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 Regular expressions and glob(7) syntax
223 APT also supports pinning by glob(7) expressions, and regular
224 expressions surrounded by slashes. For example, the following example
225 assigns the priority 500 to all packages from experimental where the
226 name starts with gnome (as a glob(7)-like expression) or contains the
227 word kde (as a POSIX extended regular expression surrounded by
228 slashes).
229 Package: gnome* /kde/
231 Pin: release a=experimental
232 Pin-Priority: 500
233 The rule for those expressions is that they can occur anywhere where a
235 string can occur. Thus, the following pin assigns the priority 990 to
236 all packages from a release starting with hirsute.
237 Package: *
239 Pin: release n=hirsute*
240 Pin-Priority: 990
241 If a regular expression occurs in a Package field, the behavior is the
243 same as if this regular expression were replaced with a list of all
244 package names it matches. It is undecided whether this will change in
245 the future; thus you should always list wild-card pins first, so later
246 specific pins override it. The pattern "*" in a Package field is not
247 considered a glob(7) expression in itself.
248 Pinning by source package
250 APT supports pinning by source packages. To pin by a source package,
251 prepend "src:" to the package name.
252 For example, to pin all binaries produced by the apt source package of
254 this APT's version to 990, you can do:
255 Package: src:apt
257 Pin: version 2.3.5
258 Pin-Priority: 990
259 Source package pinning can be combined with regular expressions and
261 glob patterns, and can also take a binary architecture.
262 For example, let's pin all binaries for all architectures produced by
264 any source package containing apt in its name to 990:
265 Package: src:*apt*:any
267 Pin: version *
268 Pin-Priority: 990
269 How APT Interprets Priorities
271 Priorities (P) assigned in the APT preferences file must be positive or
272 negative integers. They are interpreted as follows (roughly speaking):
273 P >= 1000
275 causes a version to be installed even if this constitutes a
276 downgrade of the package
277 990 <= P < 1000
279 causes a version to be installed even if it does not come from the
280 target release, unless the installed version is more recent
281 500 <= P < 990
283 causes a version to be installed unless there is a version
284 available belonging to the target release or the installed version
285 is more recent
286 100 <= P < 500
288 causes a version to be installed unless there is a version
289 available belonging to some other distribution or the installed
290 version is more recent
291 0 < P < 100
293 causes a version to be installed only if there is no installed
294 version of the package
295 P < 0
297 prevents the version from being installed
298 P = 0
300 has undefined behaviour, do not use it.
301 The first specific-form record matching an available package version
303 determines the priority of the package version. Failing that, the
304 priority of the package is defined as the maximum of all priorities
305 defined by generic-form records matching the version. Records defined
306 using patterns in the Pin field other than "*" are treated like
307 specific-form records.
308 For example, suppose the APT preferences file contains the three
310 records presented earlier:
311 Package: perl
313 Pin: version 5.20*
314 Pin-Priority: 1001
315 Package: *
317 Pin: origin ""
318 Pin-Priority: 999
319 Package: *
321 Pin: release unstable
322 Pin-Priority: 50
323 Then:
325 • The most recent available version of the perl package will be
327 installed, so long as that version's version number begins with
328 "5.20". If any 5.20* version of perl is available and the installed
329 version is 5.24*, then perl will be downgraded.
330 • A version of any package other than perl that is available from the
332 local system has priority over other versions, even versions
333 belonging to the target release.
334 • A version of a package whose origin is not the local system but
336 some other site listed in sources.list(5) and which belongs to an
337 unstable distribution is only installed if it is selected for
338 installation and no version of the package is already installed.
339 Determination of Package Version and Distribution Properties
342 The locations listed in the sources.list(5) file should provide
343 Packages and Release files to describe the packages available at that
344 location.
345 The Packages file is normally found in the directory
347 .../dists/dist-name/component/arch: for example,
348 .../dists/stable/main/binary-i386/Packages. It consists of a series of
349 multi-line records, one for each package available in that directory.
350 Only two lines in each record are relevant for setting APT priorities:
351 the Package: line
353 gives the package name
354 the Version: line
356 gives the version number for the named package
357 The Release file is normally found in the directory
359 .../dists/dist-name: for example, .../dists/stable/Release, or
360 .../dists/bullseye/Release. It consists of a single multi-line record
361 which applies to all of the packages in the directory tree below its
362 parent. Unlike the Packages file, nearly all of the lines in a Release
363 file are relevant for setting APT priorities:
364 the Archive: or Suite: line
366 names the archive to which all the packages in the directory tree
367 belong. For example, the line "Archive: stable" or "Suite: stable"
368 specifies that all of the packages in the directory tree below the
369 parent of the Release file are in a stable archive. Specifying this
370 value in the APT preferences file would require the line:
371 Pin: release a=stable
373 the Codename: line
375 names the codename to which all the packages in the directory tree
376 belong. For example, the line "Codename: bookworm" specifies that
377 all of the packages in the directory tree below the parent of the
378 Release file belong to a version named bookworm. Specifying this
379 value in the APT preferences file would require the line:
380 Pin: release n=bookworm
382 the Version: line
384 names the release version. For example, the packages in the tree
385 might belong to Debian release version 11. Note that there is
386 normally no version number for the testing and unstable
387 distributions because they have not been released yet. Specifying
388 this in the APT preferences file would require one of the following
389 lines.
390 Pin: release v=11
392 Pin: release a=stable, v=11
393 Pin: release 11
394 the Component: line
396 names the licensing component associated with the packages in the
397 directory tree of the Release file. For example, the line
398 "Component: main" specifies that all the packages in the directory
399 tree are from the main component, which entails that they are
400 licensed under terms listed in the Debian Free Software Guidelines.
401 Specifying this component in the APT preferences file would require
402 the line:
403 Pin: release c=main
405 the Origin: line
407 names the originator of the packages in the directory tree of the
408 Release file. Most commonly, this is Debian. Specifying this origin
409 in the APT preferences file would require the line:
410 Pin: release o=Debian
412 the Label: line
414 names the label of the packages in the directory tree of the
415 Release file. Most commonly, this is Debian. Specifying this label
416 in the APT preferences file would require the line:
417 Pin: release l=Debian
419 All of the Packages and Release files retrieved from locations listed
421 in the sources.list(5) file are stored in the directory
422 /var/lib/apt/lists, or in the file named by the variable
423 Dir::State::Lists in the apt.conf file. For example, the file
424 debian.lcs.mit.edu_debian_dists_unstable_contrib_binary-i386_Release
425 contains the Release file retrieved from the site debian.lcs.mit.edu
426 for binary-i386 architecture files from the contrib component of the
427 unstable distribution.
428 Optional Lines in an APT Preferences Record
430 Each record in the APT preferences file can optionally begin with one
431 or more lines beginning with the word Explanation:. This provides a
432 place for comments.
433
435 Tracking Stable
436 The following APT preferences file will cause APT to assign a priority
437 higher than the default (500) to all package versions belonging to a
438 stable distribution and a prohibitively low priority to package
439 versions belonging to other Debian distributions.
440 Explanation: Uninstall or do not install any Debian-originated
442 Explanation: package versions other than those in the stable distro
443 Package: *
444 Pin: release a=stable
445 Pin-Priority: 900
446 Package: *
448 Pin: release o=Debian
449 Pin-Priority: -10
450 With a suitable sources.list(5) file and the above preferences file,
452 any of the following commands will cause APT to upgrade to the latest
453 stable version(s).
454 apt-get install package-name
456 apt-get upgrade
457 apt-get dist-upgrade
458 The following command will cause APT to upgrade the specified package
460 to the latest version from the testing distribution; the package will
461 not be upgraded again unless this command is given again.
462 apt-get install package/testing
464 Tracking Testing or Unstable
467 The following APT preferences file will cause APT to assign a high
468 priority to package versions from the testing distribution, a lower
469 priority to package versions from the unstable distribution, and a
470 prohibitively low priority to package versions from other Debian
471 distributions.
472 Package: *
474 Pin: release a=testing
475 Pin-Priority: 900
476 Package: *
478 Pin: release a=unstable
479 Pin-Priority: 800
480 Package: *
482 Pin: release o=Debian
483 Pin-Priority: -10
484 With a suitable sources.list(5) file and the above preferences file,
486 any of the following commands will cause APT to upgrade to the latest
487 testing version(s).
488 apt-get install package-name
490 apt-get upgrade
491 apt-get dist-upgrade
492 The following command will cause APT to upgrade the specified package
494 to the latest version from the unstable distribution. Thereafter,
495 apt-get upgrade will upgrade the package to the most recent testing
496 version if that is more recent than the installed version, otherwise,
497 to the most recent unstable version if that is more recent than the
498 installed version.
499 apt-get install package/unstable
501 Tracking the evolution of a codename release
504 The following APT preferences file will cause APT to assign a priority
505 higher than the default (500) to all package versions belonging to a
506 specified codename of a distribution and a prohibitively low priority
507 to package versions belonging to other Debian distributions, codenames
508 and archives. Note that with this APT preference APT will follow the
509 migration of a release from the archive testing to stable and later
510 oldstable. If you want to follow for example the progress in testing
511 notwithstanding the codename changes you should use the example
512 configurations above.
513 Explanation: Uninstall or do not install any Debian-originated package versions
515 Explanation: other than those in the distribution codenamed with bookworm or sid
516 Package: *
517 Pin: release n=bookworm
518 Pin-Priority: 900
519 Explanation: Debian unstable is always codenamed with sid
521 Package: *
522 Pin: release n=sid
523 Pin-Priority: 800
524 Package: *
526 Pin: release o=Debian
527 Pin-Priority: -10
528 With a suitable sources.list(5) file and the above preferences file,
530 any of the following commands will cause APT to upgrade to the latest
531 version(s) in the release codenamed with bookworm.
532 apt-get install package-name
534 apt-get upgrade
535 apt-get dist-upgrade
536 The following command will cause APT to upgrade the specified package
538 to the latest version from the sid distribution. Thereafter, apt-get
539 upgrade will upgrade the package to the most recent bookworm version if
540 that is more recent than the installed version, otherwise, to the most
541 recent sid version if that is more recent than the installed version.
542 apt-get install package/sid
544
547 /etc/apt/preferences
548 Version preferences file. This is where you would specify
549 "pinning", i.e. a preference to get certain packages from a
550 separate source or from a different version of a distribution.
551 Configuration Item: Dir::Etc::Preferences.
552 /etc/apt/preferences.d/
554 File fragments for the version preferences. Configuration Item:
555 Dir::Etc::PreferencesParts.
556
558 apt-get(8) apt-cache(8) apt.conf(5) sources.list(5)
559
561 APT bug page[1]. If you wish to report a bug in APT, please see
562 /usr/share/doc/debian/bug-reporting.txt or the reportbug(1) command.
563
565 APT team
566
568 1. APT bug page
569 http://bugs.debian.org/src:apt
570APT 2.3.5 10 August 2020 APT_PREFERENCES(5)