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diff --git a/man/dpkg-maintscript-helper.man b/man/dpkg-maintscript-helper.man new file mode 100644 index 0000000..a927b9f --- /dev/null +++ b/man/dpkg-maintscript-helper.man @@ -0,0 +1,267 @@ +.\" dpkg manual page - dpkg-maintscript-helper(1) +.\" +.\" Copyright © 2010-2012 Raphaël Hertzog <hertzog@debian.org> +.\" Copyright © 2011-2015 Guillem Jover <guillem@debian.org> +.\" +.\" This is free software; you can redistribute it and/or modify +.\" it under the terms of the GNU General Public License as published by +.\" the Free Software Foundation; either version 2 of the License, or +.\" (at your option) any later version. +.\" +.\" This is distributed in the hope that it will be useful, +.\" but WITHOUT ANY WARRANTY; without even the implied warranty of +.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +.\" GNU General Public License for more details. +.\" +.\" You should have received a copy of the GNU General Public License +.\" along with this program. If not, see <https://www.gnu.org/licenses/>. +. +.TH dpkg\-maintscript\-helper 1 "%RELEASE_DATE%" "%VERSION%" "dpkg suite" +.nh +.SH NAME +dpkg\-maintscript\-helper \- works around known dpkg limitations in maintainer scripts +. +.SH SYNOPSIS +.B dpkg\-maintscript\-helper +.IR command " [" parameter "...] \fB\-\-\fP " maint-script-parameter ... +. +.SH COMMANDS AND PARAMETERS +.P +\fBsupports\fP \fIcommand\fP +.P +\fBrm_conffile\fP \fIconffile\fP [\fIprior-version\fP [\fIpackage\fP]] +.P +\fBmv_conffile\fP \fIold-conffile\fP \fInew-conffile\fP [\fIprior-version\fP [\fIpackage\fP]] +.P +\fBsymlink_to_dir\fP \fIpathname\fP \fIold-target\fP [\fIprior-version\fP [\fIpackage\fP]] +.P +\fBdir_to_symlink\fP \fIpathname\fP \fInew-target\fP [\fIprior-version\fP [\fIpackage\fP]] +. +.SH DESCRIPTION +.P +This program is designed to be run within maintainer scripts to achieve +some tasks that \fBdpkg\fP can't (yet) handle natively either because of +design decisions or due to current limitations. +.P +Many of those tasks require coordinated actions from several maintainer +scripts (\fBpreinst\fP, \fBpostinst\fP, \fBprerm\fP, \fBpostrm\fP). To +avoid mistakes the same call simply needs to be put in all scripts and the +program will automatically adapt its behaviour based on the environment +variable \fBDPKG_MAINTSCRIPT_NAME\fP and on the maintainer scripts arguments +that you have to forward after a double hyphen. +. +.SH COMMON PARAMETERS +.TP +.I prior-version +Defines the latest version of the package whose upgrade should trigger the +operation. It is important to calculate \fIprior-version\fP correctly so +that the operations are correctly performed even if the user rebuilt the +package with a local version. If \fIprior-version\fP is empty or omitted, +then the operation is tried on every upgrade (note: it's safer to give +the version and have the operation tried only once). + +If the conffile has not been shipped for several versions, and you are +now modifying the maintainer scripts to clean up the obsolete file, +\fIprior-version\fP should be based on the version of the package that +you are now preparing, not the first version of the package that lacked +the conffile. This applies to all other actions in the same way. + +For example, for a conffile removed in version \fB2.0\-1\fP of a package, +\fIprior-version\fP should be set to \fB2.0\-1~\fP. This will cause the +conffile to be removed even if the user rebuilt the previous version +\fB1.0\-1\fP as \fB1.0\-1local1\fP. Or a package switching a path from +a symlink (shipped in version \fB1.0\-1\fP) to a directory (shipped in +version \fB2.0\-1\fP), but only performing the actual switch in the +maintainer scripts in version \fB3.0\-1\fP, should set \fIprior-version\fP +to \fB3.0\-1~\fP. +.TP +.I package +The package name owning the pathname(s). +When the package is “Multi\-Arch: same” this parameter +must include the architecture qualifier, otherwise it should \fBnot\fP +usually include the architecture qualifier (as it would disallow +cross-grades, or switching from being architecture specific to +architecture \fBall\fP or vice versa). +If the parameter is empty or omitted, the \fBDPKG_MAINTSCRIPT_PACKAGE\fP +and \fBDPKG_MAINTSCRIPT_ARCH\fP environment variables (as set by \fBdpkg\fP +when running the maintainer scripts) will be used to generate an +arch-qualified package name. +.TP +.B \-\- +All the parameters of the maintainer scripts have to be forwarded to the +program after \fB\-\-\fP. +.SH CONFFILE RELATED TASKS +.P +When upgrading a package, \fBdpkg\fP will not automatically remove a conffile +(a configuration file for which \fBdpkg\fP should preserve user changes) if +it is not present in the newer version. There are two principal reasons for +this; the first is that the conffile could've been dropped by accident and +the next version could restore it, users wouldn't want their changes +thrown away. The second is to allow packages to transition files from a +dpkg\-maintained conffile to a file maintained by the package's maintainer +scripts, usually with a tool like debconf or ucf. +.P +This means that if a package is intended to rename or remove a conffile, +it must explicitly do so and \fBdpkg\-maintscript\-helper\fP can be used +to implement graceful deletion and moving of conffiles within maintainer +scripts. +. +.SS Removing a conffile +.P +If a conffile is completely removed, it should be removed from disk, +unless the user has modified it. If there are local modifications, they +should be preserved. If the package upgrades aborts, the newly obsolete +conffile should not disappear. +.P +All of this is implemented by putting the following shell snippet in the +\fBpreinst\fP, \fBpostinst\fP and \fBpostrm\fP maintainer scripts: +.P + dpkg\-maintscript\-helper rm_conffile \\ + \fIconffile\fP \fIprior-version\fP \fIpackage\fP \-\- "$@" +.P +\fIconffile\fP is the filename of the conffile to remove. +.P +Current implementation: in the \fBpreinst\fP, it checks if the conffile +was modified and renames it either to \fIconffile\fP\fB.dpkg\-remove\fP (if not +modified) or to \fIconffile\fP\fB.dpkg\-backup\fP (if modified). In the +\fBpostinst\fP, the latter file is renamed to \fIconffile\fP\fB.dpkg\-bak\fP +and kept for reference as it contains user modifications but the former will +be removed. If the package upgrade aborts, the \fBpostrm\fP reinstalls the +original conffile. During purge, the \fBpostrm\fP will also delete the +\fB.dpkg\-bak\fP file kept up to now. +. +.SS Renaming a conffile +.P +If a conffile is moved from one location to another, you need to make sure +you move across any changes the user has made. This may seem a simple +change to the \fBpreinst\fP script at first, however that will result in +the user being prompted by \fBdpkg\fP to approve the conffile edits even +though they are not responsible of them. +.P +Graceful renaming can be implemented by putting the following shell +snippet in the \fBpreinst\fP, \fBpostinst\fP and \fBpostrm\fP maintainer +scripts: +.P + dpkg\-maintscript\-helper mv_conffile \\ + \fIold-conffile\fP \fInew-conffile\fP \fIprior-version\fP \fIpackage\fP \-\- "$@" +.P +\fIold-conffile\fP and \fInew-conffile\fP are the old and new name of the +conffile to rename. +.P +Current implementation: the \fBpreinst\fP checks if the conffile has been +modified, if yes it's left on place otherwise it's renamed to +\fIold-conffile\fP\fB.dpkg\-remove\fP. On configuration, the \fBpostinst\fP +removes \fIold-conffile\fP\fB.dpkg\-remove\fP and renames \fIold-conffile\fP +to \fInew-conffile\fP if \fIold-conffile\fP is still available. On +abort\-upgrade/abort\-install, the \fBpostrm\fP renames +\fIold-conffile\fP\fB.dpkg\-remove\fP back to \fIold-conffile\fP if required. +. +.SH SYMLINK AND DIRECTORY SWITCHES +. +When upgrading a package, \fBdpkg\fP will not automatically switch a symlink +to a directory or vice-versa. Downgrades are not supported and the path +will be left as is. +. +.SS Switching a symlink to directory +. +If a symlink is switched to a real directory, you need to make sure +before unpacking that the symlink is removed. This may seem a simple +change to the \fBpreinst\fP script at first, however that will result +in some problems in case of admin local customization of the symlink +or when downgrading the package. +.P +Graceful renaming can be implemented by putting the following shell +snippet in the \fBpreinst\fP, \fBpostinst\fP and \fBpostrm\fP maintainer +scripts: +.P + dpkg\-maintscript\-helper symlink_to_dir \\ + \fIpathname\fP \fIold-target\fP \fIprior-version\fP \fIpackage\fP \-\- "$@" +.P +\fIpathname\fP is the absolute name of the old symlink (the path will be a +directory at the end of the installation) and \fIold-target\fP is +the target name of the former symlink at \fIpathname\fP. It can either be +absolute or relative to the directory containing \fIpathname\fP. +.P +Current implementation: the \fBpreinst\fP checks if the symlink exists +and points to \fIold-target\fP, if not then it's left in place, otherwise +it's renamed to \fIpathname\fP\fB.dpkg\-backup\fP. On configuration, +the \fBpostinst\fP removes \fIpathname\fP\fB.dpkg\-backup\fP if +\fIpathname\fP\fB.dpkg\-backup\fP is still a symlink. On +abort\-upgrade/abort\-install, the \fBpostrm\fP renames +\fIpathname\fP\fB.dpkg\-backup\fP back to \fIpathname\fP if required. +. +.SS Switching a directory to symlink +. +If a real directory is switched to a symlink, you need to make sure +before unpacking that the directory is removed. This may seem a simple +change to the \fBpreinst\fP script at first, however that will result +in some problems in case the directory contains conffiles, pathnames +owned by other packages, locally created pathnames, or when downgrading +the package. +.P +Graceful switching can be implemented by putting the following shell +snippet in the \fBpreinst\fP, \fBpostinst\fP and \fBpostrm\fP maintainer +scripts: +.P + dpkg\-maintscript\-helper dir_to_symlink \\ + \fIpathname\fP \fInew-target\fP \fIprior-version\fP \fIpackage\fP \-\- "$@" +.P +\fIpathname\fP is the absolute name of the old directory (the path +will be a symlink at the end of the installation) and \fInew-target\fP is +the target of the new symlink at \fIpathname\fP. It can either be absolute +or relative to the directory containing \fIpathname\fP. +.P +Current implementation: the \fBpreinst\fP checks if the directory +exists, does not contain conffiles, pathnames owned by other packages, +or locally created pathnames, if not then it's left in place, otherwise +it's renamed to \fIpathname\fP\fB.dpkg\-backup\fP, and an empty staging +directory named \fIpathname\fP is created, marked with a file so that +dpkg can track it. On configuration, the \fBpostinst\fP finishes the +switch if \fIpathname\fP\fB.dpkg\-backup\fP is still a directory and +\fIpathname\fP is the staging directory; it removes the staging directory +mark file, moves the newly created files inside the staging directory +to the symlink target \fInew-target\fP/, replaces the now empty staging +directory \fIpathname\fP with a symlink to \fInew-target\fP, and +removes \fIpathname\fP\fB.dpkg\-backup\fP. On +abort\-upgrade/abort\-install, the \fBpostrm\fP renames +\fIpathname\fP\fB.dpkg\-backup\fP back to \fIpathname\fP if required. +. +.SH INTEGRATION IN PACKAGES +.P +When using a packaging helper, please check if it has native +\fBdpkg-maintscript-helper\fP integration, which might make your life +easier. See for example \fBdh_installdeb\fP(1). +.P +Given that \fBdpkg\-maintscript\-helper\fP is used in the \fBpreinst\fP, +using it unconditionally requires a pre-dependency to ensure that the +required version of \fBdpkg\fP has been unpacked before. The required version +depends on the command used, for \fBrm_conffile\fP and \fBmv_conffile\fP +it is 1.15.7.2, for \fBsymlink_to_dir\fP and \fBdir_to_symlink\fP +it is 1.17.14: +.P + \fBPre\-Depends:\fP dpkg (>= 1.17.14) +.P +But in many cases the operation done by the program is not critical for +the package, and instead of using a pre-dependency we can call the +program only if we know that the required command is supported by +the currently installed \fBdpkg\fP: +.P + if dpkg\-maintscript\-helper supports \fIcommand\fP; then + dpkg\-maintscript\-helper \fIcommand\fP ... + fi +.P +The command \fBsupports\fP will return 0 on success, 1 otherwise. The +\fBsupports\fP command will check if the environment variables as set +by dpkg and required by the script are present, and will consider it a +failure in case the environment is not sufficient. +. +.SH ENVIRONMENT +.TP +.B DPKG_COLORS +Sets the color mode (since dpkg 1.19.1). +The currently accepted values are: \fBauto\fP (default), \fBalways\fP and +\fBnever\fP. +. +.SH SEE ALSO +.ad l +.BR dh_installdeb (1). |