ITI481: Unix Administration

1
ITI-481 Unix Administration

• Meeting 4

2
Todays Agenda

• Disk Partitioning
• Directories and File Systems
• Mounting Local File systems
• Network File System (NFS)

3
Disk Partitions.

• A typical Linux installation will divide one or
  more hard drives into multiple partitions.
• Each disk is given its own device name/dev/hdX
  (X can range from a-z) IDE disks/dev/sdX (X
  can range from a-z) SCSI disks
• A partition number is added to the device
  name/dev/hdXY (Y is the partition number) IDE
  disks/dev/sdXY (Y is the partition number)
  SCSI disks For example, the first partition on
  the first IDE drive on a system would be
  /dev/hda1.
• Disk partition information can be viewed using
  the df command.

4
Creating a New Partition

• During the Red Hat installation, you are prompted
  to partition your hard drive using Druid Disk.
• After installation, can modify existing
  partitions using fdisk
• Need to identify partition as primary (only up to
  4) or extended.
• Need to identify file system type usually Linux
  or Linux swap.
• Can create ext2 file systems with mke2fs and can
  create swap file systems with mkswap.
• Always backup your data before modifying the
  partition table!!!

5
fdisk

• /sbin/fdisk /dev/hda
• Command (m for help) m
• Command action
• a toggle a bootable flag
• b edit bsd disklabel
• c toggle the dos compatibility flag
• d delete a partition
• l list known partition types
• m print this menu
• n add a new partition
• o create a new empty DOS partition table
• p print the partition table
• q quit without saving changes
• s create a new empty Sun disklabel
• t change a partition's system id
• u change display/entry units
• v verify the partition table
• w write table to disk and exit
• x extra functionality (experts only)

6
Exercise Creating a New Partition

• Launch fdisk edit hard disk /dev/hdagt
  /sbin/fdisk /dev/hda
• You are now working within the fdisk application.
  Type the followingp ltentergt (to view the
  current partition table)n ltentergt (to add a new
  partition)l ltentergt (for a logical
  partitionltentergt (accept the default first
  cylinder)100M ltentergt (100MB partition)p
  ltentergt (verify that partition /dev/hda10 has
  been addedgtw ltentergt (write table to disk and
  exit)
• If you get an error when attempting to write out
  the partition table to the disk, you may need to
  reboot.
• Create a Linux ext2 file system on the new
  partitiongt /sbin/mke2fs /dev/hda10

7
File Systems

• Key partitions are mounted as file systems at
  boot time through rc scripts.
• File systems overlay directories (i.e /boot is
  mounted on /dev/hda1).
• Can use df to view currently mounted file systems.

8
Some Common File System Types

• Type
• ext2
• swap
• NFS
• msdos
• vfat
• iso9660
• proc

• File System
• linux extended
• linux swap
• network file system
• DOS-FAT
• VFAT
• ISO 9660
• /proc

9
Typical Directory Structure

• / - begins the file system structure (root)
• /boot - kernel files
• /usr scripts and binary applications
• /sbin basic system tools
• /home user home directories
• /var log files and other time sensitive data
• /etc configuration files
• /dev device drivers
• /opt typical install location for some
  commercial software
• /tmp temporary storage
• /mnt mount points for floppy disks and CD-ROMS
• swap swap space

10
Sample Directory Tree with Mount Points
11
Mounting and Unmounting File Systems

• File Systems mounted with the mount
  commandmount options device directoryFor
  examplemount o rw t ext2 /dev/hda10 /tmp
• File systems umounted with the umount
  commandumount -f directory For
  exampleumount /tmp
• File systems should only be umounted when they
  are not in use.

12
/etc/fstab

• Configuration file for all partitions known to
  the system.
• Entry format/dev/device /dir/to/mount fstype
  parameters fs_freq fs_passnoSample
  entry/dev/hda10 /tmp ext2 defaults 1 2
• For entries in /etc/fstab, can run mount command
  with just mount pointgt mount /tmpTo mount all
  file systemsgt mount -a

13
Network File System (NFS)

• NFS allows access to file systems on remote file
  servers.
• Remote file systems can be mounted to provide
  services comparable to local file systems.
• Uses TCP/IP.
• Uses client/server model.
• There are some security risks associated with
  NFS.

14
NFS Server

• Started though rc script/etc/rc.d/init.d/nfsMus
  t be started after/etc/rc.d/init.d/portmap
• Uses these RPC daemons in /usr/sbin
• rpc.nfsd main component of NFS system
• rcp.mountd handles mount requests
• rpc.quotad allows for quota enforcement via
  NFS.
• /etc/exports configuration file
• Above utilities are part of knfsd package.

15
/etc/exports

• Contains information about partitions that are
  sharable and hosts they can be shared with.
• Entry format/dir/to/export client1(permissions)
  client2 (permissions)Sample entry/tmp
  trainee101.rutgers.edu (rw,no_root_squash)
• Need to run exportfs to inform NFS server process
  about changes in /etc/exportsgt
  /usr/sbin/exportfs a (exports all entries)

16
NFS Clients

• Requires knfsd-clients package.
• Necessary services started from/etc/rc.d/init.d/
  nfslock
• RPC daemons in /sbin handle file locking between
  client and server
• rpc.locked
• rpc.statd
• Remote file systems usually mounted at boot time
  through /etc/rc.d/init.d/netfs that reads entries
  for remote mounts from /etc/fstab.

17
Mounting Remote File Systems from the Client

• Mount command is used to mount remote file
  systemsgt mount trainee101.rutgers.edu/tmp /foo
• Frequently used mounts can be added to
  /etc/fstabtrainee101.rutgers.edu/tmp /foo nfs
  rw,bg 0 0

18
Homework

• Read chapters 11 and 19 and in Linux
  Administration A Beginners Guide.