[Linux] Re : ordi fixe, tv , was [Lug] ordi fixe, tv

[Michel Besançon]

Le 11.01.2008 15:57:50, Antoine Delaporte a écrit :

> Alors evidement, que le FS donnera a l'appli (bon, ok ici le kernel,
> cad himself), une visu sur un block. Mais de la a dire qu'il bypasse 
> le fs, il y a un pas, qui a mon sens n'est pas a franchir.

Avec 8 G de ram, c'est super cool d"y placer un (ou plusieurs)
répertoire(s) virtuels pour des accès "rapides".

J'utilise ce truc parfois :  :-)

#!/bin/bash
# ramdisk.sh

#  A "ramdisk" is a segment of system RAM memory
#+ which acts as if it were a filesystem.
#  Its advantage is very fast access (read/write time).
#  Disadvantages: volatility, loss of data on reboot or powerdown.
#+                less RAM available to system.
#
#  Of what use is a ramdisk?
#  Keeping a large dataset, such as a table or dictionary on ramdisk,
#+ speeds up data lookup, since memory access is much faster than disk 
access.


E_NON_ROOT_USER=70             # Must run as root.
ROOTUSER_NAME=root

MOUNTPT=/mnt/ramdisk
SIZE=2000                      # 2K blocks (change as appropriate)
BLOCKSIZE=1024                 # 1K (1024 byte) block size
DEVICE=/dev/ram0               # First ram device

username=`id -nu`
if [ "$username" != "$ROOTUSER_NAME" ]
then
  echo "Must be root to run \"`basename $0`\"."
  exit $E_NON_ROOT_USER
fi

if [ ! -d "$MOUNTPT" ]         #  Test whether mount point already 
there,
then                           #+ so no error if this script is run
  mkdir $MOUNTPT               #+ multiple times.
fi

##############################################################################
dd if=/dev/zero of=$DEVICE count=$SIZE bs=$BLOCKSIZE  # Zero out RAM 
device.
                                                      # Why is this 
necessary?
mke2fs $DEVICE                 # Create an ext2 filesystem on it.
mount $DEVICE $MOUNTPT         # Mount it.
chmod 777 $MOUNTPT             # Enables ordinary user to access 
ramdisk.
                               # However, must be root to unmount it.
##############################################################################
# Need to test whether above commands succeed. Could cause problems 
otherwise.
# Exercise: modify this script to make it safer.

echo "\"$MOUNTPT\" now available for use."
# The ramdisk is now accessible for storing files, even by an ordinary 
user.

#  Caution, the ramdisk is volatile, and its contents will disappear
#+ on reboot or power loss.
#  Copy anything you want saved to a regular directory.

# After reboot, run this script to again set up ramdisk.
# Remounting /mnt/ramdisk without the other steps will not work.

#  Suitably modified, this script can by invoked in /etc/rc.d/rc.local,
#+ to set up ramdisk automatically at bootup.
#  That may be appropriate on, for example, a database server.

exit 0

A+
-- 
http://www.michel-besancon.fr