CSIS 82
Tutorial: Disks and File Systems
Gagne Ch8
Prime Directive: Everything is a file –
Ordinary files ( data, text, any format)
Directory files ( like folders that contain other folders and files)
Special files ( devices such as floppy drive, terminal, sound card, keyboard)
File System Directories
each top level dir is a file system, & could be made into a partition
(see Lecture notes for description of each top level dir)
use find, which or whereis to determine location of a file or utility
Filesystem is the way the data are organised and stored (in physical level) on disks
Common Filesystems in Linux
1. Ext2/ext3
2. ReiserFS
3. Swap
4. NFS
5. Vfat
6. /proc filesystem
/proc File System lives in RAM
ls -1 /
( shows proc has 0 size)
ls /proc lots of stuff
cat /proc/cpuinfo
Information about CPU hardware
cat /proc/interrupts Information about hardware interrupts
cat /proc/meminfo
Information about memory statistics, physical and swap
cat /proc/sound
Sound card's configuration
kcore
system's memory
compare ls /proc
with
ps ax | cut –c1-5
/proc can be used to improve performance (chapter 26)
/lost+found File System
where bad blocks go when detected by fsck
Monitoring disk usage
df
gives information on every mounted file system
df –T –h
-T Identify file system type, -h Human readable
df /usr/local just looks at individual file systems
gdiskfree
Gnome graphical disk monitor
KDiskFree
KDE—find under system menu
inode
df -i
for each file/dir a small data block stores permission, creation, access time and location
on disk—Limited number for each file system
Shows the inodes used & available on disk
Mouting and Unmounting File Systems
In order to access any filesystem under Linux, you must mount it on a certain directory.
mount -t type device mount-point
where type is the type name of the filesystem, device is the physical device where the filesystem resides
(the device file in /dev), and mount-point is the directory on which to mount the
filesystem. You have to create the mount-point directory before issuing mount
mount -t vfat /dev/hda2 /mnt/windows
To mount a windows hda2 FAT32 partition (dual boot)
mount -t iso9660 -r /dev/cdrom /mnt/cdrom
mount
[with no args] tells what filesystem are mounted
umount
Unmount a filesystem: makes the filesystem no longer available from its mount point.
need to do before running fsck disk checking
umount <mount_dir>, e.g. umount mnt/windows
cat /etc/fstab view mount instructions used at bootup. Each line in this file is of the format:
device
mount-point
type
options
/dev/hda2
/mnt/windows
vfat defaults
At boot time mount –a command is called that mounts everything listed in /etc/fstab
usermount
graphical tool lets you mount, unmount and format devices
fdisk
Lets you create new file systems/partitions … major disk operation requires back up
Quotas disk quotas keep users from expanding outside limits
To activate disk quotas, in /etc/fstab add ,usrquota
after defaults for / partition
quotacheck –uagv
Builds a quota database for all users
repquota –av
Reports on quotas & limits (hard, soft, grace)
To always report on quotas at boot:
add to /etc/rc.d/rc.local the following line: /usr/sbin/quotacheck -augv
/sbin/shutdown –r now
reboot
quotas are now activated
quotaoff -auvg
Turn off quotas for group and user
quotaon -auvg
Turn on quotas
edquota –u guest
edquota –t guest
edquota –p guest tux
Allows you to set quotas for a user such as guest
Allows you to set grace period
Clones settings for guest and applies to user tux
quota –v
Lets a user know what their quota status is
Add to /etc/profile script so everyone sees at log in