What is The vmstat UNIX command used for?
vmstat command in Linux/Unix is a performance monitoring command of the system as it gives the information about processes, memory, paging, block IO, disk and CPU scheduling. All these functionalities makes the command vmstat also known as virtual memory statistic reporter.
How to read vmstat output?
- total: The total count of disk writes.
- merged: The total count of grouped writes.
- sectors: The total count of sectors written to.
- ms = Total count of time in milliseconds that were used writing data to the disk.
What are the most unknown commands in Linux?
which - looks through the directories in your search path in order and locates the utility. type - display information about the command. There is nothing we can define as (most) unknown commands in Linux. People get to know about the various commands as and when he/she troubleshoots an issue (s).
How to automate some Linux commands?
Using Shell Scripting to Automate Linux System Maintenance Tasks – Part 4
- Writing a script to display system information. And open a new text file named system_info.sh with your preferred text editor. ...
- Automating Tasks. The tasks that you may need to automate may vary from case to case. ...
- Using Cron. To take efficiency one step further, you will not want to sit in front of your computer and run those scripts manually.
- Summary. ...
What is use of vmstat command?
The vmstat command reports statistics about kernel threads in the run and wait queue, memory, paging, disks, interrupts, system calls, context switches, and CPU activity. The reported CPU activity is a percentage breakdown of user mode, system mode, idle time, and waits for disk I/O.
What is vmstat command What does it report?
The vmstat command reports statistics about kernel threads, virtual memory, disks, hypervisor pages, traps, and processor activity. Reports that are generated by the vmstat command can be used to balance system load activity.
How do I run vmstat?
How to Use vmstatIf you don't have vmstat on your machine, install it by running: ... Enter your password and wait for the installation to finish.Run vmstat without parameters to display a system report with average statistics since the last boot.For additional reports, use vmstat options, delay, and count.
What does vmstat stand for?
virtual memory statisticsResolution. vmstat (virtual memory statistics) is a valuable monitoring utility, which also provides information about block IO and CPU activity in addition to memory. vmstat Basics.
What is vmstat and iostat?
vmstat command (also known as virtual memory statistic tool) shows information about processes, memory, disk, and CPU activity in Linux, whereas the iostat command is used to monitor CPU utilization, system input/output statistics for all the disks and partitions.
What should I look for in vmstat?
What to Look for in vmstatr (runqueue) The runqueue value shows the number of tasks executing and waiting for CPU resources. ... pi (page in) A page-in operation occurs when the server is experiencing a shortage of RAM memory. ... us (user CPU) This is the amount of CPU that is servicing user tasks.More items...
What is swap in vmstat?
By reporting “swapping” separately from total disk activity, vmstat allows you to determine how much disk activity is related to the swap system. The si column reports the amount of memory that is moved from swap to “real” memory per second.
How do I exit vmstat?
Every five seconds vmstat will add another line of data to the table. You'll need to hit Ctrl+C to stop this.
What is Linux Htop?
Htop is an interactive real-time process monitoring application for Linux/Unix-like systems and also a handy alternative to top command, which is a default process monitoring tool that comes pre-installed on all Linux operating systems.
How does vmstat calculate memory utilization?
As per the above commands output,Free memory in GB =6917436*8192/1024/1024/1024=52.77GB.Free swap in GB=89634194*512/1024/1024/1024=42.74GB.Free swap in GB=44905096/1024/1024=42.82GB.
What is sar command in Linux?
sar: System Activity Report. It can be used to monitor Linux system's resources like CPU usage, Memory utilization, I/O devices consumption, Network monitoring, Disk usage, process and thread allocation, battery performance, Plug and play devices, Processor performance, file system and more.
How do I check virtual memory utilization in Linux?
How to Check Memory Usage in Linux, 5 Simple Commandscat Command to Show Linux Memory Information.free Command to Display the Amount of Physical and Swap Memory.vmstat Command to Report Virtual Memory Statistics.top Command to Check Memory Use.htop Command to Find Memory Load of Each Process.
What does a delay value do in VMstat?
Using too low a delay value will put additional strain on your system. If you need to have rapid updates to try to diagnose a problem, it is recommended that you use a count value as well as a delay value. The count value tells vmstat how many updates to perform before it exits and returns you to the command prompt.
Does Linux use vmstat?
The kernel—and hence, the CPU—must do more work as it swaps memory out, swaps memory in, and keeps all the plates spinning to satisfy the memory needs of the different processes. Linux provides a way for you to monitor all of this activity in the shape of the vmstat command, which reports on virtual memory statistics.
DESCRIPTION
vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity.
FIELD DESCRIPTION FOR VM MODE
r: The number of processes waiting for run time. b: The number of processes in uninterruptible sleep.
FIELD DESCRIPTION FOR DISK PARTITION MODE
reads: Total number of reads issued to this partition read sectors: Total read sectors for partition writes : Total number of writes issued to this partition requested writes: Total number of write requests made for partition
FIELD DESCRIPTION FOR SLAB MODE
cache: Cache name num: Number of currently active objects total: Total number of available objects size: Size of each object pages: Number of pages with at least one active object totpages: Total number of allocated pages pslab: Number of pages per slab
BUGS
Does not tabulate the block io per device or count the number of system calls.
Why does VMstat return inconsistent statistics?
The vmstat command might return inconsistent statistics because the statistics are not read atomically. If you run the vmstat command without flags, the report contains a summary of the virtual memory activity since system startup. If you specify the -f flag, the vmstat command reports the number of forks since system startup.
What does -f mean in command line?
Note: If the -f (or -s ) flag is entered on the command line, then the system accepts the -f (or -s ) flag and ignores other flags. If both the -f and -s flags are specified, the system accepts only the first flag and ignore the second flag.
Why use vmstat in Linux?
Linux developers often use this tool to solve issues related to memory. Running the vmstat command without any options gives the summary of memory statistics since the last re-boot of the system. Alternatively, you can use vmstat to report on memory periodically after a fixed interval also.
What is vmstat in Windows 10?
The vmstat command is short for ‘Virtual Memory Statistics’. It is a tool that reports on Virtual memory statistics. To be specific, it reports data about your system’s memory, swaps, and processor resource utilization, kernel threads, and disks in real-time.
What is vmstat?
Vmstat is a built-in Linux system monitoring tool. Its primary job is measuring a system’s usage of virtual memory. No matter how powerful it is, a Linux server has a finite amount of random access memory (RAM). A Linux system can run out of RAM for several reasons, such as demands on the operating system and its running applications.
How to Use vmstat
You can run vmstat both as an interactive program and in shell programs. When you run vmstat without any parameters, it shows system values based on the averages for each element since the server was last rebooted. These results are not a snapshot of current values.
How to Interpret vmstat Output
vmstat reports describe the current state of a Linux system. Information regarding the running state of a system is useful when diagnosing performance related issues.
More Information
You may wish to consult the following resources for additional information on this topic. While these are provided in the hope that they will be useful, please note that we cannot vouch for the accuracy or timeliness of externally hosted materials.
What is virtual memory?
As virtual memory, we should not understand it as an additional module that our computer has but as a technique of computer memory management, whose use lies in the joint use of the main memory of the system and our storage unit, such as a hard disk.
The vmstat command
The vmstat command is used in UNIX operating systems, it provides data about virtual memory, gives information about processes, memory, paging, block I/O, traps, and CPU activity.
Using the vmstat commmand
If you run the command without any options or parameters you will get an output screen similar to this one
Conclusion
A terminal is an incredible tool and in Unix, there are commands for everything. In this case, we have presented you with a command to monitor virtual memory usage. This kind of command helps us not to miss anything about our computer. Sysadmins appreciate this kind of command that does not consume resources and provides useful information.
Display Number of CPUs in Solaris
In Solaris, the prsinfo command can be used to count the number of CPUs on the processor. Here we see that we have two CPUs on this server:
Display Number of CPUs in Linux
To see the number of CPUs on a Linux server, you can cat the /proc/cpuinfo file. In the example here we see that our Linux server has four CPUs:
