freebsd-ports/sysutils/etcmerge/src/etcmerge.8

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.Dd July 5, 2003
.Dt ETCMERGE 1
.Sh NAME
.Nm etcmerge
.Nd 3-way merge of /etc with updates from /usr/src
.Sh SYNOPSIS
.Nm etcmerge
.Cm init
.Nm
.Cm install
.Sh DESCRIPTION
.Pp
WARNING: ETCMERGE HAS NOT UNDERGONE EXTENSIVE PRODUCTION USE, SO USE AT YOUR
OWN RISK.
Taking a backup of
.Pa /etc
before running it won't hurt.
.Pp
.Nm
is a tool for keeping your
.Pa /etc
up to date as you update your system.
It fills the same niche as
.Xr mergemaster 8 ,
with the primary difference being that
.Nm
requires much less manual work.
This is because
.Nm
merges two sets of changes instead of two copies of etc:
The changes you have done locally are merged with the changes done by
.Fx .
.Nm
does this by tracking three instead of two copies of
.Pa etc
- the active
.Pa /etc
(the one you are running your system on), the new etc distributed from
.Fx
(generated from
.Pa /usr/src
by
.Nm
), and a reference copy of the etc that was originally distributed from
.Fx
and which you have changed to get the active
.Pa /etc .
.Pp
The use of all three copies allow
.Nm
to find the two sets of changes - changes by you (the difference from
reference to installed etc) and changes by
.Fx
(the difference from reference etc to new etc).
.Pp
A three way merge is usually fully automated - no user interaction is needed
for the merge itself.
However, sometimes conflicting changes have been made - you have done one
change, and
.Fx
has done a different change to the same part of
.Pa /etc .
.Sh "ROUGH DESCRIPTION OF USE"
.Pp
First, ensure you have a copy of the /etc distributed by FreeBSD (BEFORE you or
.Xr sysinstall 8
started modifying it) stored in
.Pa /var/db/etc .
There are two easy ways to do this:
.Bl -enum -compact
.It
Download a copy matching your
installation from
.Pa http://people.freebsd.org/~eivind/etc/
and extract this in
.Pa /var/db/ .
.It
Run
.Xr mergemaster 8
one last time to get your /etc up to date.
Then rerun
.Xr mergemaster 8
with the
.Fl v
option, exit after it creates
.Pa /var/tmp/temproot ,
and copy
.Pa /var/tmp/temproot/etc
to
.Pa /var/db/etc .
.El
.Pp
When you have
.Pa /var/db/etc
initialized, start a merge with
.Ic "etcmerge init"
(as root).
.Nm
will run for a while, and start printing out information about what operations
it does, prefixed with ETCMERGE:.
When it is finished, it will print out a line saying which work directory it
has worked in (by default, ${HOME}/etc-work/<date>).
Change to this directory, and check if you have any .conflicts files there.
If you do, check through them, and resolve the conflicts.
The conflicts will be recorded in different ways depending on what kind of
conflicts they are.
Under the directory
.Pa etc-merged
you'll find a replacement for /etc, including both changes done by you and
FreeBSD.
Any files that have normal change conflicts (you and FreeBSD have made
different changes) will have conflict markers ("<<<<<<<<", "=====" and
">>>>>>>") indicating where the conflict is.
See
.Xr merge 1
for details.
The files with this kind of conflict will be listed in
.Pa 7.conflicts .
Other forms of conflicts will be listed in other .conflict files; see below
for details if you get any of these.
.Pp
When you are finished with resolving conflicts, type
.Ic "etcmerge install"
to make the present
.Pa etc-merged
directory replace
.Pa /etc ,
and make
.Pa etc-new
(newly generated etc, based on the present
.Pa /usr/src )
the new reference etc.
.Sh "INTERNAL DESCRIPTION"
.Pp
In order to do its work,
.Nm
divides the files it operate in into different classes, and do different
operations depending on which class the files belong in.
This division makes a difference for how each file is treated.
The exact treatment of each class will be printed out by
.Nm
when you run it, along with how many files is in each class, and how many
conflicts occur.
Each conflict is registered in
.Pa <class-number>.conflicts -
e.g.
.Pa 7.conflicts
for conflicts in class 7 (3-way merged files).
.Sh CLASSES
.Pp
The following table define what the class numbers refer to.
The headings "Reference", "New", and "Active" refers to various copies of
.Pa etc
- the one generated from
.Pa /usr/src
(New), the one stored as a Reference copy (basically the one generated from
.Pa /usr/src
the last time you ran
.Nm
or the one distributed with the
.Fx
you installed), and the one presently Active (ie, the one stored in
.Pa /etc
when you run
.Nm etcmerge ).
.Bl -column -offset indent ".Sy Class" ".Sy Reference" "Reference" ".Sy Active"
.It Sy Class Ta Sy Reference Ta Sy New Ta Sy Active
.It Li 1 Ta Absent Ta Absent Ta Present
.It Li 2 Ta Absent Ta Present Ta Absent
.It Li 3 Ta Absent Ta Present Ta Present
.It Li 4 Ta Present Ta Absent Ta Absent
.It Li 5 Ta Present Ta Absent Ta Present
.It Li 6 Ta Present Ta Present Ta Absent
.It Li 7 Ta Present Ta Present Ta Present
.El
.Pp
Depending on what class each file (and I'm talking flat files here) is in, it
will be handled differently.
(See separate description for handling of directories and special files.)
The following table describes how each class of files are handled when there
are no conflicts in the file.
.Bl -column -offset indent ".Sy Class" ".Sy Reference" "Reference" ".Sy Active"
.It Sy Class Ta Sy "File merge handling"
.It Li 1 Ta "Copy from Active"
.It Li 2 Ta "Copy from New"
.It Li 3 Ta "Copy from New"
.It Li 4 Ta "Drop file"
.It Li 5 Ta "Drop file (store in conflict dir if diffs)"
.It Li 6 Ta "Drop file (store in conflict dir)"
.It Li 7 Ta "Do a 3-way merge between all variant, and store result in etc-merged"
.El
Depending on what class a file is in, conflicts will be detected differently,
and handled differently.
The below table detail how conflicts are detected and handled for each class.
.Bl -column -offset indent ".Sy Class" ".Sy Reference" "Reference" ".Sy Active"
.It Sy Class Ta Sy "File conflict handling"
.It Li 1 Ta "Cannot be a conflict"
.It Li 2 Ta "Cannot be a conflict"
.It Li 3 Ta "If there are differences between New and Active, store a diff file in merged-changed."
.It Li 4 Ta "Cannot be a conflict"
.It Li 5 Ta "If there are differences between New and Active, store a diff file in merged-removed."
.It Li 6 Ta "Store file in merged-conflicts, with a diff file if there are diffs between Reference and New"
.It Li 7 Ta "Conflicts are indicated inside the file, using <<<<<<<<<, ======= and >>>>>>>>> as markers.  See merge(1)."
.El
Directories and special files are also handled by
.Nm etcmerge .
Empty directories and special files are handled by class (see the tables
below).
Directories with content is handled alongside files.
When a file is copied over to the merged etc (the one
.Nm
generates), all prefix directories will be copied too, using permissions
either from the active (if available) or the new
.Pa etc .
Ie, if
.Nm
decide to copy
.Pa etc/ssh/ssh_config
from
.Pa /etc ,
then
.Pa merged-etc/ssh
will get the same permissions as
.Pa /etc/ssh .
.Pp
This table details how special files (symlinks, device nodes, pipes, etc) and
empty directories are handled.
.Nm
does not look for conflicts for these, but just copies them as appropriate.
.Bl -column -offset indent ".Sy Class" ".Sy Directory/special.file.handling"
.It Sy Class Ta Sy "Directory/special file handling"
.It Li 1 Ta "Copy from Active"
.It Li 2 Ta "Copy from New"
.It Li 3 Ta "Copy from Active"
.It Li 4 Ta "Ignore dir/special file"
.It Li 5 Ta "Ignore dir/special file"
.It Li 6 Ta "Ignore dir/special file"
.It Li 7 Ta "Copy from Active"
.El
.Sh "DIRECTORIES USED"
.Pp
.Bl -column -offset indent "Directory" "Description"
.It Li "etc-merged" Ta "Merged etc directory, based on etc-new but customized with on your changes."
.It Li "etc-new" Ta "New etc directory, as distributed by FreeBSD.  Created based on /usr/src."
.It Li "classes" Ta "Data about what goes in what class"
.It Li "merged-removed" Ta "Files that have been removed, along with .diff files if the active file was different from the reference file."
.It Li "merged-changed" Ta "Files that have been replaced by the update, along with .diff files saying what changes this has resulted in."
.It Li "merged-conflicts" Ta "Files that are present in new and reference, but
not in the active etc.  If these are changed, a .diff is also stored here."
.El
.Sh REFERENCES
.Pp
.Xr mergemaster 8 ,
.Xr merge 1 .
.Sh AUTHOR
.Pp
Eivind Eklund <eivind@FreeBSD.org>