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diff --git a/man/update-alternatives.man b/man/update-alternatives.man new file mode 100644 index 0000000..a1023d8 --- /dev/null +++ b/man/update-alternatives.man @@ -0,0 +1,519 @@ +.\" dpkg manual page - update-alternatives(1) +.\" +.\" Copyright © 1997-1998 Charles Briscoe-Smith +.\" Copyright © 1999 Ben Collins <bcollins@debian.org> +.\" Copyright © 2000 Wichert Akkerman <wakkerma@debian.org> +.\" Copyright © 2003 Adam Heath <doogie@debian.org> +.\" Copyright © 2005 Scott James Remnant <scott@netsplit.com> +.\" Copyright © 2006-2015 Guillem Jover <guillem@debian.org> +.\" Copyright © 2008 Pierre Habouzit <madcoder@debian.org> +.\" Copyright © 2009-2011 Raphaël Hertzog <hertzog@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 update\-alternatives 1 "%RELEASE_DATE%" "%VERSION%" "dpkg suite" +.nh +.SH NAME +update\-alternatives \- maintain symbolic links determining default commands +. +.SH SYNOPSIS +.B update\-alternatives +.RI [ option "...] " command +. +.SH DESCRIPTION +.B update\-alternatives +creates, removes, maintains and displays information about the symbolic +links comprising the Debian alternatives system. +.PP +It is possible for several programs fulfilling the same or similar +functions to be installed on a single system at the same time. +For example, many systems have several text editors installed at once. +This gives choice to the users of a system, allowing each to use a +different editor, if desired, but makes it difficult for a program +to make a good choice for an editor to invoke if the +user has not specified a particular preference. +.PP +Debian's alternatives system aims to solve this problem. +A generic name in the filesystem is +shared by all files providing interchangeable functionality. +The alternatives system and the system administrator +together determine which actual file is referenced by this generic name. +For example, if the text editors +.BR ed (1) +and +.BR nvi (1) +are both installed on the system, the alternatives system will cause +the generic name +.I /usr/bin/editor +to refer to +.I /usr/bin/nvi +by default. The system administrator can override this and cause +it +to refer to +.I /usr/bin/ed +instead, +and the alternatives system will not alter this setting until explicitly +requested to do so. +.PP +The generic name is not a direct symbolic link to the selected alternative. +Instead, it is a symbolic link to a name in the +.I alternatives +.IR directory , +which in turn is a symbolic link to the actual file referenced. +This is done so that the system administrator's changes can be confined +within the +.I %CONFDIR% +directory: the FHS (q.v.) gives reasons why this is a Good Thing. +.PP +When each package +providing a file with a particular functionality is +installed, changed or removed, +.B update\-alternatives +is called to update information about that file in the alternatives system. +.B update\-alternatives +is usually called from the +.B postinst +(configure) or +.B prerm +(remove and deconfigure) scripts in Debian packages. +.PP +It is often useful for a number of alternatives to be synchronized, +so that they are changed as a group; for example, when several versions +of the +.BR vi (1) +editor are installed, the man page referenced by +.I /usr/share/man/man1/vi.1 +should correspond to the executable referenced by +.IR /usr/bin/vi . +.B update\-alternatives +handles this by means of +.I master +and +.I slave +links; when the master is changed, any associated slaves are changed +too. +A master link and its associated slaves make up a +.I link +.IR group . +.PP +Each link group is, at any given time, +in one of two modes: automatic or manual. +When a group is in automatic mode, the alternatives system will +automatically decide, as packages are installed and removed, +whether and how to update the links. +In manual mode, the alternatives system will retain the choice of +the administrator and avoid changing the links (except when something is +broken). +.PP +Link groups are in automatic mode when they are first introduced to +the system. +If the system administrator makes changes to the system's +automatic settings, +this will be noticed the next time +.B update\-alternatives +is run on the changed link's group, +and the group will automatically be switched to manual mode. +.PP +Each alternative has a +.I priority +associated with it. +When a link group is in automatic mode, +the alternatives pointed to by members of the group +will be those which have the highest priority. +.PP +When using the +.B \-\-config +option, +.B update\-alternatives +will list all of the choices for the link group +of which given +.I name +is the master alternative name. +The current choice is marked with a ‘*’. +You will then be prompted for your choice regarding this link group. +Depending on the choice made, the link group might no longer be in +.I auto +mode. You will need to use the +.B \-\-auto +option in order to return to the automatic mode (or you can rerun +.B \-\-config +and select the entry marked as automatic). +.PP +If you want to configure non-interactively you can use the +.B \-\-set +option instead (see below). +.PP +Different packages providing the same file need to do so +.BR cooperatively . +In other words, the usage of +.B update\-alternatives +is +.B mandatory +for all involved packages in such case. It is not possible to +override some file in a package that does not employ the +.B update\-alternatives +mechanism. +. +.SH TERMINOLOGY +Since the activities of +.B update\-alternatives +are quite involved, some specific terms will help to explain its +operation. +.TP +generic name (or alternative link) +A name, like +.IR /usr/bin/editor , +which refers, via the alternatives system, to one of a number of +files of similar function. +.TP +alternative name +The name of a symbolic link in the alternatives directory. +.TP +alternative (or alternative path) +The name of a specific file in the filesystem, which may be made +accessible via a generic name using the alternatives system. +.TP +alternatives directory +A directory, by default +.IR %CONFDIR%/alternatives , +containing the symlinks. +.TP +administrative directory +A directory, by default +.IR %ADMINDIR%/alternatives , +containing +.BR update\-alternatives ' +state information. +.TP +link group +A set of related symlinks, intended to be updated as a group. +.TP +master link +The alternative link in a link group which determines how the other links in the +group are configured. +.TP +slave link +An alternative link in a link group which is controlled by the setting of +the master link. +.TP +automatic mode +When a link group is in automatic mode, +the alternatives system ensures that the links in the group +point to the highest priority alternative +appropriate for the group. +.TP +manual mode +When a link group is in manual mode, +the alternatives system will not make any changes +to the system administrator's settings. +. +.SH COMMANDS +.TP +\fB\-\-install\fR \fIlink name path priority\fR [\fB\-\-slave\fR \fIlink name path\fR]... +Add a group of alternatives to the system. +.I link +is the generic name for the master link, +.I name +is the name of its symlink in the alternatives directory, and +.I path +is the alternative being introduced for the master link. +The arguments after \fB\-\-slave\fR are the generic name, symlink name in the +alternatives directory and the alternative path for a slave link. +Zero or more +.B \-\-slave +options, each followed by three arguments, +may be specified. Note that the master alternative must exist or the call +will fail. However if a slave alternative doesn't exist, the corresponding +slave alternative link will simply not be installed (a warning will still +be displayed). If some real file is installed where an alternative link +has to be installed, it is kept unless \fB\-\-force\fR is used. +.IP +If the alternative name specified exists already +in the alternatives system's records, +the information supplied will be added as a new +set of alternatives for the group. +Otherwise, a new group, set to automatic mode, +will be added with this information. +If the group is in automatic mode, +and the newly added alternatives' priority is higher than +any other installed alternatives for this group, +the symlinks will be updated to point to the newly added alternatives. +.TP +\fB\-\-set\fR \fIname path\fR +Set the program +.I path +as alternative for +.I name. +This is equivalent to +.B \-\-config +but is non-interactive and thus scriptable. +.TP +\fB\-\-remove\fR \fIname path\fR +Remove an alternative and all of its associated slave links. +.I name +is a name in the alternatives directory, and +.I path +is an absolute filename to which +.I name +could be linked. If +.I name +is indeed linked to +.IR path , +.I name +will be updated to point to another appropriate alternative +(and the group is put back in automatic mode), or +removed if there is no such alternative left. +Associated slave links will be updated or removed, correspondingly. +If the link is not currently pointing to +.IR path , +no links are changed; +only the information about the alternative is removed. +.TP +\fB\-\-remove\-all\fR \fIname\fR +Remove all alternatives and all of their associated slave links. +.I name +is a name in the alternatives directory. +.TP +.B \-\-all +Call \fB\-\-config\fP on all alternatives. It can be usefully combined with +\fB\-\-skip\-auto\fP to review and configure all alternatives which are +not configured in automatic mode. Broken alternatives are also displayed. +Thus a simple way to fix all broken alternatives is to call +\fByes '' | update\-alternatives \-\-force \-\-all\fR. +.TP +\fB\-\-auto\fR \fIname\fR +Switch the link group behind the alternative for +.I name +to automatic mode. +In the process, the master symlink and its slaves are updated +to point to the highest priority installed alternatives. +.TP +\fB\-\-display\fR \fIname\fR +Display information about the link group. +Information displayed includes the group's mode +(auto or manual), +the master and slave links, +which alternative the master link currently points to, +what other alternatives are available +(and their corresponding slave alternatives), +and the highest priority alternative currently installed. +.TP +\fB\-\-get\-selections\fR +List all master alternative names (those controlling a link group) +and their status (since version 1.15.0). +Each line contains up to 3 fields (separated by +one or more spaces). The first field is the alternative name, the second +one is the status (either \fBauto\fP or \fBmanual\fP), and the last one contains +the current choice in the alternative (beware: it's a filename and thus +might contain spaces). +.TP +\fB\-\-set\-selections\fR +Read configuration of alternatives on standard input in the format +generated by \fB\-\-get\-selections\fR and reconfigure +them accordingly (since version 1.15.0). +.TP +\fB\-\-query\fR \fIname\fR +Display information about the link group +like \fB\-\-display\fP does, but in a machine parseable way +(since version 1.15.0, see section \fBQUERY FORMAT\fR below). +.TP +\fB\-\-list\fR \fIname\fR +Display all targets of the link group. +.TP +\fB\-\-config\fR \fIname\fR +Show available alternatives for a link group and allow the user to +interactively select which one to use. The link group is updated. +.TP +.B \-\-help +Show the usage message and exit. +.TP +.B \-\-version +Show the version and exit. +. +.SH OPTIONS +.TP +.BI \-\-altdir " directory" +Specifies the alternatives directory, when this is to be +different from the default. +.TP +.BI \-\-admindir " directory" +Specifies the administrative directory, when this is to be +different from the default. +.TP +.BI \-\-log " file" +Specifies the log file (since version 1.15.0), when this is to be different +from the default (%LOGDIR%/alternatives.log). +.TP +.BI \-\-force +Allow replacing or dropping any real file that is installed +where an alternative link has to be installed or removed. +.TP +.BI \-\-skip\-auto +Skip configuration prompt for alternatives which are properly configured +in automatic mode. This option is only relevant with \fB\-\-config\fR or +\fB\-\-all\fR. +.TP +.B \-\-quiet +Do not generate any comments unless errors occur. +.TP +.B \-\-verbose +Generate more comments about what is being done. +.TP +.B \-\-debug +Generate even more comments, helpful for debugging, about what is being done +(since version 1.19.3). +. +.SH EXIT STATUS +.TP +.B 0 +The requested action was successfully performed. +.TP +.B 2 +Problems were encountered whilst parsing the command line +or performing the action. +. +.SH ENVIRONMENT +.TP +.B DPKG_ADMINDIR +If set and the \fB\-\-admindir\fP option has not been specified, it will +be used as the base administrative directory. +. +.SH FILES +.TP +.I %CONFDIR%/alternatives/ +The default alternatives directory. +Can be overridden by the +.B \-\-altdir +option. +.TP +.I %ADMINDIR%/alternatives/ +The default administration directory. +Can be overridden by the +.B \-\-admindir +option. +. +.SH QUERY FORMAT +The \fB\-\-query\fP format is using an +RFC822-like flat format. It's made of \fIn\fP + 1 blocks where \fIn\fP is +the number of alternatives available in the queried link group. The first +block contains the following fields: +.TP +.BI Name: " name" +The alternative name in the alternative directory. +.TP +.BI Link: " link" +The generic name of the alternative. +.TP +.BI Slaves: " list-of-slaves" +When this field is present, the \fBnext\fR lines hold all slave links +associated to the master link of the alternative. There is one slave per +line. Each line contains one space, the generic name of the slave +alternative, another space, and the path to the slave link. +.TP +.BI Status: " status" +The status of the alternative (\fBauto\fR or \fBmanual\fR). +.TP +.BI Best: " best-choice" +The path of the best alternative for this link group. Not present if +there is no alternatives available. +.TP +.BI Value: " currently-selected-alternative" +The path of the currently selected alternative. It can also take the magic +value \fBnone\fR. It is used if the link doesn't exist. +.PP +The other blocks describe the available alternatives in the queried link group: +.TP +.BI Alternative: " path-of-this-alternative" +Path to this block's alternative. +.TP +.BI Priority: " priority-value" +Value of the priority of this alternative. +.TP +.BI Slaves: " list-of-slaves" +When this field is present, the \fBnext\fR lines hold all slave alternatives +associated to the master link of the alternative. There is one slave per +line. Each line contains one space, the generic name of the slave +alternative, another space, and the path to the slave alternative. +. +.SS Example +.nf +$ update\-alternatives \-\-query editor +Name: editor +Link: /usr/bin/editor +Slaves: + editor.1.gz /usr/share/man/man1/editor.1.gz + editor.fr.1.gz /usr/share/man/fr/man1/editor.1.gz + editor.it.1.gz /usr/share/man/it/man1/editor.1.gz + editor.pl.1.gz /usr/share/man/pl/man1/editor.1.gz + editor.ru.1.gz /usr/share/man/ru/man1/editor.1.gz +Status: auto +Best: /usr/bin/vim.basic +Value: /usr/bin/vim.basic + +Alternative: /bin/ed +Priority: \-100 +Slaves: + editor.1.gz /usr/share/man/man1/ed.1.gz + +Alternative: /usr/bin/vim.basic +Priority: 50 +Slaves: + editor.1.gz /usr/share/man/man1/vim.1.gz + editor.fr.1.gz /usr/share/man/fr/man1/vim.1.gz + editor.it.1.gz /usr/share/man/it/man1/vim.1.gz + editor.pl.1.gz /usr/share/man/pl/man1/vim.1.gz + editor.ru.1.gz /usr/share/man/ru/man1/vim.1.gz +.fi +. +.SH DIAGNOSTICS +With \fB\-\-verbose\fR +.B update\-alternatives +chatters incessantly about its activities on its standard output channel. +If problems occur, +.B update\-alternatives +outputs error messages on its standard error channel and +returns an exit status of 2. +These diagnostics should be self-explanatory; +if you do not find them so, please report this as a bug. +. +.SH EXAMPLES +There are several packages which provide a text editor compatible +with \fBvi\fP, for example \fBnvi\fP and \fBvim\fP. Which one is used +is controlled by the link group \fBvi\fP, which includes links for the +program itself and the associated manpage. +.PP +To display the available packages which provide \fBvi\fP and the current +setting for it, use the \fB\-\-display\fP action: +.PP +.RS +.B update\-alternatives \-\-display vi +.RE +.PP +To choose a particular \fBvi\fP implementation, use this command as root +and then select a number from the list: +.PP +.RS +.B update\-alternatives \-\-config vi +.RE +.PP +To go back to having the \fBvi\fP implementation chosen automatically, do +this as root: +.PP +.RS +.B update\-alternatives \-\-auto vi +.RE +. +.SH SEE ALSO +.BR ln (1), +FHS, the Filesystem Hierarchy Standard. |