watch

可以动态监控变化：

watch -n1 -d 'kubectl top pod --sort-by=cpu -A'

watch -n1 -d 'date'

其中-d表示显示变化的差异内容，-n指观察间隔，后面跟数字，-n1表示1秒观察一次。

Mac没有该命令，可以通过brew install watch安装，参考osx watch。

df

查看文件系统硬盘空间使用情况：

df -h

du

查看文件空间使用情况：

du -sh ./*

top

显示系统进程信息，与CPU和内存。

find

查找文件：

$ find ./ -name "jdk*"
./jdk-8u131-linux-x64.tar.gz
./jdk1.8.0_131

id

查看用户ID，群组ID。

nc

检测端口是否可提供服务。可指定一个或多个端口，还可以指定端口范围。

$ nc -zv 127.0.0.1 80-89
Connection to 127.0.0.1 port 80 [tcp/http] succeeded!
nc: connectx to 127.0.0.1 port 81 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 82 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 83 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 84 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 85 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 86 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 87 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 88 (tcp) failed: Connection refused
nc: connectx to 127.0.0.1 port 89 (tcp) failed: Connection refused

参考：check remote port in liux

diff

对比文件。

diff file1 file2

diff --brief --recursive dir1/ dir2/

DNS相关

主要有：nslookup/dig命令

$ cat /etc/resolv.conf 
# To view the DNS configuration used by this system, use:
#   scutil --dns
#
# SEE ALSO
#   dns-sd(1), scutil(8)
#
# This file is automatically generated.
#
search DHCP HOST
nameserver 192.168.3.1
nameserver 192.168.1.1

$ nslookup www.pkslow.com
Server:		192.168.3.1
Address:	192.168.3.1#53

Non-authoritative answer:
Name:	www.pkslow.com
Address: 8.129.104.229


$ dig www.pkslow.com

; <<>> DiG 9.10.6 <<>> www.pkslow.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 6227
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 18

;; QUESTION SECTION:
;www.pkslow.com.			IN	A

;; ANSWER SECTION:
www.pkslow.com.		283	IN	A	8.129.104.229

;; AUTHORITY SECTION:
pkslow.com.		172483	IN	NS	dns20.hichina.com.
pkslow.com.		172483	IN	NS	dns19.hichina.com.

;; ADDITIONAL SECTION:
dns19.hichina.com.	172303	IN	A	140.205.81.17
dns19.hichina.com.	172303	IN	A	140.205.81.27
dns19.hichina.com.	172303	IN	A	106.11.141.117
dns19.hichina.com.	172303	IN	A	106.11.141.127
dns19.hichina.com.	172303	IN	A	106.11.211.57
dns19.hichina.com.	172303	IN	A	106.11.211.67
dns19.hichina.com.	172303	IN	A	140.205.41.17
dns19.hichina.com.	172303	IN	A	140.205.41.27
dns20.hichina.com.	3490	IN	A	140.205.41.28
dns20.hichina.com.	3490	IN	A	140.205.81.18
dns20.hichina.com.	3490	IN	A	140.205.81.28
dns20.hichina.com.	3490	IN	A	106.11.141.118
dns20.hichina.com.	3490	IN	A	106.11.141.128
dns20.hichina.com.	3490	IN	A	106.11.211.58
dns20.hichina.com.	3490	IN	A	106.11.211.68
dns20.hichina.com.	3490	IN	A	140.205.41.18
dns19.hichina.com.	3081	IN	AAAA	2400:3200:2000:38::1
dns20.hichina.com.	172303	IN	AAAA	2400:3200:2000:39::1

;; Query time: 9 msec
;; SERVER: 192.168.3.1#53(192.168.3.1)
;; WHEN: Wed May 05 09:49:22 CST 2021
;; MSG SIZE  rcvd: 408

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