usage.8

Unix操作系统minix 2.0源码

     the second level cache can be set with the ramsize boot variable.  Set it
     to a number between 0 and 512.  512 kilobytes is enough to keep  most  of
     the compiler cached.

  20. LOTS OF MEMORY ON A 386+
     Processes can be as big as you'd like on a 386, but in practice 4  Mb  is
     nice.  The installation script sets up a second level cache for Minix-386
     of up to 1024 kilobytes.  This is because the default file  system  cache
     is  only  80  kb.   Your  first point of call is to get rid of the poorly
     performing second level cache and to assign the memory used by it to  the
     normal  block  cache by enlarging the appropriate NR_BUFS and NR_BUF_HASH
     constants in <minix/config.h> with as much as you can spare.   (1024  for
     NR_BUFS  is  the minimum to keep cc -c cached.  2048 is then a nice value
     for NR_BUF_HASH.)  Disable the second level cache, compile a new  kernel,
     reboot and set ramsize to 0.


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  21. LOTS OF DISK SPACE
     The maximum file system size is 1 Gb for Minix-386 and 128 Mb for  Minix-
     86.   (Minix-86  can  handle  larger  file  systems, but fsck can't check
     them.)  Note that a Minix file  system  can  only  contain  65535  inodes
     (files),  so  the average file should be 16 kb to completely fill it.  It
     may be better to make two smaller  file  systems.   Besides,  fsck  takes
     forever on a large file system.

SYSTEM ADMINISTRATION
     The system has been set up with the idea that working as root  is  a  bad
     thing  to  do.   As  root  you  are in no way protected from doing stupid
     things.  So don't do development as root,  but  work  as  bin!   Only  in
     exceptional  cases  do  you  want  to become root.  Being root is fun for
     wannabe hackers; administrators know better.

     To make life easier for bin, some programs  like  su(1),  install(1)  and
     shutdown(8)  treat bin and other members of the operator group as special
     and allow them the privileges of root.  (One  is  an  operator  if  one's
     group id is zero.)  Operators should share the shadow password of root by
     having ##root in their password field.  This way they all have  one  face
     (password)  to  the  outside world, forming no greater security risk than
     root alone.

     The home directory of bin contains one important Makefile.  You  can  use
     it  to recompile all the commands and libraries of the system.  Type make
     to see the usage message.  If you want to compile just one  command  then
     you  can  simply  type  make to do so.  To put it in its proper place you
     have to type make install.  Read the Makefiles in the  commands  and  lib
     subdirectories  to understand how everything is put together.  If you are
     tight on memory then make may fail to traverse down the source  tree  and
     also  compile  things.   You will have to type make in each subdirectory.
     You can run make in /usr/src at the end to see if you've missed something
     or not.

     The login shell of bin is ash, the BSD shell.  It has  been  modified  to
     offer  simple  line editing using the editline(3) library.  Ash is rather
     big, so you may have to change bin's shell back to /bin/sh  with  chsh(1)
     if  you are low on memory.  Do not change root's shell to ash, and do not
     replace /bin/sh by ash.  It may run out of memory at the wrong moment.

     The kernel is not compiled from the  master  Makefile.   To  make  a  new
     kernel you have to step into the tools directory.  There you can run four
     different make commands:

     make This makes all the different kernel parts and combines them  in  the
          file named image.

     make fdboot
          As above and then makes a boot floppy that you can  use  to  restart
          your system with.  You are prompted for the floppy device name.


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     make hdboot
          First makes the image file and then copies  it  into  the  directory
          /minix.   If there are already two images in that directory then the
          newest image will be removed to make space for this newer image.  It
          is  assumed  that  the oldest image is the most stable system image,
          one that always works, and that the newest  image  is  experimental.
          Check  beforehand  what  /minix contains before you run make hdboot.
          Remove the oldest image if you want  another  image  to  become  the
          stable  image.   The Boot Monitor chooses the newest image in /minix
          to boot.  You can use the monitor  command  ls  minix  to  view  the
          images  present,  and set the image variable to the full name of the
          image you want to use instead  if  the  newest  doesn't  work.   The
          images  in  /minix  are  named  using  the Minix release and version
          numbers with an extra  revision  number  added  to  distinguish  the
          images.

     The first new kernel you would like to make is one  configured  for  your
     system.   The  kernel  you  are  running  now  contains several hard disk
     drivers you don't need, and it does not have a TCP/IP server that you may
     want  to  have.   In <minix/config.h> you can find a number of ENABLE_XXX
     variables that can be set to 0 to exclude, or 1 to include  a  particular
     driver.   Another  driver related variable is DMA_SECTORS.  This variable
     sets the size of a buffer used by DMA based disk  drivers  (all  but  the
     floppy, AT/IDE, and Adaptec drivers).  Raise its value to greatly improve
     throughput, especially writing.  A value of 16 shows good results.   (The
     BIOS  driver  benefits  most,  because  it is a long way to the BIOS from
     protected mode, especially from 286 protected mode.)   You  can  increase
     NR_CONS  if you want to have more virtual consoles.  Having more consoles
     costs little memory, because all the consoles are kept in  video  memory.
     Scrolling  speed  of  the  console  will go down if more virtual consoles
     share the available memory.  CGA cards have space for 4 consoles, EGA and
     VGA can have 8 consoles.  The NR_PTYS variable sets the number of pseudo-
     ttys.  You need pseudo-ttys to be able to login remotely over  a  network
     with the rlogin command.  Each remote login session needs one pseudo-tty.
     If you fear that the system will now run out of processes  then  increase
     NR_PROCS.  Configuring a new kernel is sometimes not enough to enable new
     devices, you sometimes need to use the MAKEDEV command to make new device
     files  in  /dev.   For  pseudo-ttys you also have to check if /etc/ttytab
     mentiones the new devices.

     New additions to the system can be made in the /usr/local tree.  An empty
     directory  tree has been set up for you and binaries and manual pages are
     already in the search paths.  You can make a  new  user  entry  with  the
     adduser command.

     The TZ variable in /etc/profile tells the time zone offset from the  wall
     clock  time  to  GMT.   You  have  to change it for your time zone.  (See
     TZ(5).)




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     The function keys produce debug dumps, showing various  interesting  data
     about  the system.  F1 lists processes and F5 shows ethernet stats, which
     may be of use now.  Read console(4) to know all the details of the screen
     and keyboard.

  22. SYSTEM SHUTDOWN
     You can't just turn a Minix system off.  Minix must be told to flush  the
     modified   data   in   the   file  system  cache  first.   The  following
     commands/keystrokes can be used to exit Minix properly:

     shutdown
          First alert all users  and  then  all  processes  of  the  impending
          shutdown then halt or reboot the system in one of various ways.  See
          shutdown(8).

     reboot / halt
          Alert all processes of the system shutdown then reboot or halt.

     CTRL-ALT-DEL
          Halt the system by running shutdown -h now.

     Minix  halts  by  returning  to  the  Boot  Monitor,  Minix  reboots   by
     instructing  the monitor to reboot Minix.  (Minix is just a subprocess to
     the monitor.)  Either halt Minix  and  use  monitor  commands  to  escape
     Minix, or use shutdown -R to reset the system.

FILES

     /usr/ast    Honorary home directory of Andew S.  Tanenbaum.   Doubles  as
                 the place where the default setup for a new user is found.

SEE ALSO
     monitor(8), boot(8), part(8), mkfs(1), mount(8), M(8), fstab(5), hier(7),
     console(4), dev(4), adduser(8), TZ(5), mkdist(8), shutdown(8).
     "Operating Systems - Design and Implementation" by Andrew S. Tanenbaum.

NOTES
     The  notation  <file.h>  refers  to  a  C  language   include   file   in
     /usr/include.

     Root and bin do not have the current directory in  their  program  search
     path  to  avoid executing programs left around by malicious people.  This
     means that to run foo from the current directory, ./foo must be typed.

     Some of the commands have changed  since  earlier  Minix  versions.   For
     instance mkfs doesn't need a size argument anymore, and vol automagically
     determines if it needs to read or write.  Keep this in mind if you use an
     older Minix version to examine the newer system.




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BUGS
     There are many PS/2 models, all different.  Some  will  run  Minix,  some
     won't,  some  crippled  if  you  lie to Minix by setting processor to 86.
     Almost no PS/2 has a standard disk, so setting hd to esdi or bios will be
     necessary.

     While testing a full library rebuild of this  distribution  it  sometimes
     happened that some things were not put back into the library.  This seems
     to be fixed, but we do not understand why the fix fixed the problem.   So
     if  you  see  strange "undefined" errors when compiling a program after a
     library rebuild then run make install again in /usr/src/lib/ to  try  and
     add the missing pieces.

     Except for the floppy driver none of the DMA based drivers know about DMA
     being  limited  to  a  24  bits  address, i.e. the first 16 Mb.  So under
     Minix-386 you run a slight risk that a tar or dd command may use a buffer
     above  16  Mb  for  reading  or writing to a character device.  This only
     happens if the low 16 Mb is taken by some huge processes,  and  you  have
     more than 16 Mb, of course.

AUTHOR
     Kees J. Bot ([e-mail])






























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