Re: [gentoo-dev] devfs is dead, let's move on

[Greg KH <gregkh@gentoo.org>]

On Thu, Jul 07, 2005 at 10:18:12AM -0400, Chris Gianelloni wrote:
> On Wed, 2005-07-06 at 15:46 -0700, Greg KH wrote:
> > To start with, the 061 version of udev offers a big memory savings if
> > you use the "default" kernel name of a device[3].  If you do that, it does
> > not create a file in its database in /dev/.udevdb/
> 
> So if we were to switch to udev 061 in genkernel, it would shrink memory
> usage in our initrd/initramfs, provided we made everything use the LSB
> device names/nodes, versus the devfs ones, correct?

Not in the initrd/initramfs, but in the tmpfs partition that udev uses
to create the /dev entries.  Well, I guess you could say the
"initrd/initramfs" if that is where udev is mounted on early startup (I
haven't looked at how genkernel does this in a long time, sorry.)

And yes, the memory savings is there, if we use the LSB names only vs
the devfs name and the symlink like we currently do.

To see this, look at how much space /dev/.udevdb/ takes up right now
with 062 udev.  Then change the following rules in
/etc/udev/rules.d/50-udev.rules with the diff at the end of this email.
Then reboot and look at the size of the /dev/.udevdb/ directory again.
I think you will notice a huge space savings.

thanks,

greg k-h

--- 50-udev.rules.orig	2005-07-08 10:10:24.000000000 -0700
+++ 50-udev.rules	2005-07-08 10:11:16.000000000 -0700
@@ -139,9 +139,9 @@
 # tty devices
 KERNEL=="console",	NAME="%k", GROUP="tty", MODE="0600"
 KERNEL=="tty",		NAME="%k", GROUP="tty", MODE="0666"
-KERNEL=="tty[0-9]*",	NAME="vc/%n", SYMLINK+="%k", GROUP="tty"
-KERNEL=="ttyS[0-9]*",	NAME="tts/%n", SYMLINK+="%k", GROUP="tty"
-KERNEL=="ttyUSB[0-9]*",	NAME="tts/USB%n", GROUP="tty", MODE="0660"
+KERNEL=="tty[0-9]*",	NAME="%k", GROUP="tty"
+KERNEL=="ttyS[0-9]*",	NAME="%k", GROUP="tty"
+KERNEL=="ttyUSB[0-9]*",	NAME="%k", GROUP="tty", MODE="0660"
 KERNEL=="ippp0",	NAME="%k", GROUP="tty"
 KERNEL=="isdn*"		NAME="%k", GROUP="tty"
 KERNEL=="dcbri*",	NAME="%k", GROUP="tty"
@@ -149,14 +149,14 @@
 
 # pty devices
 KERNEL=="ptmx",			NAME="%k", GROUP="tty", MODE="0666"
-KERNEL=="pty[p-za-e][0-9a-f]*",	NAME="pty/m%n", SYMLINK+="%k", GROUP="tty"
-KERNEL=="tty[p-za-e][0-9a-f]*",	NAME="pty/s%n", SYMLINK+="%k", GROUP="tty"
+KERNEL=="pty[p-za-e][0-9a-f]*",	NAME="%k", GROUP="tty"
+KERNEL=="tty[p-za-e][0-9a-f]*",	NAME="%k", GROUP="tty"
 
 # vc devices
-KERNEL=="vcs",		NAME="vcc/0",	SYMLINK+="%k", GROUP="tty"
-KERNEL=="vcs[0-9]*",	NAME="vcc/%n",	SYMLINK+="%k", GROUP="tty"
-KERNEL=="vcsa",		NAME="vcc/a0",	SYMLINK+="%k", GROUP="tty"
-KERNEL=="vcsa[0-9]*",	NAME="vcc/a%n",	SYMLINK+="%k", GROUP="tty"
+KERNEL=="vcs",		NAME="%k", GROUP="tty"
+KERNEL=="vcs[0-9]*",	NAME="%k", GROUP="tty"
+KERNEL=="vcsa",		NAME="%k", GROUP="tty"
+KERNEL=="vcsa[0-9]*",	NAME="%k", GROUP="tty"
 
 # memory devices
 KERNEL=="random",	NAME="%k", MODE="0666"
-- 
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