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Old 07-10-2011, 01:14 PM   #1
shariefbe
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Need basics of booting process


Dear friends,

I want to know the basics linux booting process. I googled for this but i didn't find the detailed things anywhere. I want to know the boot process including the hardware work flow. Can anyone give me the detailed tutorial to learn about this.

Thank you
 
Old 07-10-2011, 01:18 PM   #2
TobiSGD
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This may be what you are looking for.
 
Old 07-10-2011, 01:25 PM   #3
Wim Sturkenboom
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Dou you nwant the basics or the details

http://www.thegeekstuff.com/2011/02/linux-boot-process/ gives the basics

What do you mean by hardware workflow?
 
Old 07-10-2011, 01:44 PM   #4
shariefbe
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Thanks for your reply..

I mean whether all the hardwares will get active simultaneously or it will get active one by one while this boot process is going on.....
 
Old 07-10-2011, 02:37 PM   #5
tredegar
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The answer is "it depends". On your distro, and what it chooses, and how you choose.

There are:
- Traditional SysV init scripts

And competing alternatives, some of which are:
- Ubuntu's "Upstart"
- Systemd

... and probably others too.

I (personally) think that systemd is the way to go.

They all (mostly) work. Some are faster, some more resilient and robust.

There is no "right answer".

I suggest you experiment with them all and then choose whatever works best for you.
 
Old 07-10-2011, 02:55 PM   #6
PTrenholme
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What do you mean by the "hardware work flow?"

The boot process is, in outline, quite simple: A read-only, minimal, RAM-resident, Linux system is loaded for the kernel you're using. That system unpacks an "Inital RAM file system" (usually from a CPIO image file) that starts the system initialization script found in the CPIO archive. I suspect that the "work flow" you're interested is the stuff in that script, but it could be the modules loaded with the kernel.

If your system uses a zipped initrd CPIO archive with .img in it's name, here's a script you could use to "unpack" the archive.
Code:
$ cat Scripts/InitRD/DecompressInitRD 
#!/bin/bash
############################################################################################
#
# Decompress initial ram disk image files
#
# Arguments: [ directory [ output ]]
#
# Where directory is the location of the InitRD files (default: /boot)
# and   output    is the sub-directory of "directory" where
#                 the unpacked files should be stored.
#
# Note: Each image file will be unpacked into a sub-directory of "output" named with
#       the name of the image file being unpacked.
#
###########################################################################################
#
# Make sure we're running as root
if [ $(id -u) -ne 0 ]
then
  echo "FATAL: This program requires root access. Aborting." >2
  exit 1
fi
# Set the defaults
boot="/boot"            # Boot directory
dir="Initial_RAM_Disk"  # Subdirectory of $boot into which the scripts should be decompresed
# Are there any arguments?
if [ $# -gt 0 ]
then
  if [ -d "${1}" ]
  then
    boot="${1}"
  else
    echo \"$1\" is not a valid directory name.
    exit 1
  fi                                                                                           
fi                                                                                             
if [ x"$(pwd)" != x"$boot" ]
then
  echo cd ${boot}
  cd ${boot}
fi
# Is an output directory specified?
if [ $# -gt 1 ]
then
  if [ -d "${2}" ]
  then
    dir="${2}"
  else
    echo \"$2\" is not a valid directory name.
    exit 1
  fi
fi
# Create the output directory if it doesn't exist
[ -d "${dir}" ] || sudo mkdir "${dir}"
# Go to the output directory
cd "${dir}"
# Get the InitRD image file to be used
echo Enter the number corresponding to the image file you want expanded
select img in $(ls -1 ../*.img*) quit
do
  if [ ${img} == "quit" ]
  then
     break
  else
    out=$(basename ${img})
echo "out="${out}
echo "img="${img}
    mkdir -p "${out}"
    cd "${out}"
    gunzip -c "../${img}" | sudo cpio -idmv
    cd ../
  fi
done
 
  


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