十个对初学者特有用的 Linux 命令

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十个对初学者特有用的 Linux 命令

场长

运维 1 126 2024-05-05 12:44:32

21CTO 导读：

作为一名Linux管理员，或者即使是刚刚开始使用 Linux 的新手，充分了解解决网络问题时有用的命令也是至关重要的。

我们将探讨用于诊断和解决常见网络问题的 10 个基本 Linux 命令。每个命令都将附有实际示例，以说明其用法与有效性。

1. ping

例如：ping www.21cto.com

[root@VM-0-5-centos ~]# ping www.21cto.comPING www.21cto.com (81.70.105.8) 56(84) bytes of data.64 bytes from 81.70.105.8 (81.70.105.8): icmp_seq=1 ttl=63 time=0.228 ms64 bytes from 81.70.105.8 (81.70.105.8): icmp_seq=2 ttl=63 time=0.285 ms64 bytes from 81.70.105.8 (81.70.105.8): icmp_seq=3 ttl=63 time=0.282 ms64 bytes from 81.70.105.8 (81.70.105.8): icmp_seq=4 ttl=63 time=0.268 ms64 bytes from 81.70.105.8 (81.70.105.8): icmp_seq=5 ttl=63 time=0.211 ms
--- www.21cto.com ping statistics ---13 packets transmitted, 13 received, 0% packet loss, time 12018msrtt min/avg/max/mdev = 0.200/0.233/0.285/0.027 ms

ping 命令使用ICMP协议。

ICMP代表互网际网络控制消息协议（Internet Control Message Protocol），ICMP是网络设备用来通信的网络层协议。

ping有助于测试主机的可达性，帮助我们查找源和目标之间的延迟情况。

2.traceroute

例子：traceroute baidu.com

如果显示：

-bash: traceroute: command not found

表示没有安装此工具，可以使用根据自己当前操作系统环境安装。

Ubuntu类：

# For Debian based distributions like Ubuntu
sudo apt-get install traceroute

CentOS：

# For RPM based distributions like CentOS
sudo yum install traceroute

接下来，我们再来尝试：

[root@VM-0-5-centos ~]# traceroute baidu.comtraceroute to baidu.com (39.156.66.10), 30 hops max, 60 byte packets 1  * * * 2  11.66.248.84 (11.66.248.84)  0.293 ms * * 3  * * * 4  10.200.46.253 (10.200.46.253)  0.631 ms 10.200.46.93 (10.200.46.93)  1.152 ms 10.196.89.113 (10.196.89.113)  0.628 ms 5  * * * 6  39.156.0.81 (39.156.0.81)  2.165 ms  2.649 ms  2.702 ms 7  111.13.188.38 (111.13.188.38)  4.329 ms 111.13.0.174 (111.13.0.174)  4.259 ms 111.13.188.38 (111.13.188.38)  4.488 ms 8  39.156.27.5 (39.156.27.5)  4.441 ms  4.458 ms  3.997 ms 9  39.156.67.17 (39.156.67.17)  3.914 ms 39.156.67.1 (39.156.67.1)  14.343 ms  13.673 ms

Traceroute显示数据包到达目标主机所经过的路由。它显示路径上路由器的 IP 地址，并计算每一跳的往返时间 (RTT)。

Traceroute可以帮助我们识别网络拥塞或者路由问题。

3. netstat

例子：netstat -tulpn

[root@VM-0-5-centos ~]# netstat -tulpn
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
tcp        0      0 127.0.0.1:6379          0.0.0.0:*               LISTEN      870/redis-server 12
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN      1188/nginx: master
tcp        0      0 0.0.0.0:111             0.0.0.0:*               LISTEN      1/systemd
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      1188/nginx: master
tcp        0      0 0.0.0.0:7001            0.0.0.0:*               LISTEN      2059145/sshd: /usr/
tcp6       0      0 :::3306                 :::*                    LISTEN      819/mysqld
tcp6       0      0 ::1:6379                :::*                    LISTEN      870/redis-server 12
tcp6       0      0 :::33060                :::*                    LISTEN      819/mysqld
tcp6       0      0 :::443                  :::*                    LISTEN      1188/nginx: master
tcp6       0      0 :::111                  :::*                    LISTEN      1/systemd
tcp6       0      0 :::80                   :::*                    LISTEN      1188/nginx: master
tcp6       0      0 :::7001                 :::*                    LISTEN      2059145/sshd: /usr/
udp        0      0 0.0.0.0:111             0.0.0.0:*                           1/systemd
udp        0      0 127.0.0.1:323           0.0.0.0:*                           666/chronyd
udp6       0      0 :::111                  :::*                                1/systemd
udp6       0      0 ::1:323                 :::*                                666/chronyd

Netstat 显示网络连接、路由表、接口统计信息、伪装连接和多重广播成员资格。它对于排除网络连接故障、识别开放端口和监控网络性能非常有用。

4.ifconfig/ip

例子：ifconfig 或 ifconfig

[root@VM-0-5-centos ~]# ifconfig eth0
eth0: flags=4163  mtu 1500
        inet 172.21.0.5  netmask 255.255.240.0  broadcast 172.21.15.255
        inet6 fe80::5054:ff:feca:cdf8  prefixlen 64  scopeid 0x20
        ether 52:54:00:ca:cd:f8  txqueuelen 1000  (Ethernet)
        RX packets 80835008  bytes 32467819740 (30.2 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 96298531  bytes 91472563700 (85.1 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

ifconfig命令ip用于查看和配置网络参数。它们提供有关每个接口的 IP 地址、子网掩码、MAC 地址和网络状态的信息。

5.tcpdump

tcpdump也是一个外部工具，如果显示没有此命令，请使用如下方式安装：

yum install tcpdump

例子：tcpdump -i eth0 tcp port 80

[root@VM-0-5-centos ~]# tcpdump -i eth0 tcp port 80
dropped privs to tcpdump
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), snapshot length 262144 bytes
12:03:17.585041 IP VM-0-5-centos.39012 > 169.254.0.4.http: Flags [S], seq 1262259857, win 32120, options [mss 1460,sackOK,TS val 2931024914 ecr 0,nop,wscale 7], length 0
12:03:17.594474 IP 169.254.0.4.http > VM-0-5-centos.39012: Flags [S.], seq 3139790384, ack 1262259858, win 65535, options [mss 1424,nop,nop,sackOK,nop,wscale 9], length 0
12:03:17.594522 IP VM-0-5-centos.39012 > 169.254.0.4.http: Flags [.], ack 1, win 251, length 0
12:03:17.594599 IP VM-0-5-centos.39012 > 169.254.0.4.http: Flags [P.], seq 1:182, ack 1, win 251, length 181: HTTP: POST /ca_report.cgi HTTP/1.1
12:03:17.604056 IP 169.254.0.4.http > VM-0-5-centos.39012: Flags [.], ack 182, win 131, length 0
12:03:17.604092 IP VM-0-5-centos.39012 > 169.254.0.4.http: Flags [P.], seq 182:558, ack 1, win 251, length 376: HTTP
12:03:17.613436 IP 169.254.0.4.http > VM-0-5-centos.39012: Flags [.], ack 558, win 133, length 0
12:03:17.620508 IP 169.254.0.4.http > VM-0-5-centos.39012: Flags [P.], seq 1:217, ack 558, win 133, length 216: HTTP: HTTP/1.1 200 OK
12:03:17.620508 IP 169.254.0.4.http > VM-0-5-centos.39012: Flags [F.], seq 217, ack 558, win 133, length 0
12:03:17.620539 IP VM-0-5-centos.39012 > 169.254.0.4.http: Flags [.], ack 217, win 250, length 0
12:03:17.621059 IP VM-0-5-centos.39012 > 169.254.0.4.http: Flags [F.], seq 558, ack 218, win 250, length 0
12:03:17.630405 IP 169.254.0.4.http > VM-0-5-centos.39012: Flags [.], ack 559, win 133, length 0
12:03:18.291765 IP VM-0-5-centos.39028 > 169.254.0.4.http: Flags [S], seq 2462459289, win 32120, options [mss 1460,sackOK,TS val 2931025621 ecr 0,nop,wscale 7], length 0
12:03:18.301176 IP 169.254.0.4.http > VM-0-5-centos.39028: Flags [S.], seq 333977930, ack 2462459290, win 65535, options [mss 1424,nop,nop,sackOK,nop,wscale 9], length 0
^C
108 packets captured
108 packets received by filter
0 packets dropped by kernel

tcpdump是一个实时捕获和显示网络流量的数据包分析器。

tcpdump对于排除网络问题、分析数据包内容和识别异常网络行为非常有价值。用于tcpdump检查特定接口或端口上的数据包。

6. nslookup/dig

示例：nslookup google.com

如果你的系统显示没有找到该命令，请使用如下命令安装：

yum install bind-utils

接下来我们来运行：

[root@VM-0-5-centos ~]# nslookup google.com
Server:         183.60.83.19
Address:        183.60.83.19#53


Non-authoritative answer:
Name:   google.com
Address: 142.251.43.14

下一步，我们使用dig：

[root@VM-0-5-centos ~]# dig google.com


; <<>> DiG 9.16.23-RH <<>> google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 49289
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0


;; QUESTION SECTION:
;google.com.                    IN      A


;; ANSWER SECTION:
google.com.             7       IN      A       93.46.8.90


;; Query time: 5 msec
;; SERVER: 183.60.83.19#53(183.60.83.19)
;; WHEN: Sat May 04 12:10:21 CST 2024
;; MSG SIZE  rcvd: 44

nslookup和dig都是 DNS 查找工具，用于查询 DNS 服务器进行域名解析。它们提供有关与域名关联的 IP 地址的信息，并帮助诊断与 DNS 相关的问题，例如 DNS 配置不正确或服务器不可用时。

7. iptables/firewalld

示例：iptables -L或firewall-cmd --list-all

[root@VM-0-5-centos ~]# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination


Chain FORWARD (policy ACCEPT)
target     prot opt source               destination


Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

iptables和firewalld是用于配置数据包过滤和网络地址转换 ( NAT ) 规则的防火墙管理工具。它们控制传入和传出流量并保护系统免受未经授权的访问。使用它们来诊断与防火墙相关的问题并确保正常的流量。

8.ss

例子：ss -tulpn

[root@VM-0-5-centos ~]# ss -tuplpn
Netid    State      Recv-Q     Send-Q         Local Address:Port          Peer Address:Port    Process
udp      UNCONN     0          0                    0.0.0.0:111                0.0.0.0:*        users:(("rpcbind",pid=653,fd=5),("systemd",pid=1,fd=118))
udp      UNCONN     0          0                  127.0.0.1:323                0.0.0.0:*        users:(("chronyd",pid=666,fd=5))
udp      UNCONN     0          0                       [::]:111                   [::]:*        users:(("rpcbind",pid=653,fd=7),("systemd",pid=1,fd=120))
udp      UNCONN     0          0                      [::1]:323                   [::]:*        users:(("chronyd",pid=666,fd=6))
tcp      LISTEN     0          511                127.0.0.1:6379               0.0.0.0:*        users:(("redis-server",pid=870,fd=6))
tcp      LISTEN     0          511                  0.0.0.0:443                0.0.0.0:*        users:(("nginx",pid=1192,fd=9),("nginx",pid=1190,fd=9),("nginx",pid=1188,fd=9))
tcp      LISTEN     0          4096                 0.0.0.0:111                0.0.0.0:*        users:(("rpcbind",pid=653,fd=4),("systemd",pid=1,fd=117))
tcp      LISTEN     0          511                  0.0.0.0:80                 0.0.0.0:*        users:(("nginx",pid=1192,fd=7),("nginx",pid=1190,fd=7),("nginx",pid=1188,fd=7))
tcp      LISTEN     0          128                  0.0.0.0:7001               0.0.0.0:*        users:(("sshd",pid=2059145,fd=3))
tcp      LISTEN     0          151                        *:3306                     *:*        users:(("mysqld",pid=819,fd=24))
tcp      LISTEN     0          511                    [::1]:6379                  [::]:*        users:(("redis-server",pid=870,fd=7))
tcp      LISTEN     0          70                         *:33060                    *:*        users:(("mysqld",pid=819,fd=21))
tcp      LISTEN     0          511                     [::]:443                   [::]:*        users:(("nginx",pid=1192,fd=8),("nginx",pid=1190,fd=8),("nginx",pid=1188,fd=8))
tcp      LISTEN     0          4096                    [::]:111                   [::]:*        users:(("rpcbind",pid=653,fd=6),("systemd",pid=1,fd=119))
tcp      LISTEN     0          511                     [::]:80                    [::]:*        users:(("nginx",pid=1192,fd=10),("nginx",pid=1190,fd=10),("nginx",pid=1188,fd=10))
tcp      LISTEN     0          128                     [::]:7001                  [::]:*        users:(("sshd",pid=2059145,fd=4))

ss是一个调查Socket的实用程序。它显示有关 TCP、UDP 和 UNIX 域Socket的信息，包括侦听和已建立的连接、连接状态和进程 ID。ss对于解决与套接字相关的问题和监视网络活动非常有用。

9.arp

例子：arp -a

[root@VM-0-5-centos ~]# arp -a
_gateway (172.21.0.1) at fe:ee:0b:ca:e5:69 [ether] on eth0

arp（地址解析协议）显示和修改内核使用的 IP 到 MAC 地址转换表。它将 IP 地址解析为 MAC 地址，反之亦然。arp有助于解决与网络设备发现和地址解析相关的问题。

10. mtr

例子：mtr

如果没有安装此外部命令，请先安装。如CentOS：

yum install mtr

接下来运行：

My traceroute  [v0.94]
VM-0-5-centos (::1) -> localhost                                                                                                                             2024-05-04T12:20:37+0800
Keys:  Help   Display mode   Restart statistics   Order of fields   quit
                                                                                                                                             Packets               Pings
 Host                                                                                                                                      Loss%   Snt   Last   Avg  Best  Wrst StDev
 1. VM-0-5-centos                                                                                                                           0.0%    14    0.1   0.1   0.1   0.1   0.0