![]() ![]() Swap memory is usually a "set it and forget it" type of affair. How well do you know Linux? Take a quiz and get a badge.Linux system administration skills assessment.A guide to installing applications on Linux.Download RHEL 9 at no charge through the Red Hat Developer program.I hope that you have enjoyed this look at the vmstat command. It prints updates using two main variables (delay and count), and we can customize the command and output to suit our needs. The vmstat command is a powerful system statistics tool that can be used with or without options. To wrap up, let's look at what we learned. You see that there are 10 updates, printed every five seconds, with timestamp information attached.Īlso, please note that all memory stats are displayed in kilobytes by default. Procs -memory-swap-io-system-cpu-timestamp. The -t option gives us timestamp information with every update, a seen here: ~]$ vmstat -t 5 10 Total merged sectors ms total merged sectors ms cur sec The -d option gives you read/write stats for various disks: ~]$ vmstat -dĭisk-reads-writes-IO. The -s option displays various memory statistics as well as CPU and IO event counters: ~]$ vmstat -s Note that a fork is any process that spawns another processes while remaining active. The -f option will give us the number of forks since boot: ~]$ vmstat -f The -a option will give us the active and inactive memory of the system: ~]$ vmstat -a Prior to Linux 2.6.11, unknown.Īmong the important information here, you find the amount of free memory on the system, as well as the amount of swap activity you are currently experiencing. st: Time stolen from a virtual machine. Prior to Linux 2.5.41, this includes IO-wait time. us: Time spent running non-kernel code. These are percentages of total CPU time. cs: The number of context switcher per second. in: The number of interrupts per second, including the clock. bo: Blocks sent to a block device (blocks/s). bi: Blocks received from a block device (blocks/s). so: Amount of memory swapped to a block device (/s). si: Amount of memory swapped in from disk (/s). cache: the amount of memory used as cache. buff: the amount of memory used as buffers swpd: the amount of virtual memory used. b: The number of processes in uninterruptible sleep. r: The number of runnable processes (running or waiting for run times) The man page for the command states the following ( man vmstat): - Procs You see information around processes, memory, swap, IO, system, and CPU. Here is the standard output and how to read it: ~]$ vmstat The most basic form of this command uses no options at all. If no count is set, the default in an infinite number of updates every x seconds (where x = delay). Count - this defines the number of updates printed after the given delay interval.If no delay is specified, the report runs as an average since the last reboot. Delay - this defines the time interval between updates. ![]() Options - these are covered in detail in the following section.The syntax for the vmstat command is rather simple: I cover those specifically during the syntax discussion. Subsequent reports use measurements of delay and count. When you run vmstat, keep in mind that the first report is an average of the requested information since the time of the last reboot. Things like memory, paging, processes, IO, CPU, and disk scheduling are all included in the array of information provided. Virtual memory statistics reporter, also known as vmstat, is a Linux command-line tool that reports various bits of system information. ![]()
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