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Proc directory on CompactFlash
- 07-01-2006
- Murray R. Van Luyn
July 1, 2006, 1:05 pm

Hi,
I want to build a small RTLinux system on a CompactFlash, but don't know
what to do with the /proc directory.
I think I'm supposed to put the /tmp directory on a TMPFS in ram to avoid
wearing out the flash device too quickly.
I've heard of the contents of /proc being referred to as 'virtual'. Does
that mean they are not actually stored on disk and can then be forgotten
about? Otherwise, if the contents of /proc really are files stored on a
disk, then do I do the same thing with the /proc directory as the /tmp
directory?
Regards,
Murray R. Van Luyn.
I want to build a small RTLinux system on a CompactFlash, but don't know
what to do with the /proc directory.
I think I'm supposed to put the /tmp directory on a TMPFS in ram to avoid
wearing out the flash device too quickly.
I've heard of the contents of /proc being referred to as 'virtual'. Does
that mean they are not actually stored on disk and can then be forgotten
about? Otherwise, if the contents of /proc really are files stored on a
disk, then do I do the same thing with the /proc directory as the /tmp
directory?
Regards,
Murray R. Van Luyn.

Re: Proc directory on CompactFlash

Only the /proc directory itself should exist (empty) on your root drive.
Then say "mount -t proc proc /proc" somewhere in your startup or put the
equivalent line in /etc/fstab if you have that.
The *contents* of /proc are created directly by the kernel whenever it's
accessed - reading a file in proc really connects your user space
program directly to some kernel function that produces its content
on-the-fly. Same for writing - your process gets connected to some
kernel function that takes the data from your application and does
something with it.
So except for the top /proc directory itself, nothing in /proc exists on
any disk.
--
Linards Ticmanis
Linards Ticmanis

Re: Proc directory on CompactFlash

May be all root (/) system put in RAM or only / and /usr leave on CF
This my example:
#mount -t ext2 /dev/hdc /mnt/cflash
#cd /mnt/cflash
#ls
boot/
usr/
var/
#cd boot/ && ls
grub/
vmlinuz
initrd.gz
boot/ - kernel, initrd image - root system include /proc, /sys, /tmp
/bin, /sbin, /lib, /dev
usr/ - all users application
var/ - variable data
------------------------
Ex. 2
mount -t tmpfs none /tmp -o rw
mkdir -p /tmp/proc
mount -t proc none /tmp/proc -o rw
ln -s /tmp/proc /proc
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