#!/bin/bash
# Author: Brian Hilstrom
# Date: May 14, 2004
#
# Usage: new_kernel <full path to kernel>
#
# 1) Compiles the new kernel (argument)
#      with old .config file
# 2) Copies current kernel to linux.BAK
# 3) Copies linux.BAK to linux.old
# 4) Removes previous linux.old from
#
#

###  ====== SET THESE VARIABLES !!! ========
TESTING=0 # set to 1 to run in testing mode
ROOT_UID=0
KERNEL_PATH=/usr/src/
BOOT_PATH=/boot/
GRUB_PATH=/boot/grub/
KERNEL_CONFIG_PATH=/etc/kernels/
COMPILE_COMMAND="genkernel --kernel-config=/usr/src/linux.BAK/.config --kernel-cc=distcc --makeopts=-j5 all"
TO_EMERGE="nvidia-kernel"
###  =======================================

### test for number of args
if [ $# -ne 1 ]
then
    echo "Wrong number of args."
    echo "Usage: new_kernel <full path to kernel>"
    exit 1
fi 

### test for root access
if [ "$UID" -ne "$ROOT_UID" ]
then
    echo "Must be root to run this script."
    exit 1
fi

### set the path to the 1st argument
###  without the beginning KERNEL_PATH
###  (no ending '/')

NEW_VER=${1#$KERNEL_PATH}

### if it has a trailing '/' remove it
if [ ${NEW_VER:${#NEW_VER} - 1} == / ]
then
    NEW_VER=${NEW_VER%%/}
fi

### remove the linux- prefix
NEW_VER=${NEW_VER#linux-}

### test if linux-<version> is a directory in /usr/src
cd $KERNEL_PATH

if [ ! -d "linux-$NEW_VER" ]
then
    echo "Path is not a directory in $KERNEL_PATH."
    echo "Usage: new_kernel <full path to kernel>"
    exit 1
fi

### set path and version variables
BAK_PATH=`readlink linux`
OLD_PATH=`readlink linux.BAK`
DELETED_PATH=`readlink linux.OLD`

BAK_VER=${BAK_PATH#linux-}
OLD_VER=${OLD_PATH#linux-}
DELETED_VER=${DELETED_PATH#linux-}


### set OLD_BASE_VER to major version of old kernel
OLD_BASE_VER=${OLD_VER:0:3}

if [ $TESTING -eq 1 ]
then
    echo "BAK_PATH = $BAK_PATH"
    echo "OLD_PATH = $OLD_PATH"
    echo "DELETED_PATH = $DELETED_PATH"
    echo "BAL_VER = $BAK_VER"
    echo "OLD_VER = $OLD_VER"
    echo "DELETED_VER = $DELETED_VER"
    echo "OLD_BASE_VER = $OLD_BASE_VER"
fi

### check for user acknowledgement
echo $'\a'$'\n'== This will compile linux-$NEW_VER, do you wish to continue\? \(y to continue\) ==
read answer

echo $'\n'

if [ ! $answer == y ]
then
    echo "Stopping execution."
    exit 0
fi


### delete the .OLD directory
### change the kernel pointers
if [ $TESTING -eq 1 ]
then
    echo "here is where I'd be changing all the symlinks"
else 
    rm -rf linux-$DELETED_VER

    rm linux.OLD
    ln -sf linux-$OLD_VER linux.OLD

    rm linux.BAK
    ln -sf linux-$BAK_VER linux.BAK

    rm linux
    ln -sf linux-$NEW_VER linux
fi


### remove useless config
if [ $TESTING -eq 1 ]
then
    echo "now we delete $KERNEL_CONFIG_PATH kernel-config-x86-$DELETED_VER"
else
    rm "$KERNEL_CONFIG_PATH"kernel-config-x86-$DELETED_VER
fi

### compile it
if [ $TESTING -eq 1 ]
then
    echo "here we compile..."
else
    $COMPILE_COMMAND
fi

### if the compile command encounters an error, stop execution
if [ $? -ne 0 ]
then
    echo "The compile command encountered an error."
    exit 1
fi


if [ $TESTING -eq 1 ]
then
    echo "here we wrap up the process"
    exit
fi


### delete the old kernel and initrd entries
### change the kernel and boot pointers
cd $BOOT_PATH
rm kernel-$DELETED_VER

rm kernel.OLD
ln -sf kernel-$OLD_VER kernel.OLD

rm kernel.BAK
ln -sf kernel-$BAK_VER kernel.BAK

rm kernel
ln -sf kernel-$NEW_VER kernel

rm initrd-$DELETED_VER

rm initrd.OLD
ln -sf initrd-$OLD_VER initrd.OLD

rm initrd.BAK
ln -sf initrd-$BAK_VER initrd.BAK

rm initrd
ln -sf initrd-$NEW_VER initrd


### change the appropriate lines in grub.conf
cd $GRUB_PATH
cp grub.conf grub.conf.BAK
cat grub.conf | sed "s/$BAK_VER/$NEW_VER/g" | sed "s/$OLD_VER/$BAK_VER/g" > grub.conf.new
mv grub.conf.new grub.conf

### emerge packages that require recompilation
emerge $TO_EMERGE

### if it's a new base version, update modules.autoload
NEW_BASE_VER=`kernelversion`
if [ $OLD_BASE_VER -ne $NEW_BASE_VER ]
then
    cp /etc/modules.autoload.d/"$OLD_BASE_VER" /etc/modules.autoload.d/"$NEW_BASE_VER"
else
    echo "Old and new kernels have same base version."
fi

echo " ==== Completed Successfully! ==== "
echo "   Remember to check your modules "

exit