可替换系统（alternatives system）的应用浅议

来源：互联网发布：搞怪美颜相机软件编辑：程序博客网时间：2024/04/28 08:54

[root@BlueSky tv2.0]# java

Usage: gij [OPTION] ... CLASS [ARGS] ...

to invoke CLASS.main, or

gij -jar [OPTION] ... JARFILE [ARGS] ...

to execute a jar file

Try `gij --help' for more information.

于是：

[root@BlueSky tv2.0]# which java

/usr/bin/java

[root@BlueSky software]# ls /usr/bin/java -l

lrwxrwxrwx 1 root root 22 01-15 21:23 /usr/bin/java -> /etc/alternatives/java

[root@BlueSky software]# ll /etc/alternatives/java

lrwxrwxrwx 1 root root 35 05-10 13:48 /etc/alternatives/java -> /usr/lib/jvm/jre-1.4.2-gcj/bin/java

这说明java是受fc下同一软件的版本控制工具alternatives控制的，下面就是用这个工具将系统自带的GNU的java换成Sun的java版本；
查看alternatives的帮助；

[root@BlueSky software]# alternatives --help

在 GNU 公共许可的条款下，本软件可以被自由发行。

用法：alternatives --install <link> <name> <path> <priority>

[--initscript <service>]

[--slave <link> <name> <path>]*

alternatives --remove <name> <path>

alternatives --auto <name>

alternatives --config <name>

alternatives --display <name>

alternatives --set <name> <path>

公用选项：--verbose --test --help --usage --version

--altdir <directory> --admindir <directory>

并通过实验得到，install是安装同一软件的不同版本，remove则是移出某个版本，config则是选择当前系统使用那个版本，而display则是显示当前使用的版本，auto则是更改当前的状态为自动判断，也就是可以恢复GNU版本java的一个参数；
下面先安装jre1.5.0_09，此版本可以到sun的公司网站上下得；

[root@BlueSky software]# rpm -ivh jre-1_5_0_09-linux-i586.rpm

Preparing... ########################################### [100%]

1:jre ########################################### [100%]

检查是否安装成功：

[root@BlueSky software]# /usr/java/jre1.5.0_09/bin/java

Usage: java [-options] class [args...]

(to execute a class)

or java [-options] -jar jarfile [args...]

(to execute a jar file)

where options include:

-d32 use a 32-bit data model if available

-d64 use a 64-bit data model if available

-client to select the "client" VM

-server to select the "server" VM

-hotspot is a synonym for the "client" VM [deprecated]

The default VM is client.

-cp <class search path of directories and zip/jar files>

-classpath <class search path of directories and zip/jar files>

A : separated list of directories, JAR archives,

and ZIP archives to search for class files.

-D<name>=<value>

set a system property

-verbose[:class|gc|jni]

enable verbose output

-version print product version and exit

-version:<value>

require the specified version to run

-showversion print product version and continue

-jre-restrict-search | -jre-no-restrict-search

include/exclude user private JREs in the version search

-? -help print this help message

-X print help on non-standard options

-ea[:<packagename>...|:<classname>]

-enableassertions[:<packagename>...|:<classname>]

enable assertions

-da[:<packagename>...|:<classname>]

-disableassertions[:<packagename>...|:<classname>]

disable assertions

-esa | -enablesystemassertions

enable system assertions

-dsa | -disablesystemassertions

disable system assertions

-agentlib:<libname>[=<options>]

load native agent library <libname>, e.g. -agentlib:hprof

see also, -agentlib:jdwp=help and -agentlib:hprof=help

-agentpath:<pathname>[=<options>]

load native agent library by full pathname

-javaagent:<jarpath>[=<options>]

load Java programming language agent, see java.lang.instrument

出现这些字样，表明jre安装成功了；
接着，使用alternatives工具增加这个版本；

[root@BlueSky software]# alternatives --install /usr/bin/java java /usr/java/jre1.5.0_09/bin/java 300

配置：

[root@BlueSky software]# alternatives --config java

共有 2 个程序提供“java”。

选择命令

-----------------------------------------------

* 1 /usr/lib/jvm/jre-1.4.2-gcj/bin/java

2 /usr/java/jre1.5.0_09/bin/java

按 Enter 来保存当前选择[+]，或键入选择号码：2

[root@BlueSky software]# java

Usage: java [-options] class [args...]

(to execute a class)

or java [-options] -jar jarfile [args...]

(to execute a jar file)

where options include:

-d32 use a 32-bit data model if available

-d64 use a 64-bit data model if available

-client to select the "client" VM

-server to select the "server" VM

-hotspot is a synonym for the "client" VM [deprecated]

The default VM is client.

-cp <class search path of directories and zip/jar files>

-classpath <class search path of directories and zip/jar files>

A : separated list of directories, JAR archives,

and ZIP archives to search for class files.

-D<name>=<value>

set a system property

-verbose[:class|gc|jni]

enable verbose output

-version print product version and exit

-version:<value>

require the specified version to run

-showversion print product version and continue

-jre-restrict-search | -jre-no-restrict-search

include/exclude user private JREs in the version search

-? -help print this help message

-X print help on non-standard options

-ea[:<packagename>...|:<classname>]

-enableassertions[:<packagename>...|:<classname>]

enable assertions

-da[:<packagename>...|:<classname>]

-disableassertions[:<packagename>...|:<classname>]

disable assertions

-esa | -enablesystemassertions

enable system assertions

-dsa | -disablesystemassertions

disable system assertions

-agentlib:<libname>[=<options>]

load native agent library <libname>, e.g. -agentlib:hprof

see also, -agentlib:jdwp=help and -agentlib:hprof=help

-agentpath:<pathname>[=<options>]

load native agent library by full pathname

-javaagent:<jarpath>[=<options>]

load Java programming language agent, see java.lang.instrument

如此，成功；
查看效果：

[root@BlueSky software]# alternatives --display java

java - 状态是手工。

链接目前指向 /usr/java/jre1.5.0_09/bin/java

/usr/lib/jvm/jre-1.4.2-gcj/bin/java - 优先度 1420

从 keytool：/usr/lib/jvm/jre-1.4.2-gcj/bin/keytool

从 rmiregistry：/usr/lib/jvm/jre-1.4.2-gcj/bin/rmiregistry

从 jre_exports：/usr/lib/jvm-exports/jre-1.4.2-gcj

从 jre：/usr/lib/jvm/jre-1.4.2-gcj

/usr/java/jre1.5.0_09/bin/java - 优先度 300

从 keytool：(null)

从 rmiregistry：(null)

从 jre_exports：(null)

从 jre：(null)

当前“最佳”版本是 /usr/lib/jvm/jre-1.4.2-gcj/bin/java。

结论，alternaties这个工具还是不错的。。。

Trackback: http://tb.blog.csdn.net/TrackBack.aspx?PostId=1631959