Linux interview questions

-------------------------------
* How to check all open ports on linux machine and block unsed ports?
netstat -t
#nmap -v localhost for tcp
#nmap -sU localhost for udp

#netstat -tulp
or
#netstat -tulpn

to verfy the open ports
-------------------------------
* how u use the iptable firewall to restrict ssh,telnet,ftp
For SSH
iptables -A INPUT -s -p tcp --dport <22> -j
REJECT/DROP/DENY

For Telnet
iptables -A INPUT -s -p tcp --dport <23> -j
REJECT/DROP/DENY

For FTP
iptables -A INPUT -s -p tcp --dport <21> -j
REJECT/DROP/DENY

-------------------------------------

* what is the difference between unix and linux

graphics is the main difference
extra more command are in linux
userfriendly then unix

the unix is the platform dependent the linux is platform
independent. we cann't install unix in all machine we
recquired a special machine to install unix, but linux is
not like that it support all machines

filesystem are different
there diff lies in kernel
linux is under gpl and unix proprietary

Difference Between Linux and Unix
1)Linux default shell is /bin/bash, where Unix default shell
is /bin/sh (other shell also supported)
2) Linux Store all their command history,but if the default
shell is /bin/sh in Unix, then Unix not store Command history.
3) Linux support Tab key, but unix not support Tab key
-------------------------------------

Who owns the data dictionary?

The Oracle user SYS owns all base tables and user-
accessible views of the data dictionary. Therefore, no
Oracle user should ever alter (update, delete, or insert)
any rows or schema objects contained in the SYS schema,
because such activity can compromise data integrity. The
security administrator should keep strict control of this
central account.

-------------------------------------
which file contains information about os wether it's 32
bit or 64 bit?

ANS: /proc/cpuinfo
or
$uname -m
or
/usr/bin/file
--------------------------------
what contains information about file and directory creating time or modification time?

An inode is a data structure on a Unix / Linux file system.
An inode stores basic information about a regular file,
directory, or other file system object. You can use
following two commands to display an inode:

[a] ls command : list directory contents

-----------------------------------
What are RPM?s, what do they offer?

The full form of RPM is Redhat Package Manager.
rpm is a powerful Package Manager, which can be used
to build,install, query, verify, update, and erase
individual software packages. A package consists of an
archive of files and meta-data used to install and erase the
archive files.

[b] stat command : display file or file system status

eg : # stat /etc/passwd
Output:
File: `/etc/group'
Size: 566 Blocks: 16 IO Block: 4096
regular file
Device: fd00h/64768d Inode: 2443679 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: (
0/ root)
Access: 2009-08-12 08:23:31.245032672 +0530
Modify: 2002-01-01 05:54:15.000000000 +0530
Change: 2002-01-01 05:54:15.000000000 +0530
--------------------------------------------------
*how to confirm from client end about nfs server sharing?

with mount and showmount -e server IP

-------------------------------------------------
How do i check which nfs version I am using ?

rpcinfo -p localhost | grep -i nfs

This cmd is used for nfs version
rpm -qa | grep nfs
rpm -qi nfs nfs-utils
yum info nfs nfs-utils

------------------------------------------------
Through ssh whole directory structure from / is shared regardless the user we have connected with ....... how do i prevent sharing ??

vi /etc/ssh/sshd_config
"in last line enter the folowing entry"
AllowUsers "username"

And

vi /etc/hosts.deny
"in last line enter the folowing entry"
sshd: ALL EXCEPT "DOMAIN-NAME"

its benefitial to use setfacl command for secure your
stuff..
-------------------------------------------------------
* what restrict telnet for root itself but allow for other user

Root can login through telnet session, but by default it is
disabled. You can enable by appending /etc/securetty file
open /etc/securetty using vi

#vi /etc/securetty

pts/0
pts/1

don't remove anything from this /etc/securetty , just
append your entry

vi /etc/pam.d/login

auth required pam_securetty.so== 1st line
should be placed as required.if we change the option as
sufficient instead of required telnet can login as "root".
-----------------------------------------------------------
How to send automated email to a set of people at fixed time ?

1)just create a alias of people and create a command file and
create a crond entry
2)configure sendmail & postfix to configure procmail..
Or configure Q-mail / Squirrel mail & use contab
----------------------------------------------------
how do i check which package has installed some command
suppose ls , mkdir or whatever ???

rpm -qa | grep "pakage name"

rpm -qa | grep
yum install it will show already installed
or not if not then it will install
Pirut same as yum
rpm -qa /usr/bin/ls
gives you from which rpm the "ls" command is installed.

-----------------------------------------------------

What is the difference between Telnet and SSH?

ssh is a secured shell, where telnet is not a secured
one.when you ssh to trasnfer data between a system, the data
will be send in the encrypted form, where the hacker cannot
encode or decode it. While you telnet,the data send between
the system is alphabetical format(ASCII), where every one
can understand. More over as per network security, telnet
and ftp are prohibited. Always, trust SSL based data transfer.

Telnet ->
Its just getting (Telenet) a connection to the server.
Its not more secure. Anybody can use it.
It can be easly hacked.It can be easily read by anybody in
that network

SSH -> secured shocket shell
Its more secure than Telnet .
This has an encrption and decrption of the data /usr/pwd
None can hack this. It is the good way to transfer the data

---------------------------------------------------
What is the difference between home directory and working directory?

home directory is one over which user have complete control
and it is its default working directory when its logs in.
while the working directory is the users current directory
which may or may not be his home directory.
------------------------------------------
How can you see all mounted drives?

with df -hT command and
with the mount command.
#vi /etc/fstab contains perminant mounts
---------------------------------------------

When you install RedHat what is the kernel mode ? What is kernel compilation / upgrade ?

Kernel mode, also referred to as system mode, is one of the
two distinct modes of operation of the CPU in Linux. The
other is user mode, a non-privileged mode for user programs,
that is, for everything other than the kernel.
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. The kernel
is trusted software, but all other programs are considered
untrusted software. Thus, all user mode software must
request use of the kernel by means of a system call in order
to perform privileged instructions, such as process creation
or input/output.

Kernel compilation is installing a new kernel or adding
custom modules to the same kernel.
Kernel upgradation is upgrading it to a different version
altogether.
------------------------------
what is the difference between fork and thread ? and parent and child process in fork system call?
fork() system call in UNIX causes creation of a new process
the new process (child process) which is an exact copy of
the calling process(parent process).return value from fork
() is used to distinguish the parent from the child; the
parent receives the child's process id, but the child
receives zero.

A thread is a stream of instructions that can be scheduled
as an independent unit.

A thread is a stream of instructions that can be scheduled
as an independent unit. It is important to understand the
difference between a thread and a process. A process
contains two kinds of information: resources that are
available to the entire process such as program
instructions, global data and working directory, and
schedulable entities, which include program counters and
stacks. A thread is an entity within a process that
consists of the schedulable part of the process.

A fork() duplicates all the threads of a process. The
problem with this is that fork() in a process where threads
work with external resources may corrupt those resources
(e.g., writing duplicate records to a file) because neither
thread may know that the fork() has occurred.

When a new perl thread is created, all the data associated
with the current thread is copied to the new thread, and is
subsequently private to that new thread! This is similar in
feel to what happens when a UNIX process forks, except that
in this case, the data is just copied to a different part
of memory within the same process rather than a real fork
taking place.

A fork() induces a parent-child relationship between two
processes. Thread creation induces a peer relationship
between all the threads of a process.
--------------------------------------------------------
You want to create a compressed backup of the users' home directories. What utility should you use?

Tar -czf kk.tar.gz /home/username
If we want to extract
the the command is tar -xzf kk.tar.gz
--------------------------------------------------------
What is the difference between an argument and an option/switch?

A linux/unix syntax format is as follows

command option arguement

example: ls -a /boot
here ls command, -a is option,/boot is arguement

option specifies the command how to run
arguement specifies the command on what to run
---------------------------------------------------------
How does the boot process[init levels] work on Linux? How is it different from Solaris?

When an x86 computer is booted, the processor looks at the
end of the system memory for the BIOS (Basic Input/Output
System) and runs it. The BIOS program is written into
permanent read-only memory and is always available for use.
The BIOS provides the lowest level interface to peripheral
devices and controls the first step of the boot process.

The BIOS tests the system, looks for and checks peripherals,
and then looks for a drive to use to boot the system.
Usually it checks the floppy drive (or CD-ROM drive on many
newer systems) for bootable media, if present, and then it
looks to the hard drive. The order of the drives used for
booting is usually controlled by a particular BIOS setting
on the system. Once Linux is installed on the hard drive of
a system, the BIOS looks for a Master Boot Record (MBR)
starting at the first sector on the first hard drive, loads
its contents into memory, then passes control to it.

This MBR contains instructions on how to load the GRUB (or
LILO) boot-loader, using a pre-selected operating system.
The MBR then loads the boot-loader, which takes over the
process (if the boot-loader is installed in the MBR). In the
default Red Hat Linux configuration, GRUB uses the settings
in the MBR to display boot options in a menu. Once GRUB has
received the correct instructions for the operating system
to start, either from its command line or configuration
file, it finds the necessary boot file and hands off control
of the machine to that operating system.

1. The system BIOS checks the system and launches the first
stage boot loader on the MBR of the primary hard disk.

2. The Frist stage boot loader loads itself into memory and
launches the second stage boot loader from the /boot/
partition.

3. The second stage boot loader loads the kernel into
memory, which in turn loads any necessary modules and
mounts the root
partition read-only.

4. The kernel transfers control of the boot process to the /
sbin/init program.

5. The /sbin/init program loads all services and user-space
tools, and mounts all partitions
listed in /etc/fstab.

6. The user is presented with a login screen for the
freshly booted Linux system.
-------------------------------------------------------------
What are the main differences between RHEL4 & RHEL5?

XEN, YUM and improved SELinux
all the features updated with better options
Better GUI support then RHEL4
YUM over RPM package management
IPTables and SELinux for more secure environment
ext2 & ext3 file system
In RHEL 4 SELinux Block only 13 services, But on RHEL 5
SElinux Block 80 services
-------------------------------------------------------
What text filter can you use to display a binary file in octal numbers?

hexdump file1 > file2
--------------------------------------------------------
tell me some of the Linux HotKeys do you know?

alt+f1 for application menu
ctl+l to clear screen
alt+f2 to open run application window
alt+f3 for find
alt+f4 to close application
alt+f9 to minimise window
Ctrl-Alt-D Show desktop
Crtl-Alt-Backspace Restart XWindows
-------------------------------------------------

What file should you examine to determine the defined runlevels for your system?

/etc/inittab

id:X:initdefault

where X=runlevel (ex.0 to 6)
0 =system poweroff
1 = single user mode
2 = multiuser mode without network and X window
3 = multiuser mode with network without X window
4 = unused
5 = X11 (multiuser mode with network and X window
6 = reboot
--------------------------------------
What is the name and path of the main system log?

/var/log/messages system log messages can be seen here
/var/log/dmesg Kernel boot log messages can view

There are Three centralized loggin demons
1)syslogd
2)klogd
3)auditd

klogd:- collect log file created by the Kernel
syslogd:- Collect log file created by the system
auditd:- Collect log file created by the SELinux

After collecting the log system store logs on different location
/var/log/dmesg:- Created at boot time, by kernel
/var/log/messages:- standard system error message,
/var/log/secure:- authentication related log
/var/log/maillog:- Mail related log
/var/log/audit/audit.log:-Selinux related log

We can redirect the log by configuring
/etc/sysconfig/syslog
/etc/syslog.conf

-------------------------------------------------
what is the difference between semaphore, mutex & spinlock?

Kernel Locking Techniques
Semaphores in Linux are sleeping locks. Because they cause a
task to sleep on contention, instead of spin, they are used
in situations where the lock-held time may be long.
Conversely, since they have the overhead of putting a task
to sleep and subsequently waking it up, they should not be
used where the lock-held time is short. Since they sleep,
however, they can be used to synchronize user contexts
whereas spinlocks cannot. In other words, it is safe to
block while holding a semaphore.

A "mutex" (or "mutual exclusion lock") is a signal that two
or more asynchronous processes can use to reserve a shared
resource for exclusive use. The first process that obtains
ownership of the "mutex" also obtains ownership of the
shared resource. Other processes must wait for for the first
process to release it's ownership of the "mutex" before they
may attempt to obtain it.

The most common locking primitive in the kernel is the
spinlock. The spinlock is a very simple single-holder lock.
If a process attempts to acquire a spinlock and it is
unavailable, the process will keep trying (spinning) until
it can acquire the lock. This simplicity creates a small and
fast lock.
---------------------------------------------------
What are seven fields in the /etc/passwd file.

1. Username: It is used when user logs in. It should be between 1 and 32 characters in length.
2. Password: An x character indicates that encrypted password is stored in /etc/shadow file.
3. User ID (UID): Each user must be assigned a user ID (UID). UID 0 (zero) is reserved for root and UIDs 1-99 are reserved for other predefined accounts. Further UID 100-999 are reserved by system for administrative and system accounts/groups.
4. Group ID (GID): The primary group ID (stored in /etc/group file)
5. User ID Info: The comment field. It allow you to add extra information about the users such as user's full name, phone number etc. This field use by finger command.
6. Home directory: The absolute path to the directory the user will be in when they log in. If this directory does not exists then users directory becomes /
7. Command/shell: The absolute path of a command or shell (/bin/bash). Typically, this is a shell. Please note that it does not have to be a shell.

------------------------------------------------------

1. Q. How do you list files in a directory?
A. ls - list directory contents
ls -l (-l use a long listing format)

2. Q. How do you list all files in a directory, including the hidden files?
A. ls -a (-a, do not hide entries starting with .)

3. Q. How do you find out all processes that are currently running?
A. ps -f (-f does full-format listing.)

4. Q. How do you find out the processes that are currently running or a particular user?
A. ps -au Myname (-u by effective user ID (supports names)) (a - all users)

5. Q. How do you kill a process?
A. kill -9 8 (process_id 8) or kill -9 %7 (job number 7)
kill -9 -1 (Kill all processes you can kill.)
killall - kill processes by name most (useful - killall java)


6. Q. What would you use to view contents of the file?
A. less filename
cat filename
pg filename
pr filename
more filename
most useful is command: tail file_name - you can see the end of the log file.

7. Q. What would you use to edit contents of the file?
A. vi screen editor or jedit, nedit or ex line editor

8. Q. What would you use to view contents of a large error log file?
A. tail -10 file_name ( last 10 rows)

9. Q. How do you log in to a remote Unix box?
A. Using telnet server_name or ssh -l ( ssh - OpenSSH SSH client (remote login program))

10.Q. How do you get help on a UNIX terminal?
A. man command_name
info command_name (more information)

11.Q. How do you list contents of a directory including all of its
subdirectories, providing full details and sorted by modification time?
A. ls -lac
-a all entries
-c by time

12.Q. How do you create a symbolic link to a file (give some reasons of doing so)?
A. ln /../file1 Link_name
Links create pointers to the actual files, without duplicating the contents of
the files. That is, a link is a way of providing another name to the same file.
There are two types of links to a file:Hard link, Symbolic (or soft) link;

13.Q. What is a filesystem?
A. Sum of all directories called file system.
A file system is the primary means of file storage in UNIX.
File systems are made of inodes and superblocks.

14.Q. How do you get its usage (a filesystem)?
A. By storing and manipulate files.

15.Q. How do you check the sizes of all users home directories (one command)?
A. du -s
df

The du command summarizes disk usage by directory. It recurses through all subdirectories and shows disk usage by each subdirectory with a final total at the end.





More interview questions click here



 # Mary has recently gotten married and wants to change her username from mstone to mknight. Which of the following commands should you run to accomplish this? Choose one: a. usermod -l mknight mstone b. usermod -l mstone mknight c. usermod -u mknight mstone d. usermod -u mstone mknight
# After bob leaves the company you issue the command userdel bob. Although his entry in the /etc/passwd file has been deleted, his home directory is still there. What command could you have used to make sure that his home directory was also deleted? Choose one: a. userdel -m bob b. userdel -u bob c. userdel -l bob d. userdel -r bob

# All groups are defined in the /etc/group file. Each entry contains four fields in the following order. Choose one: a. groupname, password, GID, member list b. GID, groupname, password, member list c. groupname, GID, password, member list d. GID, member list, groupname, password
# You need to create a new group called sales with Bob, Mary and Joe as members. Which of the following would accomplish this? Choose one: a. Add the following line to the /etc/group file: sales:44:bob,mary,joe b. Issue the command groupadd sales. c. Issue the command groupadd -a sales bob,mary,joe d. Add the following line to the /etc/group file: sales::44:bob,mary,joe
# What command is used to remove the password assigned to a group?
# You changed the GID of the sales group by editing the /etc/group file. All of the members can change to the group without any problem except for Joe. He cannot even login to the system. What is the problem? Choose one: a. Joe forgot the password for the group. b. You need to add Joe to the group again. c. Joe had the original GID specified as his default group in the /etc/passwd file. d. You need to delete Joe’s account and recreate it.
# You need to delete the group dataproject. Which two of the following tasks should you do first before deleting the group? A. Check the /etc/passwd file to make sure no one has this group as his default group. B. Change the members of the dataproject group to another group besides users. C. Make sure that the members listed in the /etc/group file are given new login names. D. Verify that no file or directory has this group listed as its owner. Choose one: a. A and C b. A and D c. B and C d. B and D
# When you look at the /etc/group file you see the group kmem listed. Since it does not own any files and no one is using it as a default group, can you delete this group?
# When looking at the /etc/passwd file, you notice that all the password fields contain ‘x’. What does this mean? Choose one: a. That the password is encrypted. b. That you are using shadow passwords. c. That all passwords are blank. d. That all passwords have expired.
# In order to improve your system’s security you decide to implement shadow passwords. What command should you use?
# What file contains the default environment variables when using the bash shell? Choose one: a. ~/.profile b. /bash c. /etc/profile d. ~/bash
# You have created a subdirectory of your home directory containing your scripts. Since you use the bash shell, what file would you edit to put this directory on your path? Choose one: a. ~/.profile b. /etc/profile c. /etc/bash d. ~/.bash
# Which of the following interprets your actions when typing at the command line for the operating system? Choose One a. Utility b. Application c. Shell d. Command
# What can you type at a command line to determine which shell you are using?
# You want to enter a series of commands from the command-line. What would be the quickest way to do this? Choose One a. Press enter after entering each command and its arguments b. Put them in a script and execute the script c. Separate each command with a semi-colon (;) and press enter after the last command d. Separate each command with a / and press enter after the last command
# You are entering a long, complex command line and you reach the right side of your screen before you have finished typing. You want to finish typing the necessary commands but have the display wrap around to the left. Which of the following key combinations would achieve this? Choose One a. Esc, /, Enter b. /, Enter c. ctrl-d, enter d. esc, /, ctrl-d
# After typing in a new command and pressing enter, you receive an error message indicating incorrect syntax. This error message originated from.. Choose one a. The shell b. The operating system c. The command d. The kernel
# When typing at the command line, the default editor is the _____________ library.
# You typed the following at the command line ls -al /home/ hadden. What key strokes would you enter to remove the space between the ‘/’ and ‘hadden’ without having to retype the entire line? Choose one a. Ctrl-B, Del b. Esc-b, Del c. Esc-Del, Del d. Ctrl-b, Del
# You would like to temporarily change your command line editor to be vi. What command should you type to change it?
# After experimenting with vi as your command line editor, you decide that you want to have vi your default editor every time you log in. What would be the appropriate way to do this? Choose one a. Change the /etc/inputrc file b. Change the /etc/profile file c. Change the ~/.inputrc file d. Change the ~/.profile file
# You have to type your name and title frequently throughout the day and would like to decrease the number of key strokes you use to type this. Which one of your configuration files would you edit to bind this information to one of the function keys?
# In your present working directory, you have the files maryletter memo1 MyTelephoneandAddressBook What is the fewest number of keys you can type to open the file MyTelephoneandAddressBook with vi? Choose one a. 6 b. 28 c. 25 d. 4
# A variable that you can name and assign a value to is called a _____________ variable.
# You have installed a new application but when you type in the command to start it you get the error message Command not found. What do you need to do to fix this problem? Choose one a. Add the directory containing the application to your path b. Specify the directory’s name whenever you run the application c. Verify that the execute permission has been applied to the command. d. Give everyone read, write and execute permission to the application’s directory.
# You telnet into several of your servers simultaneously. During the day, you sometimes get confused as to which telnet session is connected to which server. Which of the following commands in your .profile file would make it obvious to which server you are attached? Choose one a. PS1=’\h: \w>’ b. PS1=’\s: \W>’ c. PS1=’\!: \t>’ d. PS1=’\a: \n>’
# Which of the following environment variables determines your working directory at the completion of a successful login? Choose one a. HOME b. BASH_ENV c. PWD d. BLENDERDIR
# Every time you attempt to delete a file using the rm utility, the operating system prompts you for confirmation. You know that this is not the customary behavior for the rm command. What is wrong? Choose one a. rm has been aliased as rm -i b. The version of rm installed on your system is incorrect. c. This is the normal behavior of the newest version of rm. d. There is an incorrect link on your system.
# You are running out of space in your home directory. While looking for files to delete or compress you find a large file called .bash_history and delete it. A few days later, it is back and as large as before. What do you need to do to ensure that its size is smaller? Choose one a. Set the HISTFILESIZE variable to a smaller number. b. Set the HISTSIZE to a smaller number. c. Set the NOHISTFILE variable to true. d. Set the HISTAPPEND variable to true.
# In order to display the last five commands you have entered using the history command, you would type ___________.
# In order to display the last five commands you have entered using the fc command, you would type ___________.
# You previously ran the find command to locate a particular file. You want to run that command again. What would be the quickest way to do this? Choose one a. fc -l find fc n b. history -l find history n c. Retype the command d. fc -n find
# Using command substitution, how would you display the value of the present working directory? Choose one a. echo $(pwd) b. echo pwd c. $pwd d. pwd | echo
# You need to search the entire directory structure to locate a specific file. How could you do this and still be able to run other commands while the find command is still searching for your file? Choose one a. find / -name filename & b. find / -name filename c. bg find / -name filename d. &find / -name filename &
# In order to create a file called DirContents containing the contents of the /etc directory you would type ____________.
# What would be displayed as the result of issuing the command ps ef? Choose one a. A listing of the user’s running processes formatted as a tree. b. A listing of the stopped processes c. A listing of all the running processes formatted as a tree. d. A listing of all system processes formatted as a tree.
# What utility can you use to show a dynamic listing of running processes? __________
# The top utility can be used to change the priority of a running process? Another utility that can also be used to change priority is ___________?
# What key combination can you press to suspend a running job and place it in the background?
# You issue the command jobs and receive the following output: [1]- Stopped (tty output) pine [2]+ Stopped (tty output) MyScript How would you bring the MyScript process to the foreground? Choose one: a. fg %2 b. ctrl-c c. fg MyScript d. ctrl-z
# You enter the command cat MyFile | sort > DirList & and the operating system displays [4] 3499 What does this mean? Choose one a. This is job number 4 and the PID of the sort command is 3499. b. This is job number 4 and the PID of the job is 3499. c. This is job number 3499 and the PID of the cat command is 4. d. This is job number 4 and the PID of the cat command is 3499.
# You attempt to log out but receive an error message that you cannot. When you issue the jobs command, you see a process that is running in the background. How can you fix this so that you can logout? Choose one a. Issue the kill command with the PID of each running command of the pipeline as an argument. b. Issue the kill command with the job number as an argument. c. Issue the kill command with the PID of the last command as an argument. d. Issue the kill command without any arguments.
# You have been given the job of administering a new server. It houses a database used by the sales people. This information is changed frequently and is not duplicated anywhere else. What should you do to ensure that this information is not lost? Choose one a. Create a backup strategy that includes backing up this information at least daily. b. Prepare a proposal to purchase a backup server c. Recommend that the server be made part of a cluster. d. Install an additional hard drive in the server.
# When planning your backup strategy you need to consider how often you will perform a backup, how much time the backup takes and what media you will use. What other factor must you consider when planning your backup strategy? _________
# Many factors are taken into account when planning a backup strategy. The one most important one is how often does the file ____________.
# Which one of the following factors does not play a role in choosing the type of backup media to use? Choose one: a. How frequently a file changes b. How long you need to retain the backup c. How much data needs to be backed up d. How frequently the backed up data needs to be accessed
# When you only back up one partition, this is called a ______ backup. Choose one a. Differential b. Full c. Partial d. Copy
# When you back up only the files that have changed since the last backup, this is called a ______ backup. Choose one a. Partial b. Differential c. Full d. Copy
# The easiest, most basic form of backing up a file is to _____ it to another location.
# When is the most important time to restore a file from your backup? Choose one a. On a regular scheduled basis to verify that the data is available. b. When the system crashes. c. When a user inadvertently loses a file. d. When your boss asks to see how restoring a file works.
# As a system administrator
, you are instructed to backup all the users’ home directories. Which of the following commands would accomplish this? Choose one a. tar rf usersbkup home/* b. tar cf usersbkup home/* c. tar cbf usersbkup home/* d. tar rvf usersbkup home/*
# What is wrong with the following command? tar cvfb / /dev/tape 20 Choose one a. You cannot use the c option with the b option. b. The correct line should be tar -cvfb / /dev/tape20. c. The arguments are not in the same order as the corresponding modifiers. d. The files to be backed up have not been specified.
# You need to view the contents of the tarfile called MyBackup.tar. What command would you use? __________
# After creating a backup of the users’ home directories called backup.cpio you are asked to restore a file called memo.ben. What command should you type?
# You want to create a compressed backup of the users’ home directories so you issue the command gzip /home/* backup.gz but it fails. The reason that it failed is that gzip will only compress one _______ at a time.
# You want to create a compressed backup of the users’ home directories. What utility should you use?
# You routinely compress old log files. You now need to examine a log from two months ago. In order to view its contents without first having to decompress it, use the _________ utility.
# Which two utilities can you use to set up a job to run at a specified time? Choose one: a. at and crond b. atrun and crontab c. at and crontab d. atd and crond
# You have written a script called usrs to parse the passwd file and create a list of usernames. You want to have this run at 5 am tomorrow so you can see the results when you get to work. Which of the following commands will work? Choose one: a. at 5:00 wed usrs b. at 5:00 wed -b usrs c. at 5:00 wed -l usrs d. at 5:00 wed -d usrs
# Several of your users have been scheduling large at jobs to run during peak load times. How can you prevent anyone from scheduling an at job? Choose one: a. delete the file /etc/at.deny b. create an empty file called /etc/at.deny c. create two empty files: /etc/at.deny and /etc/at.allow file d. create an empty file called /etc/at.allow
# How can you determine who has scheduled at jobs? Choose one: a. at -l b. at -q c. at -d d. atwho
# When defining a cronjob, there are five fields used to specify when the job will run. What are these fields and what is the correct order? Choose one: a. minute, hour, day of week, day of month, month b. minute, hour, month, day of month, day of week c. minute, hour, day of month, month, day of week d. hour, minute, day of month, month, day of week
# You have entered the following cronjob. When will it run? 15 * * * 1,3,5 myscript Choose one: a. at 15 minutes after every hour on the 1st, 3rd and 5th of each month. b. at 1:15 am, 3:15 am, and 5:15 am every day c. at 3:00 pm on the 1st, 3rd, and 5th of each month d. at 15 minutes after every hour every Monday, Wednesday, and Friday
# As the system administrator you need to review Bob’s cronjobs. What command would you use? Choose one: a. crontab -lu bob b. crontab -u bob c. crontab -l d. cronq -lu bob
# In order to schedule a cronjob, the first task is to create a text file containing the jobs to be run along with the time they are to run. Which of the following commands will run the script MyScript every day at 11:45 pm? Choose one: a. * 23 45 * * MyScript b. 23 45 * * * MyScript c. 45 23 * * * MyScript d. * * * 23 45 MyScript
# Which daemon must be running in order to have any scheduled jobs run as scheduled? Choose one: a. crond b. atd c. atrun d. crontab
# You want to ensure that your system is not overloaded with users running multiple scheduled jobs. A policy has been established that only the system administrators can create any scheduled jobs. It is your job to implement this policy. How are you going to do this? Choose one: a. create an empty file called /etc/cron.deny b. create a file called /etc/cron.allow which contains the names of those allowed to schedule jobs. c. create a file called /etc/cron.deny containing all regular usernames. d. create two empty files called /etc/cron.allow and /etc/cron.deny
# You notice that your server load is exceptionally high during the hours of 10 am to 2 noon. When investigating the cause, you suspect that it may be a cron job scheduled by one of your users. What command can you use to determine if your suspicions are correct? Choose one: a. crontab -u b. crond -u c. crontab -l d. crond -l
# One of your users, Bob, has created a script to reindex his database. Now he has it scheduled to run every day at 10:30 am. What command should you use to delete this job. Choose one: a. crontab -ru bob b. crontab -u bob c. crontab -du bob d. crontab -lu bob
# What daemon is responsible for tracking events on your system?
# What is the name and path of the default configuration file used by the syslogd daemon?
# You have made changes to the /etc/syslog.conf file. Which of the following commands will cause these changes to be implemented without having to reboot your computer? Choose one: a. kill SIGHINT `cat /var/run/syslogd.pid` b. kill SIGHUP `cat /var/run/syslogd.pid` c. kill SIGHUP syslogd d. kill SIGHINT syslogd
# Which of the following lines in your /etc/syslog.conf file will cause all critical messages to be logged to the file /var/log/critmessages? Choose one: a. *.=crit /var/log/critmessages b. *crit /var/log/critmessages c. *=crit /var/log/critmessages d. *.crit /var/log/critmessages
# You wish to have all mail messages except those of type info to the /var/log/mailmessages file. Which of the following lines in your /etc/syslogd.conf file would accomplish this? Choose one: a. mail.*;mail!=info /var/log/mailmessages b. mail.*;mail.=info /var/log/mailmessages c. mail.*;mail.info /var/log/mailmessages d. mail.*;mail.!=info /var/log/mailmessages
# What is the name and path of the main system log?
# Which log contains information on currently logged in users? Choose one: a. /var/log/utmp b. /var/log/wtmp c. /var/log/lastlog d. /var/log/messages
# You have been assigned the task of determining if there are any user accounts defined on your system that have not been used during the last three months. Which log file should you examine to determine this information? Choose one: a. /var/log/wtmp b. /var/log/lastlog c. /var/log/utmp d. /var/log/messages
# You have been told to configure a method of rotating log files on your system. Which of the following factors do you not need to consider? Choose one: a. date and time of messages b. log size c. frequency of rotation d. amount of available disk space
# What utility can you use to automate rotation of logs?
# You wish to rotate all your logs weekly except for the /var/log/wtmp log which you wish to rotate monthly. How could you accomplish this. Choose one: a. Assign a global option to rotate all logs weekly and a local option to rotate the /var/log/wtmp log monthly. b. Assign a local option to rotate all logs weekly and a global option to rotate the /var/log/wtmp log monthly. c. Move the /var/log/wtmp log to a different directory. Run logrotate against the new location. d. Configure logrotate to not rotate the /var/log/wtmp log. Rotate it manually every month.
# You have configured logrotate to rotate your logs weekly and keep them for eight weeks. You are running our of disk space. What should you do? Choose one: a. Quit using logrotate and manually save old logs to another location. b. Reconfigure logrotate to only save logs for four weeks. c. Configure logrotate to save old files to another location. d. Use the prerotate command to run a script to move the older logs to another location.
# What command can you use to review boot messages?
# What file defines the levels of messages written to system log files?
# What account is created when you install Linux?
# While logged on as a regular user, your boss calls up and wants you to create a new user account immediately. How can you do this without first having to close your work, log off and logon as root? Choose one: a. Issue the command rootlog. b. Issue the command su and type exit when finished. c. Issue the command su and type logoff when finished. d. Issue the command logon root and type exit when finished.
# Which file defines all users on your system? Choose one: a. /etc/passwd b. /etc/users c. /etc/password d. /etc/user.conf
# There are seven fields in the /etc/passwd file. Which of the following lists all the fields in the correct order? Choose one: a. username, UID, GID, home directory, command, comment b. username, UID, GID, comment, home directory, command c. UID, username, GID, home directory, comment, command d. username, UID, group name, GID, home directory, comment
# Which of the following user names is invalid? Choose one: a. Theresa Hadden b. thadden c. TheresaH d. T.H.
# In order to prevent a user from logging in, you can add a(n) ________at the beginning of the password field.
# The beginning user identifier is defined in the _________ file.
# Which field is used to define the user’s default shell?
# Bob Armstrong, who has a username of boba, calls to tell you he forgot his password. What command should you use to reset his command?
# Your company has implemented a policy that users’ passwords must be reset every ninety days. Since you have over 100 users you created a file with each username and the new password. How are you going to change the old passwords to the new ones? Choose one: a. Use the chpasswd command along with the name of the file containing the new passwords. b. Use the passwd command with the -f option and the name of the file containing the new passwords. c. Open the /etc/passwd file in a text editor and manually change each password. d. Use the passwd command with the -u option.

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