Linux kernel patches

• noatime-perprocess.patch
  This patch creates a 'noatime' setting per process. A process can set/reset its own 'noatime' flag by echoing 1 or 0 into /proc/noatime. Only root may do this. If the flag is set, no atime updates will be done.
  I use this patch to prevent backup programs from updating the atimes on all files.
  
  
• nfsroot-hotplug_ethernet.patch
  With this patch it is possible to boot with nfs-root using a USB (or other hotplug) Ethernet device. Normally this doesn't work because USB devices are detectly asynchronously (from a kernel thread). At the time a USB Ethernet device is discovered, the IP config code has already given up.
  With this patch, if you are using nfsroot and no Ethernet device is detected, the kernel will wait forever until one appears.
  It's against 2.4.9-ac7, but it will likely apply without problems to other 2.4.x kernels as well (update, 2002/12/26: works well with 2.4.20).
  
  
• usb-storage-root.patch
  With this patch it is possible to boot with the root filesystem on a USB (or other hotplug) harddisk. Normally this doesn't work because USB devices are detectly asynchronously (from a kernel thread). At the time a USB harddisk is discovered, the root mounting code has already given up.
  With this patch the kernel will wait forever until the root device appears.
  It's against 2.4.14-pre8. It's been reported that this patch doesn't work if you enable devfs!
  
  Robert Collins updated the patch for 2.4.22: boot-usb.patch. Thanks!
  There's another update at http://www.xenotime.net/linux/usb/usbboot-2422.patch.
  http://www.simonf.com/usb/ describes how to do it with an initrd image instead.
  http://marc.theaimsgroup.com/?l=linux-kernel&m=109122295308836&w=2 has a kernel patch for 2.6.x.
  
  
• IDE harddisk unclipping
  (Note: This feature is included in Linux 2.4.19 and later versions; turn on "Auto-Geometry Resizing support" in the kernel configuration to enable it.)
  
  This patch adds 'software unclipping' support to the ide drive.
  This is useful if you want to connect a >32GB harddisk to an old mainboard. Old bioses often hang if they see such a large drive. You can 'clip' the drive to 32GB with a jumper, but then you'll only get 32GB of harddisk space.
  Another way to counter this problem is 'software clipping'. From the bios' point of view, it works just the same: it sees a 32GB harddisk. The difference is that the kernel can undo this clipping at boot time. After that the full capacity is available again.
  Setmax is used to set the clipping. You need to do this only once. For IBM and WD harddisks you need ibmsetmax.
  
  To add 'unclip' support to the kernel, you need one of:
  • Andre Hedrick's patches for 2.2 or 2.4.
  • unclip.patch. This adds just unclipping support to 2.4.x, nothing more. This code was extracted out of Andre Hedrick's patches.
  
  Don't forget to put your /boot partition (or wherever the kernel/bootloader is stored) below 32GB!