chkconfig role: Specifies the boot service at which level to start or shut down; -h --help to view the help --list --level 345 Name <on | off>
update-rc.d certain control program in Ubuntu boot -f force may be used to force [chkconfig On Ubuntu, the need to install]
1.
High Performance Cluster (application layer) -------- Hadoop cluster = Map reduces + HDFS
2. The system starts
power
BIOS chip - | 1, POST checks the hardware is normal
| 2, * Start the system * - | reading order issue position 1, where the system (BIOS): drive network (PXE) U disk CD / DVD ...
| 2, the system will need to file hard disk, loaded into memory, so the CPU reads and runs;
| the MBR partition (BootLoader): boot the system is used to find and load the
| | - the LILO
| | - GRUB into a first stage, stage 1.5, and a second stage;
We have this kernel is loaded, but it does not run common applications
At this point, we have to run the first application --init
the init: The operating system is divided into 0--67 levels; each level will run a corresponding application; (designated default start level)
|
read default level 3 (command line) - |. chkconfig / rc * d ( each level required to start the process)
(01,356)
0 off
1 single-user mode (safe mode)
3 command line
5 graphical interface - start Desktop
6 restart
rc.local // read the file system starts last, the administrator may need to run the boot command, add here;
chkconfig role: Specifies the boot service at which level to start or shut down;
-h --help View Help
--list
--level 345 Name <on|off>
update-rc.d startup control program at some Ubuntu
-f force to force [chkconfig can be used on Ubuntu, you need to install]
3, the basic format of Linux commands
Command [options] [parameters]
[]: On behalf of the brackets, optional; specify a particular function to achieve command;
<>: object code of the command; if not added <> stands can not be omitted;
long integer options
short short options options can be combined, and the long option can not be combined;
extended: command from the command option] [parameters
4, commonly used Linux command of the basic use of
echo $ PATH (environment variable) variable: some are named in memory only; 
Ls // display file information
Pwd // display the current path
Cd // switch to the target directory
- the current user's home directory (/ root / home)
The current directory (with files beginning for hidden files)
.. the parent directory of the current directory
- on $ OLDPWD time after the catalog
Touch // modification timestamp:
Stat atime modify the contents of file access time mtime time ctime modify file attributes
T ouch 【【CC】YY】MMDDhhmm【.SS】
20 19 0 8 01 16 36 .22
Touch a.txt
-a modify the access time
-m modified Modified
-t modified to specify what time
-c modify the file Mtime not create the file if the file does not exist
Mkdir // create a folder:
-p create multi-level directory recursive
-v detailed display creation process
-L only display a directory specified in the current directory
-NLM see how many level subdirectories
-d display only the catalog file
Rm // delete file:
-f Force forced
-i asked to delete the file to change the default command (RM Alias = 'RM -i')
\ RM abc
/ bin / RM abc
-r delete a directory file
Extended about:
1, the default does not apply in the case rm remove directories - rmdir
rmdir only removes empty directories;
* 2, we will need to delete a file or directory under / tmp directory can be;
/ tmp directory for temporary files directory, 30 days access to the file is not automatically deleted
3. If you have to delete some files, we find by matching up, and then delete the line;
[find extensions! ! ! ]
Find / -name ABC | RM xargs
Find / -name RM -exec {ABC} \;
The soft and hard links connected to the difference between:
Hard Links: New file already exists an alias file when the original file is deleted, the new file can still be used.
Soft links: Also known as a symbolic link, the new file as a "path" to represent another files, and is very similar to Windows shortcuts, the new soft links can point to a file that does not exist.
the following details about the difference between hard and soft link connection.
1. hard links and the original file is no different, but share a inode number (unique identification file on the file system); and soft link is not shared inode, it can be said is a special inode, inode so original and different.
2. If the original file is deleted, then the connection will not have access to soft, and hard connection is possible.
3. Due to the nature of symbolic links, which may lead to cross disk partitions, but hard links do not have this feature.
Create a hard link: ln create a soft link: ln -s