Copyright © 2003 The Parchive Project
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Table of Contents
List of Examples
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:FIXME:
An introduction to the general concepts of the Parity Archive Volume Set as implemented with the 1.0 version of the specification, and what this means to the user of PAR Files and Clients that adhere to this version of the specification.
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An introduction to the general concepts of the Parity Archive Volume Set as implemented with the 2.0 version of the specification, and what this means to the user of PAR Files and Clients that adhere to this version of the specification.
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This Part of the document goes into specific detail for many of the most popular Usenet news readers. It mostly pertains to best utilizing the presence of PAR v2.0 files in the binary Usenet downloading process.
Because PAR v2.0 can make use of parts down to the usenet article (or segment) level, some exploration of how well each news-reader handles this task is beneficial.
If your favorite news-reader is not present, and you are able to download and use PAR 2.0 files effectively, then please contact the project about contributing to this document.
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This chapter outlines some tips for using PAR2 files with Xnews as your primary news reader.
Much of this was contributed by Zendrax Xenward from a posting to the parchive development lists. It was compiled using XNews version 06.02.16 as the reference.
XNews is available for free from http://xnews.newsguy.com.
After having installed and configured XNews for your server follow these steps:
Getting Set Up:
Outline of steps for downloading:
Find the file set(s) you want to download queue them (single click the Q column).
If you created a Queue in step B you can send the articles into the queue to download when you are done collecting the files sets you want to place something in the queue use the menu option Main Menu >Transfer > ->/planned downloads/
Repeat step 1 (and step 2) until you have all the file sets you want from the server.
If you created a Queue in step B use menu option Folder > /planned downloads/ then in the new window sort the list of articles by date so that older articles are at the top (by clicking the Date column heading until there is a triangle pointing upwards) then select all (Ctrl+A).
If you created a Archive in step A use menu option Transfer > ->downloaded articles, this will download the oldest articles first and give less problems with articles disappearing during download.
If you created a Archive in step A use menu option Folder > downloaded articles select all files.
Use menu option Article > Decode (or press stacked cubes or press F4) select the directory were you want to download the files and press decode.
Double click on one of the par2 files to verify the file set and do any repairs that are needed.
If you created a Archive in step A you can remove all complete binaries but unless par2 could repair the file set you should keep the incomplete files if there is an backfill (single article repost).
If you created a Queue in step B you can remove all downloaded articles if there are any articles that are not downloaded you can retry later or with another Usenet server (if you have any).
In the past (before par2) I would have recommended in step 4 that you reverse the sort and download the newest articles first since then you would get the most complete files but now with par2 every article is useful so this oldest first is probably the best.
Xnews Caveats (relative to PAR2)
Like many news-readers. The version of XNews available at the time of writing does not seem to handle Uuencoded partial files properly. The problem occurs if the first article, part 01/XX, is missing or corrupted. If XNews cannot find this article, it does not know what filename to use in saving out the file, and thus fails for the entire file.
If you know a workaround, or this situation changes, please contact the Parchive Project and we'll update this document.
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This chapter goes into detail regarding the use of Forte Agent as a primary news-reader in conjunction with the use of PAR2 recovery files.
For using PAR1 recovery files, the process is as simple as downloading the binaries via the normal method with Forte Agent. Hence, this chapter does not cover any topics regarding PAR1 and Forte Agent.
The following tools are required to accomodate the use of Agent and PAR2 recovery files.
Because Forte Agent does not properly handle saving partial files when not all the articles are present, you will need a tool for manually decoding the articles. A recommended Yenc decoding tool for win32 users is listed below.
Yenc32 GUI Encoder/Decoder for Win32.
You need another tool for decoding to handle the uuencoded postings.
WinRAR for Win32.
Obviously, if you want to handle PAR2, you will need an appropriate recovery client. Two recommended options are listed below.
par2cmdline command line client.
http://parchive.sourceforge.net (See the "Clients" section)
QuickPar GUI client for Win32.
http://parchive.sourceforge.net (See the "Clients" section)
In order to handle articles correctly so that we can salvage the valid recovery blocks that they may contain, we need to configure agent's download settings to store the bodies and not immediately decode and save to file. The automatic decoding and saving to files is where agent drops articles after encountering a missing one or an encoding error.
To ensure agent keeps the article bodies for you to handle manually do the following:
Go to Agent's Main Menu > Gruop > Properties for configuring just one group. Or Main Menu > Group > Default Properties for default behaviors to affect all groups. In the Recieve Fles change the following settings:
Check Override Default Settings if editing the default properties.
Uncheck Save Attachments Automatically .
The changes described above cause agent to retain all message bodies in their raw non-decoded format. This applies to retrieving individual articles as well as files that are not missing any articles.
Unfortunately this is necessary for working-around Agent's unfortunate behavior when autmatically saving and decoding attachments.
See the "Caveats" section for problems that these settings are likely to cause.
I'll skip some here assuming you are already privy on how to mark, cue, and retrieve bodies/binaries using Forte Agent.
Lets use an example. You refresh your headers and you see a posting that you would like to have. It is accompanied by a set of PAR2 files for recovering missing chunks.
Unfortunately 10 of the 20 posted binaries are missing articles. When you highlite one of these headers you should see this in your "body" window:
Example 6.74. Incomplete article "body" view.
[114021 lines, incomplete]
[This is a multi-part message, of which only 23 of 24 parts are available.]
[These parts are unavailable: 13]
[To retrieve the incomplete message, use menu option Message | Join Sections.]
Notice in the previous example that only ONE article is missing. This is good news. It means that usually only one or two recovery blocks from the par2 set will be needed to recovery this error. Now if we can just get agent to do it!
Using this technique, you simply highlight a header that is missing articles. Then Main Menu > Message > Join Sections.
A join dialog will pop up, verify that the message parts are in numerical order and hit OK.
To get them in order it often helps to have the group sorted by subject.
If the articles were not auto-condensed to one header when you started, you can highlight all the parts of a single binary and perform the same operation.
Next, simply mark the messages for retrieval as normal. They will not be saved out to your file-system, the bodies will remain in agent's database files until you delete them or save the attachments out manually. See the "Caveats" section for known issues with this.
If you wish to immediately fetch the body, you may double-click the headers.
Choosing Save All Attachments on highlited headers is the manual equivalent of the behavior we are desparately trying to avoid. Saving attachments in this way on binaries missing articles will not yield the full set of useful data to the par2 recovery proces.
An alternate approach, when you encounter binaries that are missing articles, you may opt to retrieve the article bodies on an individual basis.
Highlite a binary header that is missing articles. Choose Main Menu > Message > Split Sections from the Main Menu.
You should see all available articles as separate headers with the notation [XX/Total] at the end of the subject line. Instead of the normal [*/Total].
Next highlite all the articles that comprise the partial binary.
You may now mark them all for retrieval, or click each one individually to fetch it's body.
For binaries that were not missing articles, you may save these to disk by: Right-Click > Save All Attachments.
For binaries that WERE missing articles (and complete ones if you wish):
Highlite a block of articles/headers that corresponds to a single binary file. From the Main Menu choose: File > Save Messages As....
An options dialog will open. Verify the following settings:
Check Save Raw Unformatted Message.
Select No Fields, Body Only.
Choose a location and a file name. For Yencoded files you will probably want to give it a .ntx extension. For Uuencoded files, give it a .uue extension.
You should now have a physical file on your system containing concatenated message bodies still in their raw, encoded format.
Many decoders (such as the two at the top of this document) can handle one big file containing lots of article bodies corresponding to many different binary output files. This tip may save you some time if you learn to utilize this feature.
The next step, we need to convert our saved bodies into a binary file that contains the actual byte data that the PAR2 files shall verify against and recovery with.
Many posters include the string 'yenc' in their posting subject-line. This is a big hint. If this string is not present, you may need to use trial and error with the two decoding methods below to determine for sure.
With yenc32 your task is simple.
Start yenc32.
From the Main Menu choose File > Decode Files(s).
Navigate to your saved file containing the encoded message bodies. Select that file and choose Open. A dialog box should appear. Then choose an output location for the decoded files to be sent.
Optionally at this point you have the chance to add more raw encoded files into the processing cue.
Press OK to decode, adn you will see the sections that decode sucessfully scroll by.
Voila, You should have one or more binaries in your specified output location saved using their posted filenames.
These generated files may be named properly, but they are most likely corrupt if they were missing articles to begin with. This is where PAR2 comes into play.
The download links for the tools in this section are provided at the top of this document.
At this point you should place all your downloaded/decoded binaries into one location along with the par2 recovery files that were provided.
Once you have the par2.exe executable in your path (dropping a copy of it in C:/windows does the trick), Open a commnd prompt.
cd into the directory containing your binaries.
Type this at the command line:
par2 verify name-of-a-par2-file.par2
par2 will return the status of the set of files, if recovery is possible it will tell you so. To then recover do:
par2 repair name-of-a-par2-file.par2
par2cmdline does not scan the current directory for misnamed files, you may have to adjust your filenames before par2cmdline sees everyting.
For More Information: Consult the documentation that comes with the tool or visit it's homepage.
For users of QuickPar, simply open the directory containing the posted binaries and double-click one of the .par2 files. QuickPar will open and immediately begin verifying and/or reparing files.
QuickPar knows a "few" ways that files are commonly mis-named, but it also does not scan the current directoy at this time. You can manually add files for it to scan using the Add button.
For More Information: Consult the documentation that comes with the tool or visit it's homepage.
At the time of writing this document, Agent leaves much to be desired when it comes to automating the process of retrieving and dealing with postings at the article level. By and large, the techniques described in this document are very HANDS ON.
The required settings that cause bodies to be retained until manually purged are a huge perormance hit for agent. It's article databases can get HUGE and you must be careful with where these are stored (configurable in the settings) and preventing them from growing too rapidly when you have large download cues.
Turn on the group settings that cause the body to be deleted upon saving an attachment. (but not the auto-save) This will free up space in your database files as you go, but avoid the broken downloads of partial postings. Just never "Save Attachments" on a partial binary, for those you must use the "Save Messages As..." technique and manually decode them.
I would suggest changing your settings to retain bodies, cue up all the partial binaries and fetch their bodies first, then change your settings back for retrieving and auto-saving (deleting bodies as it goes) for the complete postings.
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