Linux 工作常用命令(三)解释!(图文并茂)

df显示

磁盘使用情况

Df -h

它的使用场景，有时候你需要去拍错，查看你的硬盘空间的使用情况

[root@localhost log]# df

Filesystem 1K-blocks Used Available Use% Mounted on

/dev/sda3 47828156 939240 46888916 2% /

devtmpfs 924896 0 924896 0% /dev

tmpfs 934344 0 934344 0% /dev/shm

tmpfs 934344 8740 925604 1% /run

tmpfs 934344 0 934344 0% /sys/fs/cgroup

/dev/sda1 508588 120476 388112 24% /boot

tmpfs 186872 0 186872 0% /run/user/0

/dev/sr0 4227724 4227724 0 100% /mnt/cdrom

[root@localhost log]# cd /

[root@localhost /]# ls

bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var

[root@localhost /]# cd boot

[root@localhost boot]# ls

config-3.10.0-327.el7.x86_64 grub2 initramfs-3.10.0-327.el7.x86_64.img initrd-plymouth.img System.map-3.10.0-327.el7.x86_64 vmlinuz-3.10.0-327.el7.x86_64

grub initramfs-0-rescue-ff071843d0d445a79c600240884925f1.img initramfs-3.10.0-327.

du

显示文件目录使用情况

du /var/log/secure

Du和df需要联用？为什么？

因为有时候你某个硬盘的分区使用率特别高，使用df,尤其有些分区占用了98%，那么你需要删除一些文件或文件夹，这种情况下你就要使用du查看哪个目录占用率最高

它的使用场景，查看目录的使用空间或大小

[root@localhost home]#

[root@localhost home]# du

28 .

[root@localhost home]# du -h

28K .

[root@localhost home]#

useradd

添加用户

useradd -d /home test

useradd -g root test -M

场景：你去一家用户单位工作的时候，那么你有很多同事，那么同事可能去访问ftp服务器，那么有些同事的权限是不一样，比如领导的权限比较高，还有这个服务器管理员的权限比较高，不管怎么的，我们都需要去新建一个用户。

既然有超级用户root，那为什么还需要建立普通用户，因为我们有时候考虑安全性。

[root@localhost home]# cat /etc/passwd

root:x:0:0:root:/root:/bin/bash

bin:x:1:1:bin:/bin:/sbin/nologin

daemon:x:2:2:daemon:/sbin:/sbin/nologin

adm:x:3:4:adm:/var/adm:/sbin/nologin

lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin

sync:x:5:0:sync:/sbin:/bin/sync

shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown

halt:x:7:0:halt:/sbin:/sbin/halt

mail:x:8:12:mail:/var/spool/mail:/sbin/nologin

operator:x:11:0:operator:/root:/sbin/nologin

games:x:12:100:games:/usr/games:/sbin/nologin

ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin

nobody:x:99:99:Nobody:/:/sbin/nologin

avahi-autoipd:x:170:170:Avahi IPv4LL Stack:/var/lib/avahi-autoipd:/sbin/nologin

systemd-bus-proxy:x:999:997:systemd Bus Proxy:/:/sbin/nologin

systemd-network:x:998:996:systemd Network Management:/:/sbin/nologin

dbus:x:81:81:System message bus:/:/sbin/nologin

polkitd:x:997:995:User for polkitd:/:/sbin/nologin

tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin

postfix:x:89:89::/var/spool/postfix:/sbin/nologin

sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin

apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

tcpdump:x:72:72::/:/sbin/nologin

[root@localhost home]#

[root@localhost home]#

[root@localhost home]#

[root@localhost home]#

[root@localhost home]#

[root@localhost home]# useradd test1

[root@localhost home]#

[root@localhost home]#

[root@localhost home]#

[root@localhost home]# ls

test1

[root@localhost home]# cat /etc/passwd

root:x:0:0:root:/root:/bin/bash

bin:x:1:1:bin:/bin:/sbin/nologin

daemon:x:2:2:daemon:/sbin:/sbin/nologin

adm:x:3:4:adm:/var/adm:/sbin/nologin

lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin

sync:x:5:0:sync:/sbin:/bin/sync

shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown

halt:x:7:0:halt:/sbin:/sbin/halt

mail:x:8:12:mail:/var/spool/mail:/sbin/nologin

operator:x:11:0:operator:/root:/sbin/nologin

games:x:12:100:games:/usr/games:/sbin/nologin

ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin

nobody:x:99:99:Nobody:/:/sbin/nologin

avahi-autoipd:x:170:170:Avahi IPv4LL Stack:/var/lib/avahi-autoipd:/sbin/nologin

systemd-bus-proxy:x:999:997:systemd Bus Proxy:/:/sbin/nologin

systemd-network:x:998:996:systemd Network Management:/:/sbin/nologin

dbus:x:81:81:System message bus:/:/sbin/nologin

polkitd:x:997:995:User for polkitd:/:/sbin/nologin

tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin

postfix:x:89:89::/var/spool/postfix:/sbin/nologin

sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin

apache:x:48:48:Apache:/usr/share/httpd:/sbin/nologin

tcpdump:x:72:72::/:/sbin/nologin

test1:x:1000:1000::/home/test1:/bin/bash

[root@localhost home]# tail -1 /etc/passwd

test1:x:1000:1000::/home/test1:/bin/bash

[root@localhost home]#

[test1@localhost ~]$ useradd test2

-bash: /usr/sbin/useradd: Permission denied

[test1@localhost ~]$

普通用户权限比较低，一般只能查看文件内容，但是呢?不能去修改

userdel

删除用户

userdel test

passwd

设置用户密码

场景：为什么我们有时候需要去删除用户呢？因为一个单位它有员工流动，所以一旦员工辞职，那么我们有时候需要去把它删除，否则会离职的员工对公司不爽，就会可能利用自己的用户权限，去删除数据库，那么现实例子，比比皆是，比如携程等等。

[root@localhost home]# userdel test1

userdel: user test1 is currently used by process 2641

[root@localhost home]#

[root@localhost home]#

[root@localhost home]#

那么我们这个用户没有删除掉，我们需要怎么做？

我们得先退出该用户，然后再删除

[root@localhost home]# userdel test1

userdel: user test1 is currently used by process 2641

[root@localhost home]#

[root@localhost home]#

[root@localhost home]# userdel test1

[root@localhost home]#

密码修改，请看前面实验。

w

显示系统负载

[root@localhost home]# w

10:42:05 up 13 min, 2 users, load average: 0.00, 0.01, 0.03

USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT

root tty1 10:28 13:25 0.02s 0.02s -bash

root pts/0 192.168.92.1 10:29 5.00s 0.05s 0.00s w

[root@localhost home]#

[root@localhost home]#

[root@localhost home]#

[root@localhost home]# uptime

10:42:11 up 13 min, 2 users, load average: 0.00, 0.01, 0.03

[root@localhost home]#

[root@localhost home]#

[root@localhost home]#

[root@localhost home]# load

loadkeys load_policy loadunimap

[root@localhost home]# load

loadkeys load_policy loadunimap

[root@localhost home]# top

echo

打印输出

echo “hello word!”

echo $HOME

比如往文件里面写入一些内容，输出一些信息或者说查看环境变量的值，还有shell编程的时候，用得比较多

[root@localhost home]# cd /tmp

[root@localhost tmp]#

[root@localhost tmp]#

[root@localhost tmp]# touch test2.txt\

> ^C

[root@localhost tmp]# touch test2.txt

[root@localhost tmp]#

[root@localhost tmp]#

[root@localhost tmp]#

[root@localhost tmp]# echo "hello world" > test2.txt

[root@localhost tmp]#

[root@localhost tmp]#

[root@localhost tmp]# cat test2.txt

hello world

[root@localhost tmp]#

[root@localhost tmp]# echo $PATH

/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin

[root@localhost tmp]#

[root@localhost tmp]#

[root@localhost tmp]#

alias

显示别名

unalias

取消别名

[root@localhost tmp]# alias

alias cp='cp -i'

alias egrep='egrep --color=auto'

alias fgrep='fgrep --color=auto'

alias grep='grep --color=auto'

alias l.='ls -d .* --color=auto'

alias ll='ls -l --color=auto'

alias ls='ls --color=auto'

alias mv='mv -i'

alias rm='rm -i'

alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'

[root@localhost tmp]# alias test3='cp -rf'

[root@localhost tmp]#

[root@localhost tmp]#

[root@localhost tmp]# te

teamd teamdctl teamnl tee telinit test test3 testgdbm

[root@localhost tmp]#

[root@localhost tmp]#

[root@localhost tmp]# test3 test2.txt test3.txt

[root@localhost tmp]#

[root@localhost tmp]#

[root@localhost tmp]# cat test3.txt

hello world

[root@localhost tmp]#

[root@localhost tmp]# unalias test3\

>

[root@localhost tmp]# unalias test3

-bash: unalias: test3: not found

[root@localhost tmp]#

[root@localhost tmp]#

[root@localhost tmp]# test3 test2.txt test3.txt

-bash: test3: command not found

[root@localhost tmp]#

history

显示历史命令操作记录

history

场景：一般有时候我们敲的命令特别多，你有时候记不住，那么你需要翻以下你之前做的一些操作或者你需要把操作的命令做一个存档。

[root@localhost tmp]# history | more

1 ls

2 cd /

3 ls

4 cd /

5 lks

6 ls

7 init 0

8 cd /

9 ip address

10 ip addre

11 ip add show eno16777736

12 ip -s link show eno16777736

13 ip route

14 ip rouete

15 ip route

16 ss -ta

17 ps axf

18 nmcli con show

19 ip addre

20 nmcli con show –active

4、使用! 执行历史命令。

　　! number 执行第几条命令

　　! command 从最近的命令查到以command开头的命令执行

　　!! 执行上一条

[root@localhost tmp]# !19

ip addre

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN

link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

inet 127.0.0.1/8 scope host lo

valid_lft forever preferred_lft forever

inet6 ::1/128 scope host

valid_lft forever preferred_lft forever

2: eno16777736: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000

link/ether 00:0c:29:fe:83:2f brd ff:ff:ff:ff:ff:ff

inet 192.168.92.128/24 brd 192.168.92.255 scope global dynamic eno16777736

valid_lft 1791sec preferred_lft 1791sec

inet6 fe80::20c:29ff:fefe:832f/64 scope link

valid_lft forever preferred_lft forever

[root@localhost tmp]#

[root@localhost tmp]# !ip

ip addre

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN

link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

inet 127.0.0.1/8 scope host lo

valid_lft forever preferred_lft forever

inet6 ::1/128 scope host

valid_lft forever preferred_lft forever

2: eno16777736: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000

link/ether 00:0c:29:fe:83:2f brd ff:ff:ff:ff:ff:ff

inet 192.168.92.128/24 brd 192.168.92.255 scope global dynamic eno16777736

valid_lft 1744sec preferred_lft 1744sec

inet6 fe80::20c:29ff:fefe:832f/64 scope link

valid_lft forever preferred_lft forever

[root@localhost tmp]# !!

ip addre

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN

link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

inet 127.0.0.1/8 scope host lo

valid_lft forever preferred_lft forever

inet6 ::1/128 scope host

valid_lft forever preferred_lft forever

2: eno16777736: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000

link/ether 00:0c:29:fe:83:2f brd ff:ff:ff:ff:ff:ff

inet 192.168.92.128/24 brd 192.168.92.255 scope global dynamic eno16777736

valid_lft 1726sec preferred_lft 1726sec

inet6 fe80::20c:29ff:fefe:832f/64 scope link

valid_lft forever preferred_lft forever

[root@localhost tmp]# !11

ip add show eno16777736

2: eno16777736: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000

link/ether 00:0c:29:fe:83:2f brd ff:ff:ff:ff:ff:ff

inet 192.168.92.128/24 brd 192.168.92.255 scope global dynamic eno16777736

valid_lft 1723sec preferred_lft 1723sec

inet6 fe80::20c:29ff:fefe:832f/64 scope link

valid_lft forever preferred_lft forever

[root@localhost tmp]#

[root@localhost tmp]#

[root@localhost tmp]#