Target Goals

• Navigate the filesystem
• Manage the filesystem
• Maintain the filesystem

Navigating in the Linux Shell

Basic Commands

Command	What It Does
ls	lists files and directories
cd	moves through directory structure
mv	moves files and directories
cp	copies a file
rm	Deletes files and directories
touch	changes access or modification to a file
mkdir	creates directories

All objects in Linux are seen as files

The root directory is represented by a /
You are placed in your home directory by default
The current working directory is represented by a period
The parent directory is represented by a double-period

Changing Directories using CD

• CD alone returns to home directory
• CD [pathname] takes you to specified path
• CD ~ [pathname] takes you to the directory relative to home directory

Viewing Directory Contents

You can use dir or ls to view directory contents

Common Uses of LS (use man ls to see more extensive listing of options)

ls -F	lists directories with a slash to end directory name
ls -R	provides long-format listing
ls -l	Recursively list subdirectories
ls -ld	Povides long directory listing of directory but not contents
ls -la	Prints out regular and hidden files in the directory

Wildcards

Metacharacter	Action
*	Matches any or no character
?	Matches single character
Set [ ]	Matches single character
Range [ - ]	Matches any single charcter in defined range

Managing Files and Directories

The default Linux filesystem is ext3

• ext3 is built on the traditional ext2 (which provided fast access as well as rapid read and write times-but lacked journaling feature - records disk activity to speed recovery from improper shutdown)
• reiserfs - Treats partition as one database, a balanced tree is used to store directories, files and metadata (which are stored near each other for rapid access)

Filesystem Info
All filesystems must be mounted before they are available using syntax: [device] [mountpoint]
The mount command attaches the filesystem on various devices to a single tree

Various paths to devices:
/dev/hda - 1st hard drive
/dev/hda1 - 1st partition on 1st hard drive
/dev/fd0 - 1st floppy
/dev/sd -1st SCSI disk
/dev/st - 1st SCSI tape drive
/dev/console - monitor
/dev/tty - other consoles

mount without options will display the device, mount point, type and whether it is read-write or read-only.
unmount is used to unmount volumes (if you are using a directory on a mounted file system you cannot unmount it)


Mounting DOS
mount -t msdos Create a directory in /mnt for each device you will mount

nvram lets you view and change values stored in non-volatile memory (requires 2.1x kernel with /dev/nram support)

To burn a CD on a mounted CD-R create a directory for the files and make an ISO image of the files using mkisofs and burn the CD using cdrecord

Automated mounting
use /etc/fstab to list file systems to be mounted during boot and unmounted at shutdown, it is automatically created or updated.

Directory Creation
mkdir [dirname] - command for creating directories. The dirname can include a path to another location. You may include multiple dirnames in one command to create multiple directories.

Filesystem maintenance
FSCK - no I didn't just swear!

System performance is improved because disk writes aren't executed until required. Multiple read requests to the same block are served by RAM. An update utility consistentantly flushes the dirty buffers to disk to help prevent damage to data in the event of system disruption.

shutdown - synchronizes synchronizes disk buffers and cleanly exits any running process

fsck is used to check and repair the filesystem integrity. If no problems occur the number of files, blocks used and blocks free are listed. If problems occur the system prompts for correctve actions.

FSCK codes

Code	Value
0	No errors
1	Filesystem errors found and corrected
2	You should reboot the system
4	Errors found, but corrected
8	Opperational error
16	Usage/syntax error
128	Shared library error

fsck -r /dev/ [filesystem] - interactively repairs the the [filesystem] isinidcated.
Only therepair one filesystem at a time.
Journaling
Metadata includes: file creation date; last file modification date; ownership (group and user), permissions, file size, file location

Journaling helps maintain integrity of system if file is being written during a crash.

Before making a file change journaling makes note of the intended change. Once the change is made, amn entry is made indicating if the change was successful.

So....
If the system crashes before a journal entry is made the original data is intact but any changes may be lost.
If the crash occurs during a disk write, the journal entry remains to indicate impending change so that upon successful reboot the entry is read and either the change is executed or rolled back to a previous state

Performance Issues

• recovery time after failure
• bitmap tracking of the filesystem
• fragmentation

Journaling uses disk space efficiently by allowing data to be read and written faster for a variety of file sizes via dynamic space allocation.

2 common filesystems are ext3 and reiserfs

fdformat - performs a low-level format

setfdprm - sets the device type eliminating the need to specify device capacity when formatting disk

The Return of MKFS
mkfs - used to create the filesytem

Filesystems

Type	Definition
ext2	extended and most common LInux filesystem
ext3	updated ext3
romfs	ramdisk read only filesystem
NFS	Network File System - used to acces remote files on network
msdos	DOS-FAT filesystem

Creating any filesystem also creates a lost+found directory. When system crashes or improper shutdown occurs files and directories without a directory entry are reattached to the inode table and placed in lost+found upon reboot.