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Format the new hard drive in linux

acul — Tue, 29 Nov 2011 21:19:02 +0000

The first step that should be done is when you install a new hard drive in linux is to check whether the new hard disk that you attach your linux detected by what is not, for that execute the following command:
[root@dodi data]# fdisk -l | grep "Disk" Disk /dev/hdb: 41.1 GB, 41110142976 bytes
The data above shows that your hard disk space is detected by the hard drivefrom the computer you who read by the system that is equal to 40 Gb more.

After that, format your hard drive:
mkfs.ext3 /dev/hdb
After the successful format then create a new path to the new hard drive
mkdir /baru
Then mount your hard drive
mount /dev/hdb /baru
Check whether your disk unreadable in the system
df -h
And who execute the following command to insert a new partition function for the insert into the file
/etc/fstab echo "/dev/hdb /baru ext3 defaults 0 0" >> /etc/fstab
After that, please reboot your server to test the new fstab settings on your server.

source : http://blog.abdullahbaadilla.com

Viewing and stopping processes

acul — Mon, 28 Nov 2011 18:58:26 +0000

Every program that runs on your system, including the shell itself and any commands that you might have issued, creates a process. You can get a list of all running process on your system by using the ps command. For exam- ple, entering the ps command on my system gives the following output:
ps -ax PID TTY STAT TIME COMMAND 1 ? S 0:04 init [5] 2 ? SW 0:01 [keventd] 3 ? SW 0:00 [kapmd] 4 ? SWN 0:00 [ksoftirqd/0] 6 ? SW 0:00 [bdflush] 23580 ? S 1:38 /usr/lib/openoffice/ program/soffice.bin private:factory/swriter 23766 pts/1 R 0:00 ps ax

Sometimes processes don’t behave nicely and can stop responding or working as you expected. You can use the output of the ps command to find the process that is misbehaving and stop it. Notice in the preceding listing the column labeled PID: In this column is the Process ID number of the process. For example, take a look at the next-to-last PID, number 23580. If you follow the line beginning with 23580 across to the command column, you can see that this is the process started by OpenOffice. The command column always shows the command that started the process. If OpenOffice were not respond- ing, I could force it to stop running by using the kill command as follows:
kill -9 23580
The -9 in the command is referred to as a signal. In some cases, a running program can catch a signal and not act on the command. By using the -9, you are forcing the program to end because the -9 signal cannot be caught by a running program.

Checking disk space on Linux

acul — Mon, 28 Nov 2011 18:55:12 +0000

You can use two commands to find out how much space you have used on your file system. First, using the df command shows how much space is used and still available on all devices that are mounted. On my system, this command shows the following output. In this example, I use the -h option to force the output to display the space in megabytes and gigabytes rather than the standard output of 1-kilobyte blocks.
#df -h Filesystem Size Used Avail Use% Mounted on /dev/hdb5 27G 5.1G 21G 20% / /dev/hdb1 198M 6.3M 182M 4% /boot /dev/hdb2 9.7G 4.0G 5.3G 43% /home none 125M 0 125M 0% /dev/shm /dev/hda2 5.9G 3.4G 2.2G 61% /mnt/drive2
Second, to find out how much disk space is used by a directory and its subdi- rectories, you can use the du command. In the following listing, I again use the -h option to have the output displayed in megabytes and gigabytes rather than 1-kilobyte blocks.
du -h /home/tutor/website 80K website/html/cgi-bin/fileman 8.0K website/html/cgi-bin/log_files 8.0K website/html/cgi-bin/my_db 44K website/html/cgi-bin/my_html 28K website/html/cgi-bin/system_db 60K website/html/cgi-bin/system_db_html 344K website/html/cgi-bin 512K website/html/colonial 24K website/html/.xvpics 904K website/html 8.0K website/.xvpics 1.1M website

Mounting and unmounting drives on Linux

acul — Fri, 25 Nov 2011 01:37:49 +0000

Before you can use any storage device in Enterprise Linux, the device must first be made a part of the file system. This process is mounting; to attach the drive, you use the mount command. The basic syntax of the mount com- mand is

mount devicename mountpoint

The devicename identifies the device that you want to mount. All files that identify a device are located in the /dev directory. Thus, the system CD-ROM drive is typically identified as /dev/cdrom, and the system floppy drive is usually /dev/fd0.

You usually must be logged in as the root user to mount and unmount drives.

Mount point identifies the directory location on the file system where the device will be accessible. The top-level directory, /mnt, is the typical mount point for other devices, which are listed as subdirectories of /mnt. For exam- ple, if you want to access files from your CD-ROM drive, first mount the drive by entering the following command:

mount /dev/cdrom /mnt/cdrom

The preceding command mounts the cdrom device onto the file system at the directory /mnt/cdrom. To access files from the CD-ROM, all you need to do is to change into the /mnt/cdrom directory.

Although you can mount a device to any directory, I recommend using an empty directory as the mount point. Mounting a device on a directory that contains files will make those files inaccessible while the device is mounted.

To unmount a device from your file system, you use the umount command. For example, if you no longer need to access the CD-ROM drive, you can unmount the device by entering the following command:

umount /mnt/cdrom

This command tells the system to remove the mount point that was created at /mnt/cdrom.

Before you can remove a CD from the CD-ROM drive, you must unmount the device.

Searching for files On Linux

acul — Fri, 25 Nov 2011 01:34:36 +0000

Sometimes you might look for a file in your file system but can’t remember
where it is. Fortunately, the shell provides a command that you can use to
help you find the file. Easy to remember, the command is find. For example,
if you want to find the file testfile but don’t remember where it is, enter
this command:

find / -name testfile -print

The basic syntax for the find command is

find path options filename options

The preceding command begins searching in the system root directory for
a file named testfile and displays the results of the search to the system
display.

The preceding command begins searching in the system root directory for
a file named testfile and displays the results of the search to the system
display.
The find command is very powerful and useful for finding files. It is also a
complex command that lets you specify a large number of options for finding
many types of files. Be sure to use the command man find to see the com-
plete list of options for this command.

Some Files and Directories in /proc

acul — Wed, 23 Nov 2011 14:41:04 +0000

You can navigate the /proc file system just as you’d work with any other
directories and files in Linux. Use the more or cat commands to view the
contents of a file.

/proc/acpi
Information about Advanced Configuration and Power Interface
(ACPI) — an industry-standard interface for configuration and
power management on laptops, desktops, and servers

/proc/bus
Directory with bus-specific information for each bus type, such
as PCI

/proc/cmdline
The command line used to start the Linux kernel (for example,
ro root=LABEL=/ rhgb)
/proc/cpuinfo
Information about the CPU (the microprocessor)

/proc/devices
Available block and character devices in your system

/proc/dma
Information about DMA (direct memory access) channels that
are used

/proc/driver/rtc
Information about the PC’s real-time clock (RTC)

/proc/filesystems
List of supported file systems

/proc/ide
Directory containing information about IDE devices

/proc/interrupts
Information about interrupt request (IRQ) numbers and how they
are used

/proc/ioports
Information about input/output (I/O) port addresses and how
they are used

/proc/kcore
Image of the physical memory

/proc/kmsg
Kernel messages

/proc/loadavg
Load average (average number of processes waiting to run in
the last 1, 5, and 15 minutes)

/proc/locks
Current kernel locks (used to ensure that multiple processes
don’t write to a file at the same time)

/proc/meminfo
Information about physical memory and swap-space usage

/proc/misc
Miscellaneous information

/proc/modules
List of loaded driver modules

/proc/mounts
List of mounted file systems

/proc/net
Directory with many subdirectories that contain information
about networking

/proc/partitions
List of partitions known to the Linux kernel

/proc/pci
Information about PCI devices found on the system

/proc/scsi
Directory with information about SCSI devices found on the
system (present only if you have a SCSI device)

/proc/stat
Overall statistics about the system

/proc/swaps
Information about the swap space and how much is used

/proc/sys
Directory with information about the system. You can change
kernel parameters by writing to files in this directory. (Using this
method to tune system performance requires expertise to do
properly.)

/proc/uptime
Information about how long the system has been up

/proc/version
Kernel version number

Checking disk performance and disk usage

acul — Wed, 23 Nov 2011 14:28:59 +0000

Linux comes with the /sbin/hdparm program that you can use to control
IDE or ATAPI hard drives that are common on most PCs. One feature of the
hdparm program is that you can use the -t option to determine the rate at
which data is read from the disk into a buffer in memory. For example, here’s
the result of typing /sbin/hdparm -t /dev/hda on my system:
/dev/hda: Timing buffered disk reads: 178 MB in 3.03 seconds = 58.81 MB/sec

The command requires the IDE drive’s device name (/dev/hda for the first
hard drive and /dev/hdb for the second hard drive) as an argument. If you
have an IDE hard drive, you can try this command to see how fast data is
read from your system’s disk drive.
To display the space available in the currently mounted file systems, use the
df command. If you want a more readable output from df, type the following
command:

df -h

Here’s a typical output from this command:
Filesystem Size Used Avail Use% Mounted on /dev/hda5 7.1G 3.9G 2.9G 59% / /dev/hda3 99M 18M 77M 19% /boot none 125M 0 125M 0% /dev/shm /dev/scd0 2.6G 2.6G 0 100% /media/cdrecorder

As this example shows, the -h option causes the df command to show the
sizes in gigabytes (G) and megabytes (M).
To check the disk space being used by a specific directory, use the du command
— you can specify the -h option to view the output in kilobytes (K)
and megabytes (M), as shown in the following example:
du -h /var/log
Here’s a typical output of that command:
152K /var/log/cups 4.0K /var/log/vbox 4.0K /var/log/httpd 508K /var/log/gdm 4.0K /var/log/samba 8.0K /var/log/mail 4.0K /var/log/news/OLD 8.0K /var/log/news 4.0K /var/log/squid 2.2M /var/log
The du command displays the disk space used by each directory, and the
last line shows the total disk space used by that directory. If you want to see
only the total space used by a directory, use the -s option. For example,
type du -sh /home to see the space used by the /home directory. The command
produces an output that looks like this:
89M /home

Using the uptime command

acul — Wed, 23 Nov 2011 14:25:17 +0000

You can use the uptime command to get a summary of the system’s state.
Just type the command like this:
uptime
It displays output similar to the following:
15:03:21 up 32 days, 57 min, 3 users, load average: 0.13, 0.23, 0.27
This output shows the current time, how long the system has been up, the
number of users, and (finally) the three load averages — the average
number of processes that were ready to run in the past 1, 5, and 15 minutes.
Load averages greater than 1 imply that many processes are competing for
CPU time simultaneously.
The load averages give you an indication of how busy the system is.

Using the su – command

acul — Wed, 23 Nov 2011 14:22:22 +0000

If you’re logged in as a normal user, how do you do any system administration
chores? Well, you become root for the time being. If you’re working at
a terminal window or console, type
su -
Then enter the root password in response to the prompt. From this point
on, you’re root. Do whatever you have to do. To return to your usual self,
type
exit
That’s it! It’s that easy

Wavelength and antennas

acul — Wed, 23 Nov 2011 13:47:37 +0000

A term related to frequency is wavelength. Radio waves travel at the speed of
light. The term wavelength refers to how far the radio signal travels with
each cycle. For example, because the speed of light is roughly 300,000,000
meters per second, the wavelength of a 1-Hz radio wave is about 300,000,000
meters. The wavelength of a 2-Hz signal is about 150,000,000 meters.
As you can see, the wavelength decreases as the frequency increases. The
wavelength of a typical AM radio station broadcasting at 580 KHz is about
500 meters. For a TV station broadcasting at 100 MHz, it’s about 3 meters.
For a wireless network broadcasting at 2.4 GHz, the wavelength is about
12 centimeters.
It turns out that the shorter the wavelength, the smaller the antenna needs
to be in order to adequately receive the signal. As a result, higher frequency
transmissions need smaller antennas. You may have noticed that AM radio
stations usually have huge antennas mounted on top of tall towers, but cell
phone transmitters are much smaller and their towers aren’t nearly as tall.
That’s because cell phones operate on a higher frequency than do AM radio
stations. So who decides what type of radio gets to use specific frequencies?
That’s where spectrums and the FCC come in.