– General Linux 1 – Maintain the integrity of ﬁlesystems
(Linux Professional Institute Certiﬁcation)
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by: geoffrey robertson geoffrey@zip.com.au

$Id: gl1.104.2.slides.tex,v 1.3 2003/05/30 05:04:30 waratah Exp $

c 2002 Geoffrey Robertson. Permission is granted to make and distribute verbatim copies or modiﬁed versions of this document provided that this copyright notice and this permission notice are preserved on all copies under the terms of the GNU General Public License as published by the Free Software Foundation—either version 2 of the License or (at your option) any later version.

a Copyright

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Devices, Linux Filesystems & FHS
1.104.1 Create partitions and ﬁlesystems 1.104.2 Maintain the integrity of ﬁlesystems 1.104.3 Control mounting and unmounting ﬁlesystems 1.104.4 Managing disk quota 1.104.5 Use ﬁle permissions to control access to ﬁles 1.104.6 Manage ﬁle ownership 1.104.7 Create and change hard and symbolic links 1.104.8 Find system ﬁles and place ﬁles in the correct location

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Maintain the integrity of ﬁlesystems
Objective
Candidates should be able to verify the integrity of ﬁlesystems, monitor free space and inodes, and repair simple ﬁlesystem problems. This objective includes the commands required to maintain a standard ﬁlesystem, as well as the extra data associated with a journaling ﬁlesystem.

Key ﬁles, terms, and utilities include:
du df debugfs fsck e2fsck mke2fs dumpe2fs tune2fs

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Summary of Commands
Command du df fsck e2fsck mke2fs debugfs dumpe2fs tune2fs Function Display disk usage Display disk space free Check Filesystem Check an ext2 Filesystem Create an ext2 Filesystem Debug an ext2 Filesystem Dump Filesystem information Adjust parameters on ext2 Filesystem

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du - Disk Usage
• du shows disk usage • du can work with subdirectories or an entire disk • Usage is: du [options] [directory]

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Options to du
Option -a -b -c -h -k -m -s -x Function Show counts for all ﬁles & directories Display size in bytes Print total for all arguments after processing Print in human readable form Show size in Kilobytes Display size in Megabytes Display a summary for each argument Skip directories containing other ﬁlesystems

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df - Disk Free
• df shows disk space used & available • Default is to display all ﬁlesystems • Usage is: df [options] [directory]

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Options to df
Option -a -t fs type -h -k -m -i -l -x fs type Function Show counts for all ﬁlesystems Limit listing to fs type Print in human readable form Show size in Kilobytes Display size in Megabytes Display inode information Limit listing to local ﬁlesystems Exclude fs type from listing

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fsck - Check and repair a Linux ﬁle system
• fsck is used to check and optionally repair a one or more Linux ﬁle systems. • ﬁlesys can be a device name (e.g. /dev/hdc1, /dev/sdb2), a mount point (e.g. /, /usr, /home), or an ext2 label. • fsck will try to run ﬁlesystems on different physical drives in parallel to reduce total amount time to check all of the ﬁlesystems. • fsck makes 5 passes on the ﬁlesystem: – Pass 1: Check inodes, blocks & sizes – Pass 2: Check directory structure – Pass 3: Check directory connectivity – Pass 4: Check reference counts
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– Pass 5: Check group summary information

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fsck Options
Option -p -n -y -f -r -v -A -C -N Function Automatically repair without prompting Don’t make changes to ﬁlesystem Assume yes to all questions Force check even if fs is clean Interactively prompt for changes Be verbose Check all ﬁlesystems in /etc/fstab Display a progress bar Don’t execute, show what would be done

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fsck error codes
When fsck completes, it will return a value ($?) as follows: Code 0 1 2 4 8 16 128 Meaning No errors Errors found & corrected System should be rebooted Filesystem error left uncorrected Operational error Usage or syntax error Shared library error

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e2fsck - Check a Linux ext2 FS
• e2fsck is used to check a Linux second extended ﬁle system (e2fs) • e2fsck also supports ext2 ﬁlesystems containing a journal, which are also sometimes known as ext3 ﬁlesystems. • e2fsck operates in a similar manner to fsck (see man page)

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mke2fs - Create a Linux ext2 ﬁlesystem
• mke2fs is used to create an ext2 ﬁlesystem • mke2fs takes a device special ﬁle as its argument • mkfs.ext2 is the same as mke2fs • To make an ext3 ﬁlesystem, you ﬁrst make an ext2 ﬁlesystem and then add a journal to it using tune2fs or use the -j option to mke2fs • Usage is: mke2fs [options] device

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mke2fs Options
Option -V -b blocksize -c -i bytes per inode -j -L label -N inodes -n Use Be verbose Make blocks blocksize bytes Check for bad blocks on device Create an inode for each bytes per inode Create a journal (ext3) Set the volume label Create the fs with speciﬁed number of inodes Show what would be done (don’t actually create fs)

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debugfs - Ext2 ﬁlesystem debugger
• debugfs is a ﬁle system debugger • It can be used to examine and change the state of an ext2 ﬁle system. • debugfs is an interactive debugger. It understands a number of commands: cat ﬁlespec Dump the contents of the inode ﬁlespec to stdout. cd ﬁlespec Change the current working directory to ﬁlespec. chroot ﬁlespec Change the root directory to be the directory ﬁle spec. close Close the currently open ﬁle system. quit Exit debugfs.

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dumpe2fs - Dump ﬁlesystem information
• dumpe2fs prints the super block and blocks group information for the ﬁlesystem present on device • Usage is: dumpe2fs [options] device • Common options are: Option -b -h Use Display badblocks on device Display superblock information

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tune2fs - Adjust ﬁlesystem parameters on ext2 fs
• tune2fs adjusts tunable ﬁlesystem parameters on a Linux ext2 ﬁlesystem. • tune2fs can be used to add a journal to an ext2 ﬁlesystem. • Usage is: tune2fs [options] device

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tune2fs - Common options
Option -c max-mounts -g group -j -L label -r blocks Use Set no of mounts before fsck is forced Set the group who can use reserved blocks Add a journal to the ﬁlesystem Set the volume label Set the number of reserved blocks

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