[Ubuntu Wiki] Update of "DebuggingEmacs" by era

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The "DebuggingEmacs" page has been changed by era:
http://wiki.ubuntu.com/DebuggingEmacs?action=diff&rev1=11&rev2=12

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Update for 2012; expand on installation logs

  
  = Introduction =
  
- There are multiple Emacs packages, collectively referred to as "Emacsen".  They all depend on a package called `emacsen-common`, and they are divided into "flavors".  The main flavors are GNU Emacs (AKA FSF Emacs; `emacs23` and `emacs-snapshot`) and `xemacs21`.  These in turn are divided into multiple packages, in order to separate architecture-independent components (for which only one package is needed) from architecture-dependent ones (which need to be built separately for each architecture), and mandatory components from optional ones.
+ There are multiple Emacs packages, collectively referred to as "Emacsen".  They all depend on a package called `emacsen-common`, and they are divided into "flavors".  The main flavors are GNU Emacs (AKA FSF Emacs; `emacs24` and `emacs23` etc) and `xemacs21`.  These in turn are divided into multiple packages, in order to separate architecture-independent components (for which only one package is needed) from architecture-dependent ones (which need to be built separately for each architecture), and mandatory components from optional ones.
  
- If you only need one Emacs flavor, the stable GNU Emacs (currently `emacs23`) is recommended. `emacs-snapshot` contains a relatively recent non-release version of the developer sources, though you might want to obtain a more recent version from a PPA or other non-Ubuntu source if you want the really latest and greatest.  Finally, `xemacs21` is rather old and not very actively maintained, but if you are an Xemacs fan, it's still available.
+ If you only need one Emacs flavor, the stable GNU Emacs (currently `emacs24`) is recommended. At one point, Ubuntu provided an `emacs-snapshot` package containing a relatively recent non-release version of the developer sources; you can still find a PPA with what at least at some point contained the really latest and greatest.  Finally, `xemacs21` is rather old and not very actively maintained, but if you are an Xemacs fan, it's still available.
  
  There is a plethora of Emacs add-on packages.  Most of these are supported on all flavors, but there are notable exceptions.  Some add-ons are not needed on some flavors, and some add-ons provide newer and / or different versions of components which are also included with a base Emacs install (e.g. Gnus).
  
@@ -18, +18 @@

  
  If you get an error message from Emacs, you may be able to trigger a backtrace which shows which Lisp functions were being processed when the error hit.  Enable backtraces with `M-: (setq debug-on-error t)` and attach the `*Backtrace*` buffer to your bug report.
  
+ == Installation Logs ==
+ 
+ For many installation problems, you need to examine the installation logs.
+ 
+ When you install with Synaptic or Update-Manager, the terminal log is not necessarily shown to you.  You will need to examine your system's log files and dig out the useful information.
+ 
+ <!-- TODO: move this stuff to a dedicated page? -->
+ 
+ If the problematic installation was part of an upgrade of your Ubuntu installation, the log file is `/var/log/dist-upgrade/term.log`; otherwise look for `/var/log/apt/term.log`.  You will probably need `sudo` to access these read-protected files, or add yourself to the group `adm`).
+ 
+ 
  == Package Installation Errors ==
  
  Apparent Emacs errors are often caused by an add-on package which contains a bug or incompatibility with the installed Emacs flavor.  
  
  If `dpkg` prints an error message indicating that the package `postinst` failed, the actual error message is probably a few lines before this message in the `dpkg` output.
  
+ `emacs-install: /usr/lib/emacsen-common/packages/install/ecb emacs23
+ `     failed at /usr/lib/emacsen-common/emacs-install line 28, <TSORT> line 17.
+ `dpkg: error processing emacs23 (--configure):
+ ` subprocess installed post-installation script returned error exit status 1
+ 
+ This points to `ecb` as the culprit (bug || [[https://launchpad.net/bugs/466531|466531]]
+ 
+ `dpkg: dependency problems prevent configuration of emacs:
+ ` emacs depends on emacs23 | emacs23-lucid | emacs23-nox; however:
+ `  Package emacs23 is not configured yet.
+ `  Package emacs23-lucid is not installed.
+ `  Package emacs23-nox is not installed.
+ `dpkg: error processing emacs (--configure):
+ ` dependency problems - leaving unconfigured
+ 
+ This particular snippet just means that an earlier problem prevented Emacs from installing successfully.  You need to go further back in the log file to see what's wrong.
+ 
  == Byte Compilation Errors ==
  
  A particular type of installation error is the byte compilation error.
  With `emacs22` and `emacs-snapshot` the terminal log will contain a message like this:
  
+ {{{
- `!! Byte-compilation for <<flavor>> failed!`<<BR>>
+ !! Byte-compilation for <<flavor>> failed!
- `!! This indicates a bug in one of the add-on packages`<<BR>>
+ !! This indicates a bug in one of the add-on packages
- `!! installed on your system, or a bug in Emacs itself.`<<BR>>
+ !! installed on your system, or a bug in Emacs itself.
- `!! Please file a bug report against <<flavor>>`<<BR>>
+ !! Please file a bug report against <<flavor>>
- `!! and attach the file /tmp/<<flavor>>.<<suffix>>`
+ !! and attach the file /tmp/<<flavor>>.<<suffix>>
+ }}}
  
  The file name will be different each time.  This file is required in order to analyze the problem.
  
@@ -41, +71 @@

  
  You can file bugs against Emacs using Apport.
  
- There is also the built-in`M-x emacs-bug-report` but it is not fully customized for sending bug reports to Ubuntu.
+ There is also the built-in `M-x emacs-bug-report` but it is not fully customized for sending bug reports to Ubuntu.
  
  = Bug tags =
  
@@ -49, +79 @@

  
  = How to Triage =
  
- Apport bugs are generally triggered by a package failing to install, and usually include DpkgTerminalLog or VarDistUpgradeTermLog as an attachment; this log file is usually the first one to examine.
+ Apport bugs are generally triggered by a package failing to install, and usually include Dpkg``Terminal``Log or Var``DistUpgrade``Term``Log as an attachment; this log file is usually the first one to examine.  If it's missing, see the section "Installation Logs" above.
  
  Typically, it will contain an error message near the end which indicate which package failed installation and why.