Subject: EXT2FS FAQ (Was Re: A ton of questions)

From: [email-masked] (Remy CARD)
Date: Wed, 24 Mar 1993 19:56:35 GMT

In article <[email-masked]> Joshua Eli Schachter <[email-masked]> writes:
>
>B) During bootup, the drive complains that there are a lot of problems
>with the file system... i am using FS2.
>

	Hmmm, seems like there are some frequently asked questions about the
ext 2 fs.  So, I have written a quick and dirty FAQ concerning the ext 2 fs.
This FAQ is included at the end of this posting.  It is also available for
anonymous FTP from ftp.ibp.fr:/pub/linux/ALPHA/ext2fs/ext2fs.FAQ and from
tsx-11.mit.edu:/pub/linux/ALPHA/ext2fs/ext2fs.FAQ.

>j.e.s.

	Remy

-------------------------------------------------------------------------------

		FAQ for the second extended file system
                        Last change on 93/03/24

	This file contains the answers to some frequently asked questions
regarding the second extended file system.

Q: I have created an ext 2 fs on my root file system and, every time I boot
   Linux, I see these messages :
	MINIX-fs magic match failed
	EXT-fs: magic match failed
Does it mean that Linux doesn't recognize my root file system ?

A: No.
   When Linux boots, it tries to mount the root file system using the
   different file system types :
	- it first tries to mount / as a minix file system, discovers that it
	  is not a minix fs and displays the first error message,
	- then it tries to mount / as an extended file system, discovers that
	  it is not an extended fs and displays the second error message.

Q: After the two error messages, I see :
	[EXT II FS 0.2c, 93/03/06, bs=1024, fs=1024, gc=##, bpg=##, ipg=####]
	EXT2-fs warning: mounting non valid file system
   Does it mean that there is a problem with the file system ?

A: Usually no.
   In fact, the ext 2 fs keeps a valid flag on the disk.  This flag is set to
   0 when the file system is mounted and set to 1 when it is unmounted.  The
   valid flag is checked by e2fsck to know if a file system needs checking (if
   the flag is set to 1, e2fsck assumes that the file system is clean and does
   not check it).

   The root file system is the only fs which cannot be unmounted so the valid
   flag is always set to 0.  When booting, the kernel mounts it and checks its
   valid flag.  As this flag is set to 0, it displays a warning.

   You can safely ignore this warning for the root file system.  Note that it
   is a good idea to run e2fsck on the fs.

Q: I have tried to create an ext 2 file system with mke2fs and it dies with
   'Out of memory'.  What is the problem ?

A: The problem comes from mke2fs itself.  mke2fs eats lots of memory to create
   a file system since it creates a memory copy of the inode table.  The
   problem has been fixed in recent versions (0.2c+ or above).  Note that
   e2fsck still has the same problem.

Q: I have tried to create an ext 2 fs with mke2fs and it dies with the
   message :
	mke2fs: Unable to find a block for the block bitmap
   or :
	mke2fs: Unable to find a block for the inode bitmap
   or:
	mke2fs: Unable to find a block for the inode table
   What is the problem ?

A: An ext 2 fs is made of several blocks groups.  Each group contains a copy
   of the super block, a copy of the fs descriptors, two bitmap blocks and
   a part of the inode table.  Each group is 8192 blocks long.

   When you create a file system, mke2fs divides the total number of blocks by
   8192 to compute the number of groups.  Then, it tries to write the control
   informations into each group.  Sometimes, the last group may be too small to
   contain these informations and mke2fs simply dies when it detects the
   problem.  This (stupid) behaviour will be fixed in a future release.

   With the current release, you can bypass the problem by creating a smaller
   or bigger file system (i.e. decrease or increase the blocks count).

-------------------------------------------------------------------------------
--

	Remy Card
	[email-masked]