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linux question

Posted on 2014-02-09
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Last Modified: 2014-02-10
1. In linux where is the drivers are located? How do we normally install driver any devices?

2. what is the linux boot process? what is upstart?

3. how is sectory/cylinder/track works here.

Disk /dev/sda: 17.1 GB, 17179869184 bytes
255 heads, 63 sectors/track, 2088 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes


4.  what is GPT and where is used?

5.  for a given process how do i find the process tree in linux?

6.  in grub.conf , we have the following. what is kernel and initrd? why do we need initrd?

default=0
timeout=5
splashimage=(hd0,0)/grub/splash.xpm.gz
hiddenmenu
title CentOS (2.6.18-164.el5)
        root (hd0,0)
        kernel /vmlinuz-2.6.18-164.el5 ro root=/dev/VolGroup00/LogVol00
        initrd /initrd-2.6.18-164.el5.img

6.  what are process states and please explain.

7. how one can find the bottleneck of cpu contention, memory contention and disk I/O contention?


I really appreciate if you can help me to understand these questions.
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Question by:ittechlab
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Expert Comment

by:Kent Dyer
ID: 39846448
/lib/modules/`uname -r`/.

But is not just a simple matter of copying files there..  You do need to install drivers as the kernel needs to be aware they are there..
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by:
Seth Simmons earned 500 total points
ID: 39846450
1) some drivers are built into the kernel while most others can be specified manually to load

Howto: Linux Add or Remove a Linux Kernel Modules / Drivers
http://www.cyberciti.biz/faq/add-remove-list-linux-kernel-modules/

Loadable kernel module
http://en.wikipedia.org/wiki/Loadable_kernel_module

2) here is a detailed article about upstart; it's basically the newest way of handling system events (startup, shutdown, etc.) instead of init

Upstart
http://en.wikipedia.org/wiki/Upstart

3) cylinder/head/track/sector...it's how the physical disk itself is configured

http://en.wikipedia.org/wiki/Cylinder-head-sector

4) GPT is GUID Partition Table which is used primarily for hard drives larger than 2TB because that is the limit for the old MBR format; requires UEFI to boot Windows from a GPT drive

GUID Partition Table
http://en.wikipedia.org/wiki/GUID_Partition_Table

5) you could use either pstree or ps axf

6) the linux kernel (unix-like OS) is essentially what runs everything - manages applications, processes, hardware, etc.  initrd uses a small amount of physical memory during the boot process

Linux kernel
http://en.wikipedia.org/wiki/Linux_kernel

Understanding Linux initrd – initial RAM disk
http://www.cyberciti.biz/tips/understanding-linux-initrd-initial-ram-disk.html

initrd
http://en.wikipedia.org/wiki/Initrd

7) linux process states are what the process is doing - either running [R], sleeping [S], zombie [Z] (disconnected from parent process), uninterruptible sleep [D] (typically a process stuck in I/O wait such as stale NFS mount), or job stopped [T]

8) there are a few ways to determine bottlenecks.  for disk, you can use tools like sar or vmstat which will show various statistics.  top will show info also but not quite as detailed as others.  for example, if in vmstate the so and si columns are frequently non-zero values, this means there is a lot of swap usage and could point to a memory bottleneck.  the r column of vmstat is the cpu run queue.  if this number is higher than the number of processing cores, then you have cpu bottleneck
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Author Comment

by:ittechlab
ID: 39847058
"the r column of vmstat is the cpu run queue.  if this number is higher than the number of processing cores, then you have cpu bottleneck "

even though i have r is higher than number of cores i am not having cpu issue, how do you conclude this statement is true. Please justify me. thanks

[root@nagios ~]# vmstat
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 8  0      0 1386304 152940 403684    0    0     2    19  158   35  0  1 99  0  0

[root@nagios ~]# cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Xeon(R) CPU           E5345  @ 2.33GHz
stepping        : 1
cpu MHz         : 2327.524
cache size      : 4096 KB
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss syscall nx lm constant_tsc up nonstop_tsc pni cx16 lahf_lm
bogomips        : 4655.04
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management: [8]
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