Continue reading »]]> If you want to run sudo from any part of a cron job make sure you comment out the

Defaults requiretty

from /etc/sudoers. Bit me twice now so hopefully I’ll remember next time.

Ed: Apologies to those who have read this before but I had to restore from backup and my last post wasn’t in that backup.

Continue reading »]]> A few things all of us are probably interested in:

• SSD Write Amplification:
  
  
  http://www.extremetech.com/article2/0,2845,2329594,00.asp
  
  
• Journaling and write performance in ext4:
  
  
  http://thunk.org/tytso/blog/2009/03/01/ssds-journaling-and-noatimerelatime/

The bottom-line as far as wear and tear: vfat is basically the same as a journaled FS from a wear-leveling standpoint, both are worst case. Thankfully vfat, being the worst case, forced the manufacturers to deal with the problem early. So all those outlandish claims I made about the world being flat and NTFS on thumbdrives are unfounded. Ted’s evidence does not speak to the amount of effort it takes to create an NTFS thumbdrive in Windows, however

Continue reading »]]> The past few days people in Linux blogosphere have been bringing back up the noatime/nodiratime mount options. These options disable the updating of file and directory access times. On many standard systems when you read file a “last read,” or access time, timestamp is written to disk. Disabling the writing of access times can provide performance increases in some conditions. Probably in a lot of conditions. Disabling the writing of these access times can be accomplished with the noatime and nodiratime mount options on a typical FS on a Linux system. Well in OS X and hfs+ nodiratime doesn’t exist but noatime does.

These options are old news to some. I had used them in Linux in the past – heck I think it was even in the standard Gentoo install docs – but I had never them a second thought since I moved to OS X. If you know me personally you know I can’t leave something untweaked. And those recent discussions got me to thinking…

Be forewarned, I haven’t gone to great lengths to explain the concepts of the notes below so if you’ve never seen a terminal this isn’t going to be comprehendible.

I wanted to mount my filesystems with the noatime option in OS X to disable the updates to access times for files. Problem is that, at least in 10.5, OS X no longer honors /etc/fstab for system disks, only for automount disks.

After wrestling with it for awhile I gave upon trying to find a location where I could specify mount options for system disks. I decided to just remount the disk later with the correct options. I created a StartupItem entry to remount the disk. I created a directory:

# mkdir /Library/StartupItems/spencer_boot

Then I created the StartupItem plist. Pretty straight forward.

# cat /Library/StartupItems/\
spencer_boot/StartupParameters.plist

{
Description = “Spencer’s Boot Script”;
Provides = (“spencer_boot”);
OrderPreference = “None”;
Messages =
{
start = “Starting Spencer’s Boot Script”;
stop = “Stoping Spencer’s Boot Script”;
restart = “Restarting Spencer’s Boot Script”;
};
}

Now I needed the shell script that would be run on boot.

# cat /Library/StartupItems/spencer_boot/spencer_boot

#!/bin/sh

. /etc/rc.common

case “$1″ in
start)

ConsoleMessage “Starting Spencer Boot: remounting root fs noatime”
mount_hfs -o noatime /dev/disk0s2 /

;;
esac

exit 0

This solved the problem for the root fs but I also use Filevault. If you don’t use Filevault you can stop reading here. How would I go about this? Same problem as before, no where to add mount time options. Additionally the fs is mounted upon login, not boot. So our previous method of creating a StartupItem won’t work. We’re going to have to do it later after it has been mounted – again.

<redacted> I did have some other information here but after review I wasn’t happy with advocating the “hack” I’m using. But the gist of it is to run something like this: /sbin/mount -u -o noatime,nosuid,nodev /dev/disk1s2 /Users/spencer/ after the volume is mounted. This happens after you enter your password. So a good place would be login items if you can figure out how to run mount as root from a user’s startup scripts.</redacted>

After you login and the system has completely finished running your startup apps open a terminal and type “mount”. You should see “noatime” listed as a mount option for you system and Filevault disks.

spencer_boot shell script
StartupParameters.plist for the spencer_boot StartupItem
remount_filevault for noatime in Filevault volumes