Yum install
|
Installation purpoes
|
Cal
|
Display the calender
|
Clear
|
Clear Terminal
Screen
|
Chroot
|
Chang root directory
|
Cmp
|
Compare two file
|
Cut
|
Divide a file into
several parts
|
Dc
|
Desk calculator
|
Date
|
Display or Change
the date and time
|
Df
|
Display free disk
space
|
Diff
|
Display the
difference between two files
|
Dd
|
Date dump – Convert and
copy a file
|
Diff3
|
Display the
differnces between three files
|
Dir
|
Briefly list
directory contents
|
Dircolors
|
Color setup for ‘ls’
|
Dirname
|
Convert a full path
name to just a path
|
Du
|
Estimate file space
usage
|
Echo
|
Display message on
screen
|
Eject
|
Eject CD-ROM
|
Free
|
Display memory usage
|
Gzip
|
Compress or
Decompress nameed files
|
Ls
|
List information
about files
|
Passwd
|
Modify a user
password
|
Paste
|
Marge lines of files
|
Rm
|
Remove file
|
Rm dir
|
Remove folders
|
Select
|
Accept keyboard
input
|
Shut down
|
Shutdown or restart
linux
|
Sleep
|
Dealy for a
specified time
|
:q!
|
Any command out of
that command
|
Cd
|
File edit
|
I
|
Insert
|
Q) What is Linux and why is it so popular?
Answer
- Linux is an operating system that uses UNIX like Operating system.......
Q) What is LILO?
Answer
- LILO is Linux Loader is a boot loader for Linux. It is used to load Linux
into the memory and start the Operating system.......
Q) What is the difference between home
directory and working directory?
Answer
- Home directory is the default working directory when a user logs in. On the
other hand, working directory is the user’s current directory.......
Q) What is the difference between internal and
external commands?
Answer
- Internal commands are commands that are already loaded in the system. They
can be executed any time and are independent.......
Q)
Explain the difference between a static library and a dynamic library.
Answer
- Static libraries are loaded when the program is compiled and
dynamically-linked libraries are loaded in while......
Q)
What is LD_LIBRARY_PATH?
Answer
- LD_LIBRARY_PATH is an environment variable. It is used for debugging a new
library or a non standard library.......
Q)
What is the file server in Linux server?
Answer
- File server is used for file sharing. It enables the processes required fro
sharing.......
Q)
What is NFS? Q) What is its purpose?
Answer
- NFS is Network File system. It is a file system used for sharing of files
over a network.......
Q.
How do I send email with linux?
Answer
- Email can be sent in Linux using the mail command. ......
Q)
Explain RPM (Red Hat Package Manager) features.
Answer
- RPM is a package managing system (collection of tools to manage software
packages).......
Q)
What is Kernel? Q) Explain the task it performs.
Answer
- Kernel is used in UNIX like systems and is considered to be the heart of the
operating system.......
Q)
What is Linux Shell? Q) What is Shell Script?
Answer
- Linux shell is a user interface used for executing the commands. Shell is a
program the user......
Q)
What are Pipes? Q) Explain use of pipes.
Answer
- A pipe is a chain of processes so that output of one process (stdout) is fed
an input (stdin) to another.......
Q)
Explain trap command; shift Command, getopts command of linux.
Answer
- Trap command: controls the action to be taken by the shell when a signal is
received. ......
Q)
What Stateless Linux server? Q) What feature it offers?
Answer
- A stateless Linux server is a centralized server in which no state exists on
the single workstations. ......
Q)
What does nslookup do? Q) Explain its two modes.
Answer
- Nslookup is used to find details related to a Domain name server. Details
like IP addresses of a machine, MX records,......
Q)
What is Bash Shell?
Answer
- Bash is a free shell for UNIX. It is the default shell for most UNIX systems.
It has a combination of the C and Korn shell features. ......
Q)
Explain some Network-Monitoring Tools in Linux: ping, traceroute, tcpdump, ntop
Answer
- Network monitoring tools are used to monitor the network, systems present on
the network, traffic etc.......
Q) How
does the linux file system work?
Answer
- Linux file structure is a tree like structure. It starts from the root
directory, represented by '/', and then expands into sub-directories.......
Q)
What are the process states in Linux?
Answer
- Process states in Linux.......
Q)
What is a zombie?
Answer
- Zombie is a process state when the child dies before the parent process. In
this case the structural information of the process is still in the process
table.......
Q)
Explain each system calls used for process management in linux.
Answer
- System calls used for Process
management......
Q)
Which command is used to check the number of files and disk space used and the
each user’s defined quota?
Answer - Repquota
command is used to check the status of the user’s quota along with the disk
space and number of files used. This command gives a summary of the user’s
quota that how much space and files are left for the user. Every user has a
defined quota in Linux. This is done mainly for the security, as some users
have only limited access to files. This provides a security to the files from
unwanted access. The quota can be given to a single user or to a group of
users.
Q)
What is the name and path of the main system log?
Answer - By
default the main system log is /var/log/messages. This file contains all the
messages and the script written by the user. By default all scripts are saved
in this file. This is the standard system log file, which contains messages
from all system software, non-kernel boot issues, and messages that go to
'dmesg'. dmesg is a system file that is written upon system boot.
Q)
How secured is Linux? Q) Explain.
Answer - Security
is the most important aspect of an operating system. Due to its unique
authentication module, Linux is considered as more secured than other operating
systems. Linux consists of PAM. PAM is Pluggable Authentication Modules. It
provides a layer between applications and actual authentication mechanism. It
is a library of loadable modules which are called by the application for
authentication. It also allows the administrator to control when a user can log
in. All PAM applications are configured in the directory "/etc/pam.d"
or in a file "/etc/pam.conf". PAM is controlled using the
configuration file or the configuration directory.
Q)
Can Linux computer be made a router so that several machines may share a single
Internet connection? How?
Answer - Yes
a Linux machine can be made a router. This is called "IP Masquerade."
IP Masquerade is a networking function in Linux similar to the one-to-many (1:
Many) NAT (Network Address Translation) servers found in many commercial
firewalls and network routers. The IP Masquerade feature allows other
"internal" computers connected to this Linux box (via PPP, Ethernet,
etc.) to also reach the Internet as well. Linux IP Masquerading allows this
functionality even if the internal computers do not have IP addresses.
The
IP masquerading can be done by the following steps:
1.
The Linux PC must have an internet connection and a connection to LAN.
Typically, the Linux PC has two network interfaces-an Ethernet card for the LAN
and a dial-up PPP connection to the Internet (through an ISP).
2.
All other systems on your LAN use the Linux PC as the default gateway for
TCP/IP networking. Use the same ISP-provided DNS addresses on all systems.
3.
Enable IP forwarding in the kernel. By default the IP forwarding is not
enabled. To ensure that IP forwarding is enabled when you reboot your system,
place this command in the /etc/rc.d/rc.local file.
4.
Run /sbin/iptables-the IP packet filter administration program-to set up the
rules that enable the Linux PC to masquerade for your LAN.
Q)
What is the minimum number of partitions you need to install Linux?
Answer - Minimum
2 partitions are needed for installing Linux. The one is / or root which
contains all the files and the other is swap. Linux file system is function
specific which means that files and folders are organized according to their
functionality. For example, all executables are in one folder, all devices in
another, all libraries in another and so on. / or ‘root’ is the base of this
file system. All the other folders are under this one. / can be consider as C:
.Swap is a partition that will be used as virtual memory. If there is no more
available RAM a Linux computer will use an area of the hard disk, called swap,
to temporarily store data. In other words it is a way of expanding your
computers RAM.
Q) Which
command is used to review boot messages?
Answer - Dmesg
command is used to review boot messages. This command will display system
messages contained in the kernel ring buffer. We can use this command
immediately after booting to see boot messages. A ring buffer is a buffer of
fixed size for which any new data added to it overwrites the oldest data in it.
Its basic syntax is
dmesg
[options]
Invoking
dmesg without any of its options causes it to write all the kernel messages to
standard output. This usually produces far too many lines to fit into the
display screen all at once, and thus only the final messages are visible.
However, the output can be redirected to the less command through the use of a
pipe, thereby allowing the startup messages to be viewed on one screen at a
time
dmesg
| less
Q) Which
utility is used to make automate rotation of a log?
Answer - logrotate
command is used to make automate rotation of log.
Syntax
of the command is:
logrotate
[-dv] [-f|] [-s|] config_file+
It
allows automatic rotation, compression, removal, and mailing of log files. This
command is mainly used for rotating and compressing log files. This job is done
every day when a log file becomes too large. This command can also be run by
giving on command line. We can done force rotation by giving –f option with
this command in command line. This command is also used for mailing. We can
give –m option for mailing with this command. This option takes two arguments
one is subject and other is recipient name.
Q)
What are the partitions created on the mail server hard drive?
Answer - The
main partitions are done firstly which are root, swap and boot partition. But
for the mail server three different partitions are also done which are as
follows:
1.
/var/spool- This is done so that if something goes wrong with the mail server
or spool than the output cannot overrun the file system.
2.
/tmp- putting this on its own partition prevents any user item or software from
overrunning the system files.
3.
/home- putting this on its own is useful for system upgrades or reinstalls. It
allow not to wipe off the /home hierarchy along with other areas.
Q)
What are the fields in the/etc/passwd file?
Answer - It
contains all the information of the users who log into the system. It contains
a list of the system's accounts, giving for each account some useful
information like user ID, group ID, home directory, shell, etc. It should have
general read permission as many utilities, like ls use it to map user IDs to
user names, but write access only for the superuser (root). The main fields of
/etc/passwd file are:
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.
Q) Which
commands are used to set a processor-intensive job to use less CPU time?
Answer - nice
command is used for changing priority of the jobs.
Syntax:
nice [OPTION] [COMMAND [ARG]...]
Range
of priority goes from -20 (highest priority) to 19 (lowest).Priority is given
to a job so that the most important job is executed first by the kernel and
then the other least important jobs. This takes less CPU times as the jobs are
scheduled and are given priorities so the CPU executes fast. The priority is
given by numbers like -20 describe the highest priority and 19 describe the
least priority.
Q) How
to change window manager by editing your home directory?
Answer - /.xinitrc
file allows changing the window manager we want to use when logging into X from
that account. The dot in the file name shows you that the file is a hidden file
and doesn't show when you do a normal directory listing. For setting a window
manager we have to save a command in this file. The syntax of command is: exec windowmanager.After
this, save the file. Next time when you run a startx a new window manager will
open and become default. The commands for starting some popular window managers
and desktop environments are:
-KDE
= startkde
-Gnome
= gnome-session
-Blackbox
= blackbox
-FVWM
= fvwm
-Window
Maker = wmaker
-IceWM
= icewm
Q)
How documentation of an application is stored?
Answer - When
a new application is installed its documentation is also installed. This
documentation is stored under the directory named for application. For example
if my application name is App1 then the path of the documentation will be
/user/doc/App1. It contains all the information about the application. It
contains date of creating application, name of application and other important
module of the application. We can get the basic information of application from
the documentation.
Q)
How shadow passwords are given?
Answer - pwconv
command is used for giving shadow passwords. Shadow passwords are given for
better system security. The pwconv command creates the file /etc/shadow and
changes all passwords to ‘x’ in the /etc/passwd file. First, entries in the
shadowed file which don't exist in the main file are removed. Then, shadowed
entries which don't have `x' as the password in the main file are updated. Any
missing shadowed entries are added. Finally, passwords in the main file are
replaced with `x'. These programs can be used for initial conversion as well to
update the shadowed file if the main file is edited by hand.
Q)
How do you create a new user account?
Answer - useradd
command is used for creating a new user account. When invoked without the
-D
option, the useradd command creates a new user account using the values
specified on the command line and the default values from the system. The new
user account will be entered into the system files as needed, and initial files
copied, depending on the command line options. This command uses the system
default as home directory. If –m option is given then the home directory is
made.
Q)
Which password package is installed for the security of central password?
Answer - Shadow
password packages are used for security of central passwords. Security is the
most important aspect of every operating system. When this package is not
installed the user information including passwords is stored in the /etc/passwd
file. The password is stored in an encoded format. These encoded forms can be
easily identified by the System crackers by randomly encoding the passwords
from dictionaries. The Shadow Package solves the problem by relocating the
passwords to another file (usually /etc/shadow). The /etc/shadow file is set so
that it cannot be read by just anyone. Only root will be able to read and write
to the /etc/shadow file.
Q)
Which shell do you assign to a POP3 mail-only account?
Answer - POP3
mail only account is assigned to the /bin/false shell. However, assigning bash
shell to a POP3 mail only gives user login access, which is avoided.
/bin/nologin can also be used. This shell is provided to the user when we don’t
want to give shell access to the user. The user cannot access the shell and it
reject shell login on the server like on telnet. It is mainly for the security
of the shells. POP3 is basically used for downloading mail to mail program. So
for illegal downloading of emails on the shell this account is assigned to the
/bin/false shell or /bin/nologin. These both shells are same they both do the
same work of rejecting the user login to the shell. The main difference between
these two shells is that false shell shows the incorrect code and any unusual
coding when user login with it. But the nologin shell simply tells that no such
account is available. So nologin shell is used mostly in Linux.
Q)
Which daemon is responsible for tracking events on Linux system?
Answer - syslogd
is responsible for tracking system information and save it to the desired log
files. It provides two system utilities which provide system logging and kernel
message trapping. Internet and UNIX domain sockets support enable this utility
package to support both local and remote logging. Every logged message contains
at least a time and a hostname field, normally a program name field, too. So to
track these information this daemon is used. syslogd mainly reacts to the set
of signals given by the user. These are the signals given to syslogd: SIGHUP:
This lets syslogd perform a re-initialization. All open files are closed, the
configuration file (default is /etc/syslog.conf) will be reread and the syslog
facility is started again. SIGTERM: The syslogd will die. SIGINT, SIGQUIT: If
debugging is enabled these are ignored, otherwise syslogd will die. SIGUSR1:
Switch debugging on/off. This option can only be used if syslogd is started
with the - d debug option. SIGCHLD: Wait for Childs if some were born, because
of waiting messages.
Q)
Which daemon is used for scheduling of the commands?
Answer - The
crontab command is used for scheduling of the commands to run at a later time.
SYNTAX
crontab
[ -u user ] file
crontab
[ -u user ] { -l | -r | -e }
Options
-l
List - display the current crontab entries.
-r
Remove the current crontab.
-e
Edit the current crontab using the editor specified by the VISUAL or EDITOR
environment variables.
When
user exits from the editor, the modified crontab will be installed
automatically. Each user can have their own crontab, and though these are files
in /var, they are not intended to be edited directly. If the –u option is given
than the crontab gives the name of the user whose crontab is to be tweaked. If
it is given without this then it will display the crontab of the user who is
executing the command.
Q)
How environment variable is set so that the file permission can be
automatically set to the newly created files?
Answer - umask
command is used to set file permission on newly created files
automatically.
Syntax
umask
[-p] [-S] [mode]
It
is represented in octal numbers. We can simply use this command without
arguments to see the current file permissions. To change the permissions, mode
is given in the arguments. The default umask used for normal user is 0002. The
default umask for the root user is 0022. For calculating the original values,
the values shown by the umask must be subtracted by the default values. It is
mainly used for masking of the file and directory permission. The /etc/profile
script is where the umask command is usually set for all users. The –S option
can be used to see the current default permissions displayed in the alpha
symbolic format.
For
example, umask 022 ensures that new files will have at most 755 permissions
(777 NAND 022).
The permissions can be calculated
by taking the NAND of original value with the default values of files and
directories.
Q. When do you need a virtual
hosting ?
Answer - The term Virtual
Host refers to the practice of maintaining more than one server on one
machine, as differentiated by their apparent hostname. For example, it is often
desirable for companies sharing a web server to have their own domains, with
web servers accessible as www.company1.com and www.company2.com,
without requiring the user to know any extra path information.
Q. In which port telnet is
listening?
Answer - 23
Q. How to get the listening ports
which is greater than 6000 using netstat ? [OR] How to block and openrelay ?
Answer - Open relays are e-mail servers
that are configured to accept and transfer e-mail on behalf of any user
anywhere, including unrelated third parties.
The qmail-smtpd daemon will
consult the rcpthosts control file to determine valid destination addresses,
and reject anything else.
Q. What is sandwitch
configuration in qmail ?
Answer - Qmail + Clam + Spamassassin- This
is normally called Sandwitch configuration in qmail.
Q. Advantages of Qmail ?
Answer - More
secure, better designed, modular, faster, more reliable, easier to configure,
don't have to upgrade it every few months or worry about being vulnerable to
something due to some obscure feature being enabled
qmail supports host and user
masquerading, full host hiding, virtual domains, null clients, list-owner
rewriting, relay control, double-bounce recording, arbitrary RFC 822 address
lists, cross-host mailing list loop detection, per-recipient checkpointing,
downed host backoffs, independent message retry schedules, etc. qmail also
includes a drop-in ``sendmail'' wrapper so that it will be used transparently
by your current UAs.
Q.
What is the difference between POP3 and IMAP ?
Answer - The Difference
POP3 works by reviewing the inbox
on the mail server, and downloading the new messages to your computer. IMAP
downloads the headers of the new messages on the server, then retrieves the
message you want to read when you click on it.
When using POP3, your mail is
stored on your PC. When using IMAP, the mail is stored on the mail server.
Unless you copy a message to a "Local Folder" the messages are never
copied to your PC.
POP3
You only check e-mail from
one computer.
You want to remove your
e-mail from the mail server.
IMAP
You check e-mail from
multiple locations.
You use Webmail.
Q. How to drop packets using
iptables ?
Answer - Iptables -A INPUT -s xx.xx.xx.xx
-d xx.xx.xx.xx -j DROP
Q. Daily routines of Linux
Administrators ?
Answer - *.Check the health of servers
*.Check for updates
*.Check the Backup
*.Check with the trouble
ticketing system for any unread ticket.
*.Troubleshoot if there any
problem
*.Installation of new servers, if
needed.
*.Report to the Boss
Q. How to take the Dump of a
MySQL Database ?
Answer - Mysqldump databasename >
dumpname
Q. How to know the CPU usage of
each process ?
Answer - Top, uptime
Q. How to bind another IP in a
NIC ?
Answer - Copy the contents eth0 to eth1,
and change the ipaddress. Restart the network.
Q. Transparently proxy all
web-surfing through Squid box
Answer - iptables -t nat -A PREROUTING -i
eth1 -tcp --dport 80 -j DNAT --to
iptables -t nat -A PREROUTING -i
eth1 -tcp --dport 80 -j DNAT --to
Q. Transparently redirect web
connections from outside to the DMZ web server.
Answer - iptables -t nat -A PREROUTING -i
eth0 -d 192.168.1.1 -dport 80 -j DNAT –to
Q. Howto Activate the forwarding
Answer - echo 1
>/proc/sys/net/ipv4/ip_forward
Q. Kill spoofed packets
Answer - for f in
/proc/sys/net/ipv4/conf/*/rp_filter; do
echo 1 > $f
done.
$iptables -A LDROP --proto tcp -j
LOG --log-level info \ --log-prefix “TCP Drop”
Q. Why LVM is required ?
Answer - LVM stands for Logical Volume Manager , to resize filesystem’s size
online we required LVM partition in Linux. Size of LVM partition can be
extended and reduced using the lvextend & lvreduce commands respectively.
Q. How To check Memory stats and CPU stats ?
Answer - Using ‘free’ & ‘vmstat’ command we can display the physical
and virtual memory statistics respectively.With the help of ‘sar’ command we
see the CPU utilization & other stats.
Q. What does Sar provides and at which location Sar logs are stored ?
Answer - Sar Collect, report, or save system activity information. The default
version of the sar command (CPU utilization report) might be one of the first
facilities the user runs to begin system activity
investigation, because it monitors major system resources. If CPU utilization
is near 100 percent (user + nice + system), the workload sampled is CPU-bound.
By default log files of Sar command is located at
/var/log/sa/sadd file, where the dd parameter indicates the current day.
Q. How to increase the size of LVM partition ?
Answer - Below are the Logical Steps :
– Use the lvextend command (lvextend -L +100M /dev/<Name of the LVM Partition> , in this example we are extending the size by 100MB.
– resize2fs /dev/<Name of the LVM Partition>
– check the size of partition using ‘df -h’ command
– Use the lvextend command (lvextend -L +100M /dev/<Name of the LVM Partition> , in this example we are extending the size by 100MB.
– resize2fs /dev/<Name of the LVM Partition>
– check the size of partition using ‘df -h’ command
Q. How to reduce or shrink the size of LVM partition ?
Answer - Below are the logical Steps to reduce size of LVM partition :
-Umount the filesystem using umount command,
-use resize2fs command , e.g resiz2fs /dev/mapper/myvg-mylv 10G
-Now use the lvreduce command , e.g lvreduce -L 10G /dev/mapper/myvg-mylv
-Umount the filesystem using umount command,
-use resize2fs command , e.g resiz2fs /dev/mapper/myvg-mylv 10G
-Now use the lvreduce command , e.g lvreduce -L 10G /dev/mapper/myvg-mylv
Above Command will shrink the size & will make the filesystem size
10GB.
Q. How to create partition from the raw disk ?
Answer - Using fdisk utility we can create partitions from the raw disk.Below
are the steps to create partition from the raw dsik :
– fdisk /dev/hd* (IDE) or /dev/sd* (SCSI)
– Type n to create a new partition
– After creating partition , type w command to write the changes to the partition table.
– fdisk /dev/hd* (IDE) or /dev/sd* (SCSI)
– Type n to create a new partition
– After creating partition , type w command to write the changes to the partition table.
Q. Where the kernel modules are located ?
Answer - The ‘/lib/modules/kernel-version/’ directory stores all kernel
modules or compiled drivers in Linux operating system. Also with ‘lsmod’
command we can see all the installed kernel modules.
Q. What is umask ?
Answer - umask stands for ‘User file creation mask’, which determines the
settings of a mask that controls which file permissions are set for files and
directories when they are created.
Q. How to set the umask permanently for a user?
Answer - To set this value permanently for a user, it has to be put in the
appropriate profile file which depends on the default shell of the user.
Q. How to change the default run level in linux ?
Answer - To change the run level we have to edit the file “/etc/inittab” and
change initdefault entry ( id:5:initdefault:). Using ‘init’ command we change
the run level temporary like ‘init 3’ , this command will move the system in
runlevl 3.
Q. How to share a directory using nfs ?
Answer - To share a directory using nfs , first edit the configuration file
‘/etc/exportfs’ , add a entry like
‘/<directory-name> <ip or Network>(Options)’ and then restart the nfs service.
‘/<directory-name> <ip or Network>(Options)’ and then restart the nfs service.
Q. How to check and mount nfs share ?
Answer - Using ‘showmount’ command we can see what directories are shared via
nfs e.g ‘showmount -e <ip address of nfs server>’.Using mount command we
can mount the nfs share on linux machine.
Q. What are the default ports used for SMTP,DNS,FTP,DHCP,SSH and squid ?
Answer - Service Port
SMTP 25
DNS 53
FTP 20 (data transfer) , 21 ( Connection established)
DHCP 67/UDP(dhcp server) , 68/UDP(dhcp client)
SSH 22
Squid 3128
Answer - Service Port
SMTP 25
DNS 53
FTP 20 (data transfer) , 21 ( Connection established)
DHCP 67/UDP(dhcp server) , 68/UDP(dhcp client)
SSH 22
Squid 3128
Q. What is Network Bonding ?
Answer - Network bonding is the aggregation of multiple Lan cards into a
single bonded interface to provide fault tolerance and high performance.
Network bonding is also known as NIC Teaming.
Q. What are the different modes of Network bonding in Linux ?
Answer - Below are list of modes used in Network Bonding :
balance-rr or 0 – round-robin mode for fault tolerance and load balancing.
active-backup or 1 – Sets active-backup mode for fault tolerance.
balance-xor or 2 – Sets an XOR (exclusive-or) mode for fault tolerance and load balancing.
broadcast or 3 – Sets a broadcast mode for fault tolerance. All transmissions are sent on all slave interfaces.
802.3ad or 4 – Sets an IEEE 802.3ad dynamic link aggregation mode. Creates aggregation groups that share the same speed & duplex settings.
balance-tlb or 5 – Sets a Transmit Load Balancing (TLB) mode for fault tolerance & load balancing.
balance-alb or 6 – Sets an Active Load Balancing (ALB) mode for fault tolerance & load balancing.
active-backup or 1 – Sets active-backup mode for fault tolerance.
balance-xor or 2 – Sets an XOR (exclusive-or) mode for fault tolerance and load balancing.
broadcast or 3 – Sets a broadcast mode for fault tolerance. All transmissions are sent on all slave interfaces.
802.3ad or 4 – Sets an IEEE 802.3ad dynamic link aggregation mode. Creates aggregation groups that share the same speed & duplex settings.
balance-tlb or 5 – Sets a Transmit Load Balancing (TLB) mode for fault tolerance & load balancing.
balance-alb or 6 – Sets an Active Load Balancing (ALB) mode for fault tolerance & load balancing.
Q. How to check and verify the status the bond interface.
Answer - Using the command ‘cat /proc/net/bonding/bond0’ , we can check which
mode is enabled and what lan cards are used in this bond. In this example we
have one only one bond interface but we can have multiple bond interface like
bond1,bond2 and so on.
Q. How to check default route and routing table ?
Answer - Using the Commands ‘netstat -nr’ and ‘route -n’ we can see the
default route and routing tables.
Q. How to check which ports are listening in my Linux Server ?
Answer - Use the Command ‘netstat –listen’ and ‘lsof -i’
Q. List the services that are enabled at a particular run level in linux
server ?
Answer - With the help of command ‘chkconfig –list | grep 5:on’ we can list
all the service that are enabled in run level5. For other run levels just
replace 5 with the respective run level.
Q. How to enable a service at a particular run level ?
Answer - We can enable a service using the Command ‘chkconfig
<Service-Name> on –level 3’
Q. How to upgrade Kernel in Linux ?
Answer - We should never upgrade Linux Kernel , always install the new New
kernel using rpm command because upgrading a kenel can make your linux box in a
unbootable state.
Q. How To scan newly asssigned luns on linux box without rebooting ?
Answer - There are two ways to scan newly assigned luns :
Method:1 if sg3 rpm is installed , then run the command ‘rescan-scsi-bus.sh’
Method:2 Run the Command , echo ” – – – ” > /sys/class/scsi_host/hostX/scan
Method:1 if sg3 rpm is installed , then run the command ‘rescan-scsi-bus.sh’
Method:2 Run the Command , echo ” – – – ” > /sys/class/scsi_host/hostX/scan
Q. How to find WWN numbers of HBA cards in Linux Server ?
Answer - We can find the WWN numbers of HBA cards using the command ‘systool
-c fc_host -v | grep port_name’
Q. How to add & change the Kernel parameters ?
Answer - To Set the kernel parameters in linux , first edit the file
‘/etc/sysctl.conf’ after making the changes save the file and run the command
‘sysctl -p’ , this command will make the changes permanently without rebooting
the machine.
Q. What is Puppet Server ?
Answer - Puppet is an open-source & enterprise software for configuration
management toll in UNIX like operating system. Puppet is a IT
automation software used to push configuration to its clients (puppet agents)
using code. Puppet code can do a variety of tasks from installing new software,
to check file permissions, or updating user accounts & lots of other tasks.
Q. What are manifests in Puppet ?
Answer - Manifests in Puppet are the files in which the client configuration
is specified.
Q. Which Command is used to sign requested certificates in Puppet Server
?
Answer - ‘puppetca –sign hostname-of-agent’ in (2.X) & ‘puppet
ca sign hostname-of-agent’ in (3.X)
Q. At which location Puppet Master Stores Certificates ?
Answer - /var/lib/puppet/ssl/ca/signed
Q. How to find all the regular files in a directory ?
Answer - using the command ‘find /<directory -type f’.
Q. What is load average in a linux ?
Answer - Load Average is defined as the average sum of the number of
process waiting in the run queue and number of process currently executing over
the period of 1,5 and 15 minutes. Using the ‘top’ and ‘uptime’ command we
find the load average of a linux sever.
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