First, the computer performance
1, scale: Cluster (strength in numbers)
Clusters: 1) load balancing cluster
2) High Availability Cluster
3) High Performance Cluster (application layer) --- the Hadoop cluster = Mad reduces + HDFS
2, longitudinal expansion: application migration (not recommended)
Note: Under Linux, everything is a file;
Second, the system start
1, the power supply (BIOS chip)
1) Power On Self Test: Check the hardware device is working properly;
2) Start system: a reading order problem where the position of the system (BIOS):. Hard disk, network (PXE), U disk, CD / DVD ...
. B required system files on your hard disk, loaded into memory, so the CPU reads and runs;
MBR partition (BootLoader): it is used to boot the system to find and load;
MBR partition (BootLoader): LILO;
MBR partition (BootLoader): grub: into a first stage and second stage 1.5
2. At this point, the kernel has been loaded, but it does not use common applications --- kernel;
3, the first application to use --- init
init: The operating system is divided into 0-6, a total of seven levels; each level will use a corresponding application; (specify the default boot level)
1) reads the default level 3 (command line) - chkconfig, rc * d (each level required to start the process).
（0 1 3 5 6）
0: Off 1: single-user mode 3: Command Line 5: graphical interface 6: Restart
2) Restart the final step ----- rc.local (system start last read the file, the administrator may need to run the boot command to add here)
4, chkconfig role: Specifies the service, when the start-up or shut down at what level)
1) chkconfig -h --help: View Help
2) chkconfig --list: whether to start the process at all levels
3) chkconfig --level 345 Name <on | off>: Specifies the starting level
5, update-rc.d certain control program in the boot Ubuntu;
-f: Force force
6, chkconfig can On Ubuntu, the need to install;
Three, Linux command
1, the Command [Option] [parameter]
1) []: representatives bracket, optional; specify a particular command functions implemented;
2) <>: object code of the command; if not added <> is not representative of omitted;
3) long option
4) short options: short options can be combined, and the long option can not be combined;
Fourth, the basic use of commonly used Linux commands
1, echo $ PATH (environment variable) variable: some are named in memory only;
Question: If the command is no longer the PATH, how to solve?
1) an absolute path to run this command to;
is the command itself absolute path of execution; and some named, is the system default alias (add your own) ---- Alias;
Which the Command: Find command absolute path
\ ls: backslash run directly;
2) to add the path to the directory to the pATH;
pATH = $ pATH: / XXX / XXX
ls: Displays file information
-l: Detailed ll see the file (property)
-i: inode (attribute)
-h: human readable human
-F: behind the display file mark (used to distinguish the file type)
-r: reverse display file contents
-a: show all (parcels hidden files) file
2, pwd: display the current path
1) $ pwd: there is a default environment variable
3, cd: Switch to the target directory
1) to: the current user's home directory (/ root, / home)
2) .: current directory (with files beginning for hidden files)
3) ..: The current directory of the parent directory
4) -: $ OLDPQD: once through the store directory
4, Touch: modification timestamp
1) Stat atime access time; mtime modify the contents of the file time; ctime modify file attributes
2）Touch a.txt
stat abc: display time
touch [parameters] ... file ...
touch -a abc
3) [[CC] YY] MMDDhhmm [.ss]: indicates the time of 20190801163622.
Such as: touch -at 201908011632.22 abc modification time 201908011632.22
4) -a: modify access time
5) -m: Modify modification time
6) -t: modified to specify what time
7) -c: modify the file Mtime, if the file does not exist, create the file
5, Mkdir: Create a folder
1) -p: create multi-level subdirectories recursively
2) -v: detailed display creation process
tree: displays the directory, file tree view
a, -L NUM see how many level subdirectories
b, -d display only the catalog file
tree /: View all listings
mkdir abc: Create a directory
6, Rm: Delete Files
1) -f: force mandatory
2) -i: ask if this file is deleted, the default command (alias rm = 'rm -i')
\rm abc
/bin/rm abc
3) -r: delete the file directory
Expansion: 1) default does not apply in the case rm remove directories - rmdir (only delete empty directories)
2) We will need to delete the file or directory to the / tmp directory can; the / tmp directory for temporary files directory, files not accessed for 30 days will be automatically deleted;
3) If you have to delete some files, we matched up by find, and then delete the row;
find extension: find / -name abc | xargs rm
find / -name abc -exec rm {}\;
