Before linux is installed on a system. Special instructions must be Placed in
Boot Loader (Its a programme that exists on Systems Primary Hard Drive or other Media
that knows how to start the linux Kernel)used to Boot the system.Red Hat linux installation
Programme allows user to quickly and easily configure the boot loader in the
Primary hard dirve's Master Boot Record (MBR) to load the OS.
Define GRUB :
GRUB (GRand Unified Bootloader) is a programme that installs a Boot Loader to the MBR. This MBR
exists at the beginning sector of the disk.
The Grub menu is also command environmental means we can pass specific arguments as instructions.
The process of loading operating GRUB and OS involves several stages :
1)Load the primary boot Loader (stage 1):
It exists in very small space allocated for MBR ( < style="font-weight: bold;">2)Load the secondary boot Loader (stage 2):
Choosing of operating system. or give commands or modify commands
3)Load the Operating System (linux kernel on specified partition):
After receiving correct instructions for OS to start from command line or
Configuration file
Linux administration , Unix administration , Vmware Vsphere administration , Oracle DBA ,apache, backup, dhcp, dns, kvm, xen, kernel, ldap, kvm, monitoring, ticketing, networking, Mail servers, SAN,troubleshooting
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Bash Script to Analyzing Disk Usage
# fquota - Disk quota analysis tool for Unix.
# Assumes that all user accounts are >= UID 100.
MAXDISKUSAGE=20
for name in $(cut -d: -f1,3 /etc/passwd | awk -F: '$2 > 99 {print $1}')
do
echo -n "User $name exceeds disk quota. Disk usage is: "
# You might need to modify the following list of directories to match
# the layout of your disk. Most likely change: /Users to /home
find / /usr /var /Users -user $name -xdev -type f -ls | \
awk '{ sum += $7 } END { print sum / (1024*1024) " Mbytes" }'
done | awk "\$9 > $MAXDISKUSAGE { print \$0 }"
exit 0
# Assumes that all user accounts are >= UID 100.
MAXDISKUSAGE=20
for name in $(cut -d: -f1,3 /etc/passwd | awk -F: '$2 > 99 {print $1}')
do
echo -n "User $name exceeds disk quota. Disk usage is: "
# You might need to modify the following list of directories to match
# the layout of your disk. Most likely change: /Users to /home
find / /usr /var /Users -user $name -xdev -type f -ls | \
awk '{ sum += $7 } END { print sum / (1024*1024) " Mbytes" }'
done | awk "\$9 > $MAXDISKUSAGE { print \$0 }"
exit 0
Bash script to check internet connection
#!/bin/bash
WGET="/usr/bin/wget"
$WGET -q --tries=10 --timeout=5 http://www.google.com -O /tmp/index.google &> /dev/null
if [ ! -s /tmp/index.google ];then
echo "no"
else
echo "yes"
fi
It tries to download google page within 5 seconds
returns 'yes' if google page index is downloaded
else return 'no'
WGET="/usr/bin/wget"
$WGET -q --tries=10 --timeout=5 http://www.google.com -O /tmp/index.google &> /dev/null
if [ ! -s /tmp/index.google ];then
echo "no"
else
echo "yes"
fi
It tries to download google page within 5 seconds
returns 'yes' if google page index is downloaded
else return 'no'
8 Technology updates
Cloud computing. Using applications and storage in the “cloud”, instead of “on premise”, is fast becoming a cost effective alternative for enterprises. In the new setting, enterprises are likely to rely on Software-as-service (SaaS) for non-core processes allowing CIOs to focus on core processes, and save significant costs in license fees, support and maintenance.
Green IT. Enterprises will invest in technologies and solutions for compliance to regulations in the Green space, to become energy efficient and reduce carbon foot prints. Incidentally, Green IT also helps enterprises lower operating costs.
Open-source software (OSS) has established its role firmly in the IT industry, even though the rate of maturity and saturation-levels vary across market segments. Thus, most mainstream IT organizations are blending the best of open-source and closed-source solutions.
Collaboration is an important aspect of an enterprise today. It reduces the human latency in business processes and improves both cost efficiency and customer experience. The underlying technology is based on unified communications which integrates all the channels of voice and non voice communication over IP.
Social computing There is an emerging demand for integrating data in enterprise IT systems with that in social networks, to improve or promote, campaign management, community driven discounting, and intercontinental connections.
Information management is an important aspect of new enterprise as it is moving from a structured data model (text heavy and relational) to unstructured data model (multi modal and search driven).
Mobility in an enterprise is very closely linked to collaboration and social computing. With the exponential rise in the types of mobile devices and their usage in enterprises, it is fast becoming a social experience challenge in a business environment.
Green IT. Enterprises will invest in technologies and solutions for compliance to regulations in the Green space, to become energy efficient and reduce carbon foot prints. Incidentally, Green IT also helps enterprises lower operating costs.
Open-source software (OSS) has established its role firmly in the IT industry, even though the rate of maturity and saturation-levels vary across market segments. Thus, most mainstream IT organizations are blending the best of open-source and closed-source solutions.
Collaboration is an important aspect of an enterprise today. It reduces the human latency in business processes and improves both cost efficiency and customer experience. The underlying technology is based on unified communications which integrates all the channels of voice and non voice communication over IP.
Social computing There is an emerging demand for integrating data in enterprise IT systems with that in social networks, to improve or promote, campaign management, community driven discounting, and intercontinental connections.
Information management is an important aspect of new enterprise as it is moving from a structured data model (text heavy and relational) to unstructured data model (multi modal and search driven).
Mobility in an enterprise is very closely linked to collaboration and social computing. With the exponential rise in the types of mobile devices and their usage in enterprises, it is fast becoming a social experience challenge in a business environment.
10 Tech Skills an IT professional Should Develop to Survive -TechRepublic
If you want a job where you can train in a particular skill set and then never have to learn anything new, IT
isn’t the field for you. But if you like to be constantly learning new things and developing new skills, you’re in
the right business. In the late 80s, NetWare and IPX/SPX administration were the skills to have. Today, it’s
all about TCP/IP and the Internet.
Let’s take a look at some of the skills you should be thinking about developing to keep on top of things in
the tech world in the next five years.
#1: Voice over IP
Many companies and consumers are already using VoIP for telephone services due to cost and
convenience factors. According to a SearchVoIP.com article in June 2007, sales of pure IP PBX systems
for the first quarter of 2007 increased 76% over the first quarter of the previous year.
More and more companies are expected to go to VoIP, to either supplement or replace their traditional
phone lines. And because VoIP runs on the TCP/IP network, IT administrators will in many cases be
expected to take responsibility for VoIP implementation and ongoing administration.
#2: Unified communications
Along with the growing popularity of VoIP, the concept of unified communications — the convergence of
different communications technologies, such as e-mail, voicemail, text messaging, and fax — looks to be
the wave of the future. Users will expect to have access to all their communications from a single interface,
such as their Inbox, and from a variety of devices: PCs, laptops, smart phones/PDAs, traditional phones,
etc.
Convergence makes networks more complex, and IT administrators will need to develop skills for managing
converged networks to compete in tomorrow’s job market.
#3: Hybrid networks
The day of the all-Windows or all-UNIX network is already past, and networks are likely to grow more,
rather than less hybridized in the future. As new versions of Linux, such as Ubuntu, become friendlier for
end users, we’re likely to see some organizations deploying it on the desktop for certain users. However,
it’s likely that other users will continue to use Windows because of application requirements and/or personal
preferences, and there may very well be Macintosh users in the mix as well, especially in graphics
environments.
IT pros will no longer be able to get by with expertise in only one platform; you’ll need to be able to support
and troubleshoot different operating systems.
#4: Wireless technology
Wireless networking is still in its infancy in the enterprise. Companies are (often grudgingly) establishing
wireless LANs for the use of employees and visitors because it’s the most convenient way for portable
computers to connect to the network, but many organizations are still wary of wireless (rightly so),
particularly its security implications.
But wireless isn’t going away, and the future promises faster and more secure wireless technologies. You’ll
need to know about 802.11n, a new standard now in development and estimated to be released in late
2008, which will provide for a typical throughput of 74 Mbps with a theoretical maximum data rate of 248
Mbps and a longer range than current 802.11a/b/g standards (about 70 meters, or approximately 230 feet).
#5: Remote user support
The trend is toward more employees working off-site: executives taking their laptops on the road,
telecommuters working from home at least a few days per week, personnel in the field connecting back to
the LAN, and so forth. The IT staff will need to be able to support these remote users while maintaining the
security of the internal network.
It will be important to learn skills relating to different VPN technologies (including SSL VPN) and
technologies for health monitoring and quarantining of remote clients to prevent those that don’t meet
minimal criteria (antivirus installed and updated, firewall enabled, etc.) from connecting to the LAN and
putting the rest of the network at risk.
#6: Mobile user support
Cell phones, Blackberries, and other ultra-portable devices are becoming ubiquitous and will likely grow
more sophisticated in the future. Employees will expect to get their corporate e-mail on their phones and in
some cases (such as Windows Mobile devices), to use terminal services client software to connect these
small devices to the company LAN.
IT staff members will need to develop a plethora of skills to support mobile users, including expertise in
configuration of mail servers and knowledge of security implications of the devices.
#7: Software as a service
Web 2.0, the next generation of the Internet, is all about SaaS, or Software as a Service. SaaS involves
delivering applications over the Web, rather than installing those applications on individual users’ machines.
Some IT pundits have warned that SaaS will do away with IT administrators’ jobs entirely, but the more
likely scenario is that the job description will change to one with less focus on deployment and maintenance
of applications and more emphasis on broader-based planning, convergence, etc.
If SaaS takes off, the job market may also shift so that more jobs are concentrated in the application
provider sector rather than in companies’ in-house IT departments. In that situation, IT pros who have the
skills relating to service provision and multi-tenant architecture will have a head start when it comes to
getting and staying employed.
#8: Virtualization
Virtualization has been around for a while, but now, with Microsoft heavily investing in the technology with
its Windows hypervisor (Viridian), which will run on Windows Server 2008, VMWare offering VMWare
Server for free, and Red Hat and SuSE planning to include Xen hypervisor technology in the next versions
of their server products, we can expect the concept of virtual machines to go to a whole new level in the
next few years.
Managing a VM-based network environment is a skill that will be not just handy, but essential, as more and
more companies look to virtualization to consolidate servers and save on hardware costs.
#9: IPv6
Widespread adoption of the next generation of the Internet Protocol (IPv6) hasn’t come about as quickly as
originally predicted, in large part because technologies such as NAT prevented the depletion of available IP
addresses from happening as soon as anticipated.
However, with the number of hosts on the Internet growing steadily, the larger address space will eventually
be critical to further expansion. IPv6 also offers better security with IPsec, a part of the basic protocol suite.
Perhaps the inevitability of the transition is best indicated by the fact that Windows Vista, Windows Server
2008, Mac OS X 10.3, and the latest versions of other operating systems have IPv6 enabled by default.
With an entirely different address notation, called CIDR, and addresses written in hexadecimal instead of
the familiar four octets of decimal numbers used by IPv4, there will be a learning curve for IT administrators.
The time to tune up your IPv6 skills is now, before the transition becomes mandatory.
#10: Security
Smart IT pros have been developing their security skills for the last several years, but the future will bring
new security challenges and new security mechanisms. Technologies such as VoIP and mobile computing
bring new security issues and challenges. Authentication methods are evolving from a password-based
model to multifactor models and biometrics are likely to become more important in the future.
As threats become more sophisticated, shifting from teenage hackers defacing Web sites “just for fun” to
well financed corporate espionage agents and cyberterrorists bent on bringing down the country’s vital
infrastructure by attacking the networks that run it, security skills must keep up.
In addition to proactive measures, IT pros will need to know more about computer forensics and be able to
track what is happening and has happened on their networks.
isn’t the field for you. But if you like to be constantly learning new things and developing new skills, you’re in
the right business. In the late 80s, NetWare and IPX/SPX administration were the skills to have. Today, it’s
all about TCP/IP and the Internet.
Let’s take a look at some of the skills you should be thinking about developing to keep on top of things in
the tech world in the next five years.
#1: Voice over IP
Many companies and consumers are already using VoIP for telephone services due to cost and
convenience factors. According to a SearchVoIP.com article in June 2007, sales of pure IP PBX systems
for the first quarter of 2007 increased 76% over the first quarter of the previous year.
More and more companies are expected to go to VoIP, to either supplement or replace their traditional
phone lines. And because VoIP runs on the TCP/IP network, IT administrators will in many cases be
expected to take responsibility for VoIP implementation and ongoing administration.
#2: Unified communications
Along with the growing popularity of VoIP, the concept of unified communications — the convergence of
different communications technologies, such as e-mail, voicemail, text messaging, and fax — looks to be
the wave of the future. Users will expect to have access to all their communications from a single interface,
such as their Inbox, and from a variety of devices: PCs, laptops, smart phones/PDAs, traditional phones,
etc.
Convergence makes networks more complex, and IT administrators will need to develop skills for managing
converged networks to compete in tomorrow’s job market.
#3: Hybrid networks
The day of the all-Windows or all-UNIX network is already past, and networks are likely to grow more,
rather than less hybridized in the future. As new versions of Linux, such as Ubuntu, become friendlier for
end users, we’re likely to see some organizations deploying it on the desktop for certain users. However,
it’s likely that other users will continue to use Windows because of application requirements and/or personal
preferences, and there may very well be Macintosh users in the mix as well, especially in graphics
environments.
IT pros will no longer be able to get by with expertise in only one platform; you’ll need to be able to support
and troubleshoot different operating systems.
#4: Wireless technology
Wireless networking is still in its infancy in the enterprise. Companies are (often grudgingly) establishing
wireless LANs for the use of employees and visitors because it’s the most convenient way for portable
computers to connect to the network, but many organizations are still wary of wireless (rightly so),
particularly its security implications.
But wireless isn’t going away, and the future promises faster and more secure wireless technologies. You’ll
need to know about 802.11n, a new standard now in development and estimated to be released in late
2008, which will provide for a typical throughput of 74 Mbps with a theoretical maximum data rate of 248
Mbps and a longer range than current 802.11a/b/g standards (about 70 meters, or approximately 230 feet).
#5: Remote user support
The trend is toward more employees working off-site: executives taking their laptops on the road,
telecommuters working from home at least a few days per week, personnel in the field connecting back to
the LAN, and so forth. The IT staff will need to be able to support these remote users while maintaining the
security of the internal network.
It will be important to learn skills relating to different VPN technologies (including SSL VPN) and
technologies for health monitoring and quarantining of remote clients to prevent those that don’t meet
minimal criteria (antivirus installed and updated, firewall enabled, etc.) from connecting to the LAN and
putting the rest of the network at risk.
#6: Mobile user support
Cell phones, Blackberries, and other ultra-portable devices are becoming ubiquitous and will likely grow
more sophisticated in the future. Employees will expect to get their corporate e-mail on their phones and in
some cases (such as Windows Mobile devices), to use terminal services client software to connect these
small devices to the company LAN.
IT staff members will need to develop a plethora of skills to support mobile users, including expertise in
configuration of mail servers and knowledge of security implications of the devices.
#7: Software as a service
Web 2.0, the next generation of the Internet, is all about SaaS, or Software as a Service. SaaS involves
delivering applications over the Web, rather than installing those applications on individual users’ machines.
Some IT pundits have warned that SaaS will do away with IT administrators’ jobs entirely, but the more
likely scenario is that the job description will change to one with less focus on deployment and maintenance
of applications and more emphasis on broader-based planning, convergence, etc.
If SaaS takes off, the job market may also shift so that more jobs are concentrated in the application
provider sector rather than in companies’ in-house IT departments. In that situation, IT pros who have the
skills relating to service provision and multi-tenant architecture will have a head start when it comes to
getting and staying employed.
#8: Virtualization
Virtualization has been around for a while, but now, with Microsoft heavily investing in the technology with
its Windows hypervisor (Viridian), which will run on Windows Server 2008, VMWare offering VMWare
Server for free, and Red Hat and SuSE planning to include Xen hypervisor technology in the next versions
of their server products, we can expect the concept of virtual machines to go to a whole new level in the
next few years.
Managing a VM-based network environment is a skill that will be not just handy, but essential, as more and
more companies look to virtualization to consolidate servers and save on hardware costs.
#9: IPv6
Widespread adoption of the next generation of the Internet Protocol (IPv6) hasn’t come about as quickly as
originally predicted, in large part because technologies such as NAT prevented the depletion of available IP
addresses from happening as soon as anticipated.
However, with the number of hosts on the Internet growing steadily, the larger address space will eventually
be critical to further expansion. IPv6 also offers better security with IPsec, a part of the basic protocol suite.
Perhaps the inevitability of the transition is best indicated by the fact that Windows Vista, Windows Server
2008, Mac OS X 10.3, and the latest versions of other operating systems have IPv6 enabled by default.
With an entirely different address notation, called CIDR, and addresses written in hexadecimal instead of
the familiar four octets of decimal numbers used by IPv4, there will be a learning curve for IT administrators.
The time to tune up your IPv6 skills is now, before the transition becomes mandatory.
#10: Security
Smart IT pros have been developing their security skills for the last several years, but the future will bring
new security challenges and new security mechanisms. Technologies such as VoIP and mobile computing
bring new security issues and challenges. Authentication methods are evolving from a password-based
model to multifactor models and biometrics are likely to become more important in the future.
As threats become more sophisticated, shifting from teenage hackers defacing Web sites “just for fun” to
well financed corporate espionage agents and cyberterrorists bent on bringing down the country’s vital
infrastructure by attacking the networks that run it, security skills must keep up.
In addition to proactive measures, IT pros will need to know more about computer forensics and be able to
track what is happening and has happened on their networks.
what are common runlevel values on RHEL
0. Halt
1. Single user mode
6. Reboot
3. Default text
5. Default GUI
1. Single user mode
6. Reboot
3. Default text
5. Default GUI
What command is used to check a file system for errors?
fsck
fsck.ext3
fsck.nfs
fsck.ext2
fsck.vfat
fsck.reiserfs
fsck.msdos
fsck.ext3
fsck.nfs
fsck.ext2
fsck.vfat
fsck.reiserfs
fsck.msdos
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