1.学习的指令
| ping | Send an ICMP ECHO_REQUEST to network hosts |
| traceroute | Print the route packets trace to a network host |
| netstat | Print network state |
| ftp | Internet file transfer program |
| wget | Non-interactive network downloader |
| ssh | remote login program |
2.小知识
知识点1：ping命令的具体过程
ping 命令发送网络数据包，叫做 ICMP ECHO_REQUEST，到指定的主机。多数接收这个的网络设备会回复它，来进行网络连接验证。
知识点2：traceroute命令的作用
traceroute 程序会显示从本地到指定主机，要经过的所有“跳数”的网络流量列表。
知识点3：ftp操作各选项的意义
| ftp fileserver | 唤醒 ftp 程序，让它连接到 FTP 服务器，fileserver。 |
| anonymous | 登录名。输入登录名后，将出现一个密码提示。可能是空密码，也可能是 “[email protected]”。 |
| cd pub/cd_images/Ubuntu-8.04 | 跳转到远端系统中，要下载文件所在的目录下， 大多数文件都能在pub下找到 |
| ls | 列出远端系统中的目录。 |
| lcd Desktop | 跳转到本地系统中的 ~/Desktop 目录下。 这个命令把工作目录改为 ~/Desktop，多了个l |
| get ubuntu-8.04-desktop-i386.iso | 告诉远端系统传送文件到本地。因为工作目录 已经更改到 ~/Desktop，所以会被下载到此目录。 |
| bye | 退出远端服务器，结束 ftp 程序会话。也可以使用命令 quit 和 exit。 |
知识点4：lftp与ftp的区别？
没什么区别就是lftp更高级，比如直接可以用Tab键进行补全代码。
知识点5：wget与ftp的区别？
答：wget可以在网络下进行下载，也可以在ftp下进行下载。所以很有用。
知识点6：若连接主机密码也就修改，如何通过SSH进行重新连接？
答：进入~/.ssh/known_hosts 删除 offend key 即废弃的钥匙，再进行连接
3.代码实操
[me@linuxbox ~]$ ping linuxcommand.org
[me@linuxbox ~]$ ping linuxcommand.org
PING linuxcommand.org (66.35.250.210) 56(84) bytes of data.
64 bytes from vhost.sourceforge.net (66.35.250.210): icmp\_seq=1
ttl=43 time=107 ms
64 bytes from vhost.sourceforge.net (66.35.250.210): icmp\_seq=2
ttl=43 time=108 ms
64 bytes from vhost.sourceforge.net (66.35.250.210): icmp\_seq=3
ttl=43 time=106 ms
64 bytes from vhost.sourceforge.net (66.35.250.210): icmp\_seq=4
ttl=43 time=106 ms
64 bytes from vhost.sourceforge.net (66.35.250.210): icmp\_seq=5
ttl=43 time=105 ms
...
[me@linuxbox ~]$ traceroute slashdot.org
traceroute to slashdot.org (216.34.181.45), 30 hops max, 40 byte
packets
1 ipcop.localdomain (192.168.1.1) 1.066 ms 1.366 ms 1.720 ms
2 * * *
3 ge-4-13-ur01.rockville.md.bad.comcast.net (68.87.130.9) 14.622
ms 14.885 ms 15.169 ms
4 po-30-ur02.rockville.md.bad.comcast.net (68.87.129.154) 17.634
ms 17.626 ms 17.899 ms
5 po-60-ur03.rockville.md.bad.comcast.net (68.87.129.158) 15.992
ms 15.983 ms 16.256 ms
6 po-30-ar01.howardcounty.md.bad.comcast.net (68.87.136.5) 22.835
...
注：从输出结果中，我们可以看到连接测试系统到 slashdot.org 网站需要经由16个路由器。对于那些提供标
识信息的路由器，我们能看到它们的主机名，IP 地址和性能数据，这些数据包括三次从本地到此路由器的往返
时间样本。对于那些没有提供标识信息的路由器（由于路由器配置，网络拥塞，防火墙等 方面的原因），我们
会看到几个星号
[me@linuxbox ~]$ netstat -ie
eth0 Link encap:Ethernet HWaddr 00:1d:09:9b:99:67
inet addr:192.168.1.2 Bcast:192.168.1.255 Mask:255.255.255.0
inet6 addr: fe80::21d:9ff:fe9b:9967/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:238488 errors:0 dropped:0 overruns:0 frame:0
TX packets:403217 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100 RX bytes:153098921 (146.0 MB) TX
bytes:261035246 (248.9 MB) Memory:fdfc0000-fdfe0000
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
...
[me@linuxbox ~]$ netstat -r
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
192.168.1.0 * 255.255.255.0 U 0 0 0 eth0
default 192.168.1.1 0.0.0.0 UG 0 0 0 eth0
注：-ie等同于ifconfig -r 显示内核网络路由表
[me@linuxbox ~]$ ftp fileserver
Connected to fileserver.localdomain.
220 (vsFTPd 2.0.1)
Name (fileserver:me): anonymous
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> cd pub/cd\_images/Ubuntu-8.04
250 Directory successfully changed.
ftp> ls
200 PORT command successful. Consider using PASV.
150 Here comes the directory listing.
-rw-rw-r-- 1 500 500 733079552 Apr 25 03:53 ubuntu-8.04- desktop-i386.iso
226 Directory send OK.
ftp> lcd Desktop
Local directory now /home/me/Desktop
ftp> get ubuntu-8.04-desktop-i386.iso
local: ubuntu-8.04-desktop-i386.iso remote: ubuntu-8.04-desktop-
i386.iso
200 PORT command successful. Consider using PASV.
150 Opening BINARY mode data connection for ubuntu-8.04-desktop-
i386.iso (733079552 bytes).
226 File send OK.
733079552 bytes received in 68.56 secs (10441.5 kB/s)
ftp> bye
注：从匿名 FTP 服务器，其名字是 fileserver， 的/pub/_images/Ubuntu-8.04的目录下，使用 ftp 程
序下载一个 Ubuntu 系统映像文件。
[me@linuxbox ~]$ wget http://linuxcommand.org/index.php
--11:02:51-- http://linuxcommand.org/index.php
=> `index.php'
Resolving linuxcommand.org... 66.35.250.210
Connecting to linuxcommand.org|66.35.250.210|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
[ < => ] 3,120 --.--K/s
11:02:51 (161.75 MB/s) - 'index.php' saved [3120]
[me@linuxbox ~]$ ssh remote-sys
The authenticity of host 'remote-sys (192.168.1.4)' can't be
established.
RSA key fingerprint is
41:ed:7a:df:23:19:bf:3c:a5:17:bc:61:b3:7f:d9:bb.
Are you sure you want to continue connecting (yes/no)?
Warning: Permanently added 'remote-sys,192.168.1.4' (RSA) to the list
of known hosts.
me@remote-sys's password:
Last login: Sat Aug 30 13:00:48 2008
注：连接到remote-sys的远程主机
[me@linuxbox ~]$ ssh bob@remote-sys
bob@remote-sys's password:
Last login: Sat Aug 30 13:03:21 2008
注：使用不同的账号进行来连接remote-sys
[me@linuxbox ~]$ ssh remote-sys free
me@twin4's password:
total used free shared buffers cached
Mem: 775536 507184 268352 0 110068 154596
-/+ buffers/cache: 242520 533016
Swap: 0 1572856 0 110068 154596
注：通过远程操作free命令
[me@linuxbox ~]$ ssh remote-sys 'ls \*' > dirlist.txt
me@twin4's password:
注：将远程的结果导入到本地。若加单引号则传入到远程端，看下段代码。
[me@linuxbox ~]$ ssh remote-sys 'ls * > dirlist.txt'
[me@linuxbox ~]$ scp remote-sys:document.txt .
me@remote-sys's password:
document.txt
100% 5581 5.5KB/s 00:00
注：从 remote-sys 远端系统的家目录下复制文档 document.txt，到我们本地系统的当前工作目录下
[me@linuxbox ~]$ sftp remote-sys
Connecting to remote-sys...
me@remote-sys's password:
sftp> ls
ubuntu-8.04-desktop-i386.iso
sftp> lcd Desktop
sftp> get ubuntu-8.04-desktop-i386.iso
Fetching /home/me/ubuntu-8.04-desktop-i386.iso to ubuntu-8.04-
desktop-i386.iso
/home/me/ubuntu-8.04-desktop-i386.iso 100% 699MB 7.4MB/s 01:35
sftp> bye
注：SSH 文件复制程序是 sftp，顾名思义，它是 ftp 程序的安全替代品。
