1APT_PREFERENCES(5) APT APT_PREFERENCES(5)
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6 apt_preferences - Preference control file for APT
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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 "5.20". Multiple packages can be separated by spaces.
160 Package: perl
162 Pin: version 5.20*
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
203 "bookworm".
204 Package: *
206 Pin: release n=bookworm
207 Pin-Priority: 900
208 The following record assigns a high priority to all package
210 versions belonging to any release whose Archive name is "stable"
211 and whose release Version number is "11".
212 Package: *
214 Pin: release a=stable, v=11
215 Pin-Priority: 500
216 The effect of the comma operator is similar to an "and" in logic: All
218 conditions must be satisfied for the pin to match. There is one
219 exception: For any type of condition (such as two "a" conditions), only
220 the last such condition is checked.
221 Matching packages in the Package field
223 The Package field specifies the package that a pinning priority is
224 applied to. The field can either contain a binary package name, a
225 source package name (prefixed with "src:"), a glob(7) expression or a
226 regular expression (surrounded by slashes). Multiple package names,
227 glob(7) expressions and regular expressions can be listed separated by
228 whitespace in which case the record will match any of the matched
229 packages.
230 By default, only packages of the native architecture are matched. To
232 match binary packages of any architecture, add the :any suffix to the
233 package name. You can also limit matching to a specific architecture by
234 appending the architecture name to the package name, separated by a
235 colon character.
236 For example, the following example uses a glob expression and a regular
238 expression to assign the priority 500 to all packages from experimental
239 where the name starts with gnome (as a glob(7)-like expression) or
240 contains the word kde (as a POSIX extended regular expression
241 surrounded by slashes).
242 Package: gnome* /kde/
244 Pin: release a=experimental
245 Pin-Priority: 500
246 The rule for those expressions is that they can occur anywhere where a
248 string can occur. Thus, the following pin assigns the priority 990 to
249 all packages from a release starting with hirsute.
250 Package: *
252 Pin: release n=hirsute*
253 Pin-Priority: 990
254 If a regular expression occurs in a Package field, the behavior is the
256 same as if this regular expression were replaced with a list of all
257 package names it matches. It is undecided whether this will change in
258 the future; thus you should always list wild-card pins first, so later
259 specific pins override it. The pattern "*" in a Package field is not
260 considered a glob(7) expression in itself.
261 To pin all binaries produced by the apt source package of this APT's
263 version to 990, you can do:
264 Package: src:apt
266 Pin: version 2.5.5
267 Pin-Priority: 990
268 Source package pinning can be combined with regular expressions and
270 glob patterns, and can also take a binary architecture.
271 For example, let's pin all binaries for all architectures produced by
273 any source package containing apt in its name to 990:
274 Package: src:*apt*:any
276 Pin: version *
277 Pin-Priority: 990
278 The :any suffix makes sure to select binary packages from any
280 architecture. Without that suffix, apt implicitly assumes the :native
281 suffix which would only select packages from the native architecture.
282 How APT Interprets Priorities
284 Priorities (P) assigned in the APT preferences file must be positive or
285 negative integers. They are interpreted as follows (roughly speaking):
286 P >= 1000
288 causes a version to be installed even if this constitutes a
289 downgrade of the package
290 990 <= P < 1000
292 causes a version to be installed even if it does not come from the
293 target release, unless the installed version is more recent
294 500 <= P < 990
296 causes a version to be installed unless there is a version
297 available belonging to the target release or the installed version
298 is more recent
299 100 <= P < 500
301 causes a version to be installed unless there is a version
302 available belonging to some other distribution or the installed
303 version is more recent
304 0 < P < 100
306 causes a version to be installed only if there is no installed
307 version of the package
308 P < 0
310 prevents the version from being installed
311 P = 0
313 has undefined behaviour, do not use it.
314 The first specific-form record matching an available package version
316 determines the priority of the package version. Failing that, the
317 priority of the package is defined as the maximum of all priorities
318 defined by generic-form records matching the version. Records defined
319 using patterns in the Pin field other than "*" are treated like
320 specific-form records.
321 For example, suppose the APT preferences file contains the three
323 records presented earlier:
324 Package: perl
326 Pin: version 5.20*
327 Pin-Priority: 1001
328 Package: *
330 Pin: origin ""
331 Pin-Priority: 999
332 Package: *
334 Pin: release unstable
335 Pin-Priority: 50
336 Then:
338 • The most recent available version of the perl package will be
340 installed, so long as that version's version number begins with
341 "5.20". If any 5.20* version of perl is available and the installed
342 version is 5.24*, then perl will be downgraded.
343 • A version of any package other than perl that is available from the
345 local system has priority over other versions, even versions
346 belonging to the target release.
347 • A version of a package whose origin is not the local system but
349 some other site listed in sources.list(5) and which belongs to an
350 unstable distribution is only installed if it is selected for
351 installation and no version of the package is already installed.
352 Determination of Package Version and Distribution Properties
355 The locations listed in the sources.list(5) file should provide
356 Packages and Release files to describe the packages available at that
357 location.
358 The Packages file is normally found in the directory
360 .../dists/dist-name/component/arch: for example,
361 .../dists/stable/main/binary-i386/Packages. It consists of a series of
362 multi-line records, one for each package available in that directory.
363 Only two lines in each record are relevant for setting APT priorities:
364 the Package: line
366 gives the package name
367 the Version: line
369 gives the version number for the named package
370 The Release file is normally found in the directory
372 .../dists/dist-name: for example, .../dists/stable/Release, or
373 .../dists/bullseye/Release. It consists of a single multi-line record
374 which applies to all of the packages in the directory tree below its
375 parent. Unlike the Packages file, nearly all of the lines in a Release
376 file are relevant for setting APT priorities:
377 the Archive: or Suite: line
379 names the archive to which all the packages in the directory tree
380 belong. For example, the line "Archive: stable" or "Suite: stable"
381 specifies that all of the packages in the directory tree below the
382 parent of the Release file are in a stable archive. Specifying this
383 value in the APT preferences file would require the line:
384 Pin: release a=stable
386 the Codename: line
388 names the codename to which all the packages in the directory tree
389 belong. For example, the line "Codename: bookworm" specifies that
390 all of the packages in the directory tree below the parent of the
391 Release file belong to a version named bookworm. Specifying this
392 value in the APT preferences file would require the line:
393 Pin: release n=bookworm
395 the Version: line
397 names the release version. For example, the packages in the tree
398 might belong to Debian release version 11. Note that there is
399 normally no version number for the testing and unstable
400 distributions because they have not been released yet. Specifying
401 this in the APT preferences file would require one of the following
402 lines.
403 Pin: release v=11
405 Pin: release a=stable, v=11
406 Pin: release 11
407 the Component: line
409 names the licensing component associated with the packages in the
410 directory tree of the Release file. For example, the line
411 "Component: main" specifies that all the packages in the directory
412 tree are from the main component, which entails that they are
413 licensed under terms listed in the Debian Free Software Guidelines.
414 Specifying this component in the APT preferences file would require
415 the line:
416 Pin: release c=main
418 the Origin: line
420 names the originator of the packages in the directory tree of the
421 Release file. Most commonly, this is Debian. Specifying this origin
422 in the APT preferences file would require the line:
423 Pin: release o=Debian
425 the Label: line
427 names the label of the packages in the directory tree of the
428 Release file. Most commonly, this is Debian. Specifying this label
429 in the APT preferences file would require the line:
430 Pin: release l=Debian
432 All of the Packages and Release files retrieved from locations listed
434 in the sources.list(5) file are stored in the directory
435 /var/lib/apt/lists, or in the file named by the variable
436 Dir::State::Lists in the apt.conf file. For example, the file
437 debian.lcs.mit.edu_debian_dists_unstable_contrib_binary-i386_Release
438 contains the Release file retrieved from the site debian.lcs.mit.edu
439 for binary-i386 architecture files from the contrib component of the
440 unstable distribution.
441 Optional Lines in an APT Preferences Record
443 Each record in the APT preferences file can optionally begin with one
444 or more lines beginning with the word Explanation:. This provides a
445 place for comments.
446
448 Tracking Stable
449 The following APT preferences file will cause APT to assign a priority
450 higher than the default (500) to all package versions belonging to a
451 stable distribution and a prohibitively low priority to package
452 versions belonging to other Debian distributions.
453 Explanation: Uninstall or do not install any Debian-originated
455 Explanation: package versions other than those in the stable distro
456 Package: *
457 Pin: release a=stable
458 Pin-Priority: 900
459 Package: *
461 Pin: release o=Debian
462 Pin-Priority: -10
463 With a suitable sources.list(5) file and the above preferences file,
465 any of the following commands will cause APT to upgrade to the latest
466 stable version(s).
467 apt-get install package-name
469 apt-get upgrade
470 apt-get dist-upgrade
471 The following command will cause APT to upgrade the specified package
473 to the latest version from the testing distribution; the package will
474 not be upgraded again unless this command is given again.
475 apt-get install package/testing
477 Tracking Testing or Unstable
480 The following APT preferences file will cause APT to assign a high
481 priority to package versions from the testing distribution, a lower
482 priority to package versions from the unstable distribution, and a
483 prohibitively low priority to package versions from other Debian
484 distributions.
485 Package: *
487 Pin: release a=testing
488 Pin-Priority: 900
489 Package: *
491 Pin: release a=unstable
492 Pin-Priority: 800
493 Package: *
495 Pin: release o=Debian
496 Pin-Priority: -10
497 With a suitable sources.list(5) file and the above preferences file,
499 any of the following commands will cause APT to upgrade to the latest
500 testing version(s).
501 apt-get install package-name
503 apt-get upgrade
504 apt-get dist-upgrade
505 The following command will cause APT to upgrade the specified package
507 to the latest version from the unstable distribution. Thereafter,
508 apt-get upgrade will upgrade the package to the most recent testing
509 version if that is more recent than the installed version, otherwise,
510 to the most recent unstable version if that is more recent than the
511 installed version.
512 apt-get install package/unstable
514 Tracking the evolution of a codename release
517 The following APT preferences file will cause APT to assign a priority
518 higher than the default (500) to all package versions belonging to a
519 specified codename of a distribution and a prohibitively low priority
520 to package versions belonging to other Debian distributions, codenames
521 and archives. Note that with this APT preference APT will follow the
522 migration of a release from the archive testing to stable and later
523 oldstable. If you want to follow for example the progress in testing
524 notwithstanding the codename changes you should use the example
525 configurations above.
526 Explanation: Uninstall or do not install any Debian-originated package versions
528 Explanation: other than those in the distribution codenamed with bookworm or sid
529 Package: *
530 Pin: release n=bookworm
531 Pin-Priority: 900
532 Explanation: Debian unstable is always codenamed with sid
534 Package: *
535 Pin: release n=sid
536 Pin-Priority: 800
537 Package: *
539 Pin: release o=Debian
540 Pin-Priority: -10
541 With a suitable sources.list(5) file and the above preferences file,
543 any of the following commands will cause APT to upgrade to the latest
544 version(s) in the release codenamed with bookworm.
545 apt-get install package-name
547 apt-get upgrade
548 apt-get dist-upgrade
549 The following command will cause APT to upgrade the specified package
551 to the latest version from the sid distribution. Thereafter, apt-get
552 upgrade will upgrade the package to the most recent bookworm version if
553 that is more recent than the installed version, otherwise, to the most
554 recent sid version if that is more recent than the installed version.
555 apt-get install package/sid
557
560 /etc/apt/preferences
561 Version preferences file. This is where you would specify
562 "pinning", i.e. a preference to get certain packages from a
563 separate source or from a different version of a distribution.
564 Configuration Item: Dir::Etc::Preferences.
565 /etc/apt/preferences.d/
567 File fragments for the version preferences. Configuration Item:
568 Dir::Etc::PreferencesParts.
569
571 apt-get(8) apt-cache(8) apt.conf(5) sources.list(5)
572
574 APT bug page[1]. If you wish to report a bug in APT, please see
575 /usr/share/doc/debian/bug-reporting.txt or the reportbug(1) command.
576
578 APT team
579
581 1. APT bug page
582 http://bugs.debian.org/src:apt
583APT 2.5.5 03 January 2022 APT_PREFERENCES(5)