Host Management

1
Host Management
2
The Big Picture

• Think of the Total Network Solution
• Think of ways to make management easier
• Go with the Vendor standard install?
• Or Customise to suit our situation?
• Make all machines the same?
• Make all machines unique?

3
The Server Room

• Critical hardware needs protection including
• Power filter and UPS
• Air-conditioner, heater and fireproofing
• Secure access eg locked door, CCTV monitor
• Anti-static fittings eg rack mount, carpet
• Secure cable conduits and patch panels

4
Start up and Shutdown

• Know how to turn something off. Before you turn
  it on!!
• Complex systems need safe shutdown sequence to
  avoid damage
• Quiescent state difficult to predict in
  multi-tasking systems

5
Shutdown

• Complete all operations in progress
• Prevent new operations from starting
• Close files
• Terminate processes and services
• Synchronise and Flush buffers/caches
• Dismount/park/eject disks
• Power off !

6
Shutdown Unix

• Only performed by superuser
• halt stops quickly and without waiting
• reboot same as halt, restarts afterward
• shutdown warns user first
• init n where n is a run level numberBeware.
  Run Level numbers are not all the same on
  different systems!!Eg. init5 is MultiUser mode
  in Redhat and PowerOff in SvR4/Solaris

7
PC Bootstrap SequenceAn Avalanche boot

• BIOS IPL loads MBR boot
• MBR selects active partitionloads partition boot
• Partition boot can access filesloads OS loader
• OS loader loads kernel
• Kernel initialisation loads init process

8
Booting Unix

• Machine and OS dependent
• Usually boots automatically
• Some machine start in ROM monitor and require a
  monitor command like b or boot
• init
• run levels allow several alternate configs
• Runs different scripts in /etc/rc.local

9
Booting Windows NT/2000/XP

• BIOS MBR gt PartitionBoot gt C\ntldr gt
  C\ntdetect gt multiuser
• C\boot.ini allows multi-partition boot
• Any user can shutdown entire system
• Services started according to registry
• No single-user or run-levels

10
Workstation Personalisation

• Personal workstations or NetStations?
• Some local storage essential
• Operating system
• Swap or Pagefile
• Local working temporary files
• Local system and user configuration
• Some central shared storage needed

11
Disk Space Used for

• Operating system software and Data
• Application software and Data
• Shares visible to others on the Net
• Local space for temporary use
• Cache, print spool, transitory downloads
• Backup copies

12
Disk partitioning

• A convenient way to subdivide disk space
• Reserve space for a particular functioneg swap
  space, user directories, software
• Disjoint storage - protection of data
• Each partition given logical device nameeg C,
  /dev/hda1, /dev/dsk/c0t0d0s0
• Meta-devices and logical volumes seamlessly span
  multiple partitions

13
FormattingBuilding File Systems

• like painting car spaces in a carpark
• Structures disk area for addressable access
• Unique to OS usually incompatible!eg UFS not
  visible to Windows, NTFS not visible to Unix
• Sectors often grouped into Allocation
  unitscalled blocks in Unix and clusters in
  windows
• Building File System - mkfs or format
• Labels, Directories, Free list, Data area

14
Unix File System

• UFS disc format
• iNode
• Disc space allocation for each file
• A Directory implementation
• Access permission implementation

15
DOS File Allocation Table

• Disc format
• FAT disk space management

16
Swap Space

• Swapping frees RAM used by an idle process by
  storing image on disc
• Paging virtual memory stored on disc
• Few modern OSs actually do swapping
• The swap file is now used for paging
• In Unix the swapfile is usually a partition
• SwapFileSize 2.5 RAMsize
• Any more will probably never be used!

17
File SystemA working system has

• Operating system files (as distributed)
• Other application software (packages)
• User files
• User Application data
• Temporary working space

18
File SystemLogically separate because

• They have different functions
• They are owned/maintained differently
• They change at different rates
• Backup policy is different for each

19
File SystemA Typical Unix Layout

• Operating System
• /boot or /kernel boot image files
• /bin or /sbin general or system executable
  files
• /dev device files
• /lib system development library files
• /etc configs, params, scripts, etc
• /share common read-only files
• /var non-transient workspace, logfiles
• /tmp or /spool transient work and temporary
  files

20
File SystemA Typical Unix Layout

• Application Software
• /usr
• /usr/local/bin
• /usr/local/lib
• /usr/local/include
• /usr/local/etc
• /usr/local/share

21
Unix Disk Device Names

• Devices usually appear as files in /dev
• Disks have names for each partition
• Partitions may overlap
• BSD and SysV use different names
• sd0a,sd0b,sd0c
• dsk/c0t1d0s0
• Contoller Target(disk) Device Segment(partition)T
  arget or Device may be missing

22
System InstallationInstaller must specify

• Name, IP, subnet mask, domain, DNS IP
• Disc partition layout and format
• Swap space
• Timezone
• Directory Service eg NIS, Windows PDC
• Drivers for unrecognised devices eg Video, NIC,
  sound

23
Installing

• Solaris, Linux, Windows
• Workstation, Developer and Server versions
• All have easy installation programs
• Jumpstart, Kickstart, Setup
• Modern version auto-sense device (PnP) and
  network configuration (DHCP)
• Installation may require license details

24
Configuring for use of Network Services

• Host installation readies the machine for
  connection to the Net
• Also need to have information about services
  provided by the Net, including
• DNS
• NFS
• Authentication (NIS, Kerberos, LDAP)

25
DNS configuration

• Can be provided automatically by DHCP
• Complex setup needs more detail stored in local
  files
• /etc/resolv.conf
• /etc/nsswitch.conf
• Usual sequence of name search is
• hosts, bind, NIS

26
NFS configuration

• Usually requires editing of /etc/fstab
• And starting of automounter service

27
Multiple InstallationsBoot Managers

• With multi-use machines and big disks it is
  possible to have several different OSs
• Each OS has its own boot manager
• Some are generalised, some not
• Eg Windows relies on files accessed from C so
  install Windows first, then install Linux
• Unix loaders LILO, GRUB

28
Re-Installation,Multiple Installation

• OS installation programs make it easy to install
  on a single system, but what about repeat
  installations or installing to large numbers of
  machines eg in a department of a company?
• Here we need an automated process that can be
  given a configuration file and left to install
  in unattended mode

29
Multiple InstallationsImage vs Package vs Share

• Image mode writing a prepared partition image to
  the hard disk eg using Ghost
• Only possible for identical systems
• Difficult to change must recreate entire image
• Package a set of dependent moduleseg compiler
  libraries templates
• Package mode installing a sequence of packages
  in several passes over the partition
• dpkg, rpm, Windows MSI, Wise, etc
• Share mode where software is shared from server

30
Software Installation

• Usually installed as packages
• May be distributed in limited source form and
  require compilation
• Often installed by running a script command
• configmake install
• Beware of mixing versions!

31
Directory structure

• All reliable systems separate system and
  application software
• May also separate data from procedure
• Use a directory structure to achieve this

32
Shared Libraries (.so)Dynamic Link Libraries
(.dll)

• Often managed as overlays and loaded into RAM
  on demand
• Managed by some kernel routines which use an
  index to locate a required module
• When new versions are installed, the index must
  be updated (and any obsolete versions purged from
  RAM)
• Special commands used to do this eg ldconfig