Quick HOWTO : Ch06 : Installing Linux Software/zh
来自Ubuntu中文
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http://www.linuxhomenetworking.com/wiki/index.php/Quick_HOWTO_:_Ch06_:_Installing_Linux_Software |
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目录
- 1 简介
- 2 何处获得常用软件包
- 3 如何下载软件
- 4 Installing Software From RPM Files
- 5 Installing Software From DEB Files
- 6 Installing Software Using tar Files
- 7 Installing Perl Modules
- 8 Conclusion
简介
当你第一次在你的Linux服务器上安装操作系统的时候，你常常需要安装一些你认为不需要的额外的软件。这可能是因为新的业务需要更多的软件包，或者是因为要安装新的管理工具来简化你的工作。
当Linux开发人员制作它们的软件的时候，它们总是将所有的可执行文件和数据文件捆绑在一起，从而形成一个叫做“软件包”的文件。包文件有许多种不同的格式，文件里有不同的控制文件。控制文件决定了软件包中其余文件应被放置的位置、拥有的权限以及整个软件包想要正常工作所依赖的软件包。这些信息中的一部分可能也储存你计算机中的一个数据库中，包管理软件可以使用它们来安装软件从而来加强自己的管理功能。
Redhat、Centos 和Fedora下的软件主要是用RedHat Package Manager (RPM) 文件。RPM软件包通常被用于在还没有定制内核或者管理程序的系统中安装软件。在部门服务器中这种情况经常发生。当因为效率或功能问题，来定制内核以增减对特定设备或特性的支持时，会使用源RPM。安装源RPM这一过程包括重新编译源代码，以使之适应定制内核的需求。这也可以方便制作包的软件开发者，现在他只需要制作一个包就可以支持不同类型的定制内核。不同的包都使用标准命令来安装其中的软件，这使得RPM包相对来说容易使用。
Debian和Ubuntu这两个Linux发行版使用Debian格式的软件包。此软件包的文件名是以“.deb”结尾的。也因为如此，我们通常称它们为DEB文件。
想要使用universal认证的文件格式从而使其产品在所有的Linux发行版中通用的程序员，也需要将他们的作品制作成TAR包。TAR包一般比RPM包难用，因为包中的文件可能需要也可能不需要编译，而且不同的包安装软件的命令也可能不同。TAR包中通常会有使用说明书来指导安装。
Linux程序员经常使用Perl语言写程序。Perl需要一些特定的库或“模块”才能正常工作，而许多Linux发布版只安装了最常用的模块。有时候在安装你的软件包之前，首先要先安装额外的Perl模块。知道如何安装Perl模块是Linux系统管理员技能的一个重要的组成部分。
本章致力于RPM和DEB格式，它们使用于大部分的安装文件中。TAR包和Perl模块很少使用，但是它们仍是重要的软件安装工具，它们将在最后面的一个小节有所交代。
何处获得常用软件包
软件包有三种常用来源：发行光盘；通过浏览器、FTP客户端或者wget工具手动下载；自动下载。每种方法在这里都有所介绍，但是更加详细的将会在后续章节中介绍。
安装光盘中的软件包
用发行光盘安装总是比从远程网站下载来安装要容易。但是时间长了，发行光盘就不是最新版的了。稍后，我们将更加详细的讨论这种方法。
手动下载软件包
获取软件包最常见的两种方法是通过FTP或浏览器手动下载。表6-1列举了一些常用的下载站点。记住，RPM的版本和你机器上运行的Linux的发行版和版本要匹配。
表6-1包常用下载网站
注意： 如果使用Fedora，你也可以从download.fedora.redhat.com下载软件包。在/pub/fedora/linux/core/路径中搜索，然后下移路径树。如果你是第一次使用FTP，别担心，稍后会有所介绍。
自动下载软件包
手动下载的缺点是软件包通常不能安装，除非它的依赖软件包已经事先装好了。这可能会导致要下载并安装很多软件包，而这会很乏味。
所有主要的Linux发行版都有自动下载更新的工具软件。比如，Fedora用yum而Ubuntu和Debian用apt。它们在接下来的章节都有更详细的介绍。
如何下载软件
下载软件是Linux系统管理员最经常要做的事情。这通常非常简单。这节将介绍最常用的几种方法。
用基于web的FTP获取软件
有很多网站都提供软件的链接，你可以通过它们下载软件。获取软件的这种方法通常是相同的：
- 浏览网站，直到你找到要的软件包的链接。
- 点击想要的软件包的链接。
- 将那个文件保存在你的硬盘上。
有的浏览器，比如Firefox，会自动地将文件下载到你的桌面上，那桌面在哪里呢？在Linux里，桌面通常是一个在你的home或~目录下的一个叫Desktop（桌面）的子目录。在这里我们可以看到，在根用户的桌面上已经有一个下载下来的RPM文件。
[root@bigboy tmp]# cd ~/Desktop/ [root@bigboy Desktop]# ls ElectricFence-2.2.2-20.2.i386.rpm [root@bigboy Desktop]# pwd /root/Desktop [root@bigboy Desktop]#
用命令行匿名FTP获取软件
上面介绍的基于web的方法显然是使用匿名文件传输协议（FTP）。匿名FTP使你使用匿名用户名或更短的用户名ftp和符合你e-mail地址的密码，就可以登录FTP服务器并下载文件。任何人都可以通过这种方法获取数据。我们可以用一个用匿名FTP从download.fedora.redhat.com下载SSH软件包的例子来说明：
1)首先我们在命令行中向download.fedora.redhat.com发出FTP命令。
[root@bigboy tmp]# ftp download.fedora.redhat.com Trying 66.187.232.35... Connected to download.fedora.redhat.com (66.187.232.35). 220 Fedora FTP server ready. All transfers are logged. Name (download.fedora.redhat.com:root): anonymous 331 Please specify the password. Password: 230 Login successful. Have fun. Using binary mode to transfer files. ftp> pwd 257 "/" ftp> ls 227 Entering Passive Mode (66,187,232,35,57,155) 150 Here comes the directory listing. drwxr-xr-x 3 ftp ftp 4096 Oct 29 15:59 pub 226 Directory send OK. ftp>
2)登录成功后，我们可以用help命令来查看我们可以做的事情。
ftp> help Commands may be abbreviated. Commands are: （命令可能是缩写形式，有如下命令：） ! cr mdir proxy send $ delete mget sendport site account debug mkdir put size append dir mls pwd status ascii disconnect mode quit struct bell form modtime quote system binary get mput recv sunique bye glob newer reget tenex case hash nmap rstatus trace ccc help nlist rhelp type cd idle ntrans rename user cdup image open reset umask chmod lcd passive restart verbose clear ls private rmdir ? close macdef prompt runique cprotect mdelete protect safe ftp>
表6-2列举了一些常用命令：
表6-2 FTP命令
| 命令 | 描述 |
|---|---|
| binary | 在二进制模式下拷贝文件 |
| cd | 改变FTP服务器上的目录 |
| dir | 列出当前远程目录里的文件的名称 |
| exit | 退出 |
| get | 从FTP服务器获取文件 |
| lcd | 改变本地计算机上的目录 |
| ls | 同dir |
| mget | 同get，但是你可以使用如“*”的通配符 |
| mput | 同put，但是你可以使用如“*”的通配符 |
| passive | 使文件传输为被动模式 |
| put | 将本地计算机上的文件上传到FTP服务器 |
| pwd | 获取本地计算机的目录名 |
3)通过之前对网站上网页的浏览，我们可以知道Fedora Core 2 RPM包在pub/fedora/linux/core/2/i386/os/Fedora/RPMS/目录下。我们将使用cd命令将我们的目录改变到那里去。然后我们可以使用ls命令来获取那个目录下的文件的列表。
ftp> cd pub/fedora/linux/core/2/i386/os/Fedora/RPMS/ 250 Directory successfully changed. ftp> ls open* 227 Entering Passive Mode (66,187,232,35,58,3) 150 Here comes the directory listing. ... ... -rw-r--r-- ... ... 184281 Oct 28 23:29 openssh-3.6.1p2-34.i386.rpm ... ... 226 Directory send OK. ftp>
4)接下来，我们下载我们需要的文件并将其放置于本地的/usr/rpm目录下。hash命令会在下载时，在屏幕上打印井号“#”。
ftp> hash Hash mark printing on (1024 bytes/hash mark). ftp> lcd /usr/rpm Local directory now /usr/rpm ftp> get openssh-3.6.1p2-34.i386.rpm local: openssh-3.6.1p2-34.i386.rpm remote: openssh-3.6.1p2-34.i386.rpm 227 Entering Passive Mode (66,187,232,35,58,25) 150 Opening BINARY mode data connection for openssh-3.6.1p2-34.i386.rpm (184281 bytes). ################################################################################################################################################################################### 226 File send OK. 184281 bytes received in 3.41 secs (53 Kbytes/sec) ftp>
注意： 你也可以使用mget命令，从而在下载RPM时使用通配符。计算机会提示你每个符合的RPM文件名。在下个例子中，我通过键入n来中断这个下载。
ftp> mget openssh-3.6* mget openssh-3.6.1p2-34.i386.rpm? n ftp>
5)最后我们用exit命令退出FTP
ftp> exit 221 Goodbye. root@bigboy tmp]#
用wget获取软件
当你已经知道RPM的URL地址时，你可以使用wget很快地下载该文件。如果你在别机器上通过浏览器登录到了Linux系统中，这种方法尤为方便。你可以浏览下载网站来找到你要的RPM，右键点击其链接然后选择复制快捷方式（Windows）或者复制链接位置（Linux）。这一步完成后，你然后可以选择你的SSH/telnet/Linux终端登录窗口然后键入wget URL命令。这里有一个从Fedora下载DHCP更新的例子。
[root@bigboy tmp]# wget http://linux.stanford.edu/pub/mirrors/fedora/linux/core/2/i386/os/Fedora/RPMS/dhcp-3.0pl2-6.16.i386.rpm --17:38:36-- ftp://linux.stanford.edu/pub/mirrors/fedora/linux/core/2/i386/os/Fedora/RPMS/dhcp-3.0pl2-6.16.i386.rpm => `dhcp-3.0pl2-6.16.i386.rpm.5' Resolving linux.stanford.edu... done. Connecting to linux.stanford.edu[171.66.2.18]:21... connected. Logging in as anonymous ... Logged in! ==> SYST ... done. ==> PWD ... done. ==> TYPE I ... done. ==> CWD /pub/mirrors/fedora/linux/core/2/i386/os/Fedora/RPMS ... done. ==> PASV ... done. ==> RETR dhcp-3.0pl2-6.16.i386.rpm ... done. Length: 529,890 (unauthoritative) 100%[===============================>] 529,890 889.12K/s ETA 00:00 17:38:36 (889.12 KB/s) - `dhcp-3.0pl2-6.16.i386.rpm.5' saved [529890] [root@bigboy tmp]#
Installing Software From RPM Files
The Fedora, Redhat and Centos versions of Linux rely heavily upon the use of software packages in the RPM format. This section covers some of the most important topics required for you to master their use.
How To Install RPMs Manually
There are generally two ways to install RPM files manually. The first method is by using a file previously downloaded to your hard drive, and the other is to install the RPM from some sort of removable media such as a CD-ROM drive.
Using Downloaded Files
Download the RPMs (which usually have a file extension ending with .rpm) into a temporary directory, such as /tmp. The next step is to issue the rpm -Uvh command to install the package.
The -U qualifier is used for updating an RPM to the latest version, the -h qualifier gives a list of hash # characters during the installation and the -v qualifier prints verbose status messages while the command is run. Here is an example of a typical RPM installation command to install the MySQL server package:
[root@bigboy tmp]# rpm -Uvh mysql-server-3.23.58-9.i386.rpm Preparing... ####################### [100%] 1:mysql-server ####################### [100%] [root@bigboy tmp]#
Using CD-ROMs
The underlying steps to install RPMs from CDs are similar to those used when installing from your hard disk. The main difference is that you have to access your CD-ROM drive by mounting it first to the mnt/cdrom directory. Your RPMs will then be located in the CD-ROM's Fedora/RPMs subdirectory. The procedure is as follows:
1) Insert the CD-ROM, check the files in the /mnt/cdrom/Fedora/RPMS directory and then install the RPM.
[root@bigboy tmp]# mount /mnt/cdrom [root@bigboy tmp]# cd /mnt/cdrom/Fedora/RPMS [root@bigboy RPMS]# ls filename* filename.rpm [root@bigboy RPMS]# rpm -Uvh filename.rpm Preparing... ####################### [100%] 1: filename ####################### [100%] [root@bigboy RPMS]#
2) When finished, eject the CD-ROM
[root@bigboy RPMS]# cd /tmp [root@bigboy tmp]# eject cdrom [root@bigboy tmp]#
Note: You can use the rpm command's --aid switch to make it search the CD-ROM for any other RPM dependencies and install them automatically.
How to Install Source RPMs
Sometimes the packages you want to install need to be compiled in order to match your kernel version. This requires you to use source RPM files:
- Download the source RPMs or locate them on your CD collection. They usually have a file extension ending with (.src.rpm)
- Run the following commands as root:
Compiling and installing source RPMs with Fedora can be done simply with the rpmbuild command
[root@bigboy tmp]# rpmbuild --rebuild filename.src.rpm
Here is an example in which we install the tacacs plus package.
[root@bigboy rpm]# rpmbuild --rebuild tac_plus-4.0.3-2.src.rpm Installing tac_plus-4.0.3-2.src.rpm Executing(%prep): /bin/sh -e /var/tmp/rpm-tmp.61594 + umask 022 + cd /usr/src/redhat/BUILD + cd /usr/src/redhat/BUILD + rm -rf tac_plus-4.0.3 + /usr/bin/gzip -dc /usr/src/redhat/SOURCES/tac_plus-4.0.3.tgz + tar -xvvf - ... ... ... + umask 022 + cd /usr/src/redhat/BUILD + rm -rf tac_plus-4.0.3 + exit 0 [root@bigboy rpm]#
The compiled RPM file can now be found in one of the architecture subdirectories under /usr/src/redhat/RPMS directory. For example, if you compiled an i386 architecture version of the RPM it will placed in the i386 subdirectory.
You will then have to install the compiled RPMs found in their respective subdirectories as you normally would.
RPM Installation Errors
Sometimes the installation of RPM software doesn't go according to plan and you need to take corrective actions. This section shows you how to recover from some of the most common errors you'll encounter.
Failed Dependencies
Sometimes RPM installations will fail giving Failed dependencies errors which really mean that a prerequisite RPM needs to be installed. In the next example we're attempting to install the MySQL database server application, which fails because the mysql MySQL client RPM, on which it depends, needs to be installed beforehand:
[root@bigboy tmp]# rpm -Uvh mysql-server-3.23.58-9.i386.rpm
error: Failed dependencies:
libmysqlclient.so.10 is needed by mysql-server-3.23.58-9
mysql = 3.23.58 is needed by mysql-server-3.23.58-9
[root@bigboy tmp]#
Installing the MySQL client also fails because it requires the perl-DBD-MySQL package.
[root@bigboy tmp]# rpm -Uvh mysql-3.23.58-9.i386.rpm
error: Failed dependencies:
perl-DBD-MySQL is needed by mysql-3.23.58-9
[root@bigboy tmp]# rpm -Uvh perl-DBD-MySQL-2.9003-4.i386.rpm
error: Failed dependencies:
libmysqlclient.so.10 is needed by perl-DBD-MySQL-2.9003-4
[root@bigboy tmp]#
Strangely enough, the installation of the perl-DBD-MySQL package fails because it needs the mysql client package. To get around this problem you can run the rpm command with the --nodeps option to disable dependency checks. In the next example we install the MySQL client ignoring dependencies, followed by successful installation of perl-DBD-MySQL and mysql-server.
[root@bigboy tmp]# rpm -Uvh --nodeps mysql-3.23.58-9.i386.rpm Preparing... ####################### [100%] 1:mysql ####################### [100%] [root@bigboy tmp]# rpm -Uvh perl-DBD-MySQL-2.9003-4.i386.rpm Preparing... ####################### [100%] 1:perl-DBD-MySQL ####################### [100%] [root@bigboy tmp]# rpm -Uvh mysql-server-3.23.58-9.i386.rpm Preparing... ####################### [100%] 1:mysql-server ####################### [100%] [root@bigboy tmp]#
Note: If all the installation RPMs are located in the same directory, the rpm command can automatically install all the prerequisite RPMs using the --aid option. One of the advantages of using the yum facility is that you don't have to worry about this dependency process as much because the dependency RPMs are always downloaded and installed automatically also.
Signature Keys
Fedora digitally signs all its RPM files, so it's best to import their public encryption key beforehand so that the RPM installation program will be able to verify the validity of the RPM file.
This is usually done automatically in newer versions of Fedora, but will need to be done manually in legacy versions. The manual method uses the rpm command as seen in the next example, but locate the key files first as their locations can vary between Fedora distributions. It is a good idea to import both the RedHat and Fedora keys:
[root@bigboy tmp]# locate RPM-GPG-KEY /usr/share/rhn/RPM-GPG-KEY /usr/share/rhn/RPM-GPG-KEY-fedora [root@bigboy tmp]# rpm --import /usr/share/rhn/RPM-GPG-KEY [root@bigboy tmp]# rpm --import /usr/share/rhn/RPM-GPG-KEY-fedora [root@bigboy tmp]#
If you don't install the keys you'll get a DSA signature warning that alerts you to the fact that the RPM file might be bogus:
[root@bigboy tmp]# rpm -Uvh dhcp-3.0pl2-6.16.i386.rpm warning: dhcp-3.0pl2-6.16.i386.rpm: V3 DSA signature: NOKEY, key ID 4f2a6fd2 Preparing... #################################### [100%] 1:dhcp #################################### [100%] [root@bigboy tmp]#
It is always good to install the key files. If they are not there, the RPMs will install with only a warning message. If the RPM's digital signature doesn't match that in the key file, the rpm installation program also alerts you and fails to install the RPM package at all:
[root@bigboy tmp]# rpm -Uvh dhcp-3.0pl2-6.16.i386.rpm error: dhcp-3.0pl2-6.16.i386.rpm: V3 DSA signature: BAD, key ID 4f2a6fd2 error: dhcp-3.0pl2-6.16.i386.rpm cannot be installed [root@bigboy tmp]#
Signatures are therefore useful because they help protect you against tampered and otherwise corrupted RPMs being installed.
How to List Installed RPMs
The rpm -qa command will list all the packages installed on your system
[root@bigboy tmp]# rpm -qa perl-Storable-1.0.14-15 smpeg-gtv-0.4.4-9 e2fsprogs-1.27-9 libstdc++-3.2-7 audiofile-0.2.3-3 ... ... ... [root@bigboy tmp]#
You can also pipe the output of this command through the grep command if you are interested in only a specific package. In this example we are looking for all packages containing the string ssh in the name, regardless of case (-i means ignore case)
[root@bigboy tmp]# rpm -qa | grep -i ssh openssh-server-3.4p1-2 openssh-clients-3.4p1-2 openssh-askpass-gnome-3.4p1-2 openssh-3.4p1-2 openssh-askpass-3.4p1-2 [root@bigboy tmp]#
Note: You could use the rpm -q package-name command to find an installed package because it is much faster than using grep and the -qa switch, but you have to have an exact package match. If you are not sure of the package name and its capitalization, the latter method is probably more suitable.
Listing Files Associated with RPMs
Sometimes you'll find yourself installing software that terminates with an error requesting the presence of a particular file. In many cases the installation program doesn't state the RPM package in which the file can be found. It is therefore important to be able to determine the origin of certain files, by listing the contents for RPMs in which you suspect the files might reside.
Listing Files for Already Installed RPMs
This can be useful if you have to duplicate a working server that is already in a production environment. Sometimes the installation of an application fails on the new server due to the lack of a file that resides on the old one. In this case you need to know which RPM on the old server contains the file.
You can use the -ql qualifier to list all the files associated with an installed RPM. In this example we test to make sure that the NTP package is installed using the -q qualifier, and then we use the -ql qualifier to get the file listing.
[root@bigboy tmp]# rpm -q ntp ntp-4.1.2-0.rc1.2 [root@bigboy tmp]# rpm -ql ntp /etc/ntp /etc/ntp.conf /etc/ntp/drift /etc/ntp/keys ... ... ... /usr/share/doc/ntp-4.1.2/rdebug.htm /usr/share/doc/ntp-4.1.2/refclock.htm /usr/share/doc/ntp-4.1.2/release.htm /usr/share/doc/ntp-4.1.2/tickadj.htm [root@bigboy tmp]#
Listing Files in RPM Files
Sometimes you make a guess and download what you think is the RPM with the missing file. You can use the -qpl qualifier to list all the files in an RPM archive to make sure before installing it:
[root@bigboy updates]# rpm -qpl dhcp-3.0pl1-23.i386.rpm /etc/rc.d/init.d/dhcpd /etc/rc.d/init.d/dhcrelay /etc/sysconfig/dhcpd /etc/sysconfig/dhcrelay ... ... ... /usr/share/man/man8/dhcrelay.8.gz /var/lib/dhcp /var/lib/dhcp/dhcpd.leases [root@bigboy updates]#
Listing the RPM to Which a File Belongs
You might need to know the RPM that was used to install a particular file. This is useful when you have a suspicion about the function of a file but are not entirely sure. For example, the MySQL RPM uses the /etc/my.cnf file as its configuration file, not a file named /etc/mysql.conf as you'd normally expect. The following example confirms the origin of the /etc/my.cnf file.
[root@zippy tmp]# rpm -qf /etc/my.cnf mysql-3.23.58-9 [root@zippy tmp]#
Uninstalling RPMs
The rpm -e command will erase an installed package. The package name given must match that listed in the rpm -qa command because the version of the package is important.
[root@bigboy tmp]# rpm -e package-name
Which RPMs Will Start Up At Boot Time?
The best way to view and configure which RPMs will start at boot time is by using the chkconfig command with the --list switch. A more detailed explanation will be provided in Chapter 7, "The Linux Boot Process", which covers the Linux boot process.
Automatic Updates with yum
The yum automatic RPM update program comes as a standard feature of Fedora Core. It has a number of valuable features:
- You can configure the URLs of download sites containing the RPM repositories you need. This provides the added advantage of you choosing the most reliable sites in your part of the globe.
- yum makes multiple attempts to download RPMs before failing.
- yum automatically figures out not only the RPMs packages that need updating, but also all the supporting RPMs. It then installs them all.
Note: Updating packages could cause programs written by you to stop functioning especially if they rely on the older version's features or syntax.
Configuring yum
The configuration parameters that affect all packages and all yum server URLs are stored in the [main] section of the /etc/yum.conf file. You generally don't need to edit this file, but it can be useful in listing packages that you don't want yum to update. In this example the kernel and perl packages are excluded.
# # File: /etc/yum.conf # [main] exclude=kernel perl
The configurations for each RPM repository are stored in the /etc/yum.repos.d directory in individual configuration files with the .repo file extension. This directory will be populated with files for your Linux distribution's most important repositories. You can also add your own custom files for repositories containing non-standard RPM packages. These files will have the following format:
[repositoryid] name=Some name for this repository baseurl=url://path/to/repository/
The [repositoryid] is an identifier that is unique to all files in the directory and can only be one word long and is often given a name that reflects the function of the repository. For example, you may have a fedora-updates.repo file that contains a [updates], and [updates-source] sections that refer to URLs for updates of regular RPMs and source RPMs. You can create your own repository files using popular repository sites. The easiest way to determine the exact URLs to use as the baseurl parameter is to go to the http://fedora.redhat.com/download/mirrors.html Web site to get a listing of alternative download sites. Browse the listed sites to find the correct locations of the RPM files in the /updates or /fedora-version URL branches. Make sure that baseurl points to a URL with a /repodata sub-directory beneath it as this sub-directory contains files with instructions for yum to use in doing its updates. Be careful, this sub-directory can be located within the RPM directory or one level above them. Also remember to make the [repositoryid] in your .repo file unique to all other files.
Note: yum accepts the use of variables in the configuration file. The $releasever variable refers to the current version of Fedora Core running on your server and the $basearch variable maps to the base architecture of your server which is determined automatically. Here is an example of the use of these variables.
[repository-name] name=Fedora Core $releasever - $basearch - Base baseurl=http://url.com/fedora/core/$releasever/$basearch/os/
Note: It is probably best to select yum update sites that use HTTP instead of FTP. There are a number of reasons for this. FTP firewall rules are more difficult to implement than HTTP, outbound HTTP access to the Internet is often already allowed in offices, and web servers are less likely to have connection limits imposed on them, unlike FTP servers, which often have limits on the number of user logins. Note: You can list multiple URLs in a baseurl statement like this and yum will try them all. If you use multiple baseurl statements in each section then yum may act strangely, frequently only selecting the last one in the list.
baseurl=url://server1/path/to/files/
url://server2/path/to/files/
url://server3/path/to/files/
Note: You can also place all your [repositoryid] sections in the yum.conf file. This was the methodology used in some older versions of yum.
Note: The yum utility can be configured to match the downloaded RPMs against checksum files to help protect against file corruption and malicious forgeries. This is set using the gpgcheck variable in the .repo files. Checks are done when the value is set to 1, when set to 0, they are disabled. Here is an example:
# # File: example.repo # gpgcheck=1 gpgkey=http://URL/example.key
Repositories will sometimes provide you with the URL for their checksum files and it is a good idea to take advantage of them. This is a valuable feature.
How to Automate yum
Older versions of yum could be configured to run in the background as a daemon that was simple named yum that used a unified yum.conf file for all its configuration data. Newer versions use the yum-updatesd daemon instead. This uses the /etc/yum/yum-updatesd.conf configuration file which governs update frequency, the types of files to be downloaded and whether they should be automatically installed using the yum command.
To get yum started, select the commands that match your OS version:
1. Use the chkconfig command to get yum configured to start at boot:
[root@bigboy tmp]# chkconfig yum-updatesd on [root@bigboy tmp]# chkconfig yum on
2. Use the service command to instruct the /etc/init.d yum script to start/stop yum after booting
[root@bigboy tmp]# service yum-updatesd start [root@bigboy tmp]# service yum-updatesd stop [root@bigboy tmp]# service yum start [root@bigboy tmp]# service yum stop
Note: Updating packages could cause programs written by you to stop functioning especially if they rely on the older version's features or syntax. The yum daemon will do updates automatically; the yum-updatesd daemon won't do this unless the yum-updatesd.conf file has been updated as shown here:
# # File: /etc/yum/yum-updatesd.conf # [main] do_update = yes
Creating Your Own yum Server
An obvious advantage of using yum is that you can use it to update a yum server at your office with the same directory structure of the mirror download sites on the Fedora Web site. The full set of steps to do this is beyond the scope of this book, but there are some factors you should consider before doing this.
A small desktop PC with about five to six gigabytes of free disk space per distribution should be sufficient to start with for a dedicated small business yum server. Large RPMs are about twenty-five megabytes in size, and they are updated infrequently, so your network load should be minimal on average with an update once or twice a week per server. In large server farms you may want to use a more robust system that can handle many more clients, but before doing so, get trend data for its network load to help your final decision. The configuration of the MRTG graphing tool is covered in Chapter 22, " Monitoring Server Performance".
When established, you can then configure all your Fedora servers to use this local yum server for all updates which will significantly reduce your Internet congestion and the associated bandwidth costs.
yum clients can access the yum server using either FTP or HTTP requests. If you need help in setting these up, Chapter 15, "Linux FTP Server Setup", discusses Linux FTP servers and Chapter 20, "The Apache Web Server", covers the Apache Web server for HTTP requests.
Note: When setting up an HTTP based yum server, you'll need to enable the viewing of directory structures so that it will be easy for someone to use his or her Web browser to navigate down the directories to double check the location of the yum files.
How to Automate yum
As of Fedora Core 6 the yum daemon has been named yum-updatesd, whereas in the past it was just called yum. To get yum started, select the commands that match your OS version:
1) Use the chkconfig command to get yum configured to start at boot:
[root@bigboy tmp]# chkconfig yum-updatesd on [root@bigboy tmp]# chkconfig yum on
2) Use the service command to instruct the /etc/init.d yum script to start/stop yum after booting
[root@bigboy tmp]# service yum-updatesd start [root@bigboy tmp]# service yum-updatesd stop [root@bigboy tmp]# service yum start [root@bigboy tmp]# service yum stop
Keeping Your System current with Yum
You can make the installed RPM packages on your system up to date with the latest patches using the yum update command. When used without listing any packages afterwards, yum will attempt to update them all. The yum update package-name command updates only a particular RPM package.
It is always advisable to use yum after installing Linux to make sure the latest versions of software are installed for the sake of improved security and functionality. Here is an example of output of what to expect with yum updating your system.
[root@bigboy tmp]# yum update Gathering header information file(s) from server(s) Server: Fedora Core 2 - i386 - Base Server: Fedora Core 2 - i386 - Released Updates Finding updated packages Downloading needed headers Resolving dependencies Dependencies resolved I will do the following: [install: kernel 2.4.22-1.2166.nptl.i686] [update: samba-client 3.0.2-7.FC1.i386] [update: binutils 2.14.90.0.6-4.i386] ... ... ... Is this ok [y/N]: y Getting samba-client-3.0.2-7.FC1.i386.rpm samba-client-3.0.2-7.FC1. 100% |=========================| 128 kB 05:01 ... ... ... Running test transaction: Test transaction complete, Success! glibc-common 100 % done 1/127 glibc 100 % done 2/127 Stopping sshd:[ OK ] Starting sshd:[ OK ] bash 100 % done 3/127 mozilla-nspr 100 % done 4/127 sed 100 % done 5/127 ... ... ... Completing update for pango - 65/127 Completing update for samba-client - 66/127 Completing update for binutils - 67/127 ... ... ... Completing update for XFree86-font-utils - 127/127 Kernel Updated/Installed, checking for bootloader Grub found - making this kernel the default Installed: kernel 2.4.22-1.2166.nptl.i686 Updated: pango 1.2.5-4.i386 samba-client 3.0.2-7.FC1.i386 binutils 2.14.90.0.6-4.i386 XFree86-Mesa-libGLU 4.3.0-55.i386 initscripts [root@bigboy tmp]#
Note: If you don't want to be prompted to install the files use the yum with the -y switch.
Example of a yum Package Installation
Here is a sample installation of an individual package using yum. In this case the RPM installed is the net-snmp-utils package:
[root@bigboy tmp]# yum -y install net-snmp-utils Repository updates-released already added, not adding again Repository base already added, not adding again Setting up Install Process Setting up Repo: base repomd.xml 100% |=========================| 1.1 kB 00:00 Setting up Repo: updates-released repomd.xml 100% |=========================| 951 B 00:00 Reading repository metadata in from local files base : ############################################ 2622/2622 primary.xml.gz 100% |=========================| 88 kB 00:00 MD Read : ################################################## 229/229 updates-re: ################################################## 229/229 Resolving Dependencies --> Populating transaction set with selected packages. Please wait. ---> Package net-snmp-utils.i386 0:5.1.2-11 set to be installed --> Running transaction check Dependencies Resolved Transaction Listing: Install: net-snmp-utils.i386 0:5.1.2-11 Downloading Packages: net-snmp-utils-5.1.2-11.i 100% |===================| 6.2 MB 00:48 Running Transaction Test Finished Transaction Test Transaction Test Succeeded Running Transaction Installing: net-snmp-utils 100 % done 1/1 Installed: net-snmp-utils.i386 0:5.1.2-11 Complete! [root@bigboy tmp]#
Remember The Following Yum Facts
- yum does its updates using TCP port 80 for http:// update URLs and uses passive FTP for ftp:// update URLs in /etc/yum.conf. This will have importance for your firewall rules.
- More details on configuring yum can be obtained by running the man yum.conf command.
- yum runs automatically each day. The cron file is located in /etc/cron.daily/.
- Don't limit yourself to the default yum.conf URLs because they can become overloaded with requests and make yum perform poorly.
Installing Software From DEB Files
Unlike the Redhat, Fedora and Centos versions of Linux that use RPM packages, the Debian and Ubuntu versions of Linux rely on packages in the DEB format. This section covers some of the most important topics required for you to master their use.
How To Install DEBs Manually
There are generally two ways to install DEB files manually. The first method is by using a file previously downloaded to your hard drive, and the other is to install the DEB from some sort of removable media such as a CD-ROM drive.
Using Downloaded Files
Download the DEBs (which usually have a file extension ending with .deb) into a temporary directory, such as /tmp. The next step is to issue the dpkg --install command to install the package. Here is an example of a typical DEB installation command to install the ndiswrapper utilities package:
root@u-bigboy:~# dpkg --install ndiswrapper-utils_1.8-0ubuntu2_i386.deb Selecting previously deselected package ndiswrapper-utils. (Reading database ... 70221 files and directories currently installed.) Unpacking ndiswrapper-utils (from ndiswrapper-utils_1.8-0ubuntu2_i386.deb) ... Setting up ndiswrapper-utils (1.8-0ubuntu2) ... root@u-bigboy:~#
Using CD-ROMs
Installing DEB files from CDROM is similar to that with Fedora / Redhat. The difference is that the CDROM device name is /media/cdrom. The following procedure installs the ndiswrapper DEB that had previously been copied to a disk.:
1. Insert the CD-ROM, check the files in the /media/cdrom directory and then install the DEB.
root@u-bigboy:/tmp# mount /media/cdrom -o unhide mount: block device /dev/hdc is write-protected, mounting read-only root@u-bigboy:/tmp# cd /media/cdrom root@u-bigboy:/media/cdrom# ls ndiswrapper-utils_1.8-ubuntu2_i386.deb root@u-bigboy:/media/cdrom# dpkg --install ndiswrapper-utils_1.8-ubuntu2_i386.deb Selecting previously deselected package ndiswrapper-utils. (Reading database ... 70221 files and directories currently installed.) Unpacking ndiswrapper-utils (from ndiswrapper-utils_1.8-0ubuntu2_i386.deb) ... Setting up ndiswrapper-utils (1.8-0ubuntu2) ... root@u-bigboy:~#
2. When finished, eject the CD-ROM
root@u-bigboy:/media/cdrom# cd /tmp root@u-bigboy:/tmp# umount /media/cdrom root@u-bigboy:/tmp# eject cdrom root@u-bigboy:/tmp#
Note: Unlike the Fedora CD / DVD sets, Ubuntu Linux is distributed on a single CD / DVD. The Ubuntu installation process downloads any additional packages it may need on demand from the Internet. It is for this reason that you may find it easier to install Ubuntu software using the APT utility which automatically download and install most of the packages you desire. The APT utility is covered in a following section.
DEB Installation Errors
Sometimes the installation of DEB software doesn't go according to plan and you need to take corrective actions. This section shows you how to recover from some of the most common errors you'll encounter.
Failed Dependencies
As should be expected, packages often rely on the existence of other previously installed packages. This will sometimes result in dpkg installations failing with dependency problems errors which really mean that a prerequisite DEB needs to be installed. In the next example we're trying to install the mrtg-contrib package, but it needs the mrtg package to be installed first beforehand.
root@u-bigboy:/tmp# dpkg --install mrtg-contrib_2.12.2-1_all.deb Selecting previously deselected package mrtg-contrib. (Reading database ... 70759 files and directories currently installed.) Unpacking mrtg-contrib (from mrtg-contrib_2.12.2-1_all.deb) ... dpkg: dependency problems prevent configuration of mrtg-contrib: mrtg-contrib depends on mrtg (= 2.12.2-1); however: Package mrtg is not installed. dpkg: error processing mrtg-contrib (--install): dependency problems - leaving unconfigured Errors were encountered while processing: mrtg-contrib root@u-bigboy:/tmp#
After installing the mrtg package, mrtg-contrib was installed correctly. You can automatically install prerequisite packages using the APT utility. This will be covered later in th echapter.
How to List Installed DEBs
The dpkg --list command will list all the packages installed on your system
root@u-bigboy:~# dpkg --list Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Installed/Config-files/Unpacked/Failed-config/Half-installed |/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad) ||/ Name Version Description +++-===================-===================-================================ ii ssh 4.1p1-7ubuntu4 Secure shell client and server ... ... ... root@u-bigboy:~#
The output will be in six columns. The fourth column lists the name of the package, the fifth states the package version, and the sixth and last provides a description.
The first three columns are each only a single character wide and provide very specific information about the package as outlined in Table 6-3.
Table 6-3 Column Formatting for the dpkg command
| Desired State
(Col. 1) |
Current State
(Col. 2) |
Error State
(Col. 3) |
Description |
|---|---|---|---|
| u | Unknown: The package has never been installed | ||
| i | Installed: A privileged user has requested the installation of the package | ||
| r | Remove: A privileged user has requested the removal of the package. Configuration files for the package most likely remain. | ||
| p | Purge: A previously installed package has been removed. Configuration files for the package have probably been removed. | ||
| h | Hold: A privileged user has requested that the package remain at its current version with no automatic upgrades. | ||
| n | Not Installed: The package is not installed | ||
| i | Installed: The package is installed | ||
| c | Configuration Files Exist: Package was installed, but the configuration files exist. | ||
| u | Unpacked: Files have been unpacked, but not installed | ||
| f | Failed: Configuration of the package has failed. | ||
| h | Halt: The package installation failed to complete | ||
| h | Enforced Hold: Package upgrade is on hold because another dependent package with a user defined hold requires this package to remain not upgraded. | ||
| r | Reinstallation: The package is broken and requires a reinstallation. | ||
| x | The package is both broken and on enforced hold. |
You can specify the desired package in which you are interested after the --list option to get a listing specific to that package. Here we see a single listing for the openssh-server package using this method.
root@u-bigboy:~# dpkg --list openssh-server Desired=Unknown/Install/Remove/Purge/Hold | Status=Not/Installed/Config-files/Unpacked/Failed-config/Half-installed |/ Err?=(none)/Hold/Reinst-required/X=both-problems (Status,Err: uppercase=bad) ||/ Name Version Description +++-===================-===================-======================================== ii openssh-server 4.2p1-7ubuntu3 Secure shell server, an rshd replacement root@u-bigboy:~#
You can also pipe the output of this command through the grep command if you are interested in only a specific package. In this example we are looking for all packages containing the string dhcp in the name.
root@u-bigboy:~# dpkg --list | grep dhcp ii dhcp3-client 3.0.2-1ubuntu6 DHCP Client ii dhcp3-common 3.0.2-1ubuntu6 Common files - dhcp3* packages root@u-bigboy:~#
Listing Files Associated with DEBs
Sometimes you'll find yourself installing software that terminates with an error requesting the presence of a particular file. In many cases the installation program doesn't state the DEB package in which the file can be found. It is therefore important to be able to determine the origin of certain files, by listing the contents for DEBs in which you suspect the files might reside.
Listing Files for Previously Installed DEBs
As stated previously, listing the files found in a package can be very useful. With dpkg, the --listiles option can provide this information easily. Here we list the files present in the openssh-server package.
root@u-bigboy:~# dpkg --listfiles openssh-server ... ... ... /var/run/sshd /usr/lib/sftp-server /usr/share/doc/openssh-server root@u-bigboy:~#
Listing Files in DEB Files
Download sites often have packages with different functions, but similar names. It is good to be able to list the contents of a DEB package to verify you have the correct one. This can be done with the --contents option for dpkg as can be seen in this example.
root@u-bigboy:/tmp# dpkg --contents openssh-server_4.2p1-7ubuntu3_i386.deb ... ... ... -rw-r--r-- root/root 10444 2006-05-17 17:43:19 ./usr/share/man/man8/sshd.8.gz -rw-r--r-- root/root 1169 2006-05-17 17:43:19 ./usr/share/man/man8/sftp-server.8.gz drwxr-xr-x root/root 0 2006-05-17 17:43:24 ./usr/share/doc/ drwxr-xr-x root/root 0 2006-05-17 17:43:24 ./usr/share/doc/openssh-client/ drwxr-xr-x root/root 0 2006-05-17 17:43:19 ./var/ drwxr-xr-x root/root 0 2006-05-17 17:43:19 ./var/run/ drwxr-xr-x root/root 0 2006-05-17 17:43:19 ./var/run/sshd/ ... ... ... root@u-bigboy:/tmp#
Listing the DEB Package to Which a File Belongs
Searching for the ownership of a particular file is also simple when using the --search option with dpkg. In this example, we see that the /etc/syslog.conf file is a part of the sysklogd package.
root@u-bigboy:~# dpkg --search /etc/syslog.conf sysklogd: /etc/syslog.conf root@u-bigboy:~#
Uninstalling DEBs
The dpkg --remove command will erase an installed package as seen in this example.
root@u-bigboy:~# dpkg --remove ndiswrapper-utils (Reading database ... 70241 files and directories currently installed.) Removing ndiswrapper-utils ... root@u-bigboy:~#
Which DEBs Will Start Up At Boot Time?
You can view and configure which DEBs will start at boot time is by using the update-rc.d command. A more detailed explanation will be provided in Chapter 7, "The Linux Boot Process".
Automatic DEB Updates with apt-get
Like Fedora, Debian / Ubuntu Linux has its own package update application that will automatically retrieve packages from a network based repository. It is called the Advanced Package Tool (APT) and it is the most commonly used command is apt-get which we'll cover in more detail later
Configuring APT
APT uses the /etc/apt/sources.list file to instruct your server as to where to find the required packages on your network. The default file locations in this file refer to a few trusted APT download websites on the Internet.
It is important to periodically resynchronize the APT package index files from the sources listed in the /etc/apt/sources.list file. This updates your system with listings of the most current package versions. This can be done with the apt-get update command as seen here:
root@u-bigboy:/tmp# apt-get update Get:1 http://security.ubuntu.com dapper-security Release.gpg [189B] Get:2 http://us.archive.ubuntu.com dapper Release.gpg [189B] Get:3 http://us.archive.ubuntu.com dapper-updates Release.gpg [189B] ... ... ... Fetched 184kB in 2s (66.1kB/s) Reading package lists... Done root@u-bigboy:/tmp#
Note: If you install Ubuntu without Internet access, only a barebones set of packages will be installed and the URL entries in the /etc/apt/sources.list file will be commented out, but the required packages will be flagged for eventual installation in the dpkg database. When you get Internet access, uncomment the URL entries and upgrade your installation with the apt-get command which will update your system with the full complement of required packages downloaded from the Web.
You can also create an APT server on your own network if you don't want all your Debian / Ubuntu servers to have Internet access. You'll have to update your sources.list file accordingly, but the full configuration steps are beyond the scope of this book.
Keeping Your System current with APT
The apt-get utility can be used to simultaneously upgrade all the packages on your system with the upgrade option. When used without listing any packages afterwards, apt-get will attempt to update them all. The apt-get upgrade package-name command updates only a particular DEB package.
It is always advisable to use apt-get after installing Linux to make sure the latest versions of software are installed for the sake of improved security and functionality. Here is an example of output of what to expect; the -y flag causes apt-get to assume "yes" as the answer to all prompts and allows it to run non-interactively:
root@u-bigboy:/tmp# apt-get -y upgrade Reading package lists... Done Building dependency tree... Done The following packages have been kept back: linux-image-386 The following packages will be upgraded: capplets-data desktop-file-utils eog gdm gnome-about ... ... ... Setting up libgtk2.0-bin (2.8.18-0ubuntu1) ... Updating the IM modules list for GTK+-2.4.0...done. Updating the gdk-pixbuf loaders list for GTK+-2.4.0...done. root@u-bigboy:/tmp#
Example of an apt-get Package Installation
Here is a sample installation of an individual package using yum. In this case the RPM installed is the apache Web server package:
[root@ root@u-bigboy:/tmp# apt-get -y install apache Reading package lists... Done Building dependency tree... Done The following extra packages will be installed: apache-common apache2-utils libapr0 libpcre3 Suggested packages: apache-doc apache-ssl apache-perl The following NEW packages will be installed: apache apache-common apache2-utils libapr0 libpcre3 ... ... ... Creating config file /etc/apache/httpd.conf with new version Creating config file /etc/apache/srm.conf with new version Creating config file /etc/apache/access.conf with new version Creating config file /etc/apache/modules.conf with new version * Starting apache 1.3 web server... ...done. root@u-bigboy:/tmp#
Remember The Following APT Facts
- The APT utility's sources.list file primarily lists URLs using TCP port 80 (http://) for its updates This will have importance for your firewall rules.
- More details on configuring yum can be obtained by running the man sources.list and the man apt-get commands.
Installing Software Using tar Files
Another popular software installation file format is the tar file, which can frequently be obtained from the Web sites of software developers, and online software libraries such as www.sourceforge.net.
The Linux tar command is used to archive files and typically have a .tar file extension in the file name. These files are also frequently compressed in the gzip format, and when they do, their file extensions will end with .tar.gz or .tgz. The commands to extract the data from either type are similar. When a tar file is uncompressed, the command to extract the data is tar -xvf filename.tar. When the archive is compressed, the command to use is tar -xzvf filename.tar.gz.
The tar file installation process usually requires you first to uncompress and extract the contents of the archive in a local subdirectory, which frequently has the same name as the tar file. The subdirectory will usually contain a file called README or INSTALL, which outlines all the customized steps to install the software.
Here are the initial steps to take to install tar-based software:
1) Issue the tar command to extract the files.
[root@bigboy tmp]# tar -xvzf linux-software-1.3.1.tar.gz linux-software-1.3.1/ linux-software-1.3.1/plugins-scripts/ ... ... ... linux-software-1.3.1/linux-software-plugins.spec [root@bigboy tmp]#
This creates a subdirectory with the installation files inside.
[root@bigboy tmp]# ls linux-software-1.3.1 linux-software-1.3.1.tar.gz [root@bigboy tmp]#
2) Use the cd command to enter the subdirectory and follow the directions listed in the INSTALL and README files:
[root@bigboy tmp]# cd linux-software-1.3.1 [root@bigboy linux-software-1.3.1]# ls COPYING install-sh missing plugins depcomp LEGAL mkinstalldirs plugins-scripts FAQ lib linux-software.spec README Helper.pm Makefile.am linux-software.spec.in REQUIREMENTS INSTALL Makefile.in NEWS subst.in [root@bigboy linux-software-1.3.1]#
Software installation with tar files can be frustrating, frequently requiring the installation of other supporting tar files, each with its own customized installation commands. RPMs, with the single standardized command format, are usually easier to use and may be the better method to use for newer Linux users.
Installing Perl Modules
Even if you don't know how to program in Perl, you may find yourself having to install Perl modules to get some of your software packages to work.
Modules can be installed manually by downloading the TAR files from www.cpan.org, the primary Perl module site. The disadvantage is that this method doesn't automatically install any prerequisite modules you may need. Another disadvantage, though small is that the perl module names usually have a double colon (::) in their names, but the installation TAR file in which this module resides won't have the colons in its name. For example version 1.74 of the Mail::Tools module has the file name MailTools-1.74.tar.gz.
Modules can also be installed automatically using the perl command. We will cover both methods in this section.
Manual Installation of Perl Modules
Most of the commonly used Perl modules can be downloaded from the CPAN website. The installation steps are straightforward.
1. Browse the CPAN website, identify the module package you need and then download it using a utility such as wget.
[root@bigboy tmp]# wget http://www.cpan.org/authors/id/M/MA/MARKOV/MailTools-1.74.tar.gz --15:07:36-- http://www.cpan.org/authors/id/M/MA/MARKOV/MailTools-1.74.tar.gz => `MailTools-1.74.tar.gz' Resolving www.cpan.org... 66.39.76.93 Connecting to www.cpan.org|66.39.76.93|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 47,783 (47K) [application/x-tar] 100%[===================================>] 47,783 100.88K/s 15:07:38 (100.51 KB/s) - `MailTools-1.74.tar.gz' saved [47783/47783] [root@bigboy tmp]#
2. Extract the file from the package with the tar command.
[root@bigboy tmp]# tar -xzvf MailTools-1.74.tar.gz MailTools-1.74/ MailTools-1.74/t/ ... ... ... MailTools-1.74/ChangeLog MailTools-1.74/MANIFEST [root@bigboy tmp]#
3. Enter the newly created directory with the same name as the TAR file, and install the module with the following commands.
- perl Makefile.PL
- make
- make test
[root@bigboy tmp]# cd MailTools-1.74 [root@bigboy MailTools-1.74]# perl Makefile.PL Checking for Net::SMTP...ok Checking for Net::Domain...ok Checking for IO::Handle...ok Checking if your kit is complete... Looks good Writing Makefile for Mail [root@bigboy MailTools-1.74]# make cp Mail/Cap.pm blib/lib/Mail/Cap.pm cp Mail/Mailer/rfc822.pm blib/lib/Mail/Mailer/rfc822.pm ... ... ... Manifying blib/man3/Mail::Util.3pm Manifying blib/man3/Mail::Address.3pm [root@bigboy MailTools-1.74]# make test PERL_DL_NONLAZY=1 /usr/bin/perl "-MExtUtils::Command::MM" "-e" "test_harness(0, 'blib/lib', 'blib/arch')" t/*.t t/extract.....ok ... ... ... All tests successful. Files=7, Tests=95, 2 wallclock secs ( 1.28 cusr + 0.29 csys = 1.57 CPU) [root@bigboy MailTools-1.74]#
Your Perl module installation should now be complete.
Note: The output of the perl Makefile.PL command will tell you whether there are any other required modules. You can either install them all manually, running the risk of having to install more prerequisite modules for these prerequisite modules, or you can use automated updates which will be covered next.
Automatic Installation of Perl Modules
Modules can be installed automatically using the perl utility but you must first install the prerequisite ncftp package to download the packages from CPAN.
[root@bigboy tmp]# yum -y install ncftp
After the package installed you can use the following perl command to enter the CPAN utility.
perl -MCPAN -e shell
The first time it is run, Perl will prompt you for a number of configuration options. In most cases the defaults will be sufficient. After the initial setup is complete you will have a cpan> command prompt
cpan>
Installation of modules can then be done with the install command followed by the name of the module. In this example we install the Mail::Audit module using the CPAN utility.
[root@bigboy tmp]# perl -MCPAN -e shell Terminal does not support AddHistory. cpan shell -- CPAN exploration and modules installation (v1.7602) ReadLine support available (try 'install Bundle::CPAN') cpan> install Mail::Audit CPAN: Storable loaded ok LWP not available CPAN: Net::FTP loaded ok Fetching with Net::FTP: ftp://archive.progeny.com/CPAN/authors/01mailrc.txt.gz ... ... ... Installing /usr/share/man/man3/Mail::Audit::MAPS.3pm Appending installation info to /usr/lib/perl5/5.8.8/i386-linux-thread-multi/perllocal.pod /usr/bin/make install -- OK cpan> exit Terminal does not support GetHistory. Lockfile removed. [root@bigboy tmp]#
The exit command allows you to return to the Linux command prompt and your Perl module should be fully installed.
Conclusion
This is just the beginning. If the software you install is intended to make your Linux machine permanently run an application such as a Web server, mail server, or any other type of server you have to know how to get the software activated when the system reboots. This is covered in Chapter 7, "The Linux Boot Process". Subsequent chapters cover the use, configuration, testing, and troubleshooting of many of the most popular Linux server applications used today.
