There are numerous package managers available for Linux systems. Several of the package managers offer graphical front-ends, contain search capabilities, allow updates to be installed from remote locations, and provide E-mail notifications when new packages are available. One package manager that provides all of these capabilities is YUM (YellowDog Updater Modified). This article will provide an introduction to package management with yum, and will show how a server that uses yum can be configured to generate E-mail notification when new packages are available for a server.
Yum reads it's configuration from one or more configuration files. The main configuration file is typically stored in /etc/yum.conf, and contains the default settings to use when retrieving and intalling packages. A sample configuration file from a CentOS 4.0 server is shown below:
$ cat /etc/yum.conf [main] cachedir=/var/cache/yum debuglevel=2 logfile=/var/log/yum.log pkgpolicy=newest distroverpkg=centos-release tolerant=1 exactarch=1 retries=20 obsoletes=1 gpgcheck=1 # PUT YOUR REPOS HERE OR IN separate files named file.repo # in /etc/yum.repos.d
In addition to the main yum.conf configuration file which is described in the yum.conf manual page, yum will look for remote repository definitions in the directory /etc/yum.repos.d. A sample repository definition from a CentOS 4.0 server is included below:
[base] name=CentOS-$releasever - Base mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=os #baseurl=http://mirror.centos.org/centos/$releasever/os/$basearch/ gpgcheck=1 gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
Each repository definition starts with a descriptive name that is enclosed in brackets. Inside each repository definition stanza is a line with a descriptive name, a flag to indicate if GPG signatures should be checked, and the locations to retrieve updates and the GPG keys that are used to sign the updates. Variables can be be used in URLs, and in the example above the $releasever and $basearch variables are used to reference the Operating System release and the file system base where updates are located.
The yum script comes with several options to control the package management process. These options can be viewed by invoking yum with the "-h" (help) option:
$ yum -h
usage: yum [options] < update | install | info | remove | list |
clean | provides | search | check-update | groupinstall |
groupupdate | grouplist | groupinfo | groupremove |
makecache | localinstall | erase | upgrade | whatprovides |
localupdate | resolvedep | shell | deplist >
options:
-h, help show this help message and exit
-t, tolerant be tolerant of errors
-C run entirely from cache, dont update cache
-c [config file] config file location
-R [minutes] maximum command wait time
-d [debug level] debugging output level
-e [error level] error output level
-y answer yes for all questions
version show Yum version and exit
installroot=[path] set install root
enablerepo=[repo] enable one or more repositories (wildcards allowed)
disablerepo=[repo] disable one or more repositories (wildcards allowed)
exclude=[package] exclude package(s) by name or glob
obsoletes enable obsoletes processing during updates
noplugins disable Yum plugins
The following sections will describe several of these options.
Before you can update packages on a system, it is first useful to see which packages are installed. Yum contains a "list" option to display the list of installed packages. When invoked without arguments, list will show all packages installed:
$ yum list |more Setting up Repos Reading repository metadata in from local files Installed Packages 4Suite.i386 1.0-3 installed GConf2.i386 2.8.1-1 installed GConf2-devel.i386 2.8.1-1 installed HelixPlayer.i386 1:1.0.6-0.fc3.1 installed ImageMagick.i386 6.2.2.0-2.fc3 installed MAKEDEV.i386 3.13-1 installed Maelstrom.i386 3.0.6-6 installed NetworkManager.i386 0.3.4-1.1.0.fc3 installed NetworkManager-gnome.i386 0.3.4-1.1.0.fc3 installed
If a string is passed as an argument to the list option, yum will look for all packages that match that string. The following example will list all packages with the name "curl":
$ yum list curl Setting up repositories rawhide-updates 100% |=========================| 1.1 kB 00:00 updates 100% |=========================| 1.1 kB 00:00 testing-updates 100% |=========================| 951 B 00:00 Reading repository metadata in from local files Available Packages curl.i386 7.15.0-1 rawhide-updates
The previous example showed the version of the installed curl package, and listed the repository the package was part of (in this case, rawhide-updates). It is somtimes useful to get a description of what a package is. This can be accomplished by passing a package name to the yum "info" option:
$ yum info curl Setting up repositories rawhide-updates 100% |=========================| 1.1 kB 00:00 updates 100% |=========================| 1.1 kB 00:00 testing-updates 100% |=========================| 951 B 00:00 Reading repository metadata in from local files Available Packages Name : curl Arch : i386 Version: 7.15.0 Release: 1 Size : 253 k Repo : rawhide-updates Summary: A utility for getting files from remote servers (FTP, HTTP, and others). Description: cURL is a tool for getting files from FTP, HTTP, Gopher, Telnet, and Dict servers, using any of the supported protocols. cURL is designed to work without user interaction or any kind of interactivity. cURL offers many useful capabilities, like proxy support, user authentication, FTP upload, HTTP post, and file transfer resume.
The output from the info option displays the package details, the size of the package, and a detailed description of what the package can be used for.
One of yum's most powerful options is it's search capabilities. Yum allows you to query packages by keyword, package name and pathname. The following example uses the curl "search" option to locate all packages that contain the string "curl" in their name:
$ yum search curl Searching Packages: Setting up repositories updates-released 100% |=========================| 951 B 00:00 extras 100% |=========================| 1.1 kB 00:00 base 100% |=========================| 1.1 kB 00:00 Reading repository metadata in from local files primary.xml.gz 100% |=========================| 977 kB 00:01 extras : ################################################## 2714/2714 Added 8 new packages, deleted 0 old in 6.47 seconds curl.i386 7.13.1-3 base Matched from: curl cURL is a tool for getting files from FTP, HTTP, Gopher, Telnet, and Dict servers, using any of the supported protocols. cURL is designed to work without user interaction or any kind of interactivity. cURL offers many useful capabilities, like proxy support, user authentication, FTP upload, HTTP post, and file transfer resume. http://curl.haxx.se/ curl-devel.i386 7.13.1-3 base Matched from: curl-devel Files needed for building applications with libcurl. cURL is a tool for getting files from FTP, HTTP, Gopher, Telnet, and Dict servers, using any of the supported protocols. The curl-devel package includes files needed for developing applications which can use cURL's capabilities internally. http://curl.haxx.se/ curl.i386 7.13.1-3 installed Matched from: curl cURL is a tool for getting files from FTP, HTTP, Gopher, Telnet, and Dict servers, using any of the supported protocols. cURL is designed to work without user interaction or any kind of interactivity. cURL offers many useful capabilities, like proxy support, user authentication, FTP upload, HTTP post, and file transfer resume. http://curl.haxx.se/
In addition to searching for package names, yum's "whatprovides" option can be used to locate the package that contains a specific executable:
$ yum whatprovides /etc/yum.conf Searching Packages: Setting up repositories updates-released 100% |=========================| 951 B 00:00 extras 100% |=========================| 1.1 kB 00:00 base 100% |=========================| 1.1 kB 00:00 Reading repository metadata in from local files primary.xml.gz 100% |=========================| 977 kB 00:01 extras : ################################################## 2714/2714 Added 8 new packages, deleted 0 old in 6.65 seconds yum.noarch 2.3.2-7 base Matched from: /etc/yum.conf yum.noarch 2.4.0-0.fc4 updates-released Matched from: /etc/yum.conf yum.noarch 2.4.0-0.fc4 installed Matched from: /etc/yum.conf
This example shows that /etc/yum.conf is part of the yum.noarch package.
Most packages that come with a Linux distributions contain one or more dependencies. A prefect example of this is the Apache web server. Apache depends on the openssl package to provide SSL support, the zlib package to deflate content, and the PHP package if PHP is in use. Managing packages and their dependencies is one area where yum really shines. Not only does yum automatically detect and resolve dependencies, but it allows you to view package dependencies with the "deplist" option:
$ yum deplist curl Finding dependencies: Setting up repositories updates-released 100% |=========================| 951 B 00:00 extras 100% |=========================| 1.1 kB 00:00 base 100% |=========================| 1.1 kB 00:00 Reading repository metadata in from local files package: curl.i386 7.13.1-3 dependency: libdl.so.2 provider: glibc.i386 2.3.5-10 provider: glibc.i686 2.3.5-10 provider: glibc.i386 2.3.5-10.3 provider: glibc.i686 2.3.5-10.3 dependency: libkrb5.so.3 provider: krb5-libs.i386 1.4-3 provider: krb5-libs.i386 1.4.1-5 dependency: libc.so.6(GLIBC_2.1) provider: glibc.i386 2.3.5-10 provider: glibc.i686 2.3.5-10 provider: glibc.i386 2.3.5-10.3 provider: glibc.i686 2.3.5-10.3 dependency: libcrypto.so.5 provider: openssl.i686 0.9.7f-7 provider: openssl.i386 0.9.7f-7 provider: openssl.i386 0.9.7f-7.10 provider: openssl.i686 0.9.7f-7.10 dependency: libc.so.6 provider: glibc.i386 2.3.5-10 provider: glibc.i686 2.3.5-10 provider: glibc.i386 2.3.5-10.3 provider: glibc.i686 2.3.5-10.3 dependency: libc.so.6(GLIBC_2.0) provider: glibc.i386 2.3.5-10 provider: glibc.i686 2.3.5-10 provider: glibc.i386 2.3.5-10.3 provider: glibc.i686 2.3.5-10.3 dependency: libc.so.6(GLIBC_2.3.4) provider: glibc.i386 2.3.5-10 provider: glibc.i686 2.3.5-10 provider: glibc.i386 2.3.5-10.3 provider: glibc.i686 2.3.5-10.3 dependency: libdl.so.2(GLIBC_2.1) provider: glibc.i386 2.3.5-10 provider: glibc.i686 2.3.5-10 provider: glibc.i386 2.3.5-10.3 provider: glibc.i686 2.3.5-10.3 dependency: libz.so.1 provider: zlib.i386 1.2.2.2-3 provider: zlib.i386 1.2.2.2-5.fc4 dependency: libidn.so.11 provider: libidn.i386 0.5.15-1 dependency: libc.so.6(GLIBC_2.1.3) provider: glibc.i386 2.3.5-10 provider: glibc.i686 2.3.5-10 provider: glibc.i386 2.3.5-10.3 provider: glibc.i686 2.3.5-10.3 dependency: libdl.so.2(GLIBC_2.0) provider: glibc.i386 2.3.5-10 provider: glibc.i686 2.3.5-10 provider: glibc.i386 2.3.5-10.3 provider: glibc.i686 2.3.5-10.3 dependency: libcom_err.so.2 provider: e2fsprogs.i386 1.37-4 provider: e2fsprogs.i386 1.38-0.FC4.1 dependency: /bin/sh provider: bash.i386 3.0-31 dependency: openssl provider: openssl.i686 0.9.7f-7 provider: openssl.i386 0.9.7f-7 provider: openssl.i386 0.9.7f-7.10 provider: openssl.i686 0.9.7f-7.10 dependency: libresolv.so.2 provider: glibc.i386 2.3.5-10 provider: glibc.i686 2.3.5-10 provider: glibc.i386 2.3.5-10.3 provider: glibc.i686 2.3.5-10.3 dependency: libc.so.6(GLIBC_2.3) provider: glibc.i386 2.3.5-10 provider: glibc.i686 2.3.5-10 provider: glibc.i386 2.3.5-10.3 provider: glibc.i686 2.3.5-10.3 dependency: libcurl.so.3 provider: curl.i386 7.13.1-3 dependency: libgssapi_krb5.so.2 provider: krb5-libs.i386 1.4-3 provider: krb5-libs.i386 1.4.1-5 dependency: libkrb5support.so.0 provider: krb5-libs.i386 1.4-3 provider: krb5-libs.i386 1.4.1-5 dependency: libgssapi_krb5.so.2(gssapi_krb5_2_MIT) provider: krb5-libs.i386 1.4-3 provider: krb5-libs.i386 1.4.1-5 dependency: libssl.so.5 provider: openssl.i686 0.9.7f-7 provider: openssl.i386 0.9.7f-7 provider: openssl.i386 0.9.7f-7.10 provider: openssl.i686 0.9.7f-7.10 dependency: libc.so.6(GLIBC_2.2) provider: glibc.i386 2.3.5-10 provider: glibc.i686 2.3.5-10 provider: glibc.i386 2.3.5-10.3 provider: glibc.i686 2.3.5-10.3 dependency: libk5crypto.so.3 provider: krb5-libs.i386 1.4-3 provider: krb5-libs.i386 1.4.1-5
As you can see from the output, curl requires several packages to work as expected.
Up to this point we have shown how to use yum to view package metadata. The real heart of a package manager is it's ability to install packages, remove packages, and to handle the dependencies that are associated with a specific release of a package. Yum allows packages to be installed with the "install" option, which takes one or more packages to install as arguments. The following example show how to install the curl package and all of it's dependencies:
$ yum install curl Setting up Install Process Setting up repositories updates-released 100% |=========================| 951 B 00:00 extras 100% |=========================| 1.1 kB 00:00 base 100% |=========================| 1.1 kB 00:00 Reading repository metadata in from local files Parsing package install arguments Resolving Dependencies --> Populating transaction set with selected packages. Please wait. ---> Downloading header for curl to pack into transaction set. curl-7.13.1-3.i386.rpm 100% |=========================| 10 kB 00:00 ---> Package curl.i386 0:7.13.1-3 set to be updated --> Running transaction check Dependencies Resolved ============================================================================= Package Arch Version Repository Size ============================================================================= Installing: curl i386 7.13.1-3 base 262 k Transaction Summary ============================================================================= Install 1 Package(s) Update 0 Package(s) Remove 0 Package(s) Total download size: 262 k Is this ok [y/N]: y Downloading Packages: (1/1): curl-7.13.1-3.i386 100% |=========================| 262 kB 00:00 Running Transaction Test Finished Transaction Test Transaction Test Succeeded Running Transaction Installing: curl ######################### [1/1] Installed: curl.i386 0:7.13.1-3 Complete!
Packages can be removed just as easily as they can be added. To remove the curl package that we just installed, the package name can be passed as an argument to the "remove" option:
$ yum remove curl Setting up Remove Process Resolving Dependencies --> Populating transaction set with selected packages. Please wait. ---> Package curl.i386 0:7.13.1-3 set to be erased --> Running transaction check Dependencies Resolved ============================================================================= Package Arch Version Repository Size ============================================================================= Removing: curl i386 7.13.1-3 installed 521 k Transaction Summary ============================================================================= Install 0 Package(s) Update 0 Package(s) Remove 1 Package(s) Total download size: 0 Is this ok [y/N]: y Downloading Packages: Running Transaction Test Finished Transaction Test Transaction Test Succeeded Running Transaction Removing : curl ######################### [1/1] Removed: curl.i386 0:7.13.1-3 Complete!
One of yum's nicest features is it's ability to install packages from remote repositories, and to compare the currently installed packages with what is available remotely. To compare the currently installed packages with the versions that are available in one or more remote repositories, yum can be invoked with the "check-update" option:
$ curl check-update Setting up repositories updates-released 100% |=========================| 951 B 00:00 extras 100% |=========================| 1.1 kB 00:00 base 100% |=========================| 1.1 kB 00:00 Reading repository metadata in from local files primary.xml.gz 100% |=========================| 337 kB 00:01 updates-re: ################################################## 989/989 Added 105 new packages, deleted 83 old in 4.52 seconds primary.xml.gz 100% |=========================| 977 kB 00:00 extras : ################################################## 2714/2714 Added 8 new packages, deleted 0 old in 6.60 seconds bind.i386 24:9.3.1-14_FC4 updates-released bind-libs.i386 24:9.3.1-14_FC4 updates-released bind-utils.i386 24:9.3.1-14_FC4 updates-released esound.i386 1:0.2.36-0.fc4.1 updates-released esound-devel.i386 1:0.2.36-0.fc4.1 updates-released gawk.i386 3.1.4-5.3 updates-released gdb.i386 6.3.0.0-1.84 updates-released logwatch.noarch 7.0-1.fc4 updates-released mutt.i386 5:1.4.2.1-4.FC4 updates-released pam.i386 0.79-9.6 updates-released pam-devel.i386 0.79-9.6 updates-released sudo.i386 1.6.8p8-2.3 updates-released
In this example we can see that numerous packages are outdated by newer version. To update all of the outdated packages to newer versions, yum can be run with the "update" option:
$ yum update Setting up Update Process Setting up repositories updates-released 100% |=========================| 951 B 00:00 extras 100% |=========================| 1.1 kB 00:00 base 100% |=========================| 1.1 kB 00:00 Reading repository metadata in from local files Resolving Dependencies --> Populating transaction set with selected packages. Please wait. ---> Downloading header for bind to pack into transaction set. bind-9.3.1-14_FC4.i386.rp 100% |=========================| 39 kB 00:00 ---> Package bind.i386 24:9.3.1-14_FC4 set to be updated ---> Downloading header for gawk to pack into transaction set. gawk-3.1.4-5.3.i386.rpm 100% |=========================| 17 kB 00:00 ---> Package gawk.i386 0:3.1.4-5.3 set to be updated ---> Downloading header for sudo to pack into transaction set. sudo-1.6.8p8-2.3.i386.rpm 100% |=========================| 11 kB 00:00 ---> Package sudo.i386 0:1.6.8p8-2.3 set to be updated ---> Downloading header for esound-devel to pack into transaction set. esound-devel-0.2.36-0.fc4 100% |=========================| 6.6 kB 00:00 ---> Package esound-devel.i386 1:0.2.36-0.fc4.1 set to be updated ---> Downloading header for pam-devel to pack into transaction set. pam-devel-0.79-9.6.i386.r 100% |=========================| 40 kB 00:00 ---> Package pam-devel.i386 0:0.79-9.6 set to be updated ---> Downloading header for bind-libs to pack into transaction set. bind-libs-9.3.1-14_FC4.i3 100% |=========================| 31 kB 00:00 ---> Package bind-libs.i386 24:9.3.1-14_FC4 set to be updated ---> Downloading header for pam to pack into transaction set. pam-0.79-9.6.i386.rpm 100% |=========================| 62 kB 00:00 ---> Package pam.i386 0:0.79-9.6 set to be updated ---> Downloading header for bind-utils to pack into transaction set. bind-utils-9.3.1-14_FC4.i 100% |=========================| 29 kB 00:00 ---> Package bind-utils.i386 24:9.3.1-14_FC4 set to be updated ---> Downloading header for esound to pack into transaction set. esound-0.2.36-0.fc4.1.i38 100% |=========================| 11 kB 00:00 ---> Package esound.i386 1:0.2.36-0.fc4.1 set to be updated ---> Downloading header for logwatch to pack into transaction set. logwatch-7.0-1.fc4.noarch 100% |=========================| 31 kB 00:00 ---> Package logwatch.noarch 0:7.0-1.fc4 set to be updated ---> Downloading header for mutt to pack into transaction set. mutt-1.4.2.1-4.FC4.i386.r 100% |=========================| 19 kB 00:00 ---> Package mutt.i386 5:1.4.2.1-4.FC4 set to be updated ---> Downloading header for gdb to pack into transaction set. gdb-6.3.0.0-1.84.i386.rpm 100% |=========================| 48 kB 00:00 ---> Package gdb.i386 0:6.3.0.0-1.84 set to be updated --> Running transaction check Dependencies Resolved ============================================================================= Package Arch Version Repository Size ============================================================================= Updating: bind i386 24:9.3.1-14_FC4 updates-released 532 k bind-libs i386 24:9.3.1-14_FC4 updates-released 779 k bind-utils i386 24:9.3.1-14_FC4 updates-released 146 k esound i386 1:0.2.36-0.fc4.1 updates-released 127 k esound-devel i386 1:0.2.36-0.fc4.1 updates-released 31 k gawk i386 3.1.4-5.3 updates-released 1.7 M gdb i386 6.3.0.0-1.84 updates-released 2.7 M logwatch noarch 7.0-1.fc4 updates-released 217 k mutt i386 5:1.4.2.1-4.FC4 updates-released 1.1 M pam i386 0.79-9.6 updates-released 1.9 M pam-devel i386 0.79-9.6 updates-released 87 k sudo i386 1.6.8p8-2.3 updates-released 185 k Transaction Summary ============================================================================= Install 0 Package(s) Update 12 Package(s) Remove 0 Package(s) Total download size: 9.5 M Is this ok [y/N]: y Downloading Packages: (1/12): bind-9.3.1-14_FC4 100% |=========================| 532 kB 00:02 (2/12): gawk-3.1.4-5.3.i3 100% |=========================| 1.7 MB 00:03 (3/12): sudo-1.6.8p8-2.3. 100% |=========================| 185 kB 00:01 (4/12): esound-devel-0.2. 100% |=========================| 31 kB 00:00 (5/12): pam-devel-0.79-9. 100% |=========================| 87 kB 00:00 (6/12): bind-libs-9.3.1-1 100% |=========================| 779 kB 00:02 (7/12): pam-0.79-9.6.i386 100% |=========================| 1.9 MB 00:04 (8/12): bind-utils-9.3.1- 100% |=========================| 146 kB 00:00 (9/12): esound-0.2.36-0.f 100% |=========================| 127 kB 00:00 (10/12): logwatch-7.0-1.f 100% |=========================| 217 kB 00:01 (11/12): mutt-1.4.2.1-4.F 100% |=========================| 1.1 MB 00:02 (12/12): gdb-6.3.0.0-1.84 100% |=========================| 2.7 MB 00:05 Running Transaction Test Finished Transaction Test Transaction Test Succeeded Running Transaction Updating : bind-libs ####################### [ 1/24] Updating : pam ####################### [ 2/24] Updating : esound ####################### [ 3/24] Updating : bind-utils ####################### [ 4/24] Updating : bind ####################### [ 5/24] Updating : gawk ####################### [ 6/24] Updating : sudo ####################### [ 7/24] Updating : esound-devel ####################### [ 8/24] Updating : pam-devel ####################### [ 9/24] Updating : logwatch ####################### [10/24] Updating : mutt ####################### [11/24] Updating : gdb ####################### [12/24] Cleanup : bind ####################### [13/24] Cleanup : gawk ####################### [14/24] Cleanup : sudo ####################### [15/24] Cleanup : esound-devel ####################### [16/24] Cleanup : pam-devel ####################### [17/24] Cleanup : bind-libs ####################### [18/24] Cleanup : pam ####################### [19/24] Cleanup : bind-utils ####################### [20/24] Cleanup : esound ####################### [21/24] Cleanup : logwatch ####################### [22/24] Cleanup : mutt ####################### [23/24] Cleanup : gdb ####################### [24/24] Updated: bind.i386 24:9.3.1-14_FC4 bind-libs.i386 24:9.3.1-14_FC4 bind-utils.i386 24:9.3.1-14_FC4 esound.i386 1:0.2.36-0.fc4.1 esound-devel.i386 1:0.2.36-0.fc4.1 gawk.i386 0:3.1.4-5.3 gdb.i386 0:6.3.0.0-1.84 logwatch.noarch 0:7.0-1.fc4 mutt.i386 5:1.4.2.1-4.FC4 pam.i386 0:0.79-9.6 pam-devel.i386 0:0.79-9.6 sudo.i386 0:1.6.8p8-2.3 Complete!
If you would prefer to update a single package, you can pass the package name as an argument to the yum update option.
The yum package manager maintains a cache of headers and files in /var/cache/yum. This cache can grow rather large over time, and can be cleaned with the yum "clean" option:
$ yum clean all Cleaning up Everything 251 headers removed 251 packages removed 6 metadata files removed 0 cache files removed 3 cache files removed
You can also clean individual items such as headers and packages by passing the item to clean to the clean option. Since the yum cache can consume a fair amount of disk space, the clean option should be used periodically to free up disk space.
The process of managing packages is tedious, and having to manually check for updates is a pain. To simplify this process, I developed the yumnotifier shell script. Yumnotifier will process the output from the check-update command, and if it determines that updates are available, it will E-mail the address defined in the global $ADMIN variable. The script is designed to be run from cron, and will generate an E-mail similar to the following if updates are available: