Icepack-linux and Neck Pads

Speaking UNIX: About inode

admin — Mon, 12 Mar 2012 01:53:58 +0000

Do you have a number of UNIX? Commands (such as df) in Iused and% Iused confused about the meaning, or when people discuss the inode when talking? UNIX and Linux? Systems use the inode, of course, IBM? AIX? Is no exception. This article will show you what is the inode, inode Why is very important for UNIX, inode structure, and operation of the inode command.
UNIX operating system inode is a data structure that contains all files with the file system associated with some important information. Create a file in UNIX systems, and will create a lot of inode. Typically, the file system disk space of about one percent of space allocated to the inode table.
Sometimes, people use a number of different terms, such as the inode and the index number (inumber). These two terms are very similar and interrelated, but they are not talking about the same concept. inode refers to a data structure; The index number is actually the identification number of the inode, and therefore called the inode number or index number. Index number is an important file-related information content. The next section describes the inode number of other attributes.
inode table contains a list, which lists all of the corresponding file system inode number. When users search for or access a file, UNIX system inode table to find the right by the inode number. Inode number is found, the associated command can access the inode, and its appropriate changes.
For example, use vi to edit a file. When you type vi filename, in the inode table to find the inode number after only allows you to open the inode. In vi editing session, change some of the attributes in the inode, when you complete the operation and type: wq, it will shut down and release the inode. In this way, if two users attempt to edit the same file, inode has been allocated during the first editing session to another user ID (UID), so the second editing tasks must wait until the release of the inode so far.
The inode structure
For experienced UNIX developers or administrators, inode structure is relatively simple, but there may be some you do not already know, amazing insider on the inode. Only gives the following definition contained in the inode, UNIX users often use some of the important information:
inode number used to identify file types, as well as the mode for stat C function information file is the main link to the UID number of the owner of the group ID (GID) file size disk blocks the file uses the actual number of the last modification time most recent visit was the last time to fundamentally change, inode contains all the information about the file (in addition to the actual file name, and beyond the actual data content). Header files in the AIX / usr / include / jf / ino.h, or Web page http://publib.boulder.ibm.com/infocenter/systems/index.jsp?topic=/com.ibm.aix. files / doc / aixfiles / inode.h.htm can be found in the full inode structure.
The information listed above is very important for the files and frequently used in UNIX. Without this information, then the file will be considered damaged and unusable.
Compared with other operating systems, UNIX system directories and files may look different, but it is not. In UNIX, the directory file itself, but in their use of the inode number of additional settings. Is essentially a directory containing other files. In addition, the mode information corresponding to set some flag to tell the system that the file is actually a directory.
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System Administration Toolkit: Log file basics

admin — Fri, 09 Mar 2012 02:12:44 +0000

In a typical UNIX? Or Linux? Computer operation creates many log files. Some log files contain useful information; can help you with some capacity and resource planning. This article focuses on the different log files record basic information, their location and how to use this information to determine the system’s operation.
About this series
The typical UNIX administrator has a set of frequently used to aid in the process of critical utilities, tricks, and systems. There are a number of important utilities, command line and script can be used to simplify the various processes. Some of these tools from the operating system, and most of the tricks come through years of experience and ease the system administrator’s life. This series is focused on maximizing the use of various tools available in UNIX environments, including heterogeneous environment to simplify management tasks approach.
Log Files
All systems will generate a different number of log files used to track and record information on a different computer. Contents of these files and utility system dependent, but the core information provided in the document are generally consistent.
For example, all UNIX and Linux machines using syslog (operating system, applications and services, the general log to record information recording system) to record information. syslog will generally record large amounts of data, including reports from the different hardware and system registry, performance and fault information. In addition to syslog, the system is also used to record information on a variety of computer and its operating services, environment and application logs.
Although the contents of the log file analysis and extraction of information can be very time consuming and complex, but can not ignore the value of the information in these logs. Log files can provide information about potential problems, errors and security vulnerabilities, etc. tips, if used correctly, can even provide information about server load and capacity of the warning.
Log Location
The location of the log file system-dependent. In most UNIX and Linux systems, most of the log files are located in / var / log in. For example, Listing 1 shows Gentoo Linux system log files on the list.
Listing 1. Linux / var / log directory contents

$ Ll / var / logtotal 3312-rw-r —– 1 root root 8218 2007-11-03 06:21 dmesg-rw-rw —- 1 portage portage 650111 2008-02-02 13:01 emerge . log-rw ——- 1 root root 24024 2007-11-05 07:26 faillog-rw-r – r – 1 root root 386032 2007-09-28 14:39 genkernel.logdrwxr-xr -x 2 root root 4096 2007-11-03 06:47 iptraf/-rw-r–r– 1 root root 292292 2008-02-03 08:07 lastlog-rw ——- 1 root root 1346931 2008-02-03 08:50 messagesdrwxr-xr-x 2 root root 4096 2006-08-30 17:04 news / drwxr-xr-x 3 root root 4096 2007-09-28 13:22 portage/drwxrwx– – 2 root portage 4096 2007-11-03 06:40 sandbox/drwxrwx— 2 snort snort 4096 2007-10-13 11:34 snort/-rw-rw-r– 1 root utmp 496896 2008-02-03 08:07 wtmp-rw-rw-rw-1 root mc 61189 2007-06-10 11:37 Xorg.0.log-rw-rw-rw-1 root root 61189 2007-06-10 10:40 Xorg.0 . log.old
In Solaris?, IBM? AIX? And HP-UX?, The main syslog and other log files are written to the majority of / var / adm directory of the file (Listing 2).
Listing 2 is the traditional UNIX / var / adm content

$ Ls-al / var / admtotal 230drwxrwxr-x 9 root sys 512 Feb 3 15:30. Drwxr-xr-x 48 root sys 1024 Feb 3 15:32 .. drwxrwxr-x 5 adm adm 512 Feb 2 16:13 acct -rw ——- 1 uucp bin 0 Jan 12 18:49 aculogdrwxr-xr-x 2 adm adm 512 Feb 2 16:03 exacct-r – r – r – 1 root root 2856 Feb 3 16 : 10 lastlogdrwxr-xr-x 2 adm adm 512 Feb 2 16:03 log-rw-r – r – 1 root root 69065 Feb 3 16:08 messagesdrwxr-xr-x 2 root sys 512 Feb 2 16:09 pooldrwxrwxr -x 2 adm sys 512 Feb 2 16:13 sadrwxr-xr-x 2 root sys 512 Feb 2 17:03 sm.bin-rw-rw-rw-1 root bin 0 Jan 12 18:47 spellhistdrwxr-xr-x 2 root sys 512 Feb 2 16:03 streams-rw ——- 1 root root 93 Feb 3 16:08 sulog-rw-r – r – 1 root bin 3720 Feb 3 16:14 utmpx-rw- r – r – 1 adm adm 29760 Feb 3 16:10 wtmpx
In addition, some non-system-level messages and information are written in the / var / log in the log (Listing 3). For example, on Solaris, mail debug entry is written in the default / var / log / syslog.
Listing 3. Solaris on the / var / log the other log

$ Ls-al / var / log / total 48158drwxr-xr-x 7 root sys 512 Feb 3 16:07. Drwxr-xr-x 48 root sys 1024 Feb 3 15:32 ..- rw ——- 1 root sys 0 Jan 12 18:48 authlog-rw-r – r – 1 root other 27 Feb 2 16:17 brlogdrwxr-xr-x 2 root root 512 Feb 2 16:39 gdmdrwxr-xr-x 2 root sys 512 Feb 2 16:09 pool-rw-r – r – 1 root sys 24480410 Feb 3 12:51 postrun.logdrwxr-xr-x 2 root sys 512 Feb 2 16:41 swupas-rw-r – r- – 1 root other 635 Feb 2 17:25 sysidconfig.log-rw-r–r – 1 root sys 3967 Feb 3 16:08 syslogdrwxr-xr-x 3 root sys 512 Feb 2 17:25 webconsoledrwxr-xr-x 2 root sys 512 Feb 2 16:37 xen-rw-r – r – 1 root root 66171 Feb 3 16:07 Xorg.0.log-rw-r–r – 1 root root 66256 Feb 3 16: 06 Xorg.0.log.old
Of course, to find the file is the most basic questions. You need to know what the file contains useful information.
According to a variant of UNIX, some of the logs in other places may be more messy, but the standardized file location has some interesting attempts to make the log files are classified as already mentioned before, one of the directories.
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Completely hand-built custom LINUX

admin — Mon, 27 Feb 2012 02:33:16 +0000

LFS-related

Linux From Scratch LFS is short, LFS there is an important reason is to help people learn how linux works within the system. Building an LFS system helps demonstrate what makes linux running, how the various components work together, rely on each other. One of the best things you can get through this study completely customized according to their needs linux systems.

A key benefit of LFS is that it allows the user more control for the system, rather than relying on other people’s linux implementation. In the LFS world, you sit in the driver’s position, control of every detail of the system, such as the directory layout and boot script configuration and so on. You can also control where, why, and how to install each program. Relevant information about LFS can go to this link to find. http://www.linuxfromscratch.org/.

This environment is VM5.5 structures, which assigned to the virtual machine’s memory is 256M, hard disk size is 8G, of course, the real size of the system after less than 600M, but at least at compile time, the 3G space. For ease of use, which the package can go to the LFS project, the ISO download ready-made package, address http://kerrek.linuxfromscratch.org/pub/lfs-livecd/ lfslivecd-x86-6.3-r2130.iso, of course, if the want to use the updated software, please go to the site to download. Used here is lfslivecd-x86-6.3-r2130.iso.

As the production process is relatively long and may last for several days, if it is done through the VM, then you can use it to protect the site of pause, time to start using the site to continue the production process.

Note: The instructions here are the instructions must be input, unlike the previous article style.
I: Initialize the production environment.

When using the VM in a troublesome place, it can not save the file from the physical machine by way of copy and paste commands to install production, while the LFS has a lot of compiler directives, or other commands are similar, the reasons for the supremacy of the spirit of convenience, So open its network capabilities, and remote connectivity tools (Putty, SshClient) for instruction.

Use CD-ROM, there’s really nothing, to set the system time and time region as shown below:

1: Upon the completion of boot to user mode, enter the following command to use to open the network function and set the administrator password. Note: When setting the VM virtual machine settings in the card, please use the “bridge” mode, or it may get less than IP, but also to meet the LAN can access by way DHCP IP.

[Root ~] # / etc / rc.d / init.d / sshd start [root ~] # passwd root

2: SshClient connected to the host, to the hard disk partitioning operations

Here you can follow the needs of partition, I set a root partition, and in accordance with a swap partition, for example, the swap partition occupies 512M, the remaining part to the whole root partition, / dev/hda1 as swap; / dev/hda2 as target system root directory.

cfdisk / dev / hda

Save and exit after the disk partition format

mkswap / dev/hda1 mkfs.ext3 / dev/hda2
3: Create the appropriate file and path.

Here to note two important directories under the LiveCD / usr/share/LFS-BOOK-6.3-HTML directory is stored in LFS Manual; / lfs-sources inside the store is required for LFS build the source package, not everywhere under the software. The role of specific instruction can refer to the documentation, do not be described in detail here. Create a symbolic link makes the tool chain will compile always located in the / tools directory, which means that the compiler, assembler and linker in the target directory for the build / tools can be used when the total.

export LFS = / mnt / lfs mkdir-pv $ LFS mount / dev/hda2 $ LFS mkdir-v $ LFS / sources chmod-v a + wt $ LFS / sources chmod-v a + wt $ LFS / sources ln-sv / mnt / lfs / tools / /

Log in as root when a mistake is enough to damage or even destroy the system, therefore, this chapter, we recommend using a non-privileged user to compile and install the package. You can use your own user name, but in order to establish a clean work environment, we recommend that you create a new group called lfs, and add a user called lfs, we will use this user during the installation process.

groupadd lfs useradd-s / bin / bash-g lfs-m-k / dev / null lfs passwd lfs chown-v lfs / mnt / lfs / tools / chown-v lfs / mnt / lfs / sources / su – lfs
Login as user lfs, the initial shell is usually a login shell (login shell), it first reads the host system’s / etc / profile file (which may contain some of the settings and environment variables), then continue reading. Bash_profile file to complete the login initialization. . Bash_profile file exec env -i…/bin/bash command with a completely empty environment to replace the current environment (in addition to inherited HOME, TERM, PS1 variables). This will ensure that we build environment in the host system will not be unnecessary or potentially dangerous effects of environmental variables to ensure a clean work environment.

cat ~ /. bash_profile “EOF” exec env-i HOME = $ HOME TERM = $ TERM PS1 = ‘u: w $’ / bin / bash EOF cat ~ /. bashrc “EOF” set + h umask 022 LFS = / mnt / lfs LC_ALL = POSIX PATH = / tools / bin: / bin: / usr / bin export LFS LC_ALL PATH EOF source ~ /. bash_profile export cd / mnt / lfs / sources /
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Microsoft — linux crusade against evil idea of a fool

admin — Fri, 24 Feb 2012 08:40:17 +0000

Tomato Garden case fights uproar recently, those who have the sympathy Hong Lei, tomato version due to benefit from the convenience of supporters, because tomato promote the Microsoft monopoly objectors; from a legal point of view crusade against those who have. In any case, this incident has once again pushed the windows to the cusp of public opinion, the piracy problem to world attention.

Awareness of the problem of piracy, this is a good thing, until now many people do not know the difference between legitimate and pirated, that take a genuine installation disc out is genuine; a lot of people think that the tomato garden and the windows are two different operating system, like many people think that Maxthon and ie are the two browsers. Many people think that Microsoft has promoted China’s proliferation of computers, in fact, not Microsoft essentially to promote, not Microsoft, still there will be Kingsoft, Rising like to come, is to promote the popularity of computer piracy, Microsoft also created a general dependent, resulting in a hundred of billions of dollars on software imports.

Some people say that hundreds of thousands of genuine, who can afford, which is thousands of consumers to easily create, as a monopoly, Microsoft can do whatever they want, Microsoft, family history, and also a history of piracy, so Microsoft will play piracy reached a pinnacle, lose ground, into a disadvantage, now cast aside the bow once the birds are gone, Xiemoshalv.

So, will the masses of the piracy problem will deepen understanding of the software are also numerous modifications done scattered. Against the non-conversion law, to see what your change is, if we regard the effort spent on the cause of open source software and free software, not better, anyway, who converted from the modified software itself does not receive any money.

(About Maxthon, in fact, is the same as modified software and tomato problem, ie the same as for the promotion played a role contributed to, if not the appearance of firefox, we are still fully dependent on Microsoft, even so, consequences have been the beginning significantly, many sites only support ie core browser, if it continues to develop, then, is an absolute monopoly in the emergence and development of firefox, malware and Trojans played a role contributed to, ie6 spread under the horse, so that People have switched to firefox, Microsoft’s an oversight, caused firefox to flourish, we can have a second choice of course we can not rely on the rogue and Trojans to help us promote anti-trust, help us promote the normal development of software industry, We should, through legislation, it is best to prosecution system.)

Operating system can occur tomato sector windows, it is also possible tomato linux. Hong Lei event while giving everyone a reminder, if linux can modify to fool the point style, linux can be popular, creators through advertising revenue, most critical is not illegal. For consumer habits, if coupled with a windows virtual machine as a transition, so that we can gradually quit Windows.

Linux platform Maya: Blender Description

admin — Wed, 22 Feb 2012 06:28:09 +0000

Linux platform Maya: 3D art and game development environment Blender scene Profile
[Blender] is based on [GNU / GPL] generic open source software, open protocols. Three-dimensional computer is a professional content creation software. It is common to all operating system platforms. As an open source software, [Linux] platform [blender] the most important working environment.
[Blender] originated in a very arcade game fans the receipt of the company, the Netherlands [NeoGeo]. It was originally as [NeoGeo] within the three-dimensional animation tools exist. , The company’s partner Rosen said [Ton Roosendaal] established a new company, “not a number” [Not a Number, NaN], and as a developer Maya [Maya] competitors [Blender] basis. Unfortunately, after 1998, as the technology bubble burst, the number of non-closure of the company in 2001. A year later, Rosen said initiated [Blender] Foundation, the purpose is to [Blender] into an open-source project. In a number of enthusiastic volunteers and the number of former non-employees with the help of only seven weeks to raise a million dollars. Thus, [Blender] on the [GNU / GPL] under the banner of a free software.
Ton Roosendaal
Currently, [Blender] development is still mainly done by volunteers. Therefore, [Blender] in the continuous recruitment of new foundations. If you own in order to have confidence, you can also try to join the development and maintenance team. See specific details refer to the source [3].
And [ubuntu] is very similar, [Blender] also has a global user community. In China, [blender] community has been gathering a lot of popularity. Many of which are previously used [maya] and [3Dmax] users. In addition to this communication technology, you can also here the master who display their works

According to [GNU] terms, any use of [Blender] development work (including the [python] source code), all of its intellectual property rights belong to the developer their own. Works can be displayed on any occasion, whether profit or not, are not [Blender] developer of any restrictions. However, note that, [GNU / GPL] protocol requires the source code of the work itself is also open.
[Blender] is currently widely used [blender] 2.4 series. The series continues the tradition of some of Blender 2.46 in the fixed bugs that exist after the latest Blender 2.47 is a more stable “polyclonal” version. Also, some new tools are added in this version.

Reference Source:
[1] Blender 2.47 official profile. [2] Blender Noob to Pro Wikibook. [3] “http://www.blender.org/community/get-involved/” Blender Download: linux-glibc236-py24-i386.tar.bz2 “> Blender 2.47 x86-32 bit Linux systems, the need to python2. 4 linux-glibc236-py25-i386.tar.bz2 “> Blender 2.47 x86-32 bit Linux systems, the need python2.5 Blender 2.47 x86-64 bit Linux systems, the need python2.4 Blender 2.47 x86-64 bit Linux systems, the need python2.5

Original link: http://www.ownlinux.cn/2008/08/31/maya-3d-blender-linux/

Ubuntu system to teach you four ways to capture

admin — Mon, 20 Feb 2012 13:02:21 +0000

Have some basic computer friends should know that there is a PrintScreen key on the keyboard, which is used to intercept the screen. The method in most operating systems are effective under the Ubuntu Linux as well. But only use this method to look beyond their grasp at some screenshots, here we take a look at Ubuntu Campus magazine: “Taoyuan” super students of Tu written in Ubuntu screenshot method.
1 screenshots directly using the keyboard (most systems, including Windows also provides the method).
Press the PrintScreen key: the interception of the current entire desktop.
Press Alt + PrintScreen: the interception of the current active window.
(2) use compiz screenshot.
If your system is installed compiz effects, compiz is located in the screenshot key, and then super + left click to capture. Specific methods: Click: System / Preferences / Advanced Desktop Effects Settings, which found in Extras Screenshot, check the front of the box. Here you can change the default button and the image storage path. To facilitate, we have adopted the default values. Then you can hold down the super key, then press and hold the left mouse button drag to the interception of the picture. Note: The intercept of the image stored in the Desktop directory by default.
3 Take Screenshot comes with system software screenshot (below left)
Click: Applications / Accessories / Take Screenshot, a window will pop up. Above, there are several options: Grab the whole desktop: the interception of the entire desktop. Grab the current window: the interception of the current active window. Grab after a delay of ** seconds: ** seconds after the interception of pictures, mainly for the interception of dynamic images, such as 3D effects. Recommendation: If the current active window is the intercept, then select Grab the current window, the best click the window you want to intercept, and finally click the Take Screenshot button.

4 pictures in GIMP intercept (above right)
Click Applications / Graphics / GIMP Image Editor to open GIMP. Select: File / Acquire / Screenshot, will also pop up a window, this is a bit similar to the system in the Take Screenshot software. The most common of course is: Select a region to grab (select a region intercept), and then click Snap button, then the mouse becomes a? Cross?, Hold down the left click directly on it.
Download Ubuntu magazine: “Taoyuan” Read more

How to configure a Linux system RAID1?

admin — Thu, 16 Feb 2012 03:05:33 +0000

How to configure a Linux system RAID1?
A: First, Linux kernel can support RAID. The first thing to do is to buy two identical hard disk, and then divided into equally sized partitions. Then you can download the mdadm tool to create and manage RAID arrays.
Execute the following command, you can create your first disk array:
# Modprobe md # mdadm – create – verbose / dev/md0 – level = 1 – raid-devices = 2 / dev/hda1 / dev/hde1
The above command creates the array (/ dev/md0), and mapped to two physical disk (/ dev/hda1 and / dev/hde1). This RAID array is known as RAID1, which directly mirror mode. When you create a good, you can format it, and the same operation as the operation of other partitions it.
RAID does not require any configuration files. When the system boots, RAID array, will take effect immediately. So you can treat other physical partition on the RAID device, like any operation.

Tencent Linux QQ for the trial version of Godson-2F Notes

admin — Tue, 14 Feb 2012 02:21:38 +0000

August 29, 2008 Tencent released shortly after the x86 version of linux QQ such as online news said finally released a version of Godson-2F, I just upgrade the system for this version of the QQ Godson was about the trial.

I now introduce the hardware and software environment:
Hardware: PC 6002 Long Fu Long Dream Godson 2f, 512M memory, 80G hard drive, dual Gigabit Ethernet Software: Liu Shiwei provided Godson 2F mipsel debian-based optimization system 20080808a X desktop is gnome

Software Download linux / download.shtml “> http://im.qq.com/qq/linux/download.shtml
Download unzip (tar-zxvf) directly executable. Double-click that to run qq QQ.

Log interface is very simple, speed is not slow, style that became the win on style, with the x86 version of linux qq same.

After landing more familiar interface, simple and tried a little common functions and menu, discovery is quite simple, Tencent’s QQ have not see a value-added services.

Interface skin, as well as the background pattern.

Default chat window in the form of the label page, saving the desktop display space not used to clicking on the left button can also be separated from the window.

The current version only supports the standard expression of sending graphics, no screenshots, 自定义表情 function, send the file does not function. This may allow some of the QQ fans, sorry.

You can simply view chat history than win much weaker version of the history function

View personal information, the content is relatively simple, there is no support for custom avatars, all value-added services has not. However, individuals can maintain basic information, you can meet their basic needs.

System Settings is the most basic functions.

The way to the system installed a few skin, gnome-line skin very much, here I use a mac’s.

Overall, the current Preview 1.0 (106) version can handle the most basic communication needs, Preview or Preview (preview version), according to the progress of Tencent update this a few times, or in the continuous development should be the, I believe that soon there will be brings more features and surprises us!

How to migrate to ext4 Linux file system

admin — Fri, 10 Feb 2012 03:52:09 +0000

Ext4 is the number of Linux? The latest version of the file system, it is as important as the previous version and popular. As a Linux system administrator, you should know the advantages and disadvantages of migrating to ext4 and basic steps. This article describes when to adopt ext4, how to use the ext4 file system maintenance tools of traditional and how to take full advantage of the file system.
Ext4 features
Linux supports several different file systems. These file systems, some are dedicated network file system or operating system developed for other file systems, but most still used as a Linux native file system – you can Linux root (/) and put the file system directory system. Currently, this type of file systems including ext2, ext3, ReiserFS, XFS and Journaled File System (JFS). But the file system has been continuously design and development, the new file system are also expected to come out.
Is currently developing the most important Linux file system is ext4 – it is specifically developed for the original Linux extended file system (ext or extfs) of the fourth edition. As the successor of the previous version, ext4 in the near future is likely to become an important standard Linux file system (perhaps a standard file system).
Ext4 compared with ext3
Extended file system (ext or extfs) is the fourth edition of the causes of the developers in the ext3 into a new advanced features. However, during implementation there have been several problems:
Contrary to some of the new features backward compatibility. Ext3 code becomes more complex and difficult to maintain. These changes make a very reliable ext3 had become unreliable.
For these reasons, beginning in June 2006, the developer decided to ext4 from ext3 to separate independent development. Ext4 since the beginning of the development work carried out, but most Linux users and administrators do not pay attention to how this matter. With the 2.6.19 kernel release in November 2006, ext4 first appeared in the mainstream kernel, but it was still in the experimental stage (or now), so many people ignore it.
As is still in development stage, starting from the 2.6.24.4 kernel, ext4 feature list has been in flux. Ext4 features, including current and expected evolved from ext3 features, shown in Table 1.
Table 1. Ext4 features of the current and future capabilities to make it beyond the ext3

Function
Superiority

Larger file systems
Ext3 can hold up to 32 TiB file systems and 2 TiB files, depending on the specific architecture and system settings, the actual capacity limit may be lower than this figure – perhaps the only accommodate 2 TiB file systems and 16 gibibyte (GiB ) files. On the contrary, Ext4 file system capacity of 1024 pebibyte (PiB), or 1 exbibyte (EiB), and the file size reached 16 TiB. Of general desktop computers and servers, this may not be important, but for large disk array users, which is very important.

extent
extent is a way to improve the efficiency of disk file descriptors method, which can reduce the time required to remove the large files and so on.

Persistent pre-allocation
If an application requires the actual use of disk space allocated to it before, most file systems are not used by the disk space to write 0 to achieve the allocation. The ext4 allow early distribution, no need to carry out such operations, which can increase some of the performance of databases and multimedia tools.

Delay distribution
Ext4 can try to delay the allocation of disk space, which can improve performance.

More subdirectories
If ext3 in a directory can contain up to 32,000 subdirectories can not meet your needs, then do not worry, because ext4 to cancel this limitation.

Log checksum
Ext4 adds data to the log and check (checksum) function, which can improve the reliability and performance.

Online Defrag
Although ext3 is generally not affected by debris, but the files stored on it will produce some number of pieces. Ext4 support online defragmentation, which can improve overall performance.

Recover deleted files
Although this feature has not been achieved, but ext4 will support restoration of deleted files. When a file is accidentally deleted, this function will be extremely useful.

Faster file system checking
Ext4 adds a new data structure, allowing fsck to skip checking the unused portion of the disk, thus speeding up file system checks.

Nanosecond timestamps
Most of the file system (including ext3) contains a time stamp accurate to the second data, and ext4 the accuracy to the nanosecond. Some data also show that the ext4 timestamps support dates to April 25, 2514, while ext3 only to January 18, 2038.
Since ext4 is still in development stage, this menu will vary. List of features some of the features in actual use do not have backward compatibility with ext3 – that may not be able to use the ext3 file system type mount ext4 file system code. But ext4 retain forward compatibility – you can mount the ext4 file system is the same as the mount ext3 file system.
the use of object ext4
Ext4 is the most significant improvements in the size of files and file systems. Therefore, the users most likely to need ext4 are those few TB of disk space the size of the user. However, the feature list in Table 1 also shows some other interesting improvements. For example, if your directory with a large number of subdirectories, or to request time stamp accuracy is less than one second, you may want to try to use ext4.
Because ext4 is currently at an experimental stage, it must be used to re-compile the kernel, otherwise, there will be trouble when using ext4. In fact, ext4 in the pilot phase means that only want to contribute to the development of ext4, or some of its features are very eager, these cases only need to use it. If you want a stable release of ext4 before reliable large disk support, consider using XFS or JFS.
Of course, ext4 can not always be in the experimental stage. It will soon become a stable file system. By then, ext4 as ext3 as the best choice for all users, but requires attention to several issues. First of all, ext4 has some unique bug, so when the first stable release version of ext4 should pay more attention. Second, the use of ext4 may cause some older versions of the tools can not access the disk. This will involve emergency recovery tools, so make sure you use the tools do not support ext4 before the update. The good news is, it should be a smooth migration from ext3 to ext4, if you need to save the existing data, which will enable easy transfer.
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How to add a password to Grub

admin — Mon, 06 Feb 2012 02:38:31 +0000

Purpose is to prevent others modify grub, with a single-user mode.
Add password only need to modify the grub grub boot file, add a line password keyword, can be stored in plain text or MD5 encrypted storage. Here we introduce a way to use MD5 encryption.
1, first / sbin/grub-md5-crypt generate a MD5 password string

/ Sbin/grub-md5-crypt
Password:
Retype password:
$ 1 $ oWpTe $ / MWUUYbBlF.2RUZK8nbWU0
The original password is “abc”.
2, modify the grub.conf file

default = 0
timeout = 5
splashimage = (hd0, 0) / boot / grub / splash.xpm.gz
hiddenmenu
password – md5 $ 1 $ oWpTe $ / MWUUYbBlF.2RUZK8nbWU0
title Red Hat Enterprise Linux AS (2.6.x-xx.EL)
………
Here we must note, password that must be added in the interim between the splashimage and title, or can not take effect.
Restart your machine, you will find you want to modify the grub menu, you must first press P and enter the correct password before they can continue.
Then attach a method of using sed to modify grub.conf, this method can be used to modify all of the server volume.

GRUB = / boot / grub / grub.conf
TEMP = / tmp / grub.conf
grep-v password $ GRUB cat $ TEMP | sed-e ‘s / hiddenmenu / hiddenmenu password – md5 $ 1 $ oWpTe $ / MWUUYbBlF.2RUZK8nbWU0 / g’ $ GRUB