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📁 一份很好的linux入门资料
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<HTML><HEAD>  <TITLE>BBS水木清华站∶精华区</TITLE></HEAD><BODY><CENTER><H1>BBS水木清华站∶精华区</H1></CENTER>发信人:&nbsp;raner&nbsp;(lilo),&nbsp;信区:&nbsp;Linux&nbsp;<BR>标&nbsp;&nbsp;题:&nbsp;关于Linux下的undelete&nbsp;<BR>发信站:&nbsp;BBS&nbsp;水木清华站&nbsp;(Tue&nbsp;Sep&nbsp;23&nbsp;18:28:19&nbsp;1997)&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Linux中没有象DOS中undelete这样简单的工具,&nbsp;它安装好后只是做了个&nbsp;<BR>&nbsp;&nbsp;alias&nbsp;rm='rm&nbsp;-i'的alias,&nbsp;先confirm一下才删.&nbsp;但假如真错删了重要&nbsp;<BR>&nbsp;文件怎么办?&nbsp;一个解决办法是用mc(midnight&nbsp;commander),&nbsp;它有个undelete&nbsp;<BR>&nbsp;功能，可以找到ext2&nbsp;fs上被删掉的i-node,&nbsp;文件名是无法恢复了(因为ext2&nbsp;<BR>&nbsp;也用Unix的传统，目录文件中保存文件名和i-node&nbsp;index,&nbsp;删除时将i-node&nbsp;<BR>&nbsp;清为0,&nbsp;因此从i-node&nbsp;table是无法反查到目录文件的),&nbsp;但文件的其余信息&nbsp;<BR>&nbsp;都还在.&nbsp;&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;我在恢复一个重要文件时发现mc只能恢复前12K内容，觉得很奇怪,&nbsp;用&nbsp;<BR>&nbsp;lde(Linux&nbsp;Disk&nbsp;Editor,&nbsp;仿Norton做的,&nbsp;编辑硬盘block很好用)学了一下&nbsp;<BR>&nbsp;ext2&nbsp;fs,&nbsp;结构很简单,&nbsp;每个i-node中12个direct&nbsp;block,&nbsp;3个1/2/3次indirect&nbsp;<BR>&nbsp;block.&nbsp;而Linux&nbsp;Kernel在删文件时做了一件令我费解的事:&nbsp;&nbsp;它把所有的&nbsp;<BR>&nbsp;indirect&nbsp;block全清0!&nbsp;按道理在block&nbsp;bitmap中标为free就得了，将其&nbsp;<BR>&nbsp;zero简直是吃力不讨好.&nbsp;这也就是为什么mc只能恢复12K(direct&nbsp;block)的原因&nbsp;<BR>&nbsp;而且若文件的block不是连续存放的，那将导致后面的block根本无法恢复!&nbsp;<BR>&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;不过幸好，我那个文件只几十K(源程序),&nbsp;而且是unfragmented的，即&nbsp;<BR>&nbsp;block连续，用lde手工恢复了个indirect&nbsp;block就OK了.&nbsp;据说在2.1.x板的&nbsp;<BR>&nbsp;kernel中已将zero&nbsp;indirect&nbsp;block的举动去掉了,&nbsp;那样恢复起来就好办多了.&nbsp;<BR>&nbsp;(干完后才发现有篇mini-HOWTO是讲undelete的&nbsp;:-(&nbsp;)&nbsp;<BR>&nbsp;&nbsp;<BR>&nbsp;&nbsp;&nbsp;&nbsp;吸取这次教训，我装了个safedelete,&nbsp;alias&nbsp;rm=safedelete,&nbsp;alias&nbsp;purge=rm&nbsp;<BR>&nbsp;&nbsp;它起Win95中RecycleBin的作用，删掉的文件存于一个地方，过指定时间自动&nbsp;<BR>&nbsp;&nbsp;purge,&nbsp;还廷好用。&nbsp;<BR>&nbsp;<BR>--&nbsp;<BR>※&nbsp;来源:·BBS&nbsp;水木清华站&nbsp;bbs.net.tsinghua.edu.cn·[FROM:&nbsp;166.111.5.84]&nbsp;<BR><CENTER><H1>BBS水木清华站∶精华区</H1></CENTER></BODY></HTML>
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