Master these Linux commands to check IO status, and don’t ask for help at critical moments!
Source: https://www.cnblogs.com/arthinking/p/14450337.html
Introduce three commonly used I/O related commands in Linux. Use iostat to solve the problem of excessive I/O pressure, use iotop to check the I/O status of the disk, and use lsof to check the I/O process ranking.
1. iostat
The iostat tool will monitor the system's disk operation activities. Its characteristic is to report disk activity statistics, and also report CPU usage. To use the iostat command, you need to install the sysstat software
[root@localhost ~]# yum -y install sysstat[root@localhost ~]# iostatLinux 5.14.0-162.6.1.el9_1.x86_64 (localhost.localdomain) 12/02/22 _x86_64_ (2 CPU)avg-cpu: %user %nice %system %iowait %steal %idle1.75 0.02 5.84 0.60 0.00 91.79Device tps kB_read/s kB_wrtn/s kB_dscd/s kB_read kB_wrtn kB_dscddm-0 73.70 2078.84 358.65 0.00 162919 28107 0dm-1 1.26 29.96 0.00 0.00 2348 0 0nvme0n1 104.45 2809.71 385.01 0.00 220197 30173 0sr0 1.03 40.12 0.00 0.00 3144 0 0
Output information:
avg-cpu segment
user: 用户程序占用CPU的百分比nice: nice操作占用CPU的百分比system: 系统占用CPU的百分比iowait: CPU等待硬件I/O时占用CPU百分比idle: CPU空闲时间的百分比
Device segment
tps: 每秒钟I/O请求数kB_read /s: 每秒读取的块数kB_wrtn/s: 每秒写入的块数kB_read: 读入的块总数kB_wrtn: 写入的块总数
Common parameters
-c 仅显示CPU统计信息，与-d互斥-d 仅显示磁盘统计信息，与-c互斥-k 以K为单位显示每秒的磁盘请求数，默认单位块-p 设备名 | ALL，只显示某个设备的信息，或者全部设备-x 输出扩展信息sec 间隔sec秒显示一次
2. iotop
iotop is a top tool used to monitor disk I/O usage. It has a UI similar to top, including PID, user, I/O, process and other related information. iotop is not a command that comes with the system. If you want to use the iotop command, you need to install the iotop software.
~]# yum -y install iotop~]# iotopTotal DISK READ : 0.00 B/s | Total DISK WRITE : 0.00 B/sActual DISK READ: 0.00 B/s | Actual DISK WRITE: 0.00 B/sTID PRIO USER DISK READ DISK WRITE> COMMAND1 be/4 root 0.00 B/s 0.00 B/s systemd --switched-root --system --deserialize 282 be/4 root 0.00 B/s 0.00 B/s [kthreadd]3 be/4 root 0.00 B/s 0.00 B/s [rcu_gp]4 be/4 root 0.00 B/s 0.00 B/s [rcu_par_gp]5 be/4 root 0.00 B/s 0.00 B/s [netns]7 be/4 root 0.00 B/s 0.00 B/s [kworker/0:0H-events_highpri]9 be/4 root 0.00 B/s 0.00 B/s [kworker/0:1H-events_highpri]10 be/4 root 0.00 B/s 0.00 B/s [mm_percpu_wq]12 be/4 root 0.00 B/s 0.00 B/s [rcu_tasks_kthre]13 be/4 root 0.00 B/s 0.00 B/s [rcu_tasks_rude_]14 be/4 root 0.00 B/s 0.00 B/s [rcu_tasks_trace]15 be/4 root 0.00 B/s 0.00 B/s [ksoftirqd/0]16 be/4 root 0.00 B/s 0.00 B/s [rcu_preempt]17 be/4 root 0.00 B/s 0.00 B/s [migration/0]19 be/4 root 0.00 B/s 0.00 B/s [cpuhp/0]20 be/4 root 0.00 B/s 0.00 B/s [cpuhp/1]
Through the output results, we can clearly know what program is reading and writing to the disk, speed, command line, pid and other information.
Common parameters
-b 批量显示，无交互。主要用作记录到文件-n NUM 显示NUM次，主要用于非交互式模式-d SEC 间隔SEC秒显示一次-p PID 监控的进程pid-u USER 监控的进程用户
3. lsof
lsof (list open files) is a tool that lists open files in the current system. lsof needs to access core memory and various files, so it must be executed as root to take full advantage. lsof is not a command that comes with the system. If you want to use the lsof command, you need to install the lsof software.
~]# yum -y install lsof~]# lsofCOMMAND PID TID TASKCMD USER FD TYPE DEVICE SIZE/OFF NODE NAMEsystemd 1 root cwd DIR 253,0 235 128 /systemd 1 root rtd DIR 253,0 235 128 /systemd 1 root txt REG 253,0 1945080 67508326 /usr/lib/systemd/systemdsystemd 1 root mem REG 253,0 45416 67348788 /usr/lib64/libffi.so.8.1.0systemd 1 root mem REG 253,0 153600 67348802 /usr/lib64/libgpg-error.so.0.32.0systemd 1 root mem REG 253,0 28568 67348896 /usr/lib64/libattr.so.1.1.2501systemd 1 root mem REG 253,0 102568 67348636 /usr/lib64/libz.so.1.2.11systemd 1 root mem REG 253,0 32528 67348775 /usr/lib64/libcap-ng.so.0.0.0systemd 1 root mem REG 253,0 41064 67420376 /usr/lib64/libeconf.so.0.4.1systemd 1 root mem REG 253,0 637880 67348851 /usr/lib64/libpcre2-8.so.0.11.0systemd 1 root mem REG 253,0 906176 67323555 /usr/lib64/libm.so.6systemd 1 root mem REG 253,0 178744 67348640 /usr/lib64/liblzma.so.5.2.5systemd 1 root mem REG 253,0 882384 67348653 /usr/lib64/libzstd.so.1.5.1systemd 1 root mem REG 253,0 1293840 67348792 /usr/lib64/libp11-kit.so.0.3.0systemd 1 root mem REG 253,0 4459096 67420748 /usr/lib64/libcrypto.so.3.0.1systemd 1 root mem REG 253,0 144144 67348822 /usr/lib64/liblz4.so.1.9.3systemd 1 root mem REG 253,0 1305536 67348868 /usr/lib64/libgcrypt.so.20.4.0systemd 1 root mem REG 253,0 201832 67348663 /usr/lib64/libcrypt.so.2.0.0systemd 1 root mem REG 253,0 36944 67348643 /usr/lib64/libcap.so.2.48
Parameter Description:
PID: Process identifier
USER: Process owner
FD: File descriptor
TYPE: File type, such as DIR, REG, etc.
DEVICE: The name of the specified disk
SIZE: The size of the file
NODE: Index node
NAME: The exact name of the open file Common parameters lsof
abc.txt
displays
the process of
opening the
file
abc.txt
Common usage methods:
lsof -c abc 显示abc进程现在打开的文件lsof -p 1234 列出进程号为1234的进程所打开的文件lsof -g gid 显示归属gid的进程情况lsof +d /DIR/ 显示DIR目录下被进程打开的文件
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