afserver.conf.8.in

一套客户/服务器模式的备份系统代码,跨平台,支持linux,AIX, IRIX, FreeBSD, Digital Unix (OSF1), Solaris and HP-UX.

.TH AFSERVER.CONF 8 "2001 April 1" "Debian Project"
.SH NAME
@serverconf@ \- server side configuration file for afbackup
.SH DESCRIPTION
This file needs not be edited by hand with an editor,
instead the program @serverbindir@/afserverconfig
can be used. If you are 
running X, the programs are the same, but start with an 'x';
(Tcl/Tk must be installed): 
and @serverbindir@/xafserverconfig.
The parameters described below are the same for both versions.
Entries consist of lines starting with the parameter name,
then follows a colon and the value of the parameter. Comment
lines can be inserted as desired starting with the # character.
.SH ENTRIES
.TP
.B Backup-Device
This is the device the backup is written to. It can be any
tape device with the capability to distinguish between several
files on the media. It is mandatory to supply the no-rewind 
device here, otherwise this package won't work properly. 
Suitable device names for some OS-es:
.br
  AIX:          /dev/rmt0.1
.br
  Solaris:      /dev/rmt/0bn
.br
  IRIX:         /dev/rmt/tps0d4nr
.br
  HP-UX:        /dev/rmt/0hn
.br
  Linux:        /dev/nst0
.br
  Digital UNIX: /dev/nrmt0h
.br
  FreeBSD:      /dev/nsa0
.br
If the drive has a media handler attached, a specifier for
this may follow the device name. The format for this
is =<drive-count>@<device>#<num-slots>^<num-loadbays> , 
for example =1@/dev/sg0#6^2 . Whitespace before and following
the special
characters = @ and # is allowed for readability. The example
means: The drive is number 1 in the changer, /dev/sg0 is the
changer device, that has 6 media slots and 2 loadbays. The
parts =<drive-count> and ^<num-loadbays> are optional.
.br
If the server is only used for remote start and no real backup
device should be accessed, a dash - should be configured here
as device, so a respective warning to the server log will be
suppressed

.TP
.B ServerIdentifier
The identifier for the server. Default: The official hostname,
followed by a colon and the full path to the configuration file.
The server identifier can be used to become independent of the
server machine name. This might be helpful, if the backup server
should move to another machine. Whitespace characters may be
used in this identifier, but they are replaced with asterisks *
before comparing, so they are not significant
.TP
.B Tape-Blocksize
The blocksize of the tape device. This value specifies how many
bytes are written to tape or read from it with one system call.
Usually this value is at least 512 or a multiple of it.
It is not very important if the blocksize is set to 2048
or 1024. The main thing to keep in mind is that if there is a
minimum, it should be respected (e.g. 1024 on AIX), otherwise
media space is wasted.
.TP
.B Tape-Buffer
Three numbers and a filename can be given here. The first number
is the desired size of the tape buffer in bytes. The optional
second number is the high-watermark while writing in percent
(default: 67), the optional third number is the low watermark,
also in percent (default: 0). As long as the buffer fill rate
does not reach the high watermark, nothing is written, but when
it is reached, writing does not stop until the buffer fill rate
is equal or below the low watermark. This procedure hopefully
reduces tape wear and increases average writing speed, because
excessive tape stops/starts are avoided. If the optional filename
is given, buffering is done in the given file, which is mapped
into the server's address space for that purpose. In the filename,
patterns are replaced like with Changer-Configuration-File.
.TP
.B Cartridge-Handler
This value must be 1 or 0, which means, that you either have a
cartridge handling system (i.e. some kind of robot) (1) or
not (0). If you don't have a robot, you may nonetheless maintain
a set of cartridges, that you will have to manually number. 
The backup server side will inform you via email or console output,
whenever another cartridge has to be inserted into the drive and what
number it requires it is.
.TP
.B Number Of Cartridges
This number specifies, how many cartridges you are maintaining.
If you have a cartridge handling system (some kind of robot),
this is usually the number of cartridges, your system is juggling.
.TP
.B Cartridge-Sets
Several cartridge sets can be used. Here they can be specified.
The specifiers for the cartridge sets must be separated by
whitespace. Each specifier may consist of digits, commas and
dashes. Examples for cartridge set specifiers: 1-5 7-9,12 6,10,11 .
This example shows how to specify three cartridge sets. If the
access to a cartridge set should be allowed only for certain
clients, this may specified with a colon immediately following
the set specifier without whitespace, followed by one of three
forms: Either a list of hostnames, separated by commas and no
whitespace inbetween, or the full path to a file containing the
hostnames one per line, or by a command to be executed. The
command must start with a bar | and must be enclosed in double
quotes, if it is containing whitespace. If %H occurres in the
command it will be replaced with the client name, who wants to
gain access to the cartridge set. The command must exit with a
status of 0, if access is to be granted, otherwise with an exit
status unequal to 0. The name of the host to be checked is also
written to standard input of this command, so %H needs not to
be used. Examples specifying cartridge sets with restricted
access:
       1-5:apollo,localhost,taurus
       6-8,16:/usr/local/backup/etc/set2clients
       9-15:"| fgrep .my.domain.com"
.br
Remember, that grep will exit with 0, if a match has been found,
otherwise 1. Note, that localhost and the network name of the
machine should be both given, if the server is also a client.
The names to be supplied here are not the client IDs configured
on the client side, but the network names of the machines.
.br
If this parameter is not given, there is only the default set
number 1 with all available cartridges, access is permitted to
any client. Not all cartridges need to be included in a set and
sets must not overlap.
.TP
.B Max Bytes Per File
The stream of data, that represents your backup, is divided into
pieces (files on tape). This is done to find the files faster
during a restore. This value determines, how large the pieces on
tape may be in bytes. Some good values for a few tape technologies:
.br
  QIC:              20000000
.br
  DAT:              30000000
.br
  Exabyte:          50000000
.br
  DLT:             100000000
.br
.TP
.B Max Bytes Per Tape
With this entry the number of bytes written to a single tape
can be limited. Serveral entries with a leading range specifier
allow to handle certain tapes differently. The range specifier
must end in a colon : and may contain lists of ranges and numbers.
A given number without a leading range specifier will be valid for
all tapes not explicitly described. Default is use of full tape
capacity. Several entries must be separated by whitespace and may
look like the following examples:
.br
4000000000 1,3-5:3500000000 7,9-:5000000000
.br
This means: 3.5 GB for cartridges 1 and 3 through 5, 5 GB
for cartridges 7 and 9 up to the last cartridge, 4 GB for the
rest.
.TP
.B Full Append Mode
Normally, when the insert (writing) position is forced to
another tape with the cartis command or with the clientside
option -G, the rest of the current tape remains unused. When
this option is set to 1, it will nonetheless be used to write
data on, if there is no free tape left.
.TP
.B Variable Append Mode
In default mode, the place (tape and tapefile), where the next data
will be written, is fix and can only manipulated using the command
cartis or the clientside option -G. When the server wants to write
with variable append mode enabled, any cartridge, that is in the
drive, is belonging to the right cartridge set and is allowed to be
written, will be accepted and appended to. Note, that this will also
override the settings of cartis or option -G.
.TP
.B Reject Unlabeled Tapes
Default is to accept an unlabeled tape as the requested one and
to label it automatically. If this behaviour is unwanted and only
tapes with a recognized label should be permitted for writing,
this parameter should be set.
.TP
.B PreferCartInChanger
When a tape gets full and another one must be chosen to continue
writing, the server does not make a difference, whether a tape
is available in a changer or not, if this flag is not set. This
is the default. If this parameter is set, the next cartridge is
chosen from those, that are available in the slots of a changer,
if present and configured. If there is no tape found inside the
changer, that is allowed to be overwritten, manual administrator
interaction is nonetheless required.
.TP
.B Cart-Insert-Gracetime
This is the time in seconds, the program waits after another
cartridge has been put into the drive. Normal devices need a
certain time span to mount the tape to get it ready for use.
Normally this value is not critical. If you estimate it too
low, the ioctl-system-call will wait until the device becomes 
available. This time is sometimes longer than two minutes,
so if you want to proceed quickly after a cartridge
change, you may measure the maximum time your system needs.
Some tried values for a few tape technologies:
.br
  QIC:         20
.br
  DAT:         30