CentOS 7 - 系统管理-CFANZ编程社区

uptime

uptime

top

查看CPU，内存等使用状态，P 按CPU排序，M 按内存排序，q 退出

top
# P - 按CPU排序
# M - 按内存排序
# c - 显示COMMAND详细
# q - 退出

top -u user01
top -p pid_number
top -p pid_number_01,pid_number_02,pid_number_03
cat /proc/pid_number/status

结果输出到文件

top -b -n1
top -b -n1 > top.log

统计在线用户

who
who | cut -d" " -f1 | sort | uniq
# -F可以指定分隔符" "，默认为空格
who | awk -F" " '{print $1}' | sort | uniq
who | awk '{print $1}' | sort | uniq | wc -l

iftop

iftop - display bandwidth usage on an interface by host

                 12.5Kb            25.0Kb           37.5Kb            50.0Kb      62.5Kb
+----------------+-----------------+----------------+-----------------+-----------------
dev-c801                      => unknown.alphabook.cn              832b   1.55Kb  1.42Kb
                                 <=                              22.1Kb   39.8Kb  36.2Kb
----------------------------------------------------------------------------------------
TX:             cum:   18.0KB   peak:   16.9Kb          rates:   2.84Kb  7.78Kb  7.98Kb
RX:                    90.7KB           82.7Kb                   22.3Kb  43.4Kb  40.3Kb
TOTAL:                  109KB           99.6Kb                   25.1Kb  51.2Kb  48.3Kb

Nethogs

List putting the most intensive processes

yum install epel-release
yum install nethogs

pgrep & pkill & kill

查看和结束用户进程

SIGHUP 1 Hangup

SIGKILL 9 Kill Signal

SIGTERM 15 Terminate (Default)

pgrep -u user01 firefox
pkill -u user01 firefox
pkill -9 -u user01 firefox
pkill -u user01
pkill -t pts/10
kill pid_number
kill -9 pid_number

查询和结束僵尸进程

ps -A -o stat,pid,cmd,user | grep -e '^[Zz]' | awk '{print $2}' | xargs kill

查看进程树

pstree -p 12416

查看进程启动时间

ps -p PID -o lstart

不可中断睡眠 D (TASK_UNINTERRUPTIBLE)

进程处于D状态，基本上需要重启系统

atop

dnf install epel-release -y
dnf install atop -y
atop

free

查看内存使用情况（Cached内存在需要的时候自动释放）

https://www.linuxatemyram.com/

free -h
# cache memory 系统在需要的时候会自动释放

iostat

IO性能

iostat -dxh

df

查看磁盘使用情况

df -hT

du

查看文件夹的使用情况

du -sh
du -h --max-depth=3

服务

# 服务基本操作
systemctl status httpd
systemctl start httpd
systemctl stop httpd
systemctl restart httpd
systemctl reload httpd
systemctl is-enabled httpd
systemctl enable httpd
# 列出系统所有服务
systemctl list-unit-files

Process history

#!/bin/bash

# Capture process information every 5 minutes
# Archive for one week (recycle)

my_day=$(date | awk '{print $1}')
my_time=$(date +%H%M)
my_host=$(hostname)
my_folder="/one/scripts/phistory/$my_host/$my_day"
my_file="/one/scripts/phistory/$my_host/$my_day/$my_time"

if [ ! -d $my_folder ]; then
mkdir -p $my_folder
fi

hostname > $my_file
date >> $my_file
top -b -n1 >> $my_file
ps aux >> $my_file

lsof

lsof | grep my_file

ulimt

ulimit -n
# 配置文件
/etc/security/limits.conf

Out of Memory

grep -i "out of memory" /var/log/message

Disable over commit

In major Linux distributions, the kernel allows by default for processes to request more memory than is currently free in the system to improve the memory utilization. This is based on heuristics that the processes never truly use all the memory they request. However, if your system is at risk of running out of memory, and you wish to prevent losing tasks to OOM killer, it is possible to disallow memory overcommit.

To change how the system handles overcommit calls Linux has an application called ‘sysctl’ that is used to modify kernel parameters at runtime. You can list all sysctl controlled parameters using the following.

sysctl -a | grep vm.overcommit
vm.overcommit_memory = 0
vm.overcommit_ratio = 50
vm.overcommit_kbytes = 0

# This parameter has 3 different values:
# 0 means to “Estimate if we have enough RAM”
# 1 equals to “Always allow”
# 2 that is used here tells the kernel to “Say no if the system doesn’t have the memory”

# disable over commit(immediately and lost after system reboot)
sysctl -w vm.overcommit_memory=2
sysctl -w vm.overcommit_ratio=100

# disable over commit(permanently)
vi /etc/sysctl.conf
# Add below lines
vm.overcommit_memory=2
vm.overcommit_ratio=100

Reference:

https://www.kernel.org/doc/html/latest/vm/overcommit-accounting.html

rsyslog

# systemctl status rsyslog
● rsyslog.service - System Logging Service
   Loaded: loaded (/usr/lib/systemd/system/rsyslog.service; enabled; vendor preset: enabled)
   Active: active (running) since Mon 2021-06-21 11:27:46 CST; 1 months 11 days ago
     Docs: man:rsyslogd(8)
           http://www.rsyslog.com/doc/
 Main PID: 1158 (rsyslogd)
   CGroup: /system.slice/rsyslog.service
           └─1158 /usr/sbin/rsyslogd -n

配置文件

/etc/rsyslog.conf

删除/var/log目录下的日志文件后，不自动产生新的日志文件，尝试重启服务

systemctl restart rsyslog