YUM.CONF(5)

NAME
yum.conf - redirecting to DNF Configuration Reference

DESCRIPTION

DNF by default uses the global configuration file at /etc/dnf/dnf.conf and all *.repo files found under /etc/yum.repos.d. The latter is typically used for repository configuration and takes precedence over global configuration.

The configuration file has INI format consisting of section declaration and name=value options below each on separate line. There are two types of sections in the configuration files: main and repository. Main section defines all global configuration options and should be only one.

The repository sections define the configuration for each (remote or local) repository. The section name of the repository in brackets serve as repo ID reference and should be unique across configuration files. The allowed characters of repo ID string are lower and upper case alphabetic letters, digits, -, _, . and :. The minimal repository configuration file should aside from repo ID consists of baseurl, metalink or mirrorlist option definition.

DISTRIBUTION-SPECIFIC CONFIGURATION

Configuration options, namely best and skip_if_unavailable, can be set in the DNF configuration file by your distribution to override the DNF defaults.

[MAIN] OPTIONS

allow_vendor_change
    boolean

    If disabled dnf will stick to vendor when upgrading or downgrading rpms. Default is True

    WARNING: This option is currently not supported for downgrade and distro-sync commands

arch
    string

    The architecture used for installing packages. By default this is auto-detected. Often used together with ignorearch option.

assumeno
    boolean

    If enabled dnf will assume No where it would normally prompt for confirmation from user input. Default is False.

assumeyes
    boolean

    If enabled dnf will assume Yes where it would normally prompt for confirmation from user input (see also defaultyes). Default is False.

autocheck_running_kernel
    boolean

    Automatic check whether there is installed newer kernel module with security update than currently running kernel. Default is True.

basearch
    string

    The base architecture used for installing packages. By default this is auto-detected.

best
    boolean

    True instructs the solver to either use a package with the highest available version or fail. On False, do not fail if the latest version cannot be installed and go with the lower version. The default is False. Note this option in particular can be set in your configuration file by your distribution. Also note that the use of the highest available version is only guaranteed for the packages directly requested and not for their dependencies.

cachedir
    string

    Path to a directory used by various DNF subsystems for storing cache data. Has a reasonable root-writable default depending on the distribution. DNF needs to be able to create files and directories at this location.

cacheonly
    boolean

    If set to True DNF will run entirely from system cache, will not update the cache and will use it even in case it is expired. Default is False.

    API Notes: Must be set before repository objects are created. Plugins must set this in the pre_config hook. Later changes are ignored.

check_config_file_age
    boolean

    Specifies whether dnf should automatically expire metadata of repos, which are older than their corresponding configuration file (usually the dnf.conf file and the foo.repo file). Default is True (perform the check). Expire of metadata is also affected by metadata age. See also metadata_expire.

clean_requirements_on_remove
    boolean

    Remove dependencies that are no longer used during dnf remove. A package only qualifies for removal via clean_requirements_on_remove if it was installed through DNF but not on explicit user request, i.e. it was pulled in as a dependency. The default is True. (installonlypkgs are never automatically removed.)

config_file_path
    string

    Path to the default main configuration file. Default is /etc/dnf/dnf.conf.

debuglevel
    integer

    Debug messages output level, in the range 0 to 10. The higher the number the more debug output is put to stdout. Default is 2.

debug_solver
    boolean

    Controls whether the libsolv debug files should be created when solving the transaction. The debug files are created in the ./debugdata directory. Default is False.

defaultyes
    boolean

    If enabled the default answer to user confirmation prompts will be Yes. Not to be confused with assumeyes which will not prompt at all. Default is False.

diskspacecheck
    boolean

    Controls whether rpm should check available disk space during the transaction. Default is True.

errorlevel
    integer

    Error messages output level, in the range 0 to 10. The higher the number the more error output is put to stderr. Default is 3. This is deprecated in DNF and overwritten by --verbose commandline option.

exclude_from_weak
    list

    Prevent installing packages as weak dependencies (recommends or supplements). The packages can be specified by a name or a glob and separated by a comma. Defaults to [].

exclude_from_weak_autodetect
    boolean

    If enabled, dnf will autodetect unmet weak dependencies (recommends or supplements) of packages installed on the system. Providers of these weak dependencies will not be installed by dnf as weak dependencies any more (they will still be installed if pulled in as a regular dependency). Defaults to true.

exit_on_lock
    boolean

    Should the dnf client exit immediately when something else has the lock. Default is False.

gpgkey_dns_verification
    boolean

    Should the dnf attempt to automatically verify GPG verification keys using the DNS system. This option requires the unbound python module (python3-unbound) to be installed on the client system. This system has two main features. The first one is to check if any of the already installed keys have been revoked. Automatic removal of the key is not yet available, so it is up to the user, to remove revoked keys from the system. The second feature is automatic verification of new keys when a repository is added to the system. In interactive mode, the result is written to the output as a suggestion to the user. In non-interactive mode (i.e. when -y is used), this system will automatically accept keys that are available in the DNS and are correctly signed using DNSSEC. It will also accept keys that do not exist in the DNS system and their NON-existence is cryptographically proven using DNSSEC. This is mainly to preserve backward compatibility. Default is False.

group_package_types
    list

    List of the following: optional, default, mandatory. Tells dnf which type of packages in groups will be installed when 'groupinstall' is called. Default is: default, mandatory.

ignorearch
    boolean

    If set to True, RPM will allow attempts to install packages incompatible with the CPU's architecture. Defaults to False. Often used together with arch option.

installonlypkgs
    list

    List of provide names of packages that should only ever be installed, never upgraded. Kernels in particular fall into this category. These packages are never removed by dnf autoremove even if they were installed as dependencies (see clean_requirements_on_remove for auto removal details). This option append the list values to the default installonlypkgs list used by DNF. The number of kept package versions is regulated by installonly_limit.

installonly_limit
    integer

    Number of installonly packages allowed to be installed concurrently. Defaults to 3. The minimal number of installonly packages is 2. Value 0 means unlimited number of installonly packages. Value 1 is explicitly not allowed since it complicates kernel upgrades due to protection of the running kernel from removal.

installroot
    string

    The root of the filesystem for all packaging operations. It requires an absolute path. See also --installroot commandline option.

install_weak_deps
    boolean

    When this option is set to True and a new package is about to be installed, all packages linked by weak dependency relation (Recommends or Supplements flags) with this package will be pulled into the transaction. Default is True.

keepcache
    boolean

    Keeps downloaded packages in the cache when set to True. Even if it is set to False and packages have not been installed they will still persist until next successful transaction. The default is False.

logdir
    string

    Directory where the log files will be stored. Default is /var/log.

logfilelevel
    integer

    Log file messages output level, in the range 0 to 10. The higher the number the more debug output is put to logs. Default is 9.

    This option controls dnf.log, dnf.librepo.log and hawkey.log. Although dnf.librepo.log and hawkey.log are affected only by setting the logfilelevel to 10.

log_compress
    boolean

    When set to True, log files are compressed when they are rotated. Default is False.

log_rotate
    integer

    Log files are rotated log_rotate times before being removed. If log_rotate is 0, the rotation is not performed. Default is 4.

log_size
    storage size

    Log files are rotated when they grow bigger than log_size bytes. If log_size is 0, the rotation is not performed. The default is 1 MB. Valid units are 'k', 'M', 'G'.

    The size applies for individual log files, not the sum of all log files. See also log_rotate.

metadata_timer_sync
    time in seconds

    The minimal period between two consecutive makecache timer runs. The command will stop immediately if it's less than this time period since its last run. Does not affect simple makecache run. Use 0 to completely disable automatic metadata synchronizing. The default corresponds to three hours. The value is rounded to the next commenced hour.

module_obsoletes
    boolean

    This option controls whether dnf should apply modular obsoletes when possible. Default is False.

module_platform_id
    string

    Set this to $name:$stream to override PLATFORM_ID detected from /etc/os-release. It is necessary to perform a system upgrade and switch to a new platform.

module_stream_switch
    boolean

    This option controls whether it's possible to switch enabled streams of a module. Default is False.

multilib_policy
    string

    Controls how multilib packages are treated during install operations. Can either be "best" (the default) for the depsolver to prefer packages which best match the system's architecture, or "all" to install packages for all available architectures.

obsoletes
    boolean

    This option only has affect during an install/update. It enables dnf's obsoletes processing logic, which means it makes dnf check whether any dependencies of given package are no longer required and removes them. Useful when doing distribution level upgrades. Default is 'true'.

    Command-line option: --obsoletes

persistdir
    string

    Directory where DNF stores its persistent data between runs. Default is "/var/lib/dnf".

pluginconfpath
    list

    List of directories that are searched for plugin configurations to load. All configuration files found in these directories, that are named same as a plugin, are parsed. The default path is /etc/dnf/plugins.

pluginpath
    list

    List of directories that are searched for plugins to load. Plugins found in any of the directories in this configuration option are used. The default contains a Python version-specific path.

plugins
    boolean

    Controls whether the plugins are enabled. Default is True.

protected_packages
    list

    List of packages that DNF should never completely remove. They are protected via Obsoletes as well as user/plugin removals.

    The default is: dnf, glob:/etc/yum/protected.d/*.conf and glob:/etc/dnf/protected.d/*.conf. So any packages which should be protected can do so by including a file in /etc/dnf/protected.d with their package name in it.

    DNF will protect also the package corresponding to the running version of the kernel. See also protect_running_kernel option.

protect_running_kernel
    boolean

    Controls whether the package corresponding to the running version of kernel is protected from removal. Default is True.

releasever
    string

    Used for substitution of $releasever in the repository configuration. See also repo variables.

reposdir
    list

    DNF searches for repository configuration files in the paths specified by reposdir. The behavior of reposdir could differ when it is used along with --installroot option.

rpmverbosity
    string

    RPM debug scriptlet output level. One of: critical, emergency, error, warn, info or debug. Default is info.

strict
    boolean

    If disabled, all unavailable packages or packages with broken dependencies given to DNF command will be skipped without raising the error causing the whole operation to fail. Currently works for install command only. The default is True.

tsflags
    list

    List of strings adding extra flags for the RPM transaction.
    tsflag value | RPM Transaction Flag
    noscripts | RPMTRANS_FLAG_NOSCRIPTS
    test | RPMTRANS_FLAG_TEST
    notriggers | RPMTRANS_FLAG_NOTRIGGERS
    nodocs | RPMTRANS_FLAG_NODOCS
    justdb | RPMTRANS_FLAG_JUSTDB
    nocontexts | RPMTRANS_FLAG_NOCONTEXTS
    nocaps | RPMTRANS_FLAG_NOCAPS
    nocrypto | RPMTRANS_FLAG_NOFILEDIGEST

    The nocrypto option will also set the _RPMVSF_NOSIGNATURES and _RPMVSF_NODIGESTS VS flags. The test option provides a transaction check without performing the transaction. It includes downloading of packages, gpg keys check (including permanent import of additional keys if necessary), and rpm check to prevent file conflicts. The nocaps is supported with rpm-4.14 or later. When nocaps is used but rpm doesn't support it, DNF only reports it as an invalid tsflag.

upgrade_group_objects_upgrade
    boolean

    Set this to False to disable the automatic running of group upgrade when running the upgrade command. Default is True (perform the operation).

varsdir
    list

    List of directories where variables definition files are looked for. Defaults to "/etc/dnf/vars", "/etc/yum/vars". See variable files in Configuration reference.

zchunk
    boolean

    Enables or disables the use of repository metadata compressed using the zchunk format (if available). Default is True.

[MAIN] OPTIONS - COLORS

color
    string

    Controls if DNF uses colored output on the command line. Possible values: "auto", "never", "always". Default is "auto".

color_list_available_downgrade
    color

    Color of available packages that are older than installed packages. The option is used during list operations. Default is magenta.

color_list_available_install
    color

    Color of packages that are available for installation and none of their versions in installed. The option is used during list operations. Default is bold,cyan.

color_list_available_reinstall
    color

    Color of available packages that are identical to installed versions and are available for reinstalls. Default is bold,underline,green. The option is used during list operations.

color_list_available_upgrade
    color

    Color of available packages that are newer than installed packages. Default is bold,blue. The option is used during list operations.

color_list_installed_extra
    color

    Color of installed packages that do not have any version among available packages. The option is used during list operations. Default is bold,red.

color_list_installed_newer
    color

    Color of installed packages that are newer than any version among available packages. The option is used during list operations. Default is bold,yellow.

color_list_installed_older
    color

    Color of installed packages that are older than any version among available packages. The option is used during list operations. Default is yellow.

color_list_installed_reinstall
    color

    Color of installed packages that are among available packages and can be reinstalled. The option is used during list operations. Default is cyan.

color_search_match
    color

    Color of patterns matched in search output. Default is bold,magenta.

color_update_installed
    color

    Color of removed packages. Default is red. This option is used during displaying transactions.

color_update_local
    color

    Color of local packages that are installed from the @commandline repository. This option is used during displaying transactions. Default is green.

color_update_remote
    color

    Color of packages that are installed/upgraded/downgraded from remote repositories. This option is used during displaying transactions. Default is bold,green.

REPO OPTIONS

baseurl
    list

    List of URLs for the repository. Defaults to [].

    URLs are tried in the listed order (equivalent to yum's "failovermethod=priority" behaviour).

cost
    integer

    The relative cost of accessing this repository, defaulting to 1000. This value is compared when the priorities of two repositories are the same. The repository with the lowest cost is picked. It is useful to make the library prefer on-disk repositories to remote ones.

enabled
    boolean

    Include this repository as a package source. The default is True.

gpgkey
    list of strings

    URLs of a GPG key files that can be used for signing metadata and packages of this repository, empty by default. If a file can not be verified using the already imported keys, import of keys from this option is attempted and the keys are then used for verification.

metalink
    string

    URL of a metalink for the repository. Defaults to None.

mirrorlist
    string

    URL of a mirrorlist for the repository. Defaults to None.

module_hotfixes
    boolean

    Set this to True to disable module RPM filtering and make all RPMs from the repository available. The default is False. This allows user to create a repository with cherry-picked hotfixes that are included in a package set on a modular system.

name
    string

    A human-readable name of the repository. Defaults to the ID of the repository.

priority
    integer

    The priority value of this repository, default is 99. If there is more than one candidate package for a particular operation, the one from a repo with the lowest priority value is picked, possibly despite being less convenient otherwise (e.g. by being a lower version).

type
    string

    Type of repository metadata. Supported values are: rpm-md. Aliases for rpm-md: rpm, repomd, rpmmd, yum, YUM.

REPO VARIABLES

Right side of every repo option can be enriched by the following variables:

$arch Refers to the system’s CPU architecture e.g, aarch64, i586, i686 and x86_64.

$basearch Refers to the base architecture of the system. For example, i686 and i586 machines both have a base architecture of i386, and AMD64 and Intel64 machines have a base architecture of x86_64.

$releasever Refers to the release version of operating system which DNF derives from information available in RPMDB.

In addition to these hard coded variables, user-defined ones can also be used. They can be defined either via variable files, or by using special environmental variables. The names of these variables must be prefixed with DNF_VAR_ and they can only consist of alphanumeric characters and underscores:

$ DNF_VAR_MY_VARIABLE=value

To use such variable in your repository configuration remove the prefix. E.g.:

[myrepo]
baseurl=https://example.site/pub/fedora/$MY_VARIABLE/releases/$releasever

Note that it is not possible to override the arch and basearch variables using either variable files or environmental variables.

Although users are encouraged to use named variables, the numbered environmental variables DNF0 - DNF9 are still supported:

$ DNF1=value
[myrepo]
baseurl=https://example.site/pub/fedora/$DNF1/releases/$releasever

OPTIONS FOR BOTH [MAIN] AND REPO

Some options can be applied in either the main section, per repository, or in a combination. The value provided in the main section is used for all repositories as the default value, which repositories can then override in their configuration.

bandwidth
    storage size

    Total bandwidth available for downloading. Meaningful when used with the throttle option. Storage size is in bytes by default but can be specified with a unit of storage. Valid units are 'k', 'M', 'G'.

countme
    boolean

    Determines whether a special flag should be added to a single, randomly chosen metalink/mirrorlist query each week. This allows the repository owner to estimate the number of systems consuming it, by counting such queries over a week's time, which is much more accurate than just counting unique IP addresses (which is subject to both overcounting and undercounting due to short DHCP leases and NAT, respectively).

    The flag is a simple "countme=N" parameter appended to the metalink and mirrorlist URL, where N is an integer representing the "longevity" bucket this system belongs to. The following 4 buckets are defined, based on how many full weeks have passed since the beginning of the week when this system was installed: 1 = first week, 2 = first month (2-4 weeks), 3 = six months (5-24 weeks) and 4 = more than six months (> 24 weeks). This information is meant to help distinguish short-lived installs from long-term ones, and to gather other statistics about system lifecycle.

    Default is False.

deltarpm
    boolean

    When enabled, DNF will save bandwidth by downloading much smaller delta RPM files, rebuilding them to RPM locally. However, this is quite CPU and I/O intensive. Default is True.

deltarpm_percentage
    integer

    When the relative size of delta vs pkg is larger than this, delta is not used. Default value is 75 (Deltas must be at least 25% smaller than the pkg). Use 0 to turn off delta rpm processing. Local repositories (with file:// baseurl) have delta rpms turned off by default.

enablegroups
    boolean

    Determines whether DNF will allow the use of package groups for this repository. Default is True (package groups are allowed).

excludepkgs
    list

    Exclude packages of this repository, specified by a name or a glob and separated by a comma, from all operations. Can be disabled using --disableexcludes command line switch. Defaults to [].

fastestmirror
    boolean

    If enabled a metric is used to find the fastest available mirror. This overrides the order provided by the mirrorlist/metalink file itself. This file is often dynamically generated by the server to provide the best download speeds and enabling fastestmirror overrides this. The default is False.

gpgcheck
    boolean

    Whether to perform GPG signature check on packages found in this repository. The default is False.

    This option can only be used to strengthen the active RPM security policy set with the %_pkgverify_level macro (see the /usr/lib/rpm/macros file for details). That means, if the macro is set to 'signature' or 'all' and this option is False, it will be overridden to True during DNF runtime, and a warning will be printed. To squelch the warning, make sure this option is True for every enabled repository, and also enable localpkg_gpgcheck.

includepkgs
    list

    Include packages of this repository, specified by a name or a glob and separated by a comma, in all operations. Inverse of excludepkgs, DNF will exclude any package in the repository that doesn't match this list. This works in conjunction with excludepkgs and doesn't override it, so if you 'excludepkgs=*.i386' and 'includepkgs=python*' then only packages starting with python that do not have an i386 arch will be seen by DNF in this repo. Can be disabled using --disableexcludes command line switch. Defaults to [].

ip_resolve
    IP address type

    Determines how DNF resolves host names. Set this to '4'/'IPv4' or '6'/'IPv6' to resolve to IPv4 or IPv6 addresses only. By default, DNF resolves to either addresses.

localpkg_gpgcheck
    boolean

    Whether to perform a GPG signature check on local packages (packages in a file, not in a repository). The default is False. This option is subject to the active RPM security policy (see gpgcheck for more details).

max_parallel_downloads
    integer

    Maximum number of simultaneous package downloads. Defaults to 3. Maximum of 20.

metadata_expire
    time in seconds

    The period after which the remote repository is checked for metadata update and in the positive case the local metadata cache is updated. The default corresponds to 48 hours. Set this to -1 or never to make the repo never considered expired. Expire of metadata can be also triggered by change of timestamp of configuration files (dnf.conf, <repo>.repo). See also check_config_file_age.

minrate
    storage size

    This sets the low speed threshold in bytes per second. If the server is sending data at the same or slower speed than this value for at least timeout option seconds, DNF aborts the connection. The default is 1000. Valid units are 'k', 'M', 'G'.

password
    string

    The password to use for connecting to a repository with basic HTTP authentication. Empty by default.

proxy
    string

    URL of a proxy server to connect through. Set to an empty string in the repository configuration to disable proxy setting inherited from the main section. The expected format of this option is <scheme>://<ip-or-hostname>[:port]. (For backward compatibility, '_none_' can be used instead of the empty string.)

    Note: The curl environment variables (such as http_proxy) are effective if this option is unset (or '_none_' is set in the repository configuration). See the curl man page for details.

proxy_username
    string

    The username to use for connecting to the proxy server. Empty by default.

proxy_password
    string

    The password to use for connecting to the proxy server. Empty by default.

proxy_auth_method
    string

    The authentication method used by the proxy server. Valid values are
    method | meaning
    basic | HTTP Basic authentication
    digest | HTTP Digest authentication
    negotiate | HTTP Negotiate (SPNEGO) authentication
    ntlm | HTTP NTLM authentication
    digest_ie | HTTP Digest authentication with an IE flavor
    ntlm_wb | NTLM delegating to winbind helper
    none | None auth method
    any | All suitable methods

    Defaults to any

proxy_sslcacert
    string

    Path to the file containing the certificate authorities to verify proxy SSL certificates. Empty by default - uses system default.

proxy_sslverify
    boolean

    When enabled, proxy SSL certificates are verified. If the client can not be authenticated, connecting fails and the repository is not used any further. If False, SSL connections can be used, but certificates are not verified. Default is True.

proxy_sslclientcert
    string

    Path to the SSL client certificate used to connect to proxy server. Empty by default.

proxy_sslclientkey
    string

    Path to the SSL client key used to connect to proxy server. Empty by default.

repo_gpgcheck
    boolean

    Whether to perform GPG signature check on this repository's metadata. The default is False. Note that GPG keys for this check are stored separately from GPG keys used in package signature verification. Furthermore, they are also stored separately for each repository.

    This means that dnf may ask to import the same key multiple times. For example, when a key was already imported for package signature verification and this option is turned on, it may be needed to import it again for the repository.

retries
    integer

    Set the number of total retries for downloading packages. The number is accumulative, so e.g. for retries=10, dnf will fail after any package download fails for eleventh time. Setting this to 0 makes dnf try forever. Default is 10.

skip_if_unavailable
    boolean

    If enabled, DNF will continue running and disable the repository that couldn't be synchronized for any reason. This option doesn't affect skipping of unavailable packages after dependency resolution. To check inaccessibility of repository use it in combination with refresh command line option. The default is False. Note this option in particular can be set in your configuration file by your distribution.

sslcacert
    string

    Path to the file containing the certificate authorities to verify SSL certificates. Empty by default - uses system default.

sslverify
    boolean

    When enabled, remote SSL certificates are verified. If the client can not be authenticated, connecting fails and the repository is not used any further. If False, SSL connections can be used, but certificates are not verified. Default is True.

sslverifystatus
    boolean

    When enabled, revocation status of the server certificate is verified using the "Certificate Status Request" TLS extension (aka. OCSP stapling). Default is False.

sslclientcert
    string

    Path to the SSL client certificate used to connect to remote sites. Empty by default.

sslclientkey
    string

    Path to the SSL client key used to connect to remote sites. Empty by default.

throttle
    storage size

    Limits the downloading speed. It might be an absolute value or a percentage, relative to the value of the bandwidth option option. 0 means no throttling (the default). The absolute value is in bytes by default but can be specified with a unit of storage. Valid units are 'k', 'M', 'G'.

timeout
    time in seconds

    Number of seconds to wait for a connection before timing out. Used in combination with minrate option option. Defaults to 30 seconds.

username
    string

    The username to use for connecting to repo with basic HTTP authentication. Empty by default.

user_agent
    string

    The User-Agent string to include in HTTP requests sent by DNF. Defaults to

    libdnf (NAME VERSION_ID; VARIANT_ID; OS.BASEARCH)

    where NAME, VERSION_ID and VARIANT_ID are OS identifiers read from the os-release(5) file, and OS and BASEARCH are the canonical OS name and base architecture, respectively. Example:

    libdnf (Fedora 31; server; Linux.x86_64)

TYPES OF OPTIONS

boolean
    This is a data type with only two possible values.

    One of following options can be used: 1, 0, True, False, yes, no

integer
    It is a whole number that can be written without a fractional component.

list
    It is an option that could represent one or more strings separated by space or comma characters.

string
    It is a sequence of symbols or digits without any whitespace character.

color
    A string describing color and modifiers separated with a comma, for example "red,bold".

•   Colors: black, blue, cyan, green, magenta, red, white, yellow

•   Modifiers: bold, blink, dim, normal, reverse, underline

FILES

Cache Files
    /var/cache/dnf

Main Configuration File
    /etc/dnf/dnf.conf

Repository
    /etc/yum.repos.d/

Variables
    Any properly named file in /etc/dnf/vars is turned into a variable named after the filename (or overrides any of the above variables but those set from commandline). Filenames may contain only alphanumeric characters and underscores and be in lowercase. Variables are also read from /etc/yum/vars for YUM compatibility reasons.

SEE ALSO

•   dnf(8), DNF Command Reference

AUTHOR
See AUTHORS in DNF source distribution.

COPYRIGHT
2012-2023, Red Hat, Licensed under GPLv2+