1dpkg-maintscript-helper(1) dpkg suite dpkg-maintscript-helper(1)
2
6 dpkg-maintscript-helper - works around known dpkg limitations in
7 maintainer scripts
8
10 dpkg-maintscript-helper command [parameter...] -- maint-script-
11 parameter...
12
14 supports command
15 rm_conffile conffile [prior-version [package]]
17 mv_conffile old-conffile new-conffile [prior-version [package]]
19 symlink_to_dir pathname old-target [prior-version [package]]
21 dir_to_symlink pathname new-target [prior-version [package]]
23
25 This program is designed to be run within maintainer scripts to achieve
26 some tasks that dpkg can't (yet) handle natively either because of
27 design decisions or due to current limitations.
28 Many of those tasks require coordinated actions from several maintainer
30 scripts (preinst, postinst, prerm, postrm). To avoid mistakes the same
31 call simply needs to be put in all scripts and the program will
32 automatically adapt its behaviour based on the environment variable
33 DPKG_MAINTSCRIPT_NAME and on the maintainer scripts arguments that you
34 have to forward after a double hyphen.
35
37 prior-version
38 Defines the latest version of the package whose upgrade should
39 trigger the operation. It is important to calculate prior-
40 version correctly so that the operations are correctly performed
41 even if the user rebuilt the package with a local version. If
42 prior-version is empty or omitted, then the operation is tried
43 on every upgrade (note: it's safer to give the version and have
44 the operation tried only once).
45 If the conffile has not been shipped for several versions, and
47 you are now modifying the maintainer scripts to clean up the
48 obsolete file, prior-version should be based on the version of
49 the package that you are now preparing, not the first version of
50 the package that lacked the conffile. This applies to all other
51 actions in the same way.
52 For example, for a conffile removed in version 2.0-1 of a
54 package, prior-version should be set to 2.0-1~. This will cause
55 the conffile to be removed even if the user rebuilt the previous
56 version 1.0-1 as 1.0-1local1. Or a package switching a path from
57 a symlink (shipped in version 1.0-1) to a directory (shipped in
58 version 2.0-1), but only performing the actual switch in the
59 maintainer scripts in version 3.0-1, should set prior-version to
60 3.0-1~.
61 package
63 The package name owning the pathname(s). When the package is
64 “Multi-Arch: same” this parameter must include the architecture
65 qualifier, otherwise it should not usually include the
66 architecture qualifier (as it would disallow cross-grades, or
67 switching from being architecture specific to architecture all
68 or vice versa). If the parameter is empty or omitted, the
69 DPKG_MAINTSCRIPT_PACKAGE and DPKG_MAINTSCRIPT_ARCH environment
70 variables (as set by dpkg when running the maintainer scripts)
71 will be used to generate an arch-qualified package name.
72 -- All the parameters of the maintainer scripts have to be
74 forwarded to the program after --.
75
77 When upgrading a package, dpkg will not automatically remove a conffile
78 (a configuration file for which dpkg should preserve user changes) if
79 it is not present in the newer version. There are two principal reasons
80 for this; the first is that the conffile could've been dropped by
81 accident and the next version could restore it, users wouldn't want
82 their changes thrown away. The second is to allow packages to
83 transition files from a dpkg-maintained conffile to a file maintained
84 by the package's maintainer scripts, usually with a tool like debconf
85 or ucf.
86 This means that if a package is intended to rename or remove a
88 conffile, it must explicitly do so and dpkg-maintscript-helper can be
89 used to implement graceful deletion and moving of conffiles within
90 maintainer scripts.
91 Removing a conffile
93 If a conffile is completely removed, it should be removed from disk,
94 unless the user has modified it. If there are local modifications, they
95 should be preserved. If the package upgrades aborts, the newly obsolete
96 conffile should not disappear.
97 All of this is implemented by putting the following shell snippet in
99 the preinst, postinst and postrm maintainer scripts:
100 dpkg-maintscript-helper rm_conffile \
102 conffile prior-version package -- "$@"
103 conffile is the filename of the conffile to remove.
105 Current implementation: in the preinst, it checks if the conffile was
107 modified and renames it either to conffile.dpkg-remove (if not
108 modified) or to conffile.dpkg-backup (if modified). In the postinst,
109 the latter file is renamed to conffile.dpkg-bak and kept for reference
110 as it contains user modifications but the former will be removed. If
111 the package upgrade aborts, the postrm reinstalls the original
112 conffile. During purge, the postrm will also delete the .dpkg-bak file
113 kept up to now.
114 Renaming a conffile
116 If a conffile is moved from one location to another, you need to make
117 sure you move across any changes the user has made. This may seem a
118 simple change to the preinst script at first, however that will result
119 in the user being prompted by dpkg to approve the conffile edits even
120 though they are not responsible of them.
121 Graceful renaming can be implemented by putting the following shell
123 snippet in the preinst, postinst and postrm maintainer scripts:
124 dpkg-maintscript-helper mv_conffile \
126 old-conffile new-conffile prior-version package -- "$@"
127 old-conffile and new-conffile are the old and new name of the conffile
129 to rename.
130 Current implementation: the preinst checks if the conffile has been
132 modified, if yes it's left on place otherwise it's renamed to old-
133 conffile.dpkg-remove. On configuration, the postinst removes old-
134 conffile.dpkg-remove and renames old-conffile to new-conffile if old-
135 conffile is still available. On abort-upgrade/abort-install, the postrm
136 renames old-conffile.dpkg-remove back to old-conffile if required.
137
139 When upgrading a package, dpkg will not automatically switch a symlink
140 to a directory or vice-versa. Downgrades are not supported and the path
141 will be left as is.
142 Switching a symlink to directory
144 If a symlink is switched to a real directory, you need to make sure
145 before unpacking that the symlink is removed. This may seem a simple
146 change to the preinst script at first, however that will result in some
147 problems in case of admin local customization of the symlink or when
148 downgrading the package.
149 Graceful renaming can be implemented by putting the following shell
151 snippet in the preinst, postinst and postrm maintainer scripts:
152 dpkg-maintscript-helper symlink_to_dir \
154 pathname old-target prior-version package -- "$@"
155 pathname is the absolute name of the old symlink (the path will be a
157 directory at the end of the installation) and old-target is the target
158 name of the former symlink at pathname. It can either be absolute or
159 relative to the directory containing pathname.
160 Current implementation: the preinst checks if the symlink exists and
162 points to old-target, if not then it's left in place, otherwise it's
163 renamed to pathname.dpkg-backup. On configuration, the postinst removes
164 pathname.dpkg-backup if pathname.dpkg-backup is still a symlink. On
165 abort-upgrade/abort-install, the postrm renames pathname.dpkg-backup
166 back to pathname if required.
167 Switching a directory to symlink
169 If a real directory is switched to a symlink, you need to make sure
170 before unpacking that the directory is removed. This may seem a simple
171 change to the preinst script at first, however that will result in some
172 problems in case the directory contains conffiles, pathnames owned by
173 other packages, locally created pathnames, or when downgrading the
174 package.
175 Graceful switching can be implemented by putting the following shell
177 snippet in the preinst, postinst and postrm maintainer scripts:
178 dpkg-maintscript-helper dir_to_symlink \
180 pathname new-target prior-version package -- "$@"
181 pathname is the absolute name of the old directory (the path will be a
183 symlink at the end of the installation) and new-target is the target of
184 the new symlink at pathname. It can either be absolute or relative to
185 the directory containing pathname.
186 Current implementation: the preinst checks if the directory exists,
188 does not contain conffiles, pathnames owned by other packages, or
189 locally created pathnames, if not then it's left in place, otherwise
190 it's renamed to pathname.dpkg-backup, and an empty staging directory
191 named pathname is created, marked with a file so that dpkg can track
192 it. On configuration, the postinst finishes the switch if
193 pathname.dpkg-backup is still a directory and pathname is the staging
194 directory; it removes the staging directory mark file, moves the newly
195 created files inside the staging directory to the symlink target new-
196 target/, replaces the now empty staging directory pathname with a
197 symlink to new-target, and removes pathname.dpkg-backup. On
198 abort-upgrade/abort-install, the postrm renames pathname.dpkg-backup
199 back to pathname if required.
200
202 When using a packaging helper, please check if it has native dpkg-
203 maintscript-helper integration, which might make your life easier. See
204 for example dh_installdeb(1).
205 Given that dpkg-maintscript-helper is used in the preinst, using it
207 unconditionally requires a pre-dependency to ensure that the required
208 version of dpkg has been unpacked before. The required version depends
209 on the command used, for rm_conffile and mv_conffile it is 1.15.7.2,
210 for symlink_to_dir and dir_to_symlink it is 1.17.14:
211 Pre-Depends: dpkg (>= 1.17.14)
213 But in many cases the operation done by the program is not critical for
215 the package, and instead of using a pre-dependency we can call the
216 program only if we know that the required command is supported by the
217 currently installed dpkg:
218 if dpkg-maintscript-helper supports command; then
220 dpkg-maintscript-helper command ...
221 fi
222 The command supports will return 0 on success, 1 otherwise. The
224 supports command will check if the environment variables as set by dpkg
225 and required by the script are present, and will consider it a failure
226 in case the environment is not sufficient.
227
229 DPKG_COLORS
230 Sets the color mode (since dpkg 1.19.1). The currently accepted
231 values are: auto (default), always and never.
232
234 dh_installdeb(1).
2351.19.7 2019-06-03 dpkg-maintscript-helper(1)