Ubuntu List of Sources Cannot Be Read
Provided past: apt_1.2.10ubuntu1_amd64 
Proper name
sources.listing - List of configured APT information sources
Clarification
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 (1-line fashion) or contain multiline stanzas defining one or more sources per stanza (deb822 style), with the near preferred source listed start (in case a unmarried version is available from more than than one source). The information available from the configured sources is caused by apt-get update (or past an equivalent command from another APT front-end).
SOURCES.Listing.D
The /etc/apt/sources.list.d directory provides a way to add sources.listing entries in separate files. Two different file formats are allowed as described in the adjacent two sections. Filenames demand 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 volition print a find that it has ignored a file, unless that file matches a pattern in the Dir::Ignore-Files-Silently configuration list - in which case it volition be silently ignored.
I-LINE-Style FORMAT
Files in this format have the extension .list. Each line specifying a source starts with a type (due east.g. deb-src) followed past options and arguments for this type. Individual entries cannot be continued onto a following line. Empty lines are ignored, and a # graphic symbol anywhere on a line marks the residuum of that line as a comment. Consequently an entry tin 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 past square brackets ([]) included in the line after the type separated from it with a space. If an pick 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 += every bit separators, which instead of replacing the default with the given value(south) 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 as well that some older applications parsing this format on their own might non expect to encounter options as they were uncommon before the introduction of multi-compages support.
DEB822-Fashion FORMAT
Files in this format have the extension .sources. The format is like 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 get-go of the line marks the entire line as a comment. An entry can hence be disabled past commenting out each line belonging to the stanza, simply information technology is commonly 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 past a colon (:) and optionally spaces from its value(due south). Note particularly that multiple values are separated by spaces, not past commas equally in the i-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 ane.one. 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-mode format, as it is easier to create, extend and modify for humans and machines alike peculiarly 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 together support for this format and to contact the APT team to coordinate and share this work. Users tin freely adopt this format already, just 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 mostly a suite proper noun like stable or testing or a codename similar jessie or stretch while component is ane of main, contrib or not-free. The deb-src type references a Debian distribution'southward source code in the same grade every bit the deb type. A deb-src line is required to fetch source indexes. The format for 2 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 fashion looks like this: Types: deb deb-src URIs: uri Suites: suite Components: [component1] [component2] [...] option1: value1 option2: value2 The URI for the deb blazon must specify the base of operations of the Debian distribution, from which APT volition find the data it needs. suite can specify an exact path, in which instance the components must exist omitted and suite must cease with a slash (/). This is useful for the instance when only a particular sub-directory of the annal denoted by the URI is of involvement. If suite does non specify an verbal path, at least one component must exist present. suite may also contain a variable, $(Arch) which expands to the Debian architecture (such equally amd64 or armel) used on the system. This permits architecture-independent sources.listing files to be used. In general this is just of interest when specifying an verbal path; APT volition automatically generate a URI with the current architecture otherwise. Particularly in the 1-line-style format since only one distribution can exist specified per line it may exist necessary to have multiple lines for the aforementioned URI, if a subset of all available distributions or components at that location is desired. APT will sort the URI list after information technology has generated a consummate set internally, and will collapse multiple references to the same Internet host, for instance, into a single connectedness, and so that it does non inefficiently institute a connection, shut information technology, do something else, and and then re-establish a connection to that same host. APT also parallelizes connections to unlike hosts to more than effectively deal with sites with low bandwidth. It is important to list sources in order of preference, with the about 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). Equally an example, the sources for your distribution could look similar this in 1-line-style format: deb http://us.archive.ubuntu.com/ubuntu trusty main restricted deb http://security.ubuntu.com/ubuntu trusty-security main restricted deb http://us.annal.ubuntu.com/ubuntu trusty-updates main restricted or similar this in deb822 mode format: Types: deb URIs: http://us.archive.ubuntu.com/ubuntu Suites: trusty trusty-updates Components: main restricted Types: deb URIs: http://security.ubuntu.com/ubuntu Suites: trusty-security Components: main restricted
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 information technology. Format, syntax and names of the options vary between the one-line-style and deb822-mode formats as described, but they both take the same options available. For simplicity we list the deb822 fieldname and provide the i-line proper name in brackets. Remember that as well setting multivalue options explicitly, there is also the pick to alter 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 choice defining for which languages information such as translated package descriptions should be downloaded. If this option isn't set the default is all languages every bit divers past the Learn::Languages config option. · Targets (target) is a multivalue selection defining which download targets apt will try to larn from this source. If not specified, the default set is divers by the Acquire::IndexTargets configuration scope. Additionally, specific targets can exist enabled or disabled by using the identifier every bit field name instead of using this multivalue option. · PDiffs (pdiffs) is a yes/no value which controls if APT should effort 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 aforementioned name for a specific alphabetize file defined in the Acquire::IndexTargets scope, which itself defaults to the value of configuration option Acquire::PDiffs which defaults to aye. · Past-Hash (past-hash) can have the value aye, no or strength 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 employ 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 aforementioned proper name for a specific index file defined in the Acquire::IndexTargets telescopic, which itself defaults to the value of configuration option Larn::By-Hash which defaults to yes. Furthermore, there are options which if fix affect all sources with the same URI and Suite, so they have to be set on all such entries and tin not be varied between unlike components. APT will try to detect and fault 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 exist raised before due east.g. packages are installed from this source. This choice can be used to override that conclusion. The value yes tells APT ever to consider this source equally trusted, even if it doesn't pass hallmark checks. Information technology disables parts of apt-secure(viii), 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 tin can't be prepare explicitly. · Signed-By (signed-by) is either an absolute path to a keyring file (has to exist accessible and readable for the _apt user, so ensure everyone has read-permissions on the file) or a fingerprint of a fundamental either in the trusted.gpg keyring or in 1 of the keyrings in the trusted.gpg.d/ directory (meet apt-key fingerprint). If the option is set, only the cardinal(due south) in this keyring or only the key with this fingerprint is used for the apt-secure(8) 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 yeah/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, only no new data is provided, the data is considered expired and an fault 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 place mirrors which are no longer updated. Still, some repositories such equally celebrated archives are not updated whatsoever more by design, and so this check can exist disabled by setting this option to no. Defaults to the value of configuration option Acquire::Cheque-Valid-Until which itself defaults to yes. · Valid-Until-Min (valid-until-min) and Valid-Until-Max (valid-until-max) tin 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 fix your own value, while -Min can be used to increase the valid time on seldom updated (local) mirrors of a more than frequently updated merely less accessible archive (which is in the sources.list also) instead of disabling the cheque entirely. Default to the value of the configuration options Learn::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 apply a local CD-ROM bulldoze with media swapping. Apply the apt-cdrom(viii) program to create cdrom entries in the source list. http The http scheme specifies an HTTP server for the archive. If an environs 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.one proxies may use a string of the format http://user:pass@server:port/. Note that this is an insecure method of hallmark. ftp The ftp scheme specifies an FTP server for the archive. APT's FTP beliefs is highly configurable; for more information come across the apt.conf(v) manual page. Please note that an FTP proxy tin 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 just this environment variable. Proxies using HTTP specified in the configuration file volition exist ignored. copy The copy scheme is identical to the file scheme except that packages are copied into the cache directory instead of used direct at their location. This is useful for people using removable media to re-create 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 case, the APT squad also maintains the package apt-transport-https, which provides access methods for HTTPS URIs with features like to the http method. Methods for using due east.g. debtorrent are likewise available - run across apt-send-debtorrent(1).
EXAMPLES
Uses the archive stored locally (or NFS mounted) at /habitation/apt/debian for stable/main, stable/contrib, and stable/non-free. deb file:/home/apt/debian stable main contrib non-complimentary Types: deb URIs: file:/abode/apt/debian Suites: stable Components: chief contrib non-free Equally above, except this uses the unstable (development) distribution. deb file:/home/apt/debian unstable chief contrib non-gratis Types: deb URIs: file:/home/apt/debian Suites: unstable Components: chief contrib non-free Sources specification for the above. deb-src file:/domicile/apt/debian unstable main contrib not-free Types: deb-src URIs: file:/dwelling/apt/debian Suites: unstable Components: main contrib non-free The first line gets bundle information for the architectures in APT::Architectures while the second always retrieves amd64 and armel. deb http://httpredir.debian.org/debian jessie main deb [ arch=amd64,armel ] http://httpredir.debian.org/debian jessie main Types: deb URIs: http://httpredir.debian.org/debian Suites: jessie Components: master Types: deb URIs: http://httpredir.debian.org/debian Suites: jessie Components: main Architectures: amd64 armel Uses HTTP to access the annal at annal.debian.org, and uses merely the hamm/primary expanse. deb http://archive.debian.org/debian-archive hamm primary Types: deb URIs: http://archive.debian.org/debian-annal Suites: hamm Components: primary Uses FTP to access the archive at ftp.debian.org, nether the debian directory, and uses only the jessie/contrib area. deb ftp://ftp.debian.org/debian jessie contrib Types: deb URIs: ftp://ftp.debian.org/debian Suites: jessie Components: contrib Uses FTP to access the annal at ftp.debian.org, under the debian directory, and uses only the unstable/contrib area. If this line appears equally well as the one in the previous example in sources.list a single FTP session volition exist 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 constitute under unstable/binary-i386 on i386 machines, unstable/binary-amd64 on amd64, then along for other supported architectures. [Note this case but illustrates how to use the commutation variable; official debian athenaeum are not structured like this] deb http://ftp.tlh.debian.org/universe unstable/binary-$(Curvation)/ 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 chief 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-go(8), apt.conf(5)
BUGS
APT problems page[1]. If you wish to report a bug in APT, please see /usr/share/medico/debian/problems-reporting.txt or the reportbug(1) command.
AUTHORS
Jason Gunthorpe APT team
NOTES
one. APT bug folio http://bugs.debian.org/src:apt
Source: https://manpages.ubuntu.com/manpages/xenial/man5/sources.list.5.html
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