1APT_PREFERENCES(5) APT APT_PREFERENCES(5)
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6 apt_preferences - Preference control file for APT
7
9 The APT preferences file /etc/apt/preferences and the fragment files in
10 the /etc/apt/preferences.d/ folder can be used to control which
11 versions of packages will be selected for installation.
12 Several versions of a package may be available for installation when
14 the sources.list(5) file contains references to more than one
15 distribution (for example, stable and testing). APT assigns a priority
16 to each version that is available. Subject to dependency constraints,
17 apt-get selects the version with the highest priority for installation.
18 The APT preferences override the priorities that APT assigns to package
19 versions by default, thus giving the user control over which one is
20 selected for installation.
21 Several instances of the same version of a package may be available
23 when the sources.list(5) file contains references to more than one
24 source. In this case apt-get downloads the instance listed earliest in
25 the sources.list(5) file. The APT preferences do not affect the choice
26 of instance, only the choice of version.
27 Preferences are a strong power in the hands of a system administrator
29 but they can become also their biggest nightmare if used without care!
30 APT will not question the preferences, so wrong settings can lead to
31 uninstallable packages or wrong decisions while upgrading packages.
32 Even more problems will arise if multiple distribution releases are
33 mixed without a good understanding of the following paragraphs.
34 Packages included in a specific release aren't tested in (and therefore
35 don't always work as expected in) older or newer releases, or together
36 with other packages from different releases. You have been warned.
37 Note that the files in the /etc/apt/preferences.d directory are parsed
39 in alphanumeric ascending order and need to obey the following naming
40 convention: The files have either no or "pref" as filename extension
41 and only contain alphanumeric, hyphen (-), underscore (_) and period
42 (.) characters. Otherwise APT will print a notice that it has ignored a
43 file, unless that file matches a pattern in the
44 Dir::Ignore-Files-Silently configuration list - in which case it will
45 be silently ignored.
46 APT's Default Priority Assignments
48 If there is no preferences file or if there is no entry in the file
49 that applies to a particular version then the priority assigned to that
50 version is the priority of the distribution to which that version
51 belongs. It is possible to single out a distribution, "the target
52 release", which receives a higher priority than other distributions do
53 by default. The target release can be set on the apt-get command line
54 or in the APT configuration file /etc/apt/apt.conf. Note that this has
55 precedence over any general priority you set in the
56 /etc/apt/preferences file described later, but not over specifically
57 pinned packages. For example,
58 apt-get install -t testing some-package
60 APT::Default-Release "stable";
64 If the target release has been specified then APT uses the following
66 algorithm to set the priorities of the versions of a package. Assign:
67 priority 1
69 to the versions coming from archives which in their Release files
70 are marked as "NotAutomatic: yes" but not as "ButAutomaticUpgrades:
71 yes" like the Debian experimental archive, as well as versions that
72 are not phased on this systems.
73 priority 100
75 to the version that is already installed (if any) and to the
76 versions coming from archives which in their Release files are
77 marked as "NotAutomatic: yes" and "ButAutomaticUpgrades: yes" like
78 the Debian backports archive since squeeze-backports.
79 priority 500
81 to the versions that do not belong to the target release.
82 priority 990
84 to the versions that belong to the target release.
85 The highest of those priorities whose description matches the version
86 is assigned to the version.
87 If the target release has not been specified then APT simply assigns
89 priority 100 to all installed package versions and priority 500 to all
90 uninstalled package versions, except versions coming from archives
91 which in their Release files are marked as "NotAutomatic: yes" - these
92 versions get the priority 1 or priority 100 if it is additionally
93 marked as "ButAutomaticUpgrades: yes".
94 APT then applies the following rules, listed in order of precedence, to
96 determine which version of a package to install.
97 • Never downgrade unless the priority of an available version exceeds
99 1000. ("Downgrading" is installing a less recent version of a
100 package in place of a more recent version. Note that none of APT's
101 default priorities exceeds 1000; such high priorities can only be
102 set in the preferences file. Note also that downgrading a package
103 can be risky.)
104 • Install the highest priority version.
106 • If two or more versions have the same priority, install the most
108 recent one (that is, the one with the higher version number).
109 • If two or more versions have the same priority and version number
111 but either the packages differ in some of their metadata or the
112 --reinstall option is given, install the uninstalled one.
113 In a typical situation, the installed version of a package (priority
115 100) is not as recent as one of the versions available from the sources
116 listed in the sources.list(5) file (priority 500 or 990). Then the
117 package will be upgraded when apt-get install some-package or apt-get
118 upgrade is executed.
119 More rarely, the installed version of a package is more recent than any
121 of the other available versions. The package will not be downgraded
122 when apt-get install some-package or apt-get upgrade is executed.
123 Sometimes the installed version of a package is more recent than the
125 version belonging to the target release, but not as recent as a version
126 belonging to some other distribution. Such a package will indeed be
127 upgraded when apt-get install some-package or apt-get upgrade is
128 executed, because at least one of the available versions has a higher
129 priority than the installed version.
130 Phased Updates
132 APT understands a field called Phased-Update-Percentage which can be
133 used to control the rollout of a new version. It is an integer between
134 0 and 100.
135 A system's eligibility to a phased update is determined by seeding
137 random number generator with the package source name, the version
138 number, and /etc/machine-id, and then calculating an integer in the
139 range [0, 100]. If this integer is larger than the
140 Phased-Update-Percentage, the version is pinned to 1, and thus held
141 back. Otherwise, normal policy rules apply.
142 In case you have multiple systems that you want to receive the same set
144 of updates, you can set APT::Machine-ID to a UUID such that they all
145 phase the same, or set APT::Get::Never-Include-Phased-Updates or
146 APT::Get::Always-Include-Phased-Updates to true such that APT will
147 never/always consider phased updates.
148 The Effect of APT Preferences
150 The APT preferences file allows the system administrator to control the
151 assignment of priorities. The file consists of one or more multi-line
152 records separated by blank lines. Records can have one of two forms, a
153 specific form and a general form.
154 • The specific form assigns a priority (a "Pin-Priority") to one or
156 more specified packages with a specified version or version range.
157 For example, the following record assigns a high priority to all
158 versions of the perl package whose version number begins with
159 "5.32". Multiple packages can be separated by spaces.
160 Package: perl
162 Pin: version 5.32*
163 Pin-Priority: 1001
164 • The general form assigns a priority to all of the package versions
166 in a given distribution (that is, to all the versions of packages
167 that are listed in a certain Release file) or to all of the package
168 versions coming from a particular Internet site, as identified by
169 the site's fully qualified domain name.
170 This general-form entry in the APT preferences file applies only to
172 groups of packages. For example, the following record assigns a
173 high priority to all package versions available from the local
174 site.
175 Package: *
177 Pin: origin ""
178 Pin-Priority: 999
179 A note of caution: the keyword used here is "origin" which can be
181 used to match a hostname. The following record will assign a high
182 priority to all versions available from the server identified by
183 the hostname "ftp.de.debian.org"
184 Package: *
186 Pin: origin "ftp.de.debian.org"
187 Pin-Priority: 999
188 This should not be confused with the Origin of a distribution as
190 specified in a Release file. What follows the "Origin:" tag in a
191 Release file is not an Internet address but an author or vendor
192 name, such as "Debian" or "Ximian".
193 The following record assigns a low priority to all package versions
195 belonging to any distribution whose Archive name is "unstable".
196 Package: *
198 Pin: release a=unstable
199 Pin-Priority: 50
200 The following record assigns a high priority to all package
202 versions belonging to any distribution whose Codename is "trixie".
203 Package: *
205 Pin: release n=trixie
206 Pin-Priority: 900
207 The following record assigns a high priority to all package
209 versions belonging to any release whose Archive name is "stable"
210 and whose release Version number is "12".
211 Package: *
213 Pin: release a=stable, v=12
214 Pin-Priority: 500
215 The effect of the comma operator is similar to an "and" in logic: All
217 conditions must be satisfied for the pin to match. There is one
218 exception: For any type of condition (such as two "a" conditions), only
219 the last such condition is checked.
220 Matching packages in the Package field
222 The Package field specifies the package that a pinning priority is
223 applied to. The field can either contain a binary package name, a
224 source package name (prefixed with "src:"), a glob(7) expression or a
225 regular expression (surrounded by slashes). Multiple package names,
226 glob(7) expressions and regular expressions can be listed separated by
227 whitespace in which case the record will match any of the matched
228 packages.
229 By default, only packages of the native architecture are matched. To
231 match binary packages of any architecture, add the :any suffix to the
232 package name. You can also limit matching to a specific architecture by
233 appending the architecture name to the package name, separated by a
234 colon character.
235 For example, the following example uses a glob expression and a regular
237 expression to assign the priority 500 to all packages from experimental
238 where the name starts with gnome (as a glob(7)-like expression) or
239 contains the word kde (as a POSIX extended regular expression
240 surrounded by slashes).
241 Package: gnome* /kde/
243 Pin: release a=experimental
244 Pin-Priority: 500
245 The rule for those expressions is that they can occur anywhere where a
247 string can occur. Thus, the following pin assigns the priority 990 to
248 all packages from a release starting with lunar.
249 Package: *
251 Pin: release n=lunar*
252 Pin-Priority: 990
253 If a regular expression occurs in a Package field, the behavior is the
255 same as if this regular expression were replaced with a list of all
256 package names it matches. It is undecided whether this will change in
257 the future; thus you should always list wild-card pins first, so later
258 specific pins override it. The pattern "*" in a Package field is not
259 considered a glob(7) expression in itself.
260 To pin all binaries produced by the apt source package of this APT's
262 version to 990, you can do:
263 Package: src:apt
265 Pin: version 2.7.6
266 Pin-Priority: 990
267 Source package pinning can be combined with regular expressions and
269 glob patterns, and can also take a binary architecture.
270 For example, let's pin all binaries for all architectures produced by
272 any source package containing apt in its name to 990:
273 Package: src:*apt*:any
275 Pin: version *
276 Pin-Priority: 990
277 The :any suffix makes sure to select binary packages from any
279 architecture. Without that suffix, apt implicitly assumes the :native
280 suffix which would only select packages from the native architecture.
281 How APT Interprets Priorities
283 Priorities (P) assigned in the APT preferences file must be positive or
284 negative integers. They are interpreted as follows (roughly speaking):
285 P >= 1000
287 causes a version to be installed even if this constitutes a
288 downgrade of the package
289 990 <= P < 1000
291 causes a version to be installed even if it does not come from the
292 target release, unless the installed version is more recent
293 500 <= P < 990
295 causes a version to be installed unless there is a version
296 available belonging to the target release or the installed version
297 is more recent
298 100 <= P < 500
300 causes a version to be installed unless there is a version
301 available belonging to some other distribution or the installed
302 version is more recent
303 0 < P < 100
305 causes a version to be installed only if there is no installed
306 version of the package
307 P < 0
309 prevents the version from being installed
310 P = 0
312 has undefined behaviour, do not use it.
313 The first specific-form record matching an available package version
315 determines the priority of the package version. Failing that, the
316 priority of the package is defined as the maximum of all priorities
317 defined by generic-form records matching the version. Records defined
318 using patterns in the Pin field other than "*" are treated like
319 specific-form records.
320 For example, suppose the APT preferences file contains the three
322 records presented earlier:
323 Package: perl
325 Pin: version 5.32*
326 Pin-Priority: 1001
327 Package: *
329 Pin: origin ""
330 Pin-Priority: 999
331 Package: *
333 Pin: release unstable
334 Pin-Priority: 50
335 Then:
337 • The most recent available version of the perl package will be
339 installed, so long as that version's version number begins with
340 "5.32". If any 5.32* version of perl is available and the installed
341 version is 5.36*, then perl will be downgraded.
342 • A version of any package other than perl that is available from the
344 local system has priority over other versions, even versions
345 belonging to the target release.
346 • A version of a package whose origin is not the local system but
348 some other site listed in sources.list(5) and which belongs to an
349 unstable distribution is only installed if it is selected for
350 installation and no version of the package is already installed.
351 Determination of Package Version and Distribution Properties
354 The locations listed in the sources.list(5) file should provide
355 Packages and Release files to describe the packages available at that
356 location.
357 The Packages file is normally found in the directory
359 .../dists/dist-name/component/arch: for example,
360 .../dists/stable/main/binary-i386/Packages. It consists of a series of
361 multi-line records, one for each package available in that directory.
362 Only two lines in each record are relevant for setting APT priorities:
363 the Package: line
365 gives the package name
366 the Version: line
368 gives the version number for the named package
369 The Release file is normally found in the directory
371 .../dists/dist-name: for example, .../dists/stable/Release, or
372 .../dists/bookworm/Release. It consists of a single multi-line record
373 which applies to all of the packages in the directory tree below its
374 parent. Unlike the Packages file, nearly all of the lines in a Release
375 file are relevant for setting APT priorities:
376 the Archive: or Suite: line
378 names the archive to which all the packages in the directory tree
379 belong. For example, the line "Archive: stable" or "Suite: stable"
380 specifies that all of the packages in the directory tree below the
381 parent of the Release file are in a stable archive. Specifying this
382 value in the APT preferences file would require the line:
383 Pin: release a=stable
385 the Codename: line
387 names the codename to which all the packages in the directory tree
388 belong. For example, the line "Codename: trixie" specifies that all
389 of the packages in the directory tree below the parent of the
390 Release file belong to a version named trixie. Specifying this
391 value in the APT preferences file would require the line:
392 Pin: release n=trixie
394 the Version: line
396 names the release version. For example, the packages in the tree
397 might belong to Debian release version 12. Note that there is
398 normally no version number for the testing and unstable
399 distributions because they have not been released yet. Specifying
400 this in the APT preferences file would require one of the following
401 lines.
402 Pin: release v=12
404 Pin: release a=stable, v=12
405 Pin: release 12
406 the Component: line
408 names the licensing component associated with the packages in the
409 directory tree of the Release file. For example, the line
410 "Component: main" specifies that all the packages in the directory
411 tree are from the main component, which entails that they are
412 licensed under terms listed in the Debian Free Software Guidelines.
413 Specifying this component in the APT preferences file would require
414 the line:
415 Pin: release c=main
417 the Origin: line
419 names the originator of the packages in the directory tree of the
420 Release file. Most commonly, this is Debian. Specifying this origin
421 in the APT preferences file would require the line:
422 Pin: release o=Debian
424 the Label: line
426 names the label of the packages in the directory tree of the
427 Release file. Most commonly, this is Debian. Specifying this label
428 in the APT preferences file would require the line:
429 Pin: release l=Debian
431 All of the Packages and Release files retrieved from locations listed
433 in the sources.list(5) file are stored in the directory
434 /var/lib/apt/lists, or in the file named by the variable
435 Dir::State::Lists in the apt.conf file. For example, the file
436 debian.lcs.mit.edu_debian_dists_unstable_contrib_binary-i386_Release
437 contains the Release file retrieved from the site debian.lcs.mit.edu
438 for binary-i386 architecture files from the contrib component of the
439 unstable distribution.
440 Optional Lines in an APT Preferences Record
442 Each record in the APT preferences file can optionally begin with one
443 or more lines beginning with the word Explanation:. This provides a
444 place for comments.
445
447 Tracking Stable
448 The following APT preferences file will cause APT to assign a priority
449 higher than the default (500) to all package versions belonging to a
450 stable distribution and a prohibitively low priority to package
451 versions belonging to other Debian distributions.
452 Explanation: Uninstall or do not install any Debian-originated
454 Explanation: package versions other than those in the stable distro
455 Package: *
456 Pin: release a=stable
457 Pin-Priority: 900
458 Package: *
460 Pin: release o=Debian
461 Pin-Priority: -10
462 With a suitable sources.list(5) file and the above preferences file,
464 any of the following commands will cause APT to upgrade to the latest
465 stable version(s).
466 apt-get install package-name
468 apt-get upgrade
469 apt-get dist-upgrade
470 The following command will cause APT to upgrade the specified package
472 to the latest version from the testing distribution; the package will
473 not be upgraded again unless this command is given again.
474 apt-get install package/testing
476 Tracking Testing or Unstable
479 The following APT preferences file will cause APT to assign a high
480 priority to package versions from the testing distribution, a lower
481 priority to package versions from the unstable distribution, and a
482 prohibitively low priority to package versions from other Debian
483 distributions.
484 Package: *
486 Pin: release a=testing
487 Pin-Priority: 900
488 Package: *
490 Pin: release a=unstable
491 Pin-Priority: 800
492 Package: *
494 Pin: release o=Debian
495 Pin-Priority: -10
496 With a suitable sources.list(5) file and the above preferences file,
498 any of the following commands will cause APT to upgrade to the latest
499 testing version(s).
500 apt-get install package-name
502 apt-get upgrade
503 apt-get dist-upgrade
504 The following command will cause APT to upgrade the specified package
506 to the latest version from the unstable distribution. Thereafter,
507 apt-get upgrade will upgrade the package to the most recent testing
508 version if that is more recent than the installed version, otherwise,
509 to the most recent unstable version if that is more recent than the
510 installed version.
511 apt-get install package/unstable
513 Tracking the evolution of a codename release
516 The following APT preferences file will cause APT to assign a priority
517 higher than the default (500) to all package versions belonging to a
518 specified codename of a distribution and a prohibitively low priority
519 to package versions belonging to other Debian distributions, codenames
520 and archives. Note that with this APT preference APT will follow the
521 migration of a release from the archive testing to stable and later
522 oldstable. If you want to follow for example the progress in testing
523 notwithstanding the codename changes you should use the example
524 configurations above.
525 Explanation: Uninstall or do not install any Debian-originated package versions
527 Explanation: other than those in the distribution codenamed with trixie or sid
528 Package: *
529 Pin: release n=trixie
530 Pin-Priority: 900
531 Explanation: Debian unstable is always codenamed with sid
533 Package: *
534 Pin: release n=sid
535 Pin-Priority: 800
536 Package: *
538 Pin: release o=Debian
539 Pin-Priority: -10
540 With a suitable sources.list(5) file and the above preferences file,
542 any of the following commands will cause APT to upgrade to the latest
543 version(s) in the release codenamed with trixie.
544 apt-get install package-name
546 apt-get upgrade
547 apt-get dist-upgrade
548 The following command will cause APT to upgrade the specified package
550 to the latest version from the sid distribution. Thereafter, apt-get
551 upgrade will upgrade the package to the most recent trixie version if
552 that is more recent than the installed version, otherwise, to the most
553 recent sid version if that is more recent than the installed version.
554 apt-get install package/sid
556
559 /etc/apt/preferences
560 Version preferences file. This is where you would specify
561 "pinning", i.e. a preference to get certain packages from a
562 separate source or from a different version of a distribution.
563 Configuration Item: Dir::Etc::Preferences.
564 /etc/apt/preferences.d/
566 File fragments for the version preferences. Configuration Item:
567 Dir::Etc::PreferencesParts.
568
570 apt-get(8) apt-cache(8) apt.conf(5) sources.list(5)
571
573 APT bug page[1]. If you wish to report a bug in APT, please see
574 /usr/share/doc/debian/bug-reporting.txt or the reportbug(1) command.
575
577 APT team
578
580 1. APT bug page
581 http://bugs.debian.org/src:apt
582APT 2.7.6 03 January 2022 APT_PREFERENCES(5)