitor+   47565  0.0  1.1  82208 11272 ?        Ss   Nov20   0:06 monitorix-httpd listening on 8080
   root       69049  0.0  0.4  25260  4816 ?        Ss   Nov21   0:00 /lib/systemd/systemd-udevd
   root       69121  0.0  8.6 123048 85028 ?        Ss   Nov21   0:30 /lib/systemd/systemd-journald
   root       73301  0.0  0.8  15408  8548 ?        Ss   Nov21   0:15 sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups
   ntpsec     73560  0.0  1.9  84880 19240 ?        SLs  Nov21   0:07 /usr/sbin/ntpd -p /run/ntpd.pid -c /etc/ntpsec/ntp.conf -g -N -u ntpsec:ntpsec
   root      126843  0.0  1.0  11032  9948 ?        S<Ls 00:00   0:02 /usr/bin/atop -w /var/log/atop/atop_20231122 600
   www-data  126922  0.0  1.1 753740 10988 ?        Sl   00:00   0:00 /usr/sbin/apache2 -k start
   www-data  126923  0.0  0.7 753740  6900 ?        Sl   00:00   0:00 /usr/sbin/apache2 -k start
   root      152214  0.0  0.0      0     0 ?        I    09:11   0:06 [kworker/0:1-events]
   root      162583  0.0  1.1  17828 11140 ?        Ss   14:21   0:00 sshd: linuxuser [priv]
   linuxus+  162586  0.0  1.0  18868 10508 ?        Ss   14:21   0:00 /lib/systemd/systemd --user

3. To sort the system processes information, use the --sort= option and include your target value. For example, sort the server processes by memory usage.

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   $ ps aux --sort=-%mem

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   Other sorting values include:

   • -%cpu: Sorts running processes by the CPU usage percentage in descending order. Applying + instead of - sorts the usage values in ascending values.
   • -%mem: Displays running processes based on the memory usage percentage in descending order.
   • +rss: Displays processes based on the real-time memory usage.
   • +start_time: Displays processes based on the start time in ascending order. Old processes first are display first and newer processes last.
   • +user: Sorts the running processes based on the user and process owner values.

4. To view the processes started by a specific user, apply the -u option and the target username.

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   $ ps -u root

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5. To view the command in full format with additional values such as User ID, process ID, and CPU utilization details, use the -f option.

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   $ ps -f

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6. To view more ps process monitoring options, view the command manual.

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   $ man ps

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Htop

Htop is an interactive system process viewer that displays real-time information about active server processes, CPU, and memory usage. It's an improved version of the built-in top utility with additional monitoring features and capabilities. To use Htop on your server, install the latest version using the default system package manager.

1. Install Htop:

   • Debian/Ubuntu:

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     $ sudo apt install htop

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   • CentOS/Rocky Linux/Fedora/RHEL systems

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     $ sudo dnf install htop

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2. Verify the installed Htop version.

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   $ htop --version

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   Output:

   htop 3.2.2

3. Open the Htop interface to view active server processes.

   

   Within the Htop interface, monitor the Process section to view real-time statistics of all actively running server processes. To navigate through the additional features, use a combination of keyboard function key shortcuts and interactive commands listed at the bottom of the interface.

   Press :key_q: to stop monitoring and close the Htop interface.

4. To modify the Htop interface, define an option while starting the command. For example, display processes with a hierarchical tree view.

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   $ htop -t

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   For example:

   • -t: Displays system processes in a tree view depending on the parent directory to monitor process hierarchies.
   • -C: Start Htop in monochrome mode without any coloring.
   • -d: Sets the processes update interval in seconds. For example, -d 5 updates the process information every 5 seconds.
   • -p: Displays information about specific process IDs (PIDs). You can specify one or more PIDs as arguments using this option. For example, -p 623 displays statistics for the process ID 623.
   • -u: Displays processes owned by a specific user on the Linux server. For example, -u example-user displays all active processes started by example-user.
   • -H: Hides threads and displays only the parent process for multi-threaded applications.

5. For more information and monitoring options, view the Htop manual page.

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   $ man htop

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Lsof

List Open Files (LSof) is a built-in tool that displays information about all open files and directories in use by system processes. This allows you to keep track of open directories and server processes that actively use specific files on the server. To use lsof, start the command with sudo privileges to view all processes or monitor specific processes using the respective process ID.

1. List all open files in use by active processes and the respective process IDs on your server.

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   $ sudo lsof

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   Your output should look like the one below:

   COMMAND     PID  TID TASKCMD       USER   FD      TYPE             DEVICE SIZE/OFF       NODE NAME
   systemd       1                    root  cwd       DIR              254,2     4096          2 /
   systemd       1                    root  rtd       DIR              254,2     4096          2 /
   systemd       1                    root  txt       REG              254,2    92544       5001 /usr/lib/systemd/systemd
   systemd       1                    root  mem       REG              254,2   157768        440 /usr/lib/x86_64-linux-gnu/libgpg-error.so33.1
   systemd       1                    root  mem       REG              254,2   629384        691 /usr/lib/x86_64-linux-gnu/libpcre2-8.so.0.112
   systemd       1                    root  mem       REG              254,2   907784         56 /usr/lib/x86_64-linux-gnu/libm.so.6
   systemd       1                    root    2u      CHR                1,3      0t0          4 /dev/null
   systemd       1                    root    3w      CHR               1,11      0t0         10 /dev/kmsg
   systemd       1                    root    4u  a_inode               0,14        0       9609 [eventpoll:5,6,9,11,12,14,15,16,17,18,19,2021,26,31,34,35,49,62,71,72,73,74,75,76,77,85,86]
   systemd       1                    root    5u  a_inode               0,14        0       9609 [signalfd]    

2. List open files in use by server processes on a specific directory. For example, view open files in use by system processes on the root system directory /.

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   $ sudo lsof /

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3. List all files in use by processes started by a specific user.

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   $ sudo lsof -u linuxuser

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   Output:

   COMMAND     PID  TID TASKCMD       USER   FD      TYPE             DEVICE SIZE/OFF       NODE NAME
   sshd     1146 linuxuser    5u     unix 0x000000008a363cd1      0t0      16919 type=STREAM (CONNECTED)
   sshd     1146 linuxuser    7u      CHR                5,2      0t0         85 /dev/ptmx
   sshd     1146 linuxuser    8w     FIFO               0,23      0t0       1092 /run/systemd/sessions/2.ref
   bash     1147 linuxuser  cwd       DIR              254,2     4096    1020929 /home/linuxuser
   bash     1147 linuxuser  rtd       DIR              254,2     4096          2 /
   bash     1147 linuxuser  txt       REG              254,2  1265648       1598 /usr/bin/bash
   bash     1147 linuxuser  mem       REG              254,2  1922136         53 /usr/lib/x86_64-linux-gnu/libc.so.6

4. List all server processes that use a specific network port. For example, view all processes using the HTTP port 80.

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   $ sudo lsof -i :80

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5. List files in use by a specific program or server application. For example, view all files in use by the Apache web server

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   $ sudo lsof /usr/sbin/apache2

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   To display accurate information, use the main application executable binary file. When successful, your output should look like the one below:

   COMMAND   PID     USER  FD   TYPE DEVICE SIZE/OFF  NODE NAME
   apache2 14081     root txt    REG  254,2   725920 73333 /usr/sbin/apache2
   apache2 14083 www-data txt    REG  254,2   725920 73333 /usr/sbin/apache2
   apache2 14084 www-data txt    REG  254,2   725920 73333 /usr/sbin/apache2

   To find the binary location of a specific application on your server, use the which command to view the active path.

6. For more information and command options, view the lsof manual page.

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   $ man lsof

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Iotop

iotop is a real-time interactive Input/Output (I/O) process monitoring tool that allows you to view processes or threads actively accessing the server storage devices. It allows you to identify processes that consume the most disk I/O bandwidth and provides insights into how different processes interact with storage devices. Within the output, the read-write speed, time spent on swapping, priority class, command, and the respective process users make it possible to actively track events on the server. To use iotop, install the version using your default system package manager.

1. Install iotop:

   • On a Debian or Ubuntu server:

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     $ sudo apt install iotop

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   • CentOS/Rock Linux or Fedora Linux

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     $ sudo dnf install iotop

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2. Verify the installed iotop version

   $ sudo iotop --version

   Output:

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   iotop 0.6

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3. Open the iotop interface to start monitoring all server processes

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   $ sudo iotop

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   Output:

   Total DISK READ:         0.00 B/s | Total DISK WRITE:         0.00 B/s
   Current DISK READ:       0.00 B/s | Current DISK WRITE:       0.00 B/s
       TID  PRIO  USER     DISK READ DISK WRITE>    COMMAND                                                                                            
         1 be/4 root        0.00 B/s    0.00 B/s init vultr
         2 be/4 root        0.00 B/s    0.00 B/s [kthreadd]
         3 be/0 root        0.00 B/s    0.00 B/s [rcu_gp]
         4 be/0 root        0.00 B/s    0.00 B/s [rcu_par_gp]
         5 be/0 root        0.00 B/s    0.00 B/s [slub_flushwq]
         6 be/0 root        0.00 B/s    0.00 B/s [netns]
        10 be/0 root        0.00 B/s    0.00 B/s [mm_percpu_wq]
        11 be/4 root        0.00 B/s    0.00 B/s [rcu_tasks_kthread]
        14 be/4 root        0.00 B/s    0.00 B/s [ksoftirqd/0]
        15 be/4 root        0.00 B/s    0.00 B/s [rcu_preempt]
        16 rt/4 root        0.00 B/s    0.00 B/s [migration/0]
        18 be/4 root        0.00 B/s    0.00 B/s [cpuhp/0]

   Within the interface, identify resource-intensive server processes, troubleshoot I/O performance issues, and optimize the server storage usage based on the active processes.

   Press Q on your keyboard to close the iotop interface.

4. To view active server processes performing I/O operations instead of all system threads, use the -o option.

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   $ sudo iotop -o

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5. To include a timestamp on all server processes, apply the -t option.

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   $ sudo iotop -t

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6. To view server processes started by a specific system user, apply the -u option. For example, view processes started by linuxuser.

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   $ sudo iotop -u linuxuser

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   Output:

   Total DISK READ:         0.00 B/s | Total DISK WRITE:         0.00 B/s
   Current DISK READ:       0.00 B/s | Current DISK WRITE:       0.00 B/s
     TID  PRIO  USER     DISK READ DISK WRITE>    COMMAND 
    1122 be/4 linuxuse    0.00 B/s    0.00 B/s systemd --user
    1124 be/4 linuxuse    0.00 B/s    0.00 B/s (sd-pam)
    1146 be/4 linuxuse    0.00 B/s    0.00 B/s sshd: linuxuser@pts/0
    1147 be/4 linuxuse    0.00 B/s    0.00 B/s -bash

   To further modify your iotop output, implement more options such as:

   • -n: Sets the number of iterations in batch mode before iotop exits. For example, -n 5 runs only 5 iterations and stops.
   • -a: Shows the number if I/O processes instead of bandwidth.
   • -b: Starts iotop in batch mode with a continuous output necessary for logging or scripting operations.
   • -d: Sets the iotop update interval in seconds. For example, -d 2 updates the output every 2 seconds.
   • -p: Displays I/O information for a specific process ID. For example -p 1121 displays I/O processes started by the Process ID 1121.
   • -q: Removes the output header and summary information to display only active processes.

7. For more information and command options, view the iotop manual page.

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   $ man iotop

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Monitor Server Uptime and Kernel Messages

Uptime

Uptime is a basic Linux utility that monitors the server uptime, actively logged-in users, and system load averages. Using the tool, you can keep track of the server boot time, CPU idle time, and the uptime duration since the last reboot. To use the tool, verify the installed version on your system, then, apply fine-tune your output using the available command options.

1. Verify your system's Uptime utility version.

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   $ uptime -V

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   Output:

   uptime from procps-ng 4.0.2

2. View the Server Uptime, logged-in users, and the system load averages.

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   $ uptime

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   Output:

   01:29:57 up  7:32,  1 user,  load average: 0.00, 0.02, 0.03

3. View the Server Uptime in hours and minutes.

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   $ uptime -p

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   Output:

   up 7 hours, 32 minutes

4. View the last server reboot date.

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   $ uptime -s

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   Output:

   2023-11-19 17:57:53

Strace

strace is a Linux diagnostic utility tool that monitors system calls and signals. It runs a specific program or command until it exits to keep track of the system calls made by the process, and the signals received by the process. This allows you to monitor the performance of Kernel state functions while executing a specific command for debugging, and troubleshooting purposes.

1. Install strace if it's not available on your server:

   • Debian/Ubuntu:

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     $ sudo apt install strace

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   • CentOS/RHEL systems:

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     $ sudo dnf install strace

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2. Verify the available strace version on your server

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   $ strace --version

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   Output:

   strace -- version 6.1

3. Using strace, trace the calls of a specific server application. For example: apache2

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   $ sudo strace apache2

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   Your output should look like the one below:

   m`map(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fd3919fa000
   mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fd3919f8000
   mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fd3919f6000
   mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fd3919f4000
   mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fd3919f2000
   socket(AF_NETLINK, SOCK_RAW|SOCK_CLOEXEC, NETLINK_ROUTE) = 3
   bind(3, {sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, 12) = 0
   getsockname(3, {sa_family=AF_NETLINK, nl_pid=18776, nl_groups=00000000}, [12]) = 0
   sendto(3, [{nlmsg_len=20, nlmsg_type=RTM_GETADDR, nlmsg_flags=NLM_F_REQUEST|NLM_F_DUMP, nlmsg_seq=1700444885, nlmsg_pid=0}, {ifa_family=AF_UNSPEC, ...}], 20, 0, {sa_family=AF_NETLINK, nl_pid=0, nl_groups=00000000}, 12) = 20

4. To monitor a specific process on the server, use the -p option and include the process ID. For example, trace the process ID 1121.

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   $ sudo strace -p 1121

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5. For more information, view the strace command manual page.

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   $ man strace

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Conclusion

You have applied Linux resource monitoring tools to keep track of the server CPU usage, memory usage, system processes, and Kernel messages. To fine-tune your server performance, you should continuously track each tool's output to manage high-resource processes or upgrade necessary resources to meet the server demands. For more information about each tool, view the command manual page to explore the additional usage options.