how to install jdk in ubuntu 1、首先到oracle下载上下载jdk-7u5-linux-x64.tar.gz 2、将jdk-7u5-linux-x64.tar.gz拷贝到/usr/lib/jdk/目录下面,这里如果没有jdk文件夹,则创建该文件夹,命令: sudo mkdir jdk //创建文件夹jdk sudo cp -r ~/download/jdk-7
how to install jdk in ubuntu
1、首先到oracle下载上下载jdk-7u5-linux-x64.tar.gz
2、将jdk-7u5-linux-x64.tar.gz拷贝到/usr/lib/jdk/目录下面,这里如果没有jdk文件夹,则创建该文件夹,命令:
sudo mkdir jdk //创建文件夹jdk
sudo cp -r ~/download/jdk-7-linux-x64.tar.gz /usr/lib/jdk/ //把下载的文件拷贝到心创建的目录下面
sudo tar -zxvg jdk-7-linux-x64.tar.gz //解压缩文件
3、设置环境变量,用gedit打开/etc/profile文件
sudo gedit /etc/profile
在文件的最后面增加:
export JAVA_HOME=/usr/lib/jdk/jdk1.7.0_51
export JRE_HOME=/usr/lib/jdk/jdk1.7.0_51/jre
export PATH=$JAVA_HOME/bin:$JAVA_HOME/jre/bin:$PATH
export CLASSPATH=$CLASSPATH:.:$JAVA_HOME/lib:$JAVA_HOME/jre/lib
4、将系统默认的jdk修改过来
$ sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.7.0_05/bin/java 300
$ sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0_05/bin/javac 300
$ sudo update-alternatives --config java $ sudo update-alternatives --config javac
5、检测,输入java -version
java version "1.7.0_51" Java(TM) SE Runtime Environment (build 1.7.0_51-b05) Java HotSpot??(TM) 64-Bit Server VM (build 23.1-b03, mixed mode)
how to install hadoop 2.2.0
安装依赖包
$ sudo apt-get install g++ autoconf automake libtool cmake zlib1g-dev pkg-config libssl-dev $ sudo apt-get install openssh-client $ sudo apt-get install openssh-server 安装配置 protobuf
下载最新的protobuf: https://code.google.com/p/protobuf/downloads/list 解压,依次运行 $ ./configure --prefix=/usr $ sudo make $ sudo make check $ sudo make install 检查一下版本 $ protoc --version libprotoc 2.5.0 安装配置 maven $ sudo apt-get install maven 建立ssh信任
$ cd /home/hduser
$ ssh-keygen -t rsa -P ""
$ cat .ssh/id_rsa.pub >> .ssh/authorized_keys
用命令验证一下是否可以免密码链接localhost
$ ssh localhost
编译 hadoop 2.2.0
解压到用户目录 /home/wilbur/. 进入 hadoop-2.2.0-src 目录
因为已经安装了maven, protobuf, java环境也有了,compiler也有了所以直接运行
$ mvn package -Pdist,native -DskipTests? -Dtar
编译过程中会出现一个错误,这个错误是由于hadoop2.2.0的代码bug导致的,
解决办法如下 hadoop-common-project/hadoop-auth/pom.xml 在文件中添加以下配置
org.mortbay.jetty
jetty-util
test
org.mortbay.jetty
jetty
test
然后重新运行mvn clean package -Pdist,native -DskipTests?? -Dtar命令编译即可
(需注意文件的所有者,修改为当前用户,否则之后可能出错)
配置相关文件
1)配置etc/hadoop目录下的core-site.xml,hdfs-site.xml,mapred-site.xml
core-site.xml:
fs.default.name hdfs://localhost/
hdfs-site.xml:
dfs.replication 1
dfs.namenode.name.dir
/root/jhh/hadoop/yarn_data/hdfs/namenode
dfs.datanode.data.dir
/root/jhh/hadoop/yarn_data/hdfs/datanode
创建文件夹:
mkdir -p /root/jhh/hadoop/yarn_data/hdfs/namenode
mkdir -p /root/jhh/hadoop/yarn_data/hdfs/datanode
mapred-site.xml:
mapreduce.framework.name
yarn
yarn-site.xml:
启动hadoop
初始化 启动 停止
./bin/hdfs namenode -format
./sbin/start-dfs.sh
./sbin/start-yarn.sh
(启动nodemanager存在问题,问题可能出在yarn_damons.sh上,需要手动开启: ./sbin/yarn-daemon.sh start nodemanager)
./sbin/stop-dfs.sh
./sbin/stop-yarn.sh
jps命令来查看node是否都启起来了
问题及解决方案
1.启动过程中出现问题: JAVA_HOME IS NOT SET.
解决方法是修改etc/hadoop/hadoop-env.sh文件,添加如下内容
export JAVA_HOME=/usr/lib/jdk/jdk1.7.0_51
2.HADOOP_CONF_DIR 未配置,出现错误:Error: Cannot find configuration directory: 在/etc/profile中添加:
export HADOOP_HOME=/root/jhh/hadoop/hadoop-0.23.9
export YARN_HOME=/root/jhh/hadoop/hadoop-0.23.9
export HADOOP_CONF_DIR=$HADOOP_HOME/etc/hadoop
export YARN_CONF_DIR=$HADOOP_HOME/etc/hadoop
3.访问log文件,permisson denied。 chmod修改log文件夹权限。
总结:
今天刚配置了一遍,只是单机版的伪分布式环境,之后在测试机上搭一遍。
刚开始学习hadoop,安装配置过程也走了一些弯路,希望多多讨论,互相学习。

Stored procedures are precompiled SQL statements in MySQL for improving performance and simplifying complex operations. 1. Improve performance: After the first compilation, subsequent calls do not need to be recompiled. 2. Improve security: Restrict data table access through permission control. 3. Simplify complex operations: combine multiple SQL statements to simplify application layer logic.

The working principle of MySQL query cache is to store the results of SELECT query, and when the same query is executed again, the cached results are directly returned. 1) Query cache improves database reading performance and finds cached results through hash values. 2) Simple configuration, set query_cache_type and query_cache_size in MySQL configuration file. 3) Use the SQL_NO_CACHE keyword to disable the cache of specific queries. 4) In high-frequency update environments, query cache may cause performance bottlenecks and needs to be optimized for use through monitoring and adjustment of parameters.

The reasons why MySQL is widely used in various projects include: 1. High performance and scalability, supporting multiple storage engines; 2. Easy to use and maintain, simple configuration and rich tools; 3. Rich ecosystem, attracting a large number of community and third-party tool support; 4. Cross-platform support, suitable for multiple operating systems.

The steps for upgrading MySQL database include: 1. Backup the database, 2. Stop the current MySQL service, 3. Install the new version of MySQL, 4. Start the new version of MySQL service, 5. Recover the database. Compatibility issues are required during the upgrade process, and advanced tools such as PerconaToolkit can be used for testing and optimization.

MySQL backup policies include logical backup, physical backup, incremental backup, replication-based backup, and cloud backup. 1. Logical backup uses mysqldump to export database structure and data, which is suitable for small databases and version migrations. 2. Physical backups are fast and comprehensive by copying data files, but require database consistency. 3. Incremental backup uses binary logging to record changes, which is suitable for large databases. 4. Replication-based backup reduces the impact on the production system by backing up from the server. 5. Cloud backups such as AmazonRDS provide automation solutions, but costs and control need to be considered. When selecting a policy, database size, downtime tolerance, recovery time, and recovery point goals should be considered.

MySQLclusteringenhancesdatabaserobustnessandscalabilitybydistributingdataacrossmultiplenodes.ItusestheNDBenginefordatareplicationandfaulttolerance,ensuringhighavailability.Setupinvolvesconfiguringmanagement,data,andSQLnodes,withcarefulmonitoringandpe

Optimizing database schema design in MySQL can improve performance through the following steps: 1. Index optimization: Create indexes on common query columns, balancing the overhead of query and inserting updates. 2. Table structure optimization: Reduce data redundancy through normalization or anti-normalization and improve access efficiency. 3. Data type selection: Use appropriate data types, such as INT instead of VARCHAR, to reduce storage space. 4. Partitioning and sub-table: For large data volumes, use partitioning and sub-table to disperse data to improve query and maintenance efficiency.

TooptimizeMySQLperformance,followthesesteps:1)Implementproperindexingtospeedupqueries,2)UseEXPLAINtoanalyzeandoptimizequeryperformance,3)Adjustserverconfigurationsettingslikeinnodb_buffer_pool_sizeandmax_connections,4)Usepartitioningforlargetablestoi


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

WebStorm Mac version
Useful JavaScript development tools

SecLists
SecLists is the ultimate security tester's companion. It is a collection of various types of lists that are frequently used during security assessments, all in one place. SecLists helps make security testing more efficient and productive by conveniently providing all the lists a security tester might need. List types include usernames, passwords, URLs, fuzzing payloads, sensitive data patterns, web shells, and more. The tester can simply pull this repository onto a new test machine and he will have access to every type of list he needs.

DVWA
Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

EditPlus Chinese cracked version
Small size, syntax highlighting, does not support code prompt function

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.
