Ubuntu FAQ

1，官方的入门教程 http://ubuntu-manual.org/

2，安装ubuntu 分区建议(Linux下 1G= 1000M )

挂载点	容量	文件系统
/boot	200M	ext4
/	10G~20G	ext4
swap	<2048M	swap
/tmp	5G	ext4
/home		ext4

3，安装JRE

• 解压缩

tar -xzvf jre-version-linux-i586.tar.gz

• 配置环境变量（建议在.profile文件中配置，/etc/environment中容易出问题）

JAVA_HOME="/usr/lib/java/jre_version"
CLASSPATH="$JAVA_HOME/lib"
PATH＝"$JAVA_HOME/bin"

• 安装

sudo update-alternatives --install /usr/bin/java java /usr/lib/java/jre_version/bin/java 300

• 配置

sudo update-alternatives --config java

4，安装Qt，建议搭配 Ubuntu14.04 lts + Qt5.3.2

• 不用麻烦配置问题，我的配置，http://www.cnblogs.com/shaw-me/p/4117161.html

5， 环境变量相关

5.1，加载顺序

When bash is invoked as an interactive login shell, or as a non-interactive shell with the --login option, it first reads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile,in that order, and reads and executes commands from the first one that exists and is readable. The --noprofile option may be used when the shell is started to inhibit this behavior.

Ubuntu 14.04 中不存在 ~/.bash_profile 与 bash_login 文件。所以，对于 login shell 和 带有 --login 选项的非交互式 shell，读取顺序为：

/etc/profile ( /etc/profile.d/ ) → ~/.profile ( ~/.bashrc )
同时 /etc/profile 会加载 /etc/profile.d/ 目录下的脚本，而 ~/.profile 会加载 ~/.bashrc

所以上述的加载过程，仅会发生在使用SSH远程登陆以及使用带 --login 选项的非交互 shell 等情形的过程中，有可能仅加载一次。

When a login shell exits, bash reads and executes commands from the file ~/.bash_logout, if it exists.
When an interactive shell that is not a login shell is started, bash reads and executes commands from /etc/bash.bashrc and ~/.bashrc, if these files exist. This may be inhibited by using the --norc option. The --rcfile file option will force bash to read and execute commands from file instead of /etc/bash.bashrc and ~/.bashrc.

而平时打开的交互终端，执行的 bash shell 就执行如下的顺序：

/etc/bash.bashrc → ~/.bashrc

5.2， 其他

System-wide environment variables
/etc/environment
A suitable file for environment variable settings that affect the system as a whole (rather than just a particular user) is /etc/environment. An alternative is to create a file for the purpose in the /etc/profile.d directory.
Note: Variable expansion does not work in /etc/environment.

参考：

• man bash http://man7.org/linux/man-pages/man1/bash.1.html
• Ubuntu EnvironmentVariables https://help.ubuntu.com/community/EnvironmentVariables?highlight=((EnvironmentVariables))