df和du的区别以及磁盘空间使用问题

最新推荐文章于 2022-10-13 10:59:53 发布

最新推荐文章于 2022-10-13 10:59:53 发布 · 221 阅读

文章标签：

本文解释了du和df命令在报告文件系统磁盘使用情况和可用空间时可能出现不同结果的原因。du命令递归统计指定目录或文件的磁盘使用量，而df命令显示已挂载文件系统的磁盘占用、使用和可用空间等信息。当后台程序写入文件后该文件被删除，du和df报告的磁盘使用量会出现差异，df值更高。

solarissparc
root

df-kb结果
/dev/vx/dsk/home121972201108651598873392%/home

du-ks查看/home分区情况为
10dep
27lost+found
395517oracle
288bigml.lsof
212309wei
4041696lan
346074xue
520xue.log
du相加的结果和df的结果不同？！

下面这篇文章给出答案

DocumentId:26928Synopsis:duanddfDifferences(originallypublished8/91)
Updatedate:2001-05-13Description:duanddfDifferences
------------------

Thisarticleexplainshowreportingdiskusageduandreportingfreediskspace
onfilesystemsdfmayshowdifferentnumbers.

du
--

Theduusercommandgivesthenumberofkilobytescontainedinallfilesand,
recursively,directorieswithineachspecifieddirectoryorfile(filename).
Iffilenameismissing,`.'(thecurrentdirectory)isused.Afilewhich
hasmultiplelinkstoitisonlycountedonce.

EXAMPLE:

system%du

5./jokes
33./squash
44./tech.papers/lpr.document
217./tech.papers/new.manager
401./tech.papers
144./memos
80./letters
388./window
93./messages
15./useful.news
1211.

Notethatthelastnumber,1211isthegrandtotal(inkilobytes)forthe
directory.

df
--

Thedfusercommanddisplaysthefollowinginformation:

amountofdiskspaceoccupiedbycurrentlymountedfilesystems
theamountofusedandavailablespace
howmuchofthefilesystem'stotalcapacityhasbeenused

Usedwithoutarguments,dfreportsonallmountedfilesystems.

EXAMPLE:

system%df

FilesystemkbytesusedavailcapacityMountedon
/dev/ip0a74454714198670%/
/dev/ip0g4227735291275893%/usr

Note:usedplusavailislessthantheamountofspaceinthefilesystem
(kilobytes)becausethesystemreservesafractionofthespaceinthefile
systemtoallowitsallocationroutinestoworkwell.Theamountreservedis
typicallyabout10%.(Thismaybeadjustedusingthetunefscommand.Referto
themanpagesontunefs(8)formoreinformation.)Whenallthespaceonafile
system,exceptforthisreserve,isinuse,onlythesuper-usercanallocate
newfilesanddatablockstoexistingfiles.This,however,maycausethefile
systemtobeoverallocated.Whenafilesystemisoverallocatedinthisway,
dfmayreportthatthefilesystemismorethan100%utilized.

Ifargumentstodfarediskpartitions(forexample,/dev/ip0asorpathnames),
dfproducesareportonthefilesystemcontainingthenamedfile.Thus,df
showstheamountofspaceonthefilesystemcontainingthecurrentdirectory.

ProblemDefinition
-----------------

Thissectiongivesthetechnicalexplanationofwhyduanddfsometimesreport
differenttotalsofdiskspaceusage.

Whenaprogramthatisrunninginthebackgroundwritestoafilewhilethe
processisrunning,thefiletowhichthisprocessiswritingisdeleted.
Runningdfanddushowsadiscrepancyintheamountofdiskspaceusage.The
dfcommandshowsahighervalue.

ExplanationSummary
------------------

Whenyouopenafile,yougetapointer.Subsequentwritestothisfile
referencesthisfilepointer.Thewritecalldoesnotchecktoseeifthefile
isthereornot.Itjustwritestothespecifiednumberofcharactersstarting
atapredeterminedlocation.Regardlessofwhetherthefileexistornot,disk
blocksareusedbythewriteoperation.

Thedfcommandreportsthenumberofdiskblocksusedwhiledugoesthroughthe
filestructureandandreportsthenumberofblocksusedbyeachdirectory.As
farasduisconcerned,thefileusedbytheprocessdoesnotexist,soitdoes
notreportblocksusedbythisphantomfile.Butdfkeepstrackofdiskblocks
used,anditreportstheblocksusedbythisphantomfile.