Readme file of TCOS build generation system

INDEX: 

 * Boot from PXE network card.
 * Boot from Etherboot floppy.
 * Debug terminal that don't start.
 * Howto decrease RAM requirements.


---------------------------------------
           Boot from PXE
---------------------------------------

 1.- Configure /etc/tcos/tcos.conf and enable/disable 
     all what you want. All vars are comented.

 2.- Exec:

     # gentcos -tftp

     ( see gentcos -help or man gentcos for more options )

  3.- Configure dhcp server like this:

   host __PCNAME__ {
    # PXE boot
    hardware ethernet       00:04:75:ff:b6:aa; # mac address
    fixed-address           192.168.0.10;      # ip address
    filename                "/tcos/pxelinux.0";
    }

   4.- Restart dhcp server and boot terminal.

   5.- You can add some cmdline options before boot, you can see
       some of them presing F1 before boot starts.

      Examples:
         startx=N ( no startx)
         startx=L ( start local session Xorg + xterm + twm )
         startx=R ( start remote x default)
 
         server=10.0.0.1 ( tftpboot and XMDCP server, default is dhcp server)

         volume=80% ( volume of PCM and MASTER chanels of audio mixer )
		  value can be 1%-100% or integer from 1 to 31

         zap ( allow to kill Xorg with  Ctrl + Alt + Backspace, default disabled)

	 force-update ( delete usr.squashfs if found in local harddisk and download again )

	 noswap ( disable swap file generation, swap partittions will be used if found )

	 nounionfs ( disable unionfs mount on /usr, /usr will be read only )



---------------------------------------
     Boot with Etherboot floppy
---------------------------------------

 1.- First off all you need a Etherboot floppy
   that works with your network card.

   You can try with universal FLOPPY, download here:

   https://prdownloads.sourceforge.net/thinstation/BootDisk522b.zip?download

   Or try to build your own in:

   https://rom-o-matic.net/

 2.- Run gentcos -nbi [-nbi-output=linux-1.nb]

   This will create and put in tftp dir the nbi boot image.
   You can change default name (linux.nbi) to another one => linux-1.nb


 3.- Configure DHCP server to serve NBI image:

   Example:

    host pc3 {
      # NBI Etherboot
      hardware ethernet       00:04:75:ff:b8:31;
      fixed-address           192.168.0.30;
      # nbi generated file with: gentcos -nbi
      filename                "/tcos/linux.nbi";
     }

 4.- Restart dhcp server, boot terminal from floppy and enjoy.



---------------------------------------
   Debug terminal that don't start
---------------------------------------

  If terminal don't connect to XMDCP server and give a busybox shell
  we can read some logs and examine what is the cause.

  1.- Exec:
   
  $ more /tmp/initramfs.debug
 
  In this file are all output of many actions during boot.

  2.- View "ps" output.

  3.- View dmesg output.

  We can connect with ssh to thin client ( if enabled ):

   $ ssh root@__TERMINAL-IP__

  If we copy any rsa key, password will not be asked, else
  root password is defined (plaintext) in /etc/tcos/tcos.conf

  Is possible to mount all thin client filesystem in server:

  mkdir thin-client/
  ltspfs __TERMINAL-IP__:/ thinc-client/

  To umount
  fusermount -u thin-client/

  See help about LTSPFS and fuse.

####################################################

  Thin client gives a kernel panic !!!!

####################################################

  If terminal gives a kernel panic we can try to stop boot
  process using break stament, you can append to cmdline
  following vars: 
  (all var are sorted in same order that are exec)

  TCOS-premount breaks:

  break=network  # stop before configure lo and eth0
  break=fstab    # stop before create /etc/fstab
  break=uselocal # stop before scan local disks
  break=swapon   # stop before create/mount swap file
  break=sqmount  # stop before download usr.squashfs or allmodules.squashfs
  break=ldconfig # stop before exec ldconfig

  TCOS-bottom breaks

  break=inittcos  # stops before some daemons are started
  break=initsound # stops before sound is loaded
  break=ltspfs    # stops before ltspfs daemon is started
  break=startx    # stops before startx is started

  When thin clients stops you can do some things:

  see dmesg output
  see /tmp/initramfs.debug file
  see loaded modules (lsmod or cat /proc/modules)
  see mem usage (free or cat /proc/meminfo)
  see inet info (ifconfig or dhcp.leases file)
  view process running (ps)


---------------------------------------
Things to do, to decrease RAM requirements
---------------------------------------

* First of all disable what you don't need

 in /etc/tcos/tcos.conf

 reduce a lot of ram
   TCOS_SOUND=             ( disabled sound support )
   TCOS_USB=               ( disabled USB & SCSI support )

 reduce a few ram
   TCOS_SSH=               ( disabled ssh support )
 
 reduce a bit ram
   TCOS_INETD=             ( disabled inetd support )
   TCOS_DISCOVER=          ( disabled discover support )

 You get more info during generation process of needed space
 for each app.

* Edit /etc/tcos/initramfs.conf and set MODULES var to list

 MODULES=list

 MODULES can be one of this:
  most     ( include all of network modules and chipset)
  dep      ( include all modules loaded in server NOT RECOMENDED )
  netboot  ( include netboot modules, but not block devices )
  list     ( include all modules we need => tcos-modules.conf low RAM RECOMENDED )

 more info => man initramfs.conf

 with this setting initramfs have exactly all modules you want

* Edit /etc/tcos/modules

  you can edit some var to exactly put needed modules

  There are 2 methods of know what modules thin client need:

  1.- Use discover:
    set TCOS_DISCOVER=1 and boot with this params:

    boot: tcos startx=N

    when thin client finish to boot you will have a shell, exec this:

      cat /tmp/initramfs.debug | grep Skipping
    
    you could read something like this

       Skipping XXXXX; assuming it is compiled into kernel

   take note of all XXXXX modules and put them in 
   /etc/tcos/modules


  2.- Second method is to start terminal 
     with cmdline:
           tcos allmodules startx=N
  ( you need allmodules.squashfs in /var/lib/tcos/tftp generated with
    gentcos -allmodules [other options] )

    -allmodules requires at least 14-15 Mb of extra RAM.

    next exec lsmod or cat /proc/modules and take note of all.

#######################################################################
  WITH ALL OF THESE TCOS will start (without swap[*]) with 26 Mb of RAM  
#######################################################################

[*] swap in limited thin clients (ex: 32 Mb) is very important, because
    Xorg need free memory to run.