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understandingUNIX/linuxfilesystemsuperblock

系统运输

thisissecondpartofunderstandingunix/Linux文件系统,partiishere.letustakeanexampleof 20gb hard disk.theentirediskspacesube

UNIX/Linux文件系统块

theblocksusedfortwodifferentpurpose :

mostblocksstoresuserdataakafiles (用户数据)。

someblocksineveryfilesystemstorethefilesystem\\ s metadata.sowhatthehellisametadata?

insimplewordsmetadatadescribesthestructureofthefilesystem.mostcommonmetadatastructurearesuperblock,inodeanddirectories.fories

超级拦网

eachfilesystemisdifferentandtheyhavetypelikeext 2,ext3 etc.furthereachfilesystemhassizelike 5gb, 10gbandstatussuchasmountstatus.inshorteachfilesystemhasasuperblock,whichcontainsinformationaboutfilesystemsuchas :

文件系统类型

大小

状态

信息性boutothermetadatastructures

If this information lost,youareintrouble (数据丢失) )。 olinuxmaintainsmultipleredundantcopiesofthesuperblockineveryfilesystem.thisisveryimportantinmanyemergencysituation、 forexampleyoucanusebackupcopiestorestoredamagedprimarysuperblock.followingcommanddisplaysprimaryandbackupsuperblocklocationonocation

# dumpe2fs/dev/sda1| grep-isuperblock

Output :

主super block at 0,Group descriptors at 1-7

Backup superblock at 32768,Group descriptors at 32769-32775

Backup superblock at 98304,Group descriptors at 98305-98311

Backup superblock at 163840,groupdescriptorsat 163841-163847

Backup superblock at 229376,groupdescriptorsat 229377-229383

Backup superblock at 294912,groupdescriptorsat 294913-294919

Backup superblock at 819200,groupdescriptorsat 819201-819207

Backup superblock at 884736,groupdescriptorsat 884737-884743

Backup superblock at 1605632、groupdescriptorsat 1605633-1605639

Backup superblock at 2654208、groupdescriptorsat 2654209-2654215

Backup superblock at 4096000,groupdescriptorsat 4096001-4096007

Backup superblock at 7962624,groupdescriptorsat 7962625-7962631

Backup superblock at 11239424,groupdescriptorsat 11239425-11239431

Backup superblock at 20480000、groupdescriptorsat 20480001-20480007

Backup superblock at 23887872、groupdescriptorsat 23887873-23887879

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