Host Management Burgess, Ch.4

www.infotech.monash.edu

Host Management

Burgess, Ch.4


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• 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?

The Big Picture


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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

The Server Room


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Startup 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


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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 !


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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 number

– Note: Run Level numbers are not equivalent for different systems!! For example, run level 5 is MultiUser mode in Redhat and PowerOff in SvR4/Solaris.


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PC Bootstrap Sequence -- An Avalanche boot

• BIOS IPL loads MBR boot• MBR selects active partition

loads partition boot• Partition boot can access files

loads OS loader• OS loader loads kernel• Kernel initialisation loads init process


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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


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Booting Windows NT/2000/XP

• BIOS MBR > PartitionBoot > C:\ntldr > C:\ntdetect > 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


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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


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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


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Disk partitioning

• A convenient way to subdivide disk space• Reserve space for a particular function

eg swap space, user directories, software• Disjoint storage - protection of data• Each partition given logical device name

eg C:, /dev/hda1, /dev/dsk/c0t0d0s0• Meta-devices and logical volumes seamlessly span

multiple partitions


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Formatting -- Building 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


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Unix File System

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


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• Disc format• FAT disk space management

DOS File Allocation Table


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• 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!

Swap Space


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File System -- A working system has:

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


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File System -- Logically separate because:

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


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File System -- A 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


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File System -- A Typical Unix Layout

• Application Software– /usr

– /usr/local/bin

– /usr/local/lib

– /usr/local/include

– /usr/local/etc

– /usr/local/share


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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)Target or Device may be missing


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System Installation• 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

System Installation


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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


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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)


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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 ishosts, bind, NIS


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NFS configuration

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

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Multiple Installations -- Boot 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

– For example, Windows relies on files accessed from drive C:– so install Windows first, then install Linux

• Unix loaders: LILO (LInux LOader), GRUB (GRand Unified Bootloader)


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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


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• Image mode: writing a prepared partition image to the hard disk, e.g., 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

Multiple Installations – Image, Package or Share


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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!


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Directory structure

• All reliable systems separate system and application software

• May also separate data from procedure• Use a directory structure to achieve this


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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


Host Management

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Documents

Host Management Burgess, Ch.4