1.學習的指令
| 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.小知識
知識點1：ping命令的具體過程
ping 命令發送網絡數據包，叫做 ICMP ECHO_REQUEST，到指定的主機。多數接收這個的網絡設備會回覆它，來進行網絡連接驗證。
知識點2：traceroute命令的作用
traceroute 程序會顯示從本地到指定主機，要經過的所有“跳數”的網絡流量列表。
知識點3：ftp操作各選項的意義
| ftp fileserver | 喚醒 ftp 程序，讓它連接到 FTP 服務器，fileserver。 |
| anonymous | 登錄名。輸入登錄名後，將出現一個密碼提示。可能是空密碼，也可能是 “[email protected]”。 |
| cd pub/cd_images/Ubuntu-8.04 | 跳轉到遠端系統中，要下載文件所在的目錄下， 大多數文件都能在pub下找到 |
| ls | 列出遠端系統中的目錄。 |
| lcd Desktop | 跳轉到本地系統中的 ~/Desktop 目錄下。 這個命令把工作目錄改爲 ~/Desktop，多了個l |
| get ubuntu-8.04-desktop-i386.iso | 告訴遠端系統傳送文件到本地。因爲工作目錄 已經更改到 ~/Desktop，所以會被下載到此目錄。 |
| bye | 退出遠端服務器，結束 ftp 程序會話。也可以使用命令 quit 和 exit。 |
知識點4：lftp與ftp的區別？
沒什麼區別就是lftp更高級，比如直接可以用Tab鍵進行補全代碼。
知識點5：wget與ftp的區別？
答：wget可以在網絡下進行下載，也可以在ftp下進行下載。所以很有用。
知識點6：若連接主機密碼也就修改，如何通過SSH進行重新連接？
答：進入~/.ssh/known_hosts 刪除 offend key 即廢棄的鑰匙，再進行連接
3.代碼實操
[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：從輸出結果中，我們可以看到連接測試系統到 slashdot.org 網站需要經由16個路由器。對於那些提供標
識信息的路由器，我們能看到它們的主機名，IP 地址和性能數據，這些數據包括三次從本地到此路由器的往返
時間樣本。對於那些沒有提供標識信息的路由器（由於路由器配置，網絡擁塞，防火牆等 方面的原因），我們
會看到幾個星號
[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等同於ifconfig -r 顯示內核網絡路由表
[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：從匿名 FTP 服務器，其名字是 fileserver， 的/pub/_images/Ubuntu-8.04的目錄下，使用 ftp 程
序下載一個 Ubuntu 系統映像文件。
[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：連接到remote-sys的遠程主機
[me@linuxbox ~]$ ssh bob@remote-sys
bob@remote-sys's password:
Last login: Sat Aug 30 13:03:21 2008
注：使用不同的賬號進行來連接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：通過遠程操作free命令
[me@linuxbox ~]$ ssh remote-sys 'ls \*' > dirlist.txt
me@twin4's password:
注：將遠程的結果導入到本地。若加單引號則傳入到遠程端，看下段代碼。
[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：從 remote-sys 遠端系統的家目錄下複製文檔 document.txt，到我們本地系統的當前工作目錄下
[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 文件複製程序是 sftp，顧名思義，它是 ftp 程序的安全替代品。
