What Is System Command

1 Hadoop fs ----------------------------------------------- --------------------------------- The hadoop subcommand set executes on the root of the / home directory on the machine Is / user / root --------------------------------------------- ----------...

Start Hadoop start-all.sh Turn off Hadoop stop-all.sh View the file list to view the files in the/user/admin/aaron directory in HDFs. 　　Hadoop Fs-ls/user/admin/aaron Lists all the files (including the files under subdirectories) in the/user/admin/aaron directory in HDFs. Hadoop fs-lsr/user ...

Overview All Hadoop commands are raised by the Bin/hadoop script. Do not specify parameters running the Hadoop script prints the description of all commands. Usage: Hadoop [--config confdir] [COMMAND] [generic_options] [command_options] Hadoop has an option parsing framework for parsing general options and running classes. Command option description--config confdir overwrite default configuration directory ...

The Linux shell refers to a program that allows users to manipulate computers by typing instructions to the keyboard. The shell executes http://www.aliyun.com/zixun/aggregation/18678.html > user-entered commands and displays the execution results on the monitor. The whole process of this interaction is text-based and differs from the graphical operations described in other chapters. This command-line-oriented user interface is called the CLI (command line ...).

If a computer needs to be managed by several people at the same time, it's best not to use the root account. Because if everyone uses the same permissions, it's hard to determine who is and where and what. sudo commands are used to solve this problem. The sudo command allows users defined in the/etc/sudoers configuration file to have temporary permissions to run commands that they cannot run under normal file access permissions. These commands can be either root or other users defined in the/etc/sudoers configuration file ...

Calling the file system (FS) shell command should use the form of Bin/hadoop FS <args>. All of the FS shell commands use the URI path as a parameter. The URI format is Scheme://authority/path. For the HDFs file system, Scheme is HDFS, for the local file system, scheme is file. The scheme and authority parameters are optional, and if unspecified, the default SC specified in the configuration is used ...

1.2 Directory Operation command 1.2.1 View directory the command for viewing directory content is LS, which displays the contents of the current directory by default, and can be viewed by giving one or more directory names at the location of the command line arguments. The syntax format for the command is: LS [options] ... [filename] ... the LS command has multiple command-line options, such as:-A: Lists all files, including those with "." First file;-D: If you are following a directory, use this parameter to output only the name of the directory;-L: Displays file entries in long format, including ...

1.4 File permissions operation in a multi-user operating system, for security reasons, each file and directory need to be given access rights, and the permissions of each user are strictly defined. At the same time, users can give their own files the appropriate permissions to ensure that others can not modify and access. 1.4.1 Change File Master Linux assigns a file owner to each file, called the file Master, and the control of the file depends on the file master or Superuser (root). The creator of the file or directory has special rights to the files or directories created. All relationships in a file can be changed ...

1.free This command is used to view the current system memory usage, which can display the remaining and used physical memory, swap memory, shared memory, and kernel buffers in the system. 2. Shutdown This command is used to shut down or enter a single maintenance mode. The 3.data Data command can display the date and time of the current system. The clock command can also be used to display the current date and time of the system (by default, ordinary users cannot perform the clock command and must log on with the root account). For example: [Root@teache ...

In many cases, we want to know how much space the individual files and directories on the hard disk are using. And the total space occupied by a directory. The du command can help us. After we enter the terminal, we can use this command in any directory. Now use this command in the OPT directory of our own Linux system. We tried to enter the command: Du. In the figure above, we use the Red line to show the size of each file and directory that occupies the hard drive. The position of the green coil is relative to the name of each file and directory. And the position of the blue circle is the order of the current eye ...