Question { Oracle, 13753 }

what is jumbi process?

Answer

Zombie process or defunct process is a process that has
completed execution but still has an entry in the process
table. This entry is still being needed to allow the process
that started the zombie process to read its exit status.
Zombies can be identified in the output from the ps command
by the presence of a "Z" in the STAT column. Use kill -9 or
kill -15 to remove zombie process.

Zombie is not same as orphan process. An orphan process is a
process that is still executing, but whose parent has died.
They do not become zombie processes; instead, they are
adopted by init (process ID 1), which waits on its children.

Question { TCS, 15450 }

what is symbolic link in unix ???

Answer

Linux has two kinds of file system links: symbolic links and
hard links.

A symbolic link — also called a soft link or symlink —
resembles a Windows shortcut. A symlink is a little file
that contains the pathname of another object on the
filesystem: a file, a directory, a socket, and so on —
possibly even the pathname of another link. This pathname
can be absolute or relative. To make a symlink, use ln with
the -s option. Give the name of the target first, then the
name of the link.

# ln –s existing-file-name link-name

We can still edit the original file by opening the symbolic
link, and changes we make doing that will "stick." But if we
delete the symbolic link, it has no impact on the original
file at all. If we move or rename the original file, the
symbolic link is "broken," it continues to exist but it
points at nothing.

A hard link isn’t itself a file. Instead, it’s a directory
entry. It points to another file using the file’s inode
number. Means both have same inode number. Any changes to
the original file will get reflected in the link file also
as both are same.

# ln existing-file-name link-name

To give a file more than one name or to make the same file
appear in multiple directories, you can make links to that
file instead of copying it. One advantage of this is that a
link takes little or even no disk space. Another is that, if
you edit the target of the link, those changes can be seen
immediately through the link.

Question { 32969 }

what is user mode & kernel mode?

Answer

KERNEL-MODE

Kernel mode, also referred to as system mode, is one of the
two distinct modes of operation of the CPU in Linux. When
the CPU is in kernel mode, it is assumed to be executing
trusted software, and thus it can execute any instructions
and reference any memory addresses (i.e., locations in
memory). The kernel (which is the core of the operating
system and has complete control over everything that occurs
in the system) is trusted software, but all other programs
are considered untrusted software.

USER-MODE

User mode is the normal mode of operating for programs, web
browsers etc. They don't interact directly with the kernel,
instead, they just give instructions on what needs to be
done, and the kernel takes care of the rest. Kernel mode, on
the other hand, is where programs communicate directly with
the kernel. A good example of this would be device drivers.
A device driver must tell the kernel exactly how to interact
with a piece of hardware, so it must be run in kernel mode.
Because of this close interaction with the kernel, the
kernel is also a lot more vulnerable to programs running in
this mode, so it becomes highly crucial that drivers are
properly debugged before being released to the public.

Question { TCS, 17942 }

1.I want to change runlevel but the Users shall not be
disturbed?how?
2.Disk have 5gb disk utilization even though files unable to
create, why?
3.what are the internal and external command in linux?
4.sar command o/p?
5.how list the open files?
6.what is kernel compiling?
7.How do u See complete configuration in ur system?
8.how will u make a daily updates with cron daily?
9.which port is associated with ttys0?
10.specific some problems linux admin(if u are linux
admin)faced and how did u overcome it?

Answer

1) Same answer as above

2) Question not understood, may be ACLs

3) It is not BIOS,
A built-in (internal/resident) command is one that is
contained within the bash tool set and execute faster than
external commands.

An non-built-in (external/non-resident) command is a command
outside the shell and requires a $PATH (environment
variable) to find it.

4)Displays the activity for the CPU

# sar
Linux 2.6.18-6-686 (server.domain.local) 09/16/2008
11:31:56 AM LINUX RESTART

5) # lsof

6)The Linux kernel is a complex program which provides the
underlying services to the rest of a Linux distribution. But
it is easy to add new features or improvements to it,
requiring a kernel recompiling. There are three reasons for
a kernel compile. Firstly, you may have some hardware that
is so new that there's no kernel module for it in on your
distribution CD. Secondly, you may have come across some
kind of bug which is fixed in a revision of the operating
system. Lastly, you may have some new software which
requires a newer version of the operating system.

7)A vague question

8) Suppose we have a daily update script called dailyupdate.sh
Copy the script to /etc/cron.daily/

# cp dailyupdate.script /etc/cron.daily/

Make the file executable

# chmod +x /etc/cron.daily/dailyupdat.sh

9) COM1

10) Depends...

Question { TCS, 17942 }

1.I want to change runlevel but the Users shall not be
disturbed?how?
2.Disk have 5gb disk utilization even though files unable to
create, why?
3.what are the internal and external command in linux?
4.sar command o/p?
5.how list the open files?
6.what is kernel compiling?
7.How do u See complete configuration in ur system?
8.how will u make a daily updates with cron daily?
9.which port is associated with ttys0?
10.specific some problems linux admin(if u are linux
admin)faced and how did u overcome it?

Answer

4) Detailed sar output

Linux 2.6.18-6-686 (server.domain.local) 09/16/2008

11:31:56 AM LINUX RESTART

11:35:01 AM CPU %user %nice %system
%iowait %steal %idle
11:45:01 AM all 0.71 0.00 0.19
0.18 0.00 98.92
11:55:02 AM all 1.53 0.00 0.19
0.26 0.00 98.02
Average: all 1.12 0.00 0.19
0.22 0.00 98.47

Question { IBM, 6506 }

what is major and minor?

Answer

Major number
============
A number indicating which device driver should be used to
access a particular device. All devices controlled by the
same device driver have a common major device number.

Minor number
============
A number serving as a flag to a device driver.The minor
device numbers are used to distinguish between different
devices and their controllers.

Eg:

# ls -l /dev/sda1
brw-rw---- 1 root disk 8, 1 2008-09-04 08:28 /dev/sda1
rigel:~# ls -l /dev/sda2
brw-rw---- 1 root disk 8, 2 2008-09-04 08:28 /dev/sda2

You can see the major and minor device number (8,1) and
(8,2) in the ls listing for /dev/sdax

# ls -l /dev/scd0
brw-rw---- 1 root cdrom 11, 0 2008-09-04 08:28 /dev/scd0

You can see the major and minor device number (11,0)in the
ls listing for /dev/scd0

Question { IBM, 20534 }

what is soft mount and hard mount? i have to make permanent
nfs mount permanent what shall i do?

Answer

This is a UNIX terminology as to what the client does when
it can't talk to an NFS Server. If you just mount a file
system without specifying hard or soft, the default is a
hard mount. Hard mounts are preferable because of the
stateless nature of NFS. If a client sends an I/O request to
the server (such as an ls -la), and the server gets
rebooted, the client will wait until the server comes back
on line. This preserves data transfers in the event of a
server failure. There are disadvantages to this, as a simple
mount request could hang. A soft link will return with an
error and fail. This kills the wait time, but can cause
problems with data transfers.

To make permanent nfs mount, the above answer is right

Question { 6169 }

what is a superblock ?

Answer

A superblock is a record of the characteristics of a
filesystem, including its size, the block size, the empty
and the filled blocks and their respective counts, the size
and location of the inode tables, the disk block map and
usage information, and the size of the block groups.

Question { Logica CMG, 6039 }

how many limitations of under directories in ext2/3 linux
file system?

Answer

Ext2 Limits
============
Max file size: 2-64 TiB
Max number of files: 10 raised 18
Max filename length: 255 characters
Max volume size: 16-32 TiB
Allowed characters in filenames: Any byte except NULL and '/'

Ext3 Limits
===========
Max file size: 2 TiB
Max number of files: Variable, allocated at creation time[1]
Max filename length: 255 bytes
Max volume size: 2 TiB – 16 TiB
Allowed characters in filenames: All bytes except NULL

Question { Yahoo, 9147 }

Which priority has the process?how do u view?

Answer

Each process has a niceness value associated with it, which
is what the kernel uses to determine which processes require
more processor time than others. The higher the nice value,
the lower the priority of the process. In other words, the
“nicer” the program, the less CPU it will try to take from
other processes; programs that are less nice tend to demand
more CPU time than other programs that are nicer.
The priority is noted by a range of -20 (the highest) to 20
(the lowest). Using ps, you can see the current nice value
of all programs:
# ps axl

F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY
TIME COMMAND
4 0 1 0 16 0 2648 112 - S ?
0:01 init [3]
1 0 2 1 34 19 0 0 ksofti SN ?
0:02 [ksoftirqd/0]
5 0 3 1 10 -5 0 0 worker S< ?
0:00 [events/0]
You can see that init has a nice value of 0, while other
kernel tasks associated with PID 2 and 3 have a nice value
of 19 and -5 respectively.
Typically, a program inherits its nice value from its
parent; this prevents low priority processes from spawning
high priority children.

Question { HP, 9393 }

when zombie process fully cleared?

Answer

Do a ps and identify the zombie processes

# ps -el | grep 'Z'


Occasionally, these processes are in such a state that the
only way to get rid of them is to reboot to clear them.

In most cases, you can get rid of a zombie by normal means,
"kill -15 zombie PPID", "kill -9 zombie PPID".

Question { Satyam, 6120 }

How do display error messages instantly when command fails?

Answer

Suppose you are trying to cat a non existing file:

cat /etc/shado 2>/dev/null || echo “Failed to open file”

command 2 "echo" is executed only if command 1 "cat" returns
a non-zero exit status

# cat /etc/shado 2>/dev/null || echo "Failed to open file"
Failed to open file
#

Question { Wipro, 6689 }

how do you port scaning with netcat command?

Answer

nc -z

Is This Answer Correct ?

13 Yes

2 No

Question { Linux, 7876 }

who are the author of LINUX operation system?

Answer

Linus Torvalds ...in the above answer "s" is missing

Question { TCS, 17390 }

Write a command to find all of the files which have been
accessed within the last 30 days.

Answer

find / -type f -atime -30 = accessed
find / -type f -ctime -30 = changed
find / -type f -ctime -30 = modified