User:Rpeters

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Contents

Bootloaders

Elilo

Only for computers having EFI firmware

Fairly simple and reliable

  • but requires a running Linux to generate its config file, in advance

GRUB Legacy (aka 0.97 )

A simple, reliable bootloader, although being phased out and no longer maintained. Use situations:

  • have only Linux on /ext(n) partitions and (maybe) Windows

GRUB (aka GRUB 2 )

"on-the-fly" Mode

GRUB 2 relies on a pre-defined config file /boot/grub(2)/grub.cfg. If this is not located, for any reason, GRUB 2 may boot to a grub> prompt. To boot from here use the following commands:

grub> set root='hd0,gpt10' grub> linux /boot/vmlinuz root=/dev/sda10 grub> initrd /boot/initrd grub> boot

notes

  • drive numbers start from 0
  • must specify whether partitioned mbr or gpt
  • partition refers to location of /boot for the operating system to be booted
    • or merely the system partition for Win
    • partition numbers start from 1 (unlike in GRUB legacy)
  • this procedure is easiest if kernel & initrd have easily remembered names
    • either soft-link generic names or
    • press TAB to see possible names
  • ctrl-x or F10 may be pressed in lieu the "boot" command

The above procedure may be modified to cater for the situation where the menu is presented but the desired OS is not included or fails to boot. Press Esc to get to command line, then proceed as above.

Menu mode

Wheras GRUB legacy uses similar syntax in command and menu mode, GRUB 2 uses somewhat different syntax in the two modes. See GRUB 2 downloadable manual or use "info grub2" to obtain details.

Rescue mode

An ISO image can be prepared, that is tailored to the OS on a specific computer. See above documentation for details on preparation of this image. It can be tested by "dd" to a USB memory device.

ReFind

Only for computers having EFI firmware

  • a CD can be downloaded, to test, if uncertain of firmware


Syslinux

A proven bootloader, that continues being developed and maintained. Main limitations:

  • can't directly boot programs on other than its own partition, resulting in the need for work-arounds:
    • either chain load all but one OS or
    • put the boot code for each OS in a different sub-directory on the syslinux partition

DOS USB

For General Users

Purpose

The main requirement for a USB memory device that boots to DOS operating system arises when a BIOS/Firmware update of a computer is required.

It is advisable to use a new, or little used memory device, because any error in reading the BIOS/Firmware code during the actual update is likely to result in an unusable computer. USB "thumb" drives could be used. SD cards, which can be removed and stored in a secure place, might be more applicable.

Procedure

HP provide two techniques for producing DOS USB sticks. Both place utility software on a Windows computer, in order to generate the bootable stick - see "Getting Technical" below, if Windows is not available.

Instructions are provided on the HP support site for installing these utilities to Windows and creating bootable USB stick(s)

  • HP's generic utility HPUSBFW is not self contained but is more flexible.
    • it produces a mimimal DOS bootable USB stick containing only nnnDOS.SYS & COMMAND.COM
    • the user can then add relevant firmware and flashing utility
    • although it has an option for formatting to FAT 32 only FAT actually works
    • requires one of HP's "Softpacs" (firmware updates) for one of their recent commercial notebooks, from which to obtain the Windows utility program, plus
    • also requires FreeDOS (which can be downloaded at no cost in the form of fd11src.iso from http://www.freedos.org/download/)
  • those wanting to upgrade the firmware in a HP computer might find the second tool more suitable. HP provide some of their firmware updates as Windows dotEXE files, which:
    • install a utility program to Windows and then have facility called ROMPAQ for creating a bootable DOS on a USB device of not greater than 2 GB (FAT 16)
    • automatically adds the firmware and flashing utility to the USB stick
    • the naming convention for these files is SPnnnnn.exe

Note that in order to use the former, generic technique, general users would need to burn the above ISO image to CD. Those not familiar with ISO images should read http://www.pcug.org.au/info/index.php/Using_dotISO_Files

The step of burning the ISO image can be avoided - see "Getting Technical" below

Getting Techhnical

The techniques above contain the Windows version of Syslinux in the Windows software package and install the former as a bootloader on the USB device. The Syslinux bootloader can also be added to a USB memory device via Linux. Generic instructions are at the following site, from which (superceded versions of) the code are also available

http://goebelmeier.de/bootstick/

The following would need to be downloaded to obtain up-to-date software:

http://www.freedos.org/download/fd11src.iso

https://www.kernel.org/pub/linux/utils/boot/syslinux/6.xx/

Syslinux will already be installed on many Linux systems. However, Ubuntu and openSUSE might produce a USB stick that invokes graphics at boot time and it is undesirable to have superfluous code on a device that will be used for firmware upgrades.

FreeDOS supports FAT 32 and consequently the above procedure should also work on FAT 32 formatted sticks of > 2 GB capacity.

--Rpeters 09:05, 7 October 2013 (EST) --

CUPS

Overview

CUPS is a newer printing sub-system, that has inbuilt support for network printing. Its use can enable printing over a LAN to be achieved relatively simply, often requiring:

  • no additional installation of software or "drivers"
  • only simple configuration changes

One feature of CUPS which can frequently be useful is its ability to print to a network/shared printer when the computer from which the print job is created has no relevant printer drivers installed. Three examples:

  • a laptop/netbook/tablet computer being used away from its home location
  • an OS for which a suitable printer driver can't be obtained eg Android
  • a computer where the administrator password (which may be required to install drivers) is unknown.

CUPS is now the default print sub-system in most Operating Systems - Android, ChromeOS, MacOS, Linux and BSD.

Consequently, it is widely deployed on many devices, such as Smartphones, Tablets, Media Centres & Macintoshes, as well as emerging "pocket computers" and might/could be on other Net/Notebooks, Laptops amd Desktop computers.

Limitations with Windows OS

Windows network printing is much less flexible than CUPS

  • requires a printer driver on any computer from which a print job is prepare whereas
  • CUPS requires only that a driver be accessible on the network (typically from a server or other computer)
 and i would be of limited value bealthough work-arounds are available, these are the province of intermediate/advanced users and probably only worth pursuing in the following mid/long term scenarios:
  • routine printing from a Windows version for which a particular printer "driver" is not available
  • minimising maintenance of a mixed OS LAN

An overview of the techniques that are feasible for Windows and guides to implmenting those is available from:

http://en.opensuse.org/SDB:Printing_from_Windows_to_Linux

A lower tech solution for small LAN, having Windows as well as other OS, is long "USB" cables

  • the limit of length to 5 metres for USB cables can be overcome by using a pair of USB-Ethernet/RJ45 converters, which enable a USB printer to be accessed from up to 100 metres over Cat 5 cabling.
    • sets of these converters are available from specialisist computer hardware suppliers
    • might variously be described as "printer extenders" "USB extenders" etc
  • although this is not network printing, it can suffice.

Windows 7

This section requires input from an experienced Windows 7 user

  • CUPS, per se, is not apparently available
    • the underlying protocol IPP is available, (but not necessarily installled) for editions other than "Starter"
    • it prints via the Internet, which may not meet a user's security requirements

Windows XP

  • requires 3rd party software, which wont be installed by default
  • installing CUPS on Windows XP is complicated
  • when installed, it can work only with Postscript capable printers (this excludes most ink-jets and many low cost laser printers)
    • this limitation may also apply to Windows 7

Mac OS

Apple's implementation of CUPS includes some proprietary extensions. That is unlikely to effect Mac to Mac printing but may introduce limitations in printing between Mac OS and other Unix like OS.

Situation

This guide assumes that CUPS is installed and generally functioning on both computers. The screen shots are from CUPS version 1.4.x/1.5.x. Versions 1.3.x provide the functionality required but have different menus.

Prerequisites

Definitions

  • "client computer" means the computer/device from which the print job will be generated
  • it must have CUPS client installed, which is the default condition for Max OSX and Linux
  • it need not have any printer drivers installed
    • indeed, it is less confusing if it does not
  • "server computer" means the computer controlling the printer. It can be:
  • for network printers, which are connected directly to a network, any computer on the network, having the relevant CUPS print drivers installed
    • network may be wired, WiFi or bluetooth
    • it is perfectly acceptable to configure several computers to use a particular network printer
  • for USB/parallel attached printers, the computer to which the printer is attached
    • it must have CUPS server installed, which is the default condition for Max OSX and Linux
    • the relevant printer must appear in its "Printers" list, and be working
    • the computet must be posered on, to enable printing, although logon won't usually be required .

CUPS Versioning Issues

Devices sold by Apple Inc can deploy proprietary extensions to CUPS. Consequently, some features may not work as expected, if the print job is sent to a printer that is controlled by another version of CUPS

As a general rule, the print server should have a version not earlier than the client Version 1.5 of CUPS is likely to produce a print job as a PDF file, whereas version 1.3 & 1.4 servers accept only PostScript files

  • check in the Home tab of CUPS for version number

Cups printers listing.png


Configuration

CUPS is configured via a web browser. Its URL on the local computer is:

http://localhost:631

Windows might not implement the short-cut "localhost". If not, then substitute the real IP address of the PC. Execute "IPCONFIG" from a Windows command line to find this address.

From the server computer, in the CUPS "administration" tab, ensure that "Share printers connected to this system" is checked:


Cups admin home.png


then click "Change Settings" button to save any changes, if necessary

Then click on the "Manage Printers" button in the same tab, select the relevant printer and pull down the "Administration" menu

  1. select "modify printer" then click the "continue" button to proceed to its second screen


Cups printer network.png


Cups printer configuration2.png


  1. ensure that "share this printer" is checked
  2. it will be helpful to make the "Location" the name of the computer controlling this printer
  3. click "continue" until the process completes

From the client computer, in the CUPS "administration" tab, ensure that "Show printers shared by other systems" is checked


Cups admin home.png


then click "Change Settings" button to save any changes, if necessary

Quicktest

Both computers must be connecting to the local LAN via wired or wireless interface. A quick test is to start a web browser and check that the Internet is accessible. Provided that network access is working:

  1. Start a text editor (kate, leafpad etc)
    • if the application is already running then it may need to be shutdown and restarted to recognize newly available printers
  2. Open a new document and type a few words
  3. From the file menu, select "Print"
  4. Select the relevant printer from the drop-down dialog
    • which should list all shared printers on the LAN
  5. click on the properties/settings button
  6. ensure that the key settings are suitable eg A4 paper size, portrait orientation
  7. click OK/print

Preliminary Troubleshooting

1. No printers listed in the print dialog

This problem frequently is the result of a firewall running on one or both computers. Network printing can work only if either:

  • firewalls on each computer allow port 631 through or
  • Ethernet zones are set as "trusted/internal" in the firewalls on each computer

Only printers powered up will appear in the list

  • confirm that the relevant printer is powered on
  • if it is attached to another PC via parallel or USB cable then that PC must also be powered on
    • (it is not necessary to log in to the sharing PC)

2. Print Job accepted but no output on Printer

This can be a result of many possible causes. Some simple checks:

  1. is CUPS known to be installed and working on the computer from which the text was created ?.
  2. Can it print to some printer at its home base ?
  3. does a similar print job created on the server computer give output on the printer ?

3. Print Job rejected by Server

  • possible permissions issue - check that:
    • printer is set as "share this printer" on the server
      • follow "modify this printer" dialog
  • possibly incompatible CUPS verions
    • as a general rule, the print server should have a version not earlier than the client
    • version 1.5 clients produce jobs as PDF files, that are likely to be rejected by 1.3/1.4 servers, which expect PostScript files
    • preferably upgrade the complete CUPS system on the server to version 1.5
      • a new version of the driver for each printer is required at the server end, to support PDF print jobs
      • if a binary driver, from the manufacturer, was previously used, check whether a driver is now included in CUPS or, failing that, whether an updated driver can be obtained from the manufacturer
    • following the upgrade, follow the "modify this printer" dialog for each printer and select the most recent PPD file.

If all else fails, then the CUPS Administration page has a button "View Error Log". Text towards the end of that file may give some clues.

---[[-Rpeters 18:02, 18 August 2012 (EST)]] --

Distributions 64-bit or 32-bit

For General Users

64-bit Linux is generally recommended for computers that support it - see below for simple tests

  • it has been in general use for over a decade and is now quite mature
  • it supports an overwhelming majority of hardware
  • usually includes the NX feature, that is likely to provide additional protection against malware

Note that Linux Distributions may variously refer to 64-bit Linux as "x86_64" or "AMD64". The two are equivalent and the latter works on computers that are trade-marked "Intel Inside" as well as AMD-based computers.

Test for CPU Model

64-bit CPU

A simple and reliable way to check whether a CPU supports 64-bit code is to boot a 64-bit distribution

  • Parted Magic is a suitable distribution for this purpose, because a 64-bit only ISO is available and it is only ~ 200 MB.
  • alternatively, any 64-bit Distribution media could be used, if already to hand.
  • a 64-bit kernel will quickly present an error message along the lines of "unsupported CPU/architecture" if a 64-bit capable CPU is not detected

32-bit CPU

If the above test indicates that 64-bit Linux is not supported then most 32-bit Linux should be suitable.

  • the latter might variously be labelled "x86", "i586", "i686" or frequently no differentiator at all

Exceptions where a Distribution is unsuitable include:

  • a small minority are compiled for CPU later than "i686" (Pentium II or equivalent)
    • these would begin to boot on earlier CPU, but quickly halt and display and error message
    • beginners are faced with using a different Distribution (or obtaining a later computer)
  • some Distributions are collated for specific hardware platforms eg eeePC netbooks
    • these are likely to work incompletely on Desktops as well as other laptops
    • the purpose of the Distribution would be clearly identified by the provider

Getting Technical

NX Option

NX (non-execute) is a security feature. A common technique used by malware is to hide code in data-only areas of memory. NX makes that technique ineffective by preventing any such code from running. Consequently it is desirable to utilise NX, where available.

Advantages of 64-bit distributions include

  • NX features are provided in hardware, thereby supported and usually included in the kernel
  • 64-bit CPU include many additional instructions which can improve performance somewhat
  • 64-bit CPU and most applicable mainboards support >> 4 GB RAM
    • 8 (or more) GB of RAM is now affordable
    • 2 or 3 RAM modules improve performance if populating dual or triple-channel mainboards and the "sweet-spot" pricing would result in 8 or 12 GB RAM
  • 64-bit Linux code is mature and fairly complete
    • core hardware drivers for peripherals tend to be manufacturer-agnostic and provided with 64-bit kernels - eg for printers, scanners, usb-storage
    • manufacturer-specific code for peripherals tends to be provided via programs rather than "drivers" and 32-bit variants can be used where 64-bit are not available

PAE Kernels

Many kernel options must be included at compile time ie those cannot be loaded later "on-demand". Included in this category are:

  • NX feature
  • PAE option for 32-bit CPU, via which NX is implemented on such CPU
  • CPU instruction set - typically identified via CPU model eg Pentium, Pentium III etc

In general, it is desirable to use a PAE kernel, with 32-bit CPU, simply to obtain the NX feature. Such kernels occupy approximately 200 MB and might not be included on installation media. Typical mechanisms for obtaining them include:

  • if the option is provided via the installation routine and a broad-band Internet connection is accessible eg via Router
  • as a post-installation update either from DVD media or via direct download from the Internet

== Distributions 64-bit or 32-bit Advantages of 64-bit distributions include

  • NX features are included in hardware and thereby supported
  • 64-bit CPU and most mainboards support >> 4 GB RAM
    • 8 (or more) GB of RAM is now affordable
    • 2 or 3 RAM modules are preferable if populating dual or triple channel mainboards and the "sweet-spot" pricing would result in 8 or 13 GB RAM
  • 64-bit Linux code is mature and fairly complete
  • core hardware drivers tend to be manufacturer-agnostic and provided with 64-bit kernels - eg printers, scanners, usb-storage
    • manufacturer-specific code for peripherals tends to be programs rather than "drivers" and 32-bit can be used where 64-bit are not available
 ==

Work in Progress

eWaste

Device Issue Task/Test Result Reserved Sitrep Action Volunteer
qty 5 AOpen midATX chassis (from circa 2000 Train PC) 1.erase HDD - - - any
1.erase HDD no change - unresolved -
qty 2 short ATX chassis (from previous gen Gateway) no change - unresolved
r style="color:#ee3900;" - -
- unresolved -
style="color:green;"y - -
r - -

Equipment Issues

- || #005900 - || || - || - || - || ||
Device Issue Task/Test Result Reserved Sitrep Action Volunteer
Huawei 16 port Gb switch (main office) reposition away from Helper's desk longer, 10 m Cat 5e required - - - requisitioned Rod
- - - unresolved
- runs normally - - -
- - - - -
Additional Member Use PC (main office) redeployed Old Train 01 "freezing" - - - hardware testing required- required Rod
- - - unresolved
- runs normally - - -
- - - - -
Additional Member Use PC (main office) redeployed Old Train 05 unreliable boot from SATA HDD - - - hardware testing required- required Rod
- - - unresolved
- runs normally - - -
- - - - -
Train 01 - - - - unresolved
- - - unresolved
- runs normally - - -
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Old Train 11 powers up for only
a few seconds
1 power supply tester OK only intermittently - unresolved Rod
2 alternate power supply fails to start - unresolved - Rod
3 revert to original power supply runs normally - intermittent & unreliable set asside as spares Rod
- - - - -
Old Train 13 persistent, annoying,
random video flicker
1 set CMOS to "failsafe defaults" no change - unresolved - Rod
2.flash upgrade BIOS to F6 level no change - unresolved - Rod
3 run memtest one faulty cell at 991 MB in one only of 6 passes - unresolved - Rod
1 set CMOS to "failsafe defaults" no change - unresolved -
- - - - -

Table

Equipment Issues
Device Problem Tests Results Prognosis
Old Train 11 power supply tester erratic Rod
align="bottom" style="color:#e76700;"|
Shopping List
Bread & Butter Pie Buns Danish Croissant
"Old Train 11
  • power supply tester

OK only intermittently

set asside as spares style="border-style: solid; border-width: 1px";Rod

Templates

this is it -Rpeters13:25, 24 August 2012 (EST) --

def
definition list
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definition list

AF Drives

For General Users

Overview

Advanced Format (AF) Hard Disk Drives are used in many pre-built computers and USB drives from about 2011 onwards.. By way of explanation

  • AF drives have 4 kB hard sectors in lieu of
  • the traditional 512 B sectors

Advantages

  • much faster (less disk overhead)
  • more space efficient (larger disk capacity from same hardware)
  • overcomes immutable capacity limit of ~2.19 TeraByte for conventional drives

Disadvantages

  • Windows 32 bit systems cannot boot from AF drives
    • requires driver from HDD manufacturer, to use as data only internal drives

No action is required by the typical purchaser, because the manufacturer will have taken care of the special formatting required with AF drives. Getting Technical below, provides guidelines for those needing to:

  • repartition drives
  • install new, "bare" drives

Getting Technical

Advanced Format Drives

New HDD from about 2011 onwards are likely to be Advance Formatted

  • usually pre-formatted
  • likely to be stated on drive or packaging
  • essential for drives over 2.1 TeraByte capacity
  • has been used on new drives as small as 250GB

Avoid reformatting drives to MBR

  • performance loss of up to 40% if reformatted MBR
  • requires special procedure - see "Strictly for Geeks" below

. A new type of partition table called Globally Unique Identifier(GUID) Partition Table (GPT) is required to optimise the performance of AF disks. The partition table previously in common use has no univerwsally agreed name but is given the nomenclature Master Boot Record (MBR), because that was a unique feature of it.

Legacy partitioning tools do not handle GPT. A suitable tool for intermediate users is "parted" or its GUI front-end "gparted". The simplest way to use these is from a bootable utility CD

http://www.sysresccd.org/Download http://partedmagic.com/doku.php?id=downloads

Altering Partitions

It is not advisable to delete or alter patitions of type ef01 or ef02, because these have a special purpose in GPT. Other partitions may be re-sized or added, as required. Note that:

  • all partitons in GPT are Primary
  • up to 128 primaries are permitted
  • GPT has no concept of "Extended" or "Logical" partitions.
  • partition type numbers sometimes differ from those used with MBR partition tables

A compleat description of GPT is available at:

http://www.rodsbooks.com/gdisk

New Drives

The full capacity of Drives over 2.1 TB can be utilised only via recent mainboards or add-on SATA controllers

  • support for SATA 3 (aka 6 Gb/sec) is required

The boot flag in GPT does *not* make a disk bootable from a BIOS mainboard. See the procedures at:

http://www.sysresccd.org/Sysresccd-Partitioning-EN-The-new-GPT-disk-layout



Strictly for Geeks

Capacity

The international standard for data capacity uses multipliers of 2 ^ 10 in lieu of SI decimal multipliers of 10 ^ 3 eg

  • kiB = 1024 Bytes
  • kB = 1000 Bytes

through

  • TiB = 2.198 TB

Why does this matter ?

  1. drives have always had sectors that are multiples of kiB
    • 0.5 kiB for conventional HDD
    • 2 kiB for CD & some Magneto Optics
    • 4 kiB for AF drives
    • 32 kiB for DVD
  2. advanced formatting tools allocate partitions in MiB, GiB, TiB increments
    • partition sizes will be reported larger by older OS
    • formatted capacity of a drive will be somewhat less than manufacturer's nameplate rating, which is usually in decimal
  3. advanced formatting tools might align partitions on MiB boundaries
    • helps optimise performance

Tools

A more capable partitioning tool is required to set up the advanced features of GPT. The partitioning tool gdisk is downloadable from http://www.rodsbooks.com/gdisk/download.html

Partition Conversion

MBR drives can be converted to GPT partition table, without erasing data, subject to some limitations and risks

  • essential to backup data & system files
  • use the "r" menu option in gdisk, followed by "g"
  • some partition numbers might be changed

Advanced Patitioning Layouts

  • non-sequential partition numbering
  • spaces between partitions
  • partition alignment on 1 MiB boundaries


Re-formatting

Drives up to 2.1 TB,manufactured during the transitional period, logically divide each 4kB sector into eight 512 B sectors

  • permits partitioning using legacy programs
  • deprecated because doing so can decrease performance up to 40%
    • essential for boot drives in Windows 32 bit systems

AF drives that are re-formatted to MBR might behave unreliably unless expert options in gdisk are used

  • see "z" menu option

File Migration

The simplest approach is to install additional HDD before any systems are installed or data created. If that is not feasible then any existing files/folders at the intended mount point need to be migrated

  1. ensure that the files to be migrated are firstly backed up to independent media
  2. as user root mount the new partition to a temporary point, typically /mnt/
  3. cd to the mount point that will later be used permantly for the new partition
  4. use the "cp -ax" command to copy all files from within the folder of the mount point to ./mnt
    • do not use use file managers for this purpose, because those may set incorrect timestamps, permisisons etc for files
  5. unount from the temporary point
  6. set the permanent mount point (and change permissions, if necessary) as in sections "User Storage" or "System Storage" below
  7. the above procedure duplicates existing files. To remove the originals:
    • temporarily unmount the new partition
    • delete all files in the folder of the permanent mount point
    • remount the new partition to its permanent mount point


Firewalls

Packet-Filtering v Router

a perenniel question is whether it is preferable to run a packet-filtering style firewall on each workstation/laptop/pocket-PC or to use a single "hardware" router to protect the whole LAN

Packet-Filtering v Router

Advantages

  • no additional hardware, cost, wattage
  • zero acreage

Disadvantages

  • generally less "hardened"
    • many more background prolcesses need to be running to support user apps

Linux

Most Linux include a packet-filtering style firewall

  • usually activated, by default
    • but check
  • efficacy likely to be similar
    • based on iptables
    • may also include ip6tables and ebtables
  • administrative interface specific to distribution
    • "Guarddog" in KDE provides consistent interface

Mac OSX

citation needed

Windows

citation needed

Gateway/Router

  • generally regarded as "abandon-ware" by manufacturers - typically
    • updates are not announced
    • only a few updates provided
    • for about three years only

Firewalls

Virtually no commercial router is capable of handling all four common types of Internet connection:

  • Broadband via Cable or NBN
    • technically HFC, FTTN, FTTH/P (NBN)
    • TransACT's "cable"/Phase 1/VDSL(n)/NBN is in this category
  • Broadband via ADSL
    • also called "ULL" by some suppliers
  • Broadband via USB modem (2G/3G/4G)
  • Dial-up via phone line

If an ISP offers a "router" for their service then it is probably of the applicable type. Otherwise a user would need to choose carefully from the following types of "routers"

ADSL Modem/Routers

  • always applicable to ADSL connections
  • some provide for alternate connection via USB modem as well
    • check features carefully some USB slots support only USB printer
  • few, if any, can be used with Cable/NBN
  • need to distinguish from ADSL modem (only) devices
    • were popular ~ 10 years ago
    • supported only one computer, in absence of additional router
  • WiFi LAN included in many models

Broadband Routers

  • might be described simply as "Router"
    • primarily for use with HFC, FTTN, NBN
  • many have USB port
    • need to check whether supports USB moblie broadband modem
    • might support only USB printer
  • technically could be used in conjunction with ADSL modem or ADSL modem/router
    • new, combined ADSL modem/router device generally a better solution
    • suitable choice only when ADSL device already owned in order to:
      • extend ADSL modem service to multiple computers
      • enhance security of older ADSL devices
  • WiFi LAN included in many models

Mobile Broadband Routers

  • usually physically small devices intended for moblie use with laptop/netbook/tablet
    • require mobile phone plan of some type
    • those having slot for SIM card should have inbuilt 2/3/4G wireless broadband modem
    • others require separate, plug-in USB wireless broadband modem
      • essential to check router manufacturer's web-site for compatible modem models
  • might not be a good choice for use only at fixed location (home/office)
  • almost invariably include WiFi LAN capabliity
  • may include "wired" LAN via Ethernet or USB connection
  • some powered by internal, rechargable battery
    • these models tend to have limited transmission range
    • usable only in medium/strong signal areas for moble phone reception
    • WiFi LAN may have limited range and/or ability to penetrate walls etc
  • need to stand vertically for best signal strength

USB Wireless Broadband Modem

  • not a router
  • requires one of the above separate routers, if routing required

Selection

A wide range of devices are commercially available in each of the above categories. Suggested guidelines:

  • an ISP is likely to be better able to provide techical support for a device they sell
  • if relying on friends/relatives/acquaintances for technical assistance then choose a model with which they are familiar
  • if also relying on the router as primary firewall for a LAN, compare firewalling features

Configuration

  • Routers are generally configured via a Web Browser
    • other, more technical routers are generally unsuited to home users
  • Reputable manufacturers have their User Guides available for download from their web-site
    • peruse manual prior to purchasing device
  • user interface via web browser varies widely
    • impractical to provide generic configuration guidelines
    • good quality manuals cover the physical connections and setup procedures well

Packet-Filtering v Router

a perenniel question is whether it is preferable to run a packet-filtering style firewall on each workstation/laptop/pocket-PC or to use a single "hardware" router to protect the whole LAN

Packet-Filtering

Advantages

  • no additional hardware, cost, wattage
  • zero acreage

Disadvantages

  • generally less "hardened"
    • many more background prolcesses need to be running to support user apps

Linux

Most Linux include a packet-filtering style firewall

  • usually activated, by default
    • but check
  • efficacy likely to be similar
    • based on iptables
    • may also include ip6tables and ebtables
  • administrative interface specific to distribution
    • "Guarddog" in KDE provides consistent interface

Packet-Filtering v Router

a perenniel question is whether it is preferable to run a packet-filtering style firewall on each workstation/laptop/pocket-PC or to use a single "hardware" router to protect the whole LAN

Packet-Filtering

Advantages

  • no additional hardware, cost, wattage
  • zero acreage

Disadvantages

  • generally less "hardened"
    • many more background prolcesses need to be running to support user apps

Linux

Most Linux include a packet-filtering style firewall

  • usually activated, by default
    • but check
  • efficacy likely to be similar
    • based on iptables
    • may also include ip6tables and ebtables
  • administrative interface specific to distribution
    • "Guarddog" in KDE provides consistent interface

Mac OSX

citation needed

Windows

citation needed

Gateway/Router

Although these are typically a separate hardware item they are not necessarily an additional hardware item, often being combined with an ethernet switch and/or DSL modem

Advantages

  • generally more "hardened"
    • by eliminating many background prolcesses that are not needed to support user apps
  • single point of installation, configuration and update


Disadvantages

  • possible additional hardware, cost, wattage
  • update support for commercial units is typically infrequent and limited-term

zero acreage

Linux

Most Linux include a packet-filtering style firewall

  • usually activated, by default

Gateway/Router

For General Users

The relative advantages of a separate gateway/router are discussed at

A packaged commercial uint is the most suitable option

  • ADSL modem/router for ADSL users
  • "broadband" roiuter for other connection types
    • as of 2012, a router for dial-up connections appears to be unavailable

Disadvantages

  • generally regarded as "abandon-ware" by manufacturers - typically
    • updates are not announced
    • only a few updates provided
    • for about three years only
  • firewalling functions eg SPI, often default to DISABLED
    • apparently to ensure that it "just works"
    • ensure that these functions are re-configured to ENABLED

Recommendations

A commerical uint that overcomes the above disadvantages at a price is the FritzBox

A much lower pirced unit is the DLink DIR-615

  • this is a broadband router only (no modem)

Getting Technical

DIY routers overcome the support limitations of commercial units, although until recently this has been at a cost of:

  • acreage
  • wattage
  • additional terminology

Most DIY units have been based on superceded PC. Additional hardware will be required:

  • modem (if not provided by ISP as modem or Set Top Box)
  • ethernet switch (unless only one computer will be accessing the Internet)
  • WiFi Access Point
    • if required
    • might be implemented as a PCI/PCIe WiFi card in the routing PC

Hardware

Minimum suggested specs are approximately

  • CPU - any X86 compatible of 333 Mhz or faster
    • ARM CPU may now be viable in lieu x86 compatible see "Strictly for Geeks" below
  • RAM - 256 MB
    • additional functions, particularly caching, require extra RAM
  • storage - 2 GB
    • effective caching requires several GB more disk space
  • network interfaces
    • PCI, PCIe or USB-Ethernet required
    • 10 Mb/s suffice - unless running ADSL 2 or faster link
    • NB - speed of other devices on the LAN is irrelevant, LAN performance depends on the ethernet switch deployed

Wattage for DIY has been somewhat higher than for commerical routers. A suitable objective, using 2010 or later componentry is 25 W. Lower wattage units are addressed under "Strictly for Geeks" below. CPU wattage is a poor indicator because other chips and peripherals consume somewhat more. Suggested basis for low wattage router:

  1. HP Proliant Microserver
  2. mainboards based on C50 CPU - which appears to have been used only in netbooks
  3. mainboards based on E350 CPU
  4. mainboards based on Atom CPU are something of an enigma
    • can be the lowest cost available but
    • wattage surprisingly high, because of associated chips
  5. mainboards based on VIA CPU
    • expensive unless s/hand
    • not particularly low wattage
  6. mainboards based on Pentium III CPU
    • reliability might be reduced because of age
    • zero cost & acceptable wattage

Software

Many Linux and BSD can be configured a gateway-router, but it is generally simpler and more watt efficient to use a specialised firewall/gateway distribution. Better known ones are listed in Linux_Distribution_Recommendations Although BSD based distributions such as Monowall are quite functional, their use would involve an additional learning curve for most people

Zoning

Software for DIY routers implements similar network zoning to that in commercial routers. An aspect that is different is the colour coding of zones:

  • RED for untrusted/unfiltered Internet
  • GREEN for most trusted, wired LAN connections
  • BLUE for less trusted WiFi connections
  • PURPLE for additional LAN zone
  • ORANGE for Demilitarized Zone, (DMZ)
    • not required by most home users
    • typically used for stand-alone servers, to which access from the Internet is permitted

Strictly for Geeks

DIY routers based on ARM CPU have become viable during 2012.

  1. have potential to match commerical routers in wattage and acreage
    • whilst maintaining advantage of frequent software updates
  2. require more careful matching of hardware and software
    • ARM compilations are not as "portable" as x86 compilations
      • advisable to select hardware having an ARM CPU series matching the compilation
  3. raspberry pi is best known hardware example - see Raspberry Pi
    • IPFire is the only well-known firewall/router that has reached released level for it
    • alternatively, raspbian could be adapted as a firewall/router for it


Rescue CD

For General Users

Boot Only Rescue CD

A computer which fails to start as far as the login screen (or "Safe Mode" in the case of Windows) might have a mal-configured bootloader. Such condition can result following routine software updates. The following CD can sometimes succeed in booting a system which is failing to start from hard disk drive. Success rate varies between the rescue CD, as described below. Some can deal with greater mal-configuration of the installed system(s) than others.

  • rEFInd
  • Supergrub 1.98
  • custom Grub rescue CD

All can boot most operating systems, including Linux, MacOSX and Windows

Try rEFInd for systems manufactured from early 2011 onwards. If it does not start on your computer then try Supergrub 1.98 One of the Grub rescue CD would be required for older computers

  1. a custom Grub rescue CD, as the name implies, must be custom built for a particular compter
    • as descrbied in Getting Technical, below
    • many users would require assistance to do so
  2. The other CD are downloadable, at no cost, as a dotISO file.
  3. Use the following procedure to burn that file to a bootable CD
  4. Then insert the CD in the faulty computer and reboot
  5. enter Setup, at the early stage of reboot and move CDROM above HDD in the boot order, if necessary
    • Setup is initiated by pressing Del key on most computers.
    • brand name computers tend to use the F2 key instead
  6. save changes and exit Setup
  7. after the CD boots menu items can be selected only via arrow keys - mouse does not work at this stage of boot
    • rEFInd or a custom Grub rescue CD should find all bootable operating systems
      • highlight the required one and press enter
    • Supergrub requires an additional step
      • select the first menu line and press Enter
      • it should then identify all bootable operating systems
      • highlight the required one and press enter

Systems that don't boot via the above procedures can often still be recovered, but it gets more technical. As described below. Some prior preparation can increase the success rate of rEFInd on newer computers

Getting Technical

UEFI Mainboards

Computers manufactured from 2011 onwards are likely to use UEFI firmware in lieu of BIOS firmware on the mainboard

  • identication of boot entities on these computers is generally more reliable than with BIOS
  • the "boot order" setting in UEFI firmware can include software entities such as boot managers/loaders as well as hardware entities such as HDD, CD/DVD, USB, SD devices
    • the Windows bootloader should already be included in the boot order by the system supplier, if the system includes Windows

Quick Fix

  1. download the latest release of rEFInd CD from
  2. burn this CD to optical media or as a bootable USB device
  3. boot this CD, which should produce a display of icons, one for each boot manager/loader
    • including an icon for the Windows loader (if Windows is on the system) and
    • icons for each Linux boot loader or bootable kernel image
  4. use arrow keys to highlight the required OS and press "Enter"
    • Windows should still be bootable and some Linux may also be, if only the first stage of the boot loader is misconfigured
  5. if no icons are displayed, or the system boots to (faulty) boot entities on the HDD, then the mainboard is not truely booting in UEFI mode
    • in this situation, follow the procedures for BIOS mainboards under later heading

Create Bootable Entities

In order for this rescue mechanism to work Linux must

  • have been installed to a boot disk :
    • partitioned using GPT partition table and
    • having an ESP partition (type ef00) formatted FAT 32 (ideally as partition 1)
  • be using a kernel that has the "EFI stub-loader" compiled in
    • mainstream kernels from 3.3 onwards typically do
  1. as user "root" use "cp -a" to copy the current "vmlinuz-n.n.n" and matching "initrd-n.n.n" to the root directory of the ESP partition
    • the files must be copied because FAT 32 does not support Linux style linking
  2. rename the "vmlinuz" to have a dotefi extension
    • FAT 32 is not, strictly speaking, case sensitive
    • the "initrd" file retains any existing extension
      • or no extension, as the case may be
    • many distro give and expect it to have a dotgz extension
  1. reboot the computer and enter mainboard setup mode
  2. the UEFI reference implementation includes facility for directly editing the boot order
    • if this option is available, amend boot order to include the kernel that was added to ESP root directory above
    • if this option is not available, then the rEFInd CD can be used for emergency boot, as in the following step
  3. the rEFInd CD should now be ablt to boot kernel images directly, including when the Linux bootloader is broken or mis-configured

BIOS Mainboards

Disk Order

Booting Linux from a separate HDD will be much more reliable if it is put on the first HDD that is identified by the BIOS

  • contrary to 20th century notions, Windows XP and later do not need to be on the first HDD, nor indeed on the first primary partition
  • many BIOS default IDE HDD ahead of SATA HDD in the boot order
    • interchanging HDD logically in the BIOS settings is likely to cause ongoing boot failures.
    • ie use either two IDE or two SATA HDD and not a mixture, if Windows is to be booted on one of the disks.

Quick Fix

  1. download the latest release of a utility/rescue CD, which do a good job of providing a generic boot CD eg:
      • Parted Magic
      • Systemrescue
  2. burn this CD to optical media or as a bootable USB device
  3. boot this CD and select an option to boot from local hard disk
    • precise menu path will vary between rescue CD
    • a menu of bootable OS should be displayed
      • including an icon for the Windows loader (if Windows is on the system) and
      • including each installed Linux, notwithstanding that the boot loader on HDD might be "broken"
  4. use arrow keys to highlight the require OS and press "Enter"
    • Windows should still be bootable and some Linux may also be, "matched pairs" of kernel and initrd can be located
  5. if no bootable options are found then mainboard or HDD hardware problems , or the system boots to (faulty) boot entities on the HDD, then the mainboard is not truely booting in UEFI mode

Grub Rescue CD

GRUB-legacy and GRUB2 have provisions for making bootable GRUB CD (actually ISO images, from which a CD may be burnt)

  • the command to create the ISO image is less much complicated in GRUB2

It is diffcult to create a generic boot CD because GRUB looks for particular hard disk drives, partition numbers, kernal images and initrd images that are specified in its configuration file

  • nevertheless, downloadable r
  • if a a custom rescue CD is required for a specific PC then using the /boot/grub2/grub.cfg file from the PC to be booted is a useful starting point
  1. read the outine of process that is provided by via the command "info grub"
    • the GRUB routine to be used is "mkrescue"
  2. create a folder to hold the contents of files to be used for the image
    • a subdirectory off /boot would keep all boot routines in a single area, although it requires root privilleges
    • $mkdir ISO
    • $mkdir -p ISO/boot/grub2
    • $cp -a /boot/grub2/* ISO/boot/grub2/
    • edit the file ISO/boot/grub2/grub.cfg to remove references to specific kernel versions
    • eg linux /vmlinuz-3.4.6-12 becomes /vmlinuz
    • /initrd-3.4.6-12 becomes /initrd
    • check that your distribution has created the logical links vmlinuz & initrd. If not, then create them manually to point to the current kernel & initrd
    • if this has to be done manually, then it will need to be repeated after each kernel update, to ensure that the rescue CD will continue to sucessfully boot from HDD
    • any menu items for Windows should work unchanged
    • grub2 has scope for much "eye candy"
      • which can usefully give the menu from the rescue CD a different appearance from that of the HDD boot
      • simplest change to implement is that of background colour
        • likely to require changes in grub.cfg as well as the themes script in sub-directory.ISO/boot/grub/<distro name>/themes.txt
  3. if a background.png is implemented then save a copy of the original an edit background colour in GIMP etc
  4. if there appears to be no background image, then background colour can be changed to a desired value, specified via either RGB or HTML colour values
    • save the modified file(S)
  5. from the parent directory of ISO, invoke the command to create the ISO image
    • $grub2-mkrescue -o grub.iso ISO
      • the prefix varies with distro
      • see distro specific notes below
  6. burn the ISO image to a CDRW or "DD" it to USB stick
    • a USB memory device will provide much faster iterative testing of the rescue "CD"
    • test and iteratively modify the ISO image
    • it can be difficult to differentiate between booting from HDD and CD, if the background colour change is not "taking"
      • one option is to add a dummy menu item to one boot method
  7. put the final, tested image on a CD or USB device.


Distribution specific notes

  1. openSUSE postfixes all grub 2 related material with "2"
      • default folder becomes /boot/grub2
      • commands become eg grub2-mkrescue
  2. openSUSE invokes the command "xorriso" to create the ISO image from a script or at CLI
      • this command is in package "libburnia-tools, which is not installed by default
  3. openSUSE has long had a bunch of perl scripts which take control of the bootloader configuration and which will quickly overwrite any changes made to /boot/grub/grub.cfg
      • any customisation is best confined to the rescue CD working directory .
  4. YMMV with other distributions

Projector

Overview

The projector in PCUG Training Room is set up for optimal use with the Trainer's PC, that is also provided.

Anyone planning to give a course or presentation using their own laptop computer is strongly advised to work through these guidelines well in advance and ensure that their laptop is working with external displays.

  • output to external display enabled
    • need to bring own Displayport-to-VGA-F or Displayport-to-HDMI-F adapter for high-end notebooks, including Macbooks
  • appropriate resolution
    • optimum for projector is any of 1280 x 800, 1280 x 768, 1024 x 768
    • higher resolutions give poor quality display on the projector
    • Windows XP or 7 require the same resolution on both laptop internal screen and projector
  • appropriate screen "layout"
    • most OS default to "Extend Display" (putting the second display (projector) to the right of main display)
    • appropriate for desktop situations with dual monitors to provide larger working display
    • not usually appropriate for presentations where the requirement is to "Clone/Duplicate" the same screen to two displays

Up to three settings might might neeed to be changed to have a notebook computer display output via its external video connector. The following description is, of necessity, generic because of variations between different hardware and operating systems. Refer to the User's Guide for the notebook, if necessary, for specific guidance regarding the following settings :

Manuals for many models may be downloaded from he following site

http://www.laptopmanual.net/

Procedures

Connect Video Cable

  1. contemporary Operating Systems dynamicallly configure video devices
  2. ensure that video cable between note/netbook and external display is connected before proceeding
    • HDMI cables are the simplest to connect and provide the best quality, if the computer has relevant output socket
      • if a DVI-HDMI adapter must be used then this must be connected with both devices powered OFF
    • older devices may be connected via VGA cable

Enable External Video Output in the BIOS

  1. power up or reboot the notebook and press the key/keystroke sequence required to enter Setup mode
    • known sequences for various devices:
      • Dell - press F2 at start-up
      • manyothers - press Del at start-up
  2. find any options for external video output.
    • not all notebooks have BIOS settings for this because many have the external video permanently enabled at hardware level
    • note also that this setting is usually not related to "docking station" on larger notebooks ie external video should work regardless of whether or not use of a docking station is enabled.
    • ensure that any option for external video is "enabled"
  3. Save, then exit Setup

Configure the Second Display/Monitor/Video card

  1. note that this is done at Operating System level
    • If more than one Operating System is installed then boot to the one which will be used with the external display.
  2. typically the second display is configured by invoking "Control Panel" and selecting the option "Display" The exact nomenclature is operating system dependent
    • if there is an on-screen button labelled "identify displays" or equivalent, then left-click on that
      • a "1" appearing on the inbuilt LCD display indicates that the external display will be the second display
      • proceed to configure the display other than the inbuilt LCD
  3. it is better to pick conservative settings if the notebook will be used at various locations with different external display devices
    • most notebooks, including those having wide-screen inbuilt LCD displays, can have the external display set for conventional 4:3 ratio and that will provide the most flexible arrangement.
      • resolution 1024 x 768
      • vertical refresh rate 60 Hz
    • the above settings are also safe for most LCD monitors. Higher settings might not work and might also damage the device.
  4. the main Training Room projector, for example, does handle widescreen modes. It works best with the following settings:
    • resolution 1280 x 800
    • vertical refresh rate 60 Hz
  5. there will probably be an option to setup "multiple monitors"
    • within this option select "clone" or equivalent in order to have the full screen sent to both displays
    • Windows will operate multiple displays at identical resolutions
    • other Operating System should adjust the image sent to the two displays automatically, to cater for differing aspect ratios and resolutions.
  6. Save the settings and exit Control Panel.

Use External Power Supply

  1. the external video display will add to the power drain of the notebook and may discharge the battery much more quickly. Plug in and power up the external power supply for the notebook, if available
    • if the external power supply is not available, then do not activate the external display, as per next step, for prolonged periods

Activate Output to External Display/Projector

  1. on most notebooks this is achieved by pressing a keystroke combination. Known combinations:
    • Dell combination is Fn simultaneously with F8
  2. although a notebook will accept this change at any time, whilst running, many OS require a subsequent re-boot, in order to recognise a second display
  3. each time the combination is pressed, the notebook switches to the next of the three options:
    • internal LCD only
    • external display only
    • internal LCD plus external display
  4. note that if the external display, in particular, is in "sleep" mode, then it may take 5 to 10 seconds to respond the the input signal. Therefore, wait at least 10 seconds between each press of the keystroke combination and check whether the external display responds.

Repeat Display Configuration for other Operating Systems

  1. Configure the Second Display/Monitor/Video card is the only setting which is Operating System dependent
    • that procedure may be repeated for other Operating Systems, if desired, after output to the external display has been successfully achieved with the first Operating System

Additional Issues with Training Room Projector

Some further notes regarding the projector in the Training Room.

  1. Video Cables
    • preferably use the HDMI cable that is now provided
      • Some modern notebooks have DVI connector only and Apple brand notebooks may have a different connector again. Users would need to bring their own adapter.
    • a VGA cable is also connected to the projector, for use with older computers
      • it may be necessary to by-pass the VGA splitter
  2. Remote
    • use the menu on the remote control of the projector to select which input (HDMI or VGA) is in use
      • this function is not automatic
  3. the projector has been known to mis-interpret apparently valid resolutions and either truncate the display or not display at all. If difficulty is experienced, then:
    • try connecting the notebook to a CRT display (which are generally more tolerant of resolutions) at the Centre and try to ascertain whether the notebook is actually putting signal to the external display connector.
    • if so, then revisit "Control Panel" and check that the settings for the second display are as above.
    • in some scenarios the only solution might be to work with the truncated display on the projector and rely on the notebook's LCD screen for the bottom few rows
      • with most Operating Systems the "task bar" can temporarily be repositioned at top of screen, to minimise inconvenience in this scenario

ISO Hybrids

Using/Creating ISOhybrid Files

This task is for intermediate/advanced users

Overview

Some dotISO files are now being provided as "ISOhybrids"

  • which have the main advantage of typically booting much faster from USB/SD devices
    • because most OS use conservative settings to boot USB/SD devices, in order to cope with older/buggy BIOS
  • boot speed is also highly dependent on the "Class" of SD media and (probably) unstated/indeterminate grade of USB "thumbdrive"

ISOhybrids may also be burnt to conventional CD/DVD/Bluray optical media, or written to USB/SD media, as in general/intermediate procedures above

  • hence the "hybrid" descriptor
  • but require the alternative procedure below to achieve faster performance from USB/SD devices

Hybridisation

  1. this procedure may be skipped, if the ISO is known to already be hybridised
  2. dotISO of unknown type may safely be converted to hybridISO via the program "isohybrid"
    • the conversion adds a few tens of kB, if the ISO is not already hybridised, which may push the ISO beyond the maximum capacity of optical media
      • alhough these ISOhybrids could still be written to USB/SD media, as in ntermediate procedures above.
    • it makes no perceptable difference if the ISO is already hybridised

Writing ISOhybrids

  1. as a precaution, disconnect all other USB devices from the computer
    • including printers, scanners, mobile broadband sticks, modems etc
      • any of which could include "storage"
  2. verify the drive letter/number of the USB/SD media
    • in Windows use "Computer" menu and open the drive
    • in other OS use hdparm, fdisk etc
    • check by manufacturer ID, size, partitioning etc
  3. the partitioning/format of the USB/SD media to be used is probably immaterial
    • if in doubt, format the single/first partition as FAT 32
  4. launch a program for direct writing disk images of storage media eg
  5. more detailed instructions are at:

http://en.opensuse.org/SDB:Live_USB_stick#Bootable_USB_from_DVD_or_Net-install

execise great caution with the above programs - an error in selecting the USB/SD device could result in hard disk partition being overwritten


Printing

For General Users

New users of Linux may find that their printer (and scanner) is neither supported nor supportable. Simplest option is to (wisely) purchase a new printer.


Selection Guideance

  • be aware that Linux uses Postscript or PDF technology as the basis for its print sub-system
    • printers that use Postscript, PDF or perhaps PCL print languages are readily supportable and likely to remain so
    • most entry-level printers do not use those technologies, that require additonal processing resouces which in turn adds cost
    • be prepared to purchase a mid-range printer (or multi-function device).

All of the following pre-purchase research is strongly recommended

  • download the relevant driver from the manufacturer's web site
  • check for availability of alternate drivers at: http://www.openprinting.org/printers
  • install the relevant driver prior to purchase
    • in almost all cases this can be achieved without the printer physically present
  • seek assistance in a Linux forum if the drivers are not available or don't install


Troubleshooting

The direct interface to the Linux printing sub-system (CUPS) on your computer is via the URL http://localhost:631

  • this is also usually the most capable and reliable interface
  • other setup routines are provided in many Distributions
    • these might not detect downloaded drivers and are thus less reliable

Failure to print, although the driver is installed, can result from unsuitable settings.

  1. from the CUPS Administratin tab, select
    • Manage Printers -> Set Default Options
  2. check the settings for and adjuxt if necessary
    1. paper size (usually A4 is correct)
    2. paper source (tray (cassette) or manual)


Printer Recommendations

  • HP provide Linux support for most of their devices
    • low-end devices would be reliant on continuation of this support, as would be the case with other brands
  • Fuji-Xerox have argueably the best colour laser technology
    • CP/CM 305 series are the lowest cost models having Linux support
  • Brother multi-functions all support scanning via network
    • mid-range models do use Postscript


Scanning

Raspberry Pi

Cases

Heat Load

Quick Start Guide from distributor RS Components recommends:

  • "use in well-ventillated area"
  • "should not be covered"

It's debatable whether or hot the majority of cases being sold meet the above criteria.

Alternatives to Cases

A DIY cover can be made usiing discarded CD media. The original concept was at

http://discpi.vkspartak.sk/

That "case" does not anchor the RPi down and dimensions for accuately positioning the plastic supports are not provided. A variation, including critical dimensions is at

Raspberry Pi CD Case.png

Some construction factors to note, In either variant

  • RPi have been produced on at least two production lines
    • precise dimensions of the board might vary
    • check prior to construction, preferably using plastic vernier calipers
    • adjust position of supports accordingly
  • single plastic disks/CD media, although quite tough, are fairly flexible
    • two can be "laminated" together to form each of the top and base
    • the plastic in them is not tolerant of most solvents/glues - alternative is to place near the perimeter:
    • several small dots of hot-melt glue or
    • several strips of (non-foam) "double-sided" tape
  • metal components of the case must be well insulated
  • surprising force is required to insert/remove the SD Card & USB plugs, in particular. The supports must resist horizontal movement of the board
  • the board is offset longitudinally towards the USB/RJ45 end, in order to:
    • facilitate insertion removal of USB/Ethernet plugs
    • prevent SD card overhanging case
  • a minimium standoff of about 7 mm is required for board above lower CD.to facilitate insertion/removal of plugs
  • if actual CD media are used (in lieu of plastic spacers from CD stacks) then the reflective sides must face inwards
    • top sides of media can be conductive aluminium
    • clear any drillled holes of flaked aluminium swarf
    • reflective surfaces aid monitoring of the RPi's five tell-tale LED
  • drill CD media at slow speed
    • otherwise the plastic is inclined to melt and clog drlll bits
  • on early production (at least) of the RPi model B, the Ethernet socket is not well anchored
    • desirable to adhere plastic spacers above it so the top CD holds it down
  • a discarded case from a stack of 20/25 CD/DVD media can be used to protect the "CD-RPi" during transport
    • need to cut off the central spigot of the media case

The two (only) chips on RPi can get quite hot in operation. Small, self-adhesive heatsinks are now available from:

http://geekroo.com/site/


Arduino

For General Users

The Arduino is an interface between a controlling PC and stuff you want to control.

A set of links that should get inexperienced users started is below.

Power arduino from battery

http://www.jaycar.com.au/productView.asp?ID=XC4258

Great hardware selection http://www.pololu.com http://www.freetronics.com/

oz hardware site http://www.robotgear.com.au

arduino home http://www.arduino.cc/

arduino software http://arduino.cc/en/Main/Software

Language Reference http://arduino.cc/en/Reference/HomePage

Lots of different boards such as https://shop.ruggedcircuits.com/index.php?main_page=product_info&cPath=1&products_id=23

Simon Monk as written everal books toget you started. The code from his books can be downloaded from here http://www.arduinobook.com/downloads



--[[--Rpeters 18:15, 18 August 2012 (EST)]] --