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094 - DNS & dig

DNS is an Internet service that translates domain names into IP addresses. Each time you use a domain name,
DNS translates the name into the corresponding IP address. In order to do the translation DNS holds records
for each domain. The most important are the A, CNAME, and MX records. The A record stores the host IP address.
The CNAME is an alias record, which is used to give multiple aliases to a single computer. The MX record is the mail
exchange record, which tells mail servers how to route email for this domain.

Linux:

093 - Create alias for e-mail

1. Edit /etc/aliases to add a new alias.

2. Rebuild the aliases database.

 # newaliases

Return 0 on success, or a number greater than 0 if there wa an error.
newaleases must be run whenever /etc/aliases has been changed for the change to take effect.

 

092 - NFS mount

1. Configuration of NFS Server.

* Edit /etc/exports

NFS client : 192.168.1.34, 35

/home/share 192.168.1.34(rw, no_root_squash) 192.168.1.35(ro)

rw means read/write. no_root_squash is a setting that allows nfs clients to connect as root.
Without this setting, the root user on clients that connect has the permissions of the user 'nfsnobody', uid 65534.

* Edit /etc/hosts.allow, if you need.

091 - reboot, poweroff, halt, shutdown

1. halt, powroff, reboot

Halt notes that the system is being brought down in the file /var/log/wtmp, and then either tells the kernel to halt, reboot or poweroff the system.If halt or reboot is called when the system is not in runlevel 0 or 6, in other words when it's running normally, shutdown will be invoked instead (with the -h or -r flag). The rest of this manpage describes the behaviour in runlevels 0 and 6, that is when the systems shutdown scripts are being run.

Linux:

090 - How to setup odbc for AS400 in Ubuntu Linux

This is how to install iSeries odbc driver in your ubuntu machine.
First of all you need to download iSeries Access Linux from IBM site. Just for your notice you have to registrate yourself
before you can download anything from IBM site, this is not a big deal, cause it is so simple.

089 - Virtual Hosting using Apache2 on ubuntu/linux

Virtual Hosting allow web servers to host more than one website on a sing machine. This is how sharing hosting works.
This allows you to access to your local repository using addresses such as http://mysite.com instead of http://localhost/~myuser/www/ : ) .
If you have installed webmin in your server, it might be easy to setup apache vitrual host.

1. Prepare for your configuration file.

088 - How to install mcrypt for PHP in ubuntu

Initially ubuntu server (LAMP) does not  include mcrypt for PHP. To install it, the following steps need to be done.

apt-get install php5-mcrypt
/etc/init.d/apache2 restart

Sometimes you might get the message “php5-mcrypt is already the newest version“. If so, install with:

087 - Network Adapter Driver Instration

After Linux installation, sometimes OS recognize network card and so on. To fix a problem, you have to install an appropriate driver.

1. Move the base driver tar file to the directory of your choice.  For  example, use /home/username/e1000e or /usr/local/src/e1000e.

2. Untar/unzip archive:

tar zxf e1000e-x.x.x.tar.gz

3. Change to the driver src directory:

086 - Kernel release level

If you install Oracle database, the first system check that you should is to determine the kernel release level of the Linux operating system that you have installed.
Oracle supports Oracle 10g & 11g on any 2.6 kernel with the base release of Red Hat or SUSE.
The following command should tell you the kernel release level.

[MyServer]# uname -r

2.6.18-92.1.22.el5PAE

 

Linux:

085 - Hardware RAID vs Software RAID

  • Hardware RAID

The hardware-based array manages the RAID subsystem independently from the host. It presents a single disk per RAID array to the host.
A Hardware RAID device connects to the SCSI controller and presents the RAID arrays as a single SCSI drive. An external RAID system moves all RAID handling
"intelligence" into a controller located in the external disk subsystem. The whole subsystem is connected to the host via a normal SCSI controller and appears to
the host as a single disk.

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by Dr. Radut