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docs/ext2fs-FAQ.txt
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docs/ext2fs-FAQ.txt
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From samba!concert!gatech!howland.reston.ans.net!usc!cs.utexas.edu!uunet!mcsun!julienas!jussieu!card Wed Mar 24 17:33:56 EST 1993
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Article: 32301 of comp.os.linux
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Newsgroups: comp.os.linux
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Path: samba!concert!gatech!howland.reston.ans.net!usc!cs.utexas.edu!uunet!mcsun!julienas!jussieu!card
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From: card@masi.ibp.fr (Remy CARD)
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Subject: EXT2FS FAQ (Was Re: A ton of questions)
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Message-ID: <1993Mar24.195635.21729@jussieu.fr>
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Sender: news@jussieu.fr (Le Facteur)
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Nntp-Posting-Host: ares.ibp.fr
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Organization: Laboratoire MASI - Universite Pierre et Marie Curie - Paris - France
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References: <AffzDvS00WBOM6ZoF5@andrew.cmu.edu>
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Date: Wed, 24 Mar 1993 19:56:35 GMT
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Lines: 95
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In article <AffzDvS00WBOM6ZoF5@andrew.cmu.edu> Joshua Eli Schachter <jsct+@andrew.cmu.edu> writes:
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>
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>B) During bootup, the drive complains that there are a lot of problems
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>with the file system... i am using FS2.
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>
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Hmmm, seems like there are some frequently asked questions about the
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ext 2 fs. So, I have written a quick and dirty FAQ concerning the ext 2 fs.
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This FAQ is included at the end of this posting. It is also available for
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anonymous FTP from ftp.ibp.fr:/pub/linux/ALPHA/ext2fs/ext2fs.FAQ and from
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tsx-11.mit.edu:/pub/linux/ALPHA/ext2fs/ext2fs.FAQ.
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>
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>j.e.s.
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>
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Remy
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-------------------------------------------------------------------------------
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FAQ for the second extended file system
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Last change on 93/03/24
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This file contains the answers to some frequently asked questions
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regarding the second extended file system.
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Q: I have created an ext 2 fs on my root file system and, every time I boot
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Linux, I see these messages :
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MINIX-fs magic match failed
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EXT-fs: magic match failed
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Does it mean that Linux doesn't recognize my root file system ?
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A: No.
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When Linux boots, it tries to mount the root file system using the
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different file system types :
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- it first tries to mount / as a minix file system, discovers that it
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is not a minix fs and displays the first error message,
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- then it tries to mount / as an extended file system, discovers that
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it is not an extended fs and displays the second error message.
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Q: After the two error messages, I see :
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[EXT II FS 0.2c, 93/03/06, bs=1024, fs=1024, gc=##, bpg=##, ipg=####]
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EXT2-fs warning: mounting non valid file system
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Does it mean that there is a problem with the file system ?
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A: Usually no.
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In fact, the ext 2 fs keeps a valid flag on the disk. This flag is set to
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0 when the file system is mounted and set to 1 when it is unmounted. The
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valid flag is checked by e2fsck to know if a file system needs checking (if
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the flag is set to 1, e2fsck assumes that the file system is clean and does
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not check it).
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The root file system is the only fs which cannot be unmounted so the valid
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flag is always set to 0. When booting, the kernel mounts it and checks its
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valid flag. As this flag is set to 0, it displays a warning.
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You can safely ignore this warning for the root file system. Note that it
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is a good idea to run e2fsck on the fs.
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Q: I have tried to create an ext 2 file system with mke2fs and it dies with
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'Out of memory'. What is the problem ?
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A: The problem comes from mke2fs itself. mke2fs eats lots of memory to create
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a file system since it creates a memory copy of the inode table. The
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problem has been fixed in recent versions (0.2c+ or above). Note that
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e2fsck still has the same problem.
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Q: I have tried to create an ext 2 fs with mke2fs and it dies with the
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message :
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mke2fs: Unable to find a block for the block bitmap
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or :
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mke2fs: Unable to find a block for the inode bitmap
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or:
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mke2fs: Unable to find a block for the inode table
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What is the problem ?
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A: An ext 2 fs is made of several blocks groups. Each group contains a copy
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of the super block, a copy of the fs descriptors, two bitmap blocks and
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a part of the inode table. Each group is 8192 blocks long.
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When you create a file system, mke2fs divides the total number of blocks by
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8192 to compute the number of groups. Then, it tries to write the control
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informations into each group. Sometimes, the last group may be too small to
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contain these informations and mke2fs simply dies when it detects the
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problem. This (stupid) behaviour will be fixed in a future release.
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With the current release, you can bypass the problem by creating a smaller
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or bigger file system (i.e. decrease or increase the blocks count).
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-------------------------------------------------------------------------------
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--
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Remy Card
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card@masi.ibp.fr
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