一直以来被Linux的hostname和fqdn(Fully Qualified Domain Name)困惑了好久,今天专门抽时间把它们的使用细节弄清了。
一、设置hostname/fqdn
在Linux系统内设置hostname很简单,如:
$ hostname florian
如果要设置fqdn的话,需要对/etc/hosts进行配置。
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$ cat / etc / hosts
127.0 . 0.1 localhost
192.168 . 1.1 florian.test.com florian
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/etc/hosts配置文件的格式是:
ip fqdn [alias]...
即第一列为主机ip地址,第二列为主机fqdn地址,第三列以后为别名,可以省略,否则至少要包含hostname。
上述配置文件的配置项的第一行为localhost的配置,第二行为主机名florian配置fqdn=florian.test.com,ip=192.168.1.1。
至于fqdn的域名后缀,最好和文件/etc/sysconfig/network的HOSTNAME配置保持一致:
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$ cat / etc / sysconfig / network
NETWORKING = yes
HOSTNAME = test.com
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二、查看hostname/fqdn
配置完成后,可以使用shell命令查看hostname和fqdn:
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$ hostname && hostname - f
florian
florian.test.com
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使用ping去测试hostname的ip映射是否成功。
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$ ping florian
PING florian.test.com ( 192.168 . 1.1 ) 56 ( 84 ) bytes of data.
$ ping florian.test.com
PING florian.test.com ( 192.168 . 1.1 ) 56 ( 84 ) bytes of data.
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也可以使用python命令获取hostname和fqdn。
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$ python
Python 2.6 . 6 (r266: 84292 , Dec 7 2011 , 20 : 48 : 22 )
[GCC 4.4 . 6 20110731 (Red Hat 4.4 . 6 - 3 )] on linux2
Type "help" , "copyright" , "credits" or "license" for more information.
>>> import socket
>>> socket.gethostname()
'florian'
>>> socket.getfqdn()
'florian.test.com'
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三、使用ip设置hostname带来的fqdn问题
以上描述了正常设置hostname和fqdn的方法,但是有时会使用ip地址直接作为hostname,此时会有些不同。
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$ hostname 192.168 . 1.1
$ hostname && hostname - f
192.168 . 1.1
192.168 . 1.1
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我们发现使用ip作为hostname后,使用shell命令查询hostname和fqdn都是ip地址!!!这是因为DNS协议会解析hostname的内容,当发现其为ip地址时,则不会再去查询/etc/hosts文件。
再使用python查看一下,会发现python获取的fqdn竟然还是florian.test.com!!!
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$ python
Python 2.6 . 6 (r266: 84292 , Dec 7 2011 , 20 : 48 : 22 )
[GCC 4.4 . 6 20110731 (Red Hat 4.4 . 6 - 3 )] on linux2
Type "help" , "copyright" , "credits" or "license" for more information.
>>> import socket
>>> socket.gethostname()
'192.168.1.1'
>>> socket.getfqdn()
'florian.test.com'
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即便是刷新dns缓存也无济于事:
$ service nscd reload
将/etc/hosts文件的第二行注释:
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cat / etc / hosts
127.0 . 0.1 localhost
# 192.168.1.1 florian.test.com florian
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刷新dns缓存:
$ service nscd reload
我们发现fqdn恢复正常了。
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$ python
Python 2.6 . 6 (r266: 84292 , Dec 7 2011 , 20 : 48 : 22 )
[GCC 4.4 . 6 20110731 (Red Hat 4.4 . 6 - 3 )] on linux2
Type "help" , "copyright" , "credits" or "license" for more information.
>>> import socket
>>> socket.gethostname()
'192.168.1.1'
>>> socket.getfqdn()
'192.168.1.1'
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之所以会有这样的行为,是因为python解析fqdn的逻辑和DNS并不完全一致,它会根据hostname查询对应的ip地址,然后在/etc/hosts内获取ip地址对应的配置行(第一行有效),然后解析fqdn列和alias列,并返回第一个包含字符'.'的对应列的值。
因此,使用ip设置hostname时,需要注意两点:
•首先,将hostname设置为ip地址
•其次,将/etc/hosts内包含该ip的配置项移除
为了保险起见,我们可以在/etc/hosts内尽可能靠前的位置添加如下配置:
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cat / etc / hosts
127.0 . 0.1 localhost
192.168 . 1.1 192.168 . 1.1
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这样,即便是之后有包含该ip的配置项也不会生效,python会优先解析第二行的配置项,并获取和ip地址完全一样的fqdn地址。当然,使用shell命令hostname获取fqdn也不会出错,因为hostname已经被设为ip地址形式了。
下面给大家介绍python shell 根据ip 获取 hostname || 根据hostname 获取 ip
利用 socket 模块 里的 gethostbyname 函数
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<code class = "hljs perl has-numbering" style = "display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;" >>>> import <span class = "hljs-keyword" style = "color: rgb(0, 0, 136); box-sizing: border-box;" >socket< / span> >>> <span class = "hljs-keyword" style = "color: rgb(0, 0, 136); box-sizing: border-box;" >socket< / span>.<span class = "hljs-keyword" style = "color: rgb(0, 0, 136); box-sizing: border-box;" >gethostbyname< / span>(<span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > "www.baidu.com" < / span>) <span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > '61.135.169.125' < / span> >>> <span class = "hljs-keyword" style = "color: rgb(0, 0, 136); box-sizing: border-box;" >socket< / span>.<span class = "hljs-keyword" style = "color: rgb(0, 0, 136); box-sizing: border-box;" >gethostbyname< / span>(<span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > "rs.xidian.edu.cn" < / span>) <span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > '202.117.119.1' < / span>< / code><ul class = "pre-numbering" style = "box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);" ><li style = "box-sizing: border-box; padding: 0px 5px;" > 1 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 2 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 3 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 4 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 5 < / li>< / ul>
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方法2 利用 shell 中 hostname 命令
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<code class = "hljs livecodeserver has-numbering" style = "display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;" > def getHostName(ip): <span class = "hljs-command" style = "box-sizing: border-box;" ><span class = "hljs-keyword" style = "color: rgb(0, 0, 136); box-sizing: border-box;" >command< / span> = <span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > 'java -jar %s %s "hostname > %s.hostname"' < / span> % (<span class = "hljs-title" style = "box-sizing: border-box;" >remoteCmdLoca< / span>,<span class = "hljs-title" style = "box-sizing: border-box;" >ip< / span>,<span class = "hljs-title" style = "box-sizing: border-box;" >ip< / span>)< / span> <span class = "hljs-built_in" style = "color: rgb(102, 0, 102); box-sizing: border-box;" >result< / span> = subprocess.call(<span class = "hljs-command" style = "box-sizing: border-box;" ><span class = "hljs-keyword" style = "color: rgb(0, 0, 136); box-sizing: border-box;" >command< / span>, <span class = "hljs-title" style = "box-sizing: border-box;" >shell< / span> = <span class = "hljs-title" style = "box-sizing: border-box;" > True < / span>)< / span> <span class = "hljs-command" style = "box-sizing: border-box;" ><span class = "hljs-keyword" style = "color: rgb(0, 0, 136); box-sizing: border-box;" >command< / span> = <span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > '%s -q -r -pw Sybase123 %s root@%s:/root' < / span> % (<span class = "hljs-title" style = "box-sizing: border-box;" >pscpLoca< / span>, <span class = "hljs-title" style = "box-sizing: border-box;" >pscpLoca< / span>, <span class = "hljs-title" style = "box-sizing: border-box;" >ip< / span>)< / span> <span class = "hljs-built_in" style = "color: rgb(102, 0, 102); box-sizing: border-box;" >result< / span> = subprocess.call(<span class = "hljs-command" style = "box-sizing: border-box;" ><span class = "hljs-keyword" style = "color: rgb(0, 0, 136); box-sizing: border-box;" >command< / span>, <span class = "hljs-title" style = "box-sizing: border-box;" >shell< / span> = <span class = "hljs-title" style = "box-sizing: border-box;" > True < / span>)< / span> <span class = "hljs-command" style = "box-sizing: border-box;" ><span class = "hljs-keyword" style = "color: rgb(0, 0, 136); box-sizing: border-box;" >command< / span> = <span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > '%s -q -r -pw Sybase123 root@%s:/root/%s.hostname %s' < / span> % (<span class = "hljs-title" style = "box-sizing: border-box;" >pscpLoca< / span>,<span class = "hljs-title" style = "box-sizing: border-box;" >ip< / span>,<span class = "hljs-title" style = "box-sizing: border-box;" >ip< / span>,<span class = "hljs-title" style = "box-sizing: border-box;" >sumAutoLoca< / span>)< / span> <span class = "hljs-built_in" style = "color: rgb(102, 0, 102); box-sizing: border-box;" >result< / span> = subprocess.call(<span class = "hljs-command" style = "box-sizing: border-box;" ><span class = "hljs-keyword" style = "color: rgb(0, 0, 136); box-sizing: border-box;" >command< / span>, <span class = "hljs-title" style = "box-sizing: border-box;" >shell< / span> = <span class = "hljs-title" style = "box-sizing: border-box;" > True < / span>)< / span> fileName = sumAutoLoca + ip + <span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > '.hostname' < / span> readFile = <span class = "hljs-built_in" style = "color: rgb(102, 0, 102); box-sizing: border-box;" > open < / span>(fileName,<span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > 'r' < / span>) hostnameInfo = str (readFile.readline().strip(<span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > '\n' < / span>)) readFile.<span class = "hljs-built_in" style = "color: rgb(102, 0, 102); box-sizing: border-box;" >close< / span>() subprocess.call(<span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > 'rm ' < / span> + fileName, <span class = "hljs-built_in" style = "color: rgb(102, 0, 102); box-sizing: border-box;" >shell< / span> = True ) print <span class = "hljs-string" style = "color: rgb(0, 136, 0); box-sizing: border-box;" > "=========%s hostname is %s========" < / span> % (ip,hostnameInfo) <span class = "hljs-constant" style = "box-sizing: border-box;" > return < / span> hostnameInfo< / code><ul class = "pre-numbering" style = "box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);" ><li style = "box-sizing: border-box; padding: 0px 5px;" > 1 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 2 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 3 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 4 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 5 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 6 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 7 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 8 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 9 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 10 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 11 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 12 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 13 < / li><li style = "box-sizing: border-box; padding: 0px 5px;" > 14 < / li>< / ul>
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设计思路 ##
有时候socket不太稳定, 具体原因带查明
目的: 根据 ip 获取 hostname (适当改进也可逆转)
先设计了一个远程执行 ssh 命令jar, 或者可以用plink, 链接enter link description here
利用subprocess.call命令在远程ip机器上执行hostname > %s.hostname命令, 将hostname 信息输出到文件
用pscp将本地的pscp文件复制到远程ip机器上 /root 目录下(后来发现这步不需要)
然后利用本地的 pscp 将远程机器上带有hostname的文本文件/root/%s.hostname 复制到本地
利用 python 的文本读取功能读取信息, 从中取出hostname字符串
再利用 rm 命令把远程机器和本地的文本文件都删除