sources.list

5 APT

sources.list

List of configured APT data sources

## Description

The source list `/etc/apt/sources.list` and the files contained in `/etc/apt/sources.list.d/` are designed to support any number of active sources and a variety of source media. The files list one source per line (one-line style) or contain multiline stanzas defining one or more sources per stanza (deb822 style), with the most preferred source listed first (in case a single version is available from more than one source). The information available from the configured sources is acquired by `apt-get update` (or by an equivalent command from another APT front-end).

## sources.list.d

The `/etc/apt/sources.list.d` directory provides a way to add sources.list entries in separate files. Two different file formats are allowed as described in the next two sections. Filenames need to have either the extension `.list` or `.sources` depending on the contained format. The filenames may only contain letters (a-z and A-Z), digits (0-9), underscore (_), hyphen (-) and period (.) characters. Otherwise APT will print a notice that it has ignored a file, unless that file matches a pattern in the `Dir::Ignore-Files-Silently` configuration list - in which case it will be silently ignored.

## One-Line-Style Format

Files in this format have the extension `.list`. Each line specifying a source starts with a type (e.g. `deb-src`) followed by options and arguments for this type. Individual entries cannot be continued onto a following line. Empty lines are ignored, and a `#` character anywhere on a line marks the remainder of that line as a comment. Consequently an entry can be disabled by commenting out the entire line. If options should be provided they are separated by spaces and all of them together are enclosed by square brackets (`[]`) included in the line after the type separated from it with a space. If an option allows multiple values these are separated from each other with a comma (`,`). An option name is separated from its value(s) by an equals sign (`=`). Multivalue options also have `-=` and `+=` as separators, which instead of replacing the default with the given value(s) modify the default value(s) to remove or include the given values.

This is the traditional format and supported by all apt versions. Note that not all options as described below are supported by all apt versions. Note also that some older applications parsing this format on their own might not expect to encounter options as they were uncommon before the introduction of multi-architecture support.

## deb822-Style Format

Files in this format have the extension `.sources`. The format is similar in syntax to other files used by Debian and its derivatives, such as the metadata files that apt will download from the configured sources or the `debian/control` file in a Debian source package. Individual entries are separated by an empty line; additional empty lines are ignored, and a `#` character at the start of the line marks the entire line as a comment. An entry can hence be disabled by commenting out each line belonging to the stanza, but it is usually easier to add the field "Enabled: no" to the stanza to disable the entry. Removing the field or setting it to yes reenables it. Options have the same syntax as every other field: A fieldname separated by a colon (`:`) and optionally spaces from its value(s). Note especially that multiple values are separated by spaces, not by commas as in the one-line format. Multivalue fields like `Architectures` also have `Architectures-Add` and `Architectures-Remove` to modify the default value rather than replacing it.

This is a new format supported by apt itself since version 1.1. Previous versions ignore such files with a notice message as described earlier. It is intended to make this format gradually the default format, deprecating the previously described one-line-style format, as it is easier to create, extend and modify for humans and machines alike especially if a lot of sources and/or options are involved. Developers who are working with and/or parsing apt sources are highly encouraged to add support for this format and to contact the APT team to coordinate and share this work. Users can freely adopt this format already, but may encounter problems with software not supporting the format yet.

## The deb and deb-src Types: General Format

The `deb` type references a typical two-level Debian archive, `distribution/component`. The `distribution` is generally a suite name like `stable` or `testing` or a codename like `&debian-stable-codename;` or `&debian-testing-codename;` while component is one of `main`, `contrib` or `non-free`. The `deb-src` type references a Debian distribution's source code in the same form as the `deb` type. A `deb-src` line is required to fetch source indexes.

The format for two one-line-style entries using the `deb` and `deb-src` types is:

    deb [ option1=value1 option2=value2 ] uri suite [component1] [component2] [...]
    deb-src [ option1=value1 option2=value2 ] uri suite [component1] [component2] [...]

Alternatively the equivalent entry in deb822 style looks like this:

         Types: deb deb-src
         URIs: uri
         Suites: suite
         Components: [component1] [component2] [...]
         option1: value1
         option2: value2

The URI for the `deb` type must specify the base of the Debian distribution, from which APT will find the information it needs. `suite` can specify an exact path, in which case the components must be omitted and `suite` must end with a slash (`/`). This is useful for the case when only a particular sub-directory of the archive denoted by the URI is of interest. If `suite` does not specify an exact path, at least one `component` must be present.

`suite` may also contain a variable, `$(ARCH)` which expands to the Debian architecture (such as `amd64` or `armel`) used on the system. This permits architecture-independent `sources.list` files to be used. In general this is only of interest when specifying an exact path; `APT` will automatically generate a URI with the current architecture otherwise.

Especially in the one-line-style format since only one distribution can be specified per line it may be necessary to have multiple lines for the same URI, if a subset of all available distributions or components at that location is desired. APT will sort the URI list after it has generated a complete set internally, and will collapse multiple references to the same Internet host, for instance, into a single connection, so that it does not inefficiently establish a connection, close it, do something else, and then re-establish a connection to that same host. APT also parallelizes connections to different hosts to more effectively deal with sites with low bandwidth.

It is important to list sources in order of preference, with the most preferred source listed first. Typically this will result in sorting by speed from fastest to slowest (CD-ROM followed by hosts on a local network, followed by distant Internet hosts, for example).

As an example, the sources for your distribution could look like this in one-line-style format:

    &sourceslist-list-format;

or like this in deb822 style format:

    &sourceslist-sources-format;

## The deb and deb-src types: Options

Each source entry can have options specified to modify which source is accessed and how data is acquired from it. Format, syntax and names of the options vary between the one-line-style and deb822-style formats as described, but they both have the same options available. For simplicity we list the deb822 fieldname and provide the one-line name in brackets. Remember that besides setting multivalue options explicitly, there is also the option to modify them based on the default, but we aren't listing those names explicitly here. Unsupported options are silently ignored by all APT versions.

- `Architectures` (`arch`) is a multivalue option defining for which architectures information should be downloaded. If this option isn't set the default is all architectures as defined by the `APT::Architectures` config option.

- `Languages` (`lang`) is a multivalue option defining for which languages information such as translated package descriptions should be downloaded. If this option isn't set the default is all languages as defined by the `Acquire::Languages` config option.

- `Targets` (`target`) is a multivalue option defining which download targets apt will try to acquire from this source. If not specified, the default set is defined by the `Acquire::IndexTargets` configuration scope. Additionally, specific targets can be enabled or disabled by using the identifier as field name instead of using this multivalue option.

- `PDiffs` (`pdiffs`) is a yes/no value which controls if APT should try to use PDiffs to update old indexes instead of downloading the new indexes entirely. The value of this option is ignored if the repository doesn't announce the availability of PDiffs. Defaults to the value of the option with the same name for a specific index file defined in the `Acquire::IndexTargets` scope, which itself defaults to the value of configuration option `Acquire::PDiffs` which defaults to `yes`.

- `By-Hash` (`by-hash`) can have the value `yes`, `no` or `force` and controls if APT should try to acquire indexes via a URI constructed from a hashsum of the expected file instead of using the well-known stable filename of the index. Using this can avoid hashsum mismatches, but requires a supporting mirror. A `yes` or `no` value activates/disables the use of this feature if this source indicates support for it, while `force` will enable the feature regardless of what the source indicates. Defaults to the value of the option of the same name for a specific index file defined in the `Acquire::IndexTargets` scope, which itself defaults to the value of configuration option `Acquire::By-Hash` which defaults to `yes`.

Furthermore, there are options which if set affect all sources with the same URI and Suite, so they have to be set on all such entries and can not be varied between different components. APT will try to detect and error out on such anomalies.

- `Trusted` (`trusted`) is a tri-state value which defaults to APT deciding if a source is considered trusted or if warnings should be raised before e.g. packages are installed from this source. This option can be used to override that decision. The value `yes` tells APT always to consider this source as trusted, even if it doesn't pass authentication checks. It disables parts of &apt-secure;, and should therefore only be used in a local and trusted context (if at all) as otherwise security is breached. The value `no` does the opposite, causing the source to be handled as untrusted even if the authentication checks passed successfully. The default value can't be set explicitly.

- `Signed-By` (`signed-by`) is either an absolute path to a keyring file (has to be accessible and readable for the `_apt` user, so ensure everyone has read-permissions on the file) or a fingerprint of a key either in the `trusted.gpg` keyring or in one of the keyrings in the `trusted.gpg.d/` directory (see `apt-key fingerprint`). If the option is set, only the key(s) in this keyring or only the key with this fingerprint is used for the &apt-secure; verification of this repository. Otherwise all keys in the trusted keyrings are considered valid signers for this repository.

- `Check-Valid-Until` (`check-valid-until`) is a yes/no value which controls if APT should try to detect replay attacks. A repository creator can declare a time until which the data provided in the repository should be considered valid, and if this time is reached, but no new data is provided, the data is considered expired and an error is raised. Besides increasing security, as a malicious attacker can't send old data forever to prevent a user from upgrading to a new version, this also helps users identify mirrors which are no longer updated. However, some repositories such as historic archives are not updated any more by design, so this check can be disabled by setting this option to `no`. Defaults to the value of configuration option `Acquire::Check-Valid-Until` which itself defaults to `yes`.

- `Valid-Until-Min` (`valid-until-min`) and `Valid-Until-Max` (`valid-until-max`) can be used to raise or lower the time period in seconds in which the data from this repository is considered valid. -Max can be especially useful if the repository provides no Valid-Until field on its Release file to set your own value, while -Min can be used to increase the valid time on seldom updated (local) mirrors of a more frequently updated but less accessible archive (which is in the sources.list as well) instead of disabling the check entirely. Default to the value of the configuration options `Acquire::Min-ValidTime` and `Acquire::Max-ValidTime` which are both unset by default.

## URI Specification

The currently recognized URI types are:

`file`

- The file scheme allows an arbitrary directory in the file system to be considered an archive. This is useful for NFS mounts and local mirrors or archives.

`cdrom`

- The cdrom scheme allows APT to use a local CD-ROM drive with media swapping. Use the &apt-cdrom; program to create cdrom entries in the source list.

`http`

- The http scheme specifies an HTTP server for the archive. If an environment variable `http_proxy` is set with the format http://server:port/, the proxy server specified in `http_proxy` will be used. Users of authenticated HTTP/1.1 proxies may use a string of the format http://user:pass@server:port/. Note that this is an insecure method of authentication.

`ftp`

- The ftp scheme specifies an FTP server for the archive. APT's FTP behavior is highly configurable; for more information see the &apt-conf; manual page. Please note that an FTP proxy can be specified by using the `ftp_proxy` environment variable. It is possible to specify an HTTP proxy (HTTP proxy servers often understand FTP URLs) using this environment variable and only this environment variable. Proxies using HTTP specified in the configuration file will be ignored.

`copy`

- The copy scheme is identical to the file scheme except that packages are copied into the cache directory instead of used directly at their location. This is useful for people using removable media to copy files around with APT.

`rsh`

`ssh`

- The rsh/ssh method invokes RSH/SSH to connect to a remote host and access the files as a given user. Prior configuration of rhosts or RSA keys is recommended. The standard `find` and `dd` commands are used to perform the file transfers from the remote host.

adding more recognizable URI types

- APT can be extended with more methods shipped in other optional packages, which should follow the naming scheme `apt-transport-`method``. For instance, the APT team also maintains the package `apt-transport-https`, which provides access methods for HTTPS URIs with features similar to the http method. Methods for using e.g. debtorrent are also available - see &apt-transport-debtorrent;.

## Examples

Uses the archive stored locally (or NFS mounted) at /home/apt/debian for stable/main, stable/contrib, and stable/non-free.

    deb file:/home/apt/debian stable main contrib non-free

    Types: deb
    URIs: file:/home/apt/debian
    Suites: stable
    Components: main contrib non-free

As above, except this uses the unstable (development) distribution.

    deb file:/home/apt/debian unstable main contrib non-free

    Types: deb
    URIs: file:/home/apt/debian
    Suites: unstable
    Components: main contrib non-free

Sources specification for the above.

    deb-src file:/home/apt/debian unstable main contrib non-free

    Types: deb-src
    URIs: file:/home/apt/debian
    Suites: unstable
    Components: main contrib non-free

The first line gets package information for the architectures in `APT::Architectures` while the second always retrieves `amd64` and `armel`.

    deb http://httpredir.debian.org/debian &debian-stable-codename; main
    deb [ arch=amd64,armel ] http://httpredir.debian.org/debian &debian-stable-codename; main

    Types: deb
    URIs: http://httpredir.debian.org/debian
    Suites: &debian-stable-codename;
    Components: main

    Types: deb
    URIs: http://httpredir.debian.org/debian
    Suites: &debian-stable-codename;
    Components: main
    Architectures: amd64 armel

Uses HTTP to access the archive at archive.debian.org, and uses only the hamm/main area.

    deb http://archive.debian.org/debian-archive hamm main

    Types: deb
    URIs: http://archive.debian.org/debian-archive
    Suites: hamm
    Components: main

Uses FTP to access the archive at ftp.debian.org, under the debian directory, and uses only the &debian-stable-codename;/contrib area.

    deb ftp://ftp.debian.org/debian &debian-stable-codename; contrib

    Types: deb
    URIs: ftp://ftp.debian.org/debian
    Suites: &debian-stable-codename;
    Components: contrib

Uses FTP to access the archive at ftp.debian.org, under the debian directory, and uses only the unstable/contrib area. If this line appears as well as the one in the previous example in `sources.list` a single FTP session will be used for both resource lines.

    deb ftp://ftp.debian.org/debian unstable contrib

    Types: deb
    URIs: ftp://ftp.debian.org/debian
    Suites: unstable
    Components: contrib

Uses HTTP to access the archive at ftp.tlh.debian.org, under the universe directory, and uses only files found under `unstable/binary-i386` on i386 machines, `unstable/binary-amd64` on amd64, and so forth for other supported architectures. [Note this example only illustrates how to use the substitution variable; official debian archives are not structured like this]

    deb http://ftp.tlh.debian.org/universe unstable/binary-$(ARCH)/

    Types: deb
    URIs: http://ftp.tlh.debian.org/universe
    Suites: unstable/binary-$(ARCH)/

Uses HTTP to get binary packages as well as sources from the stable, testing and unstable suites and the components main and contrib.

    deb http://httpredir.debian.org/debian stable main contrib
    deb-src http://httpredir.debian.org/debian stable main contrib
    deb http://httpredir.debian.org/debian testing main contrib
    deb-src http://httpredir.debian.org/debian testing main contrib
    deb http://httpredir.debian.org/debian unstable main contrib
    deb-src http://httpredir.debian.org/debian unstable main contrib

    Types: deb deb-src
    URIs: http://httpredir.debian.org/debian
    Suites: stable testing unstable
    Components: main contrib

## See Also

&apt-get;, &apt-conf;

&manbugs;