Ctm is a system which was designed by Poul-Henning Kamp for making changes to a source tree available on a daily basis by email. This is a good way to stay up to date with the current source- or CVS tree if you have a bad Internet connection, for instance via modem.
Ctm uses very low bandwidth for distributing the changes to the tree, and compresses them using gzip -9. In contrast to CVSup, ctm is written in plain C and therefore available for every platform supported by OpenBSD.
The basic idea of ctm is that you subscribe to a special mailing list for a particular source tree. Each day you receive an email message containing all the changes to that tree during that period. One set of differences is called a "delta".
You begin with a base set, against which later deltas are patched. To begin using ctm you download the latest base set and all deltas generated after that. Once you have processed those you can process later deltas you receive from the mailing list. The base sets are split into pieces of 1400kB each for easier downloading over bad lines, and you can even put them onto floppies this way.
Base sets are generated once every 50 relative deltas, so you never have to grab more than 50 deltas to catch up.
There are currently two kinds of base delta. For quite a while we were making tar.gz files manually, but we are switching back to real ctm base deltas. The latter contain md5 checksums and are generated automatically, thus are a bit safer. You can distinguish these two kinds of base delta by their filename. An example for a tar.gz file is OpenBSD-cvs.1450.tar.gz, whereas a ctm base delta would be named OpenBSD-cvs.1500A.gz. See below for detailed instructions.
You obtain the base set and all relative deltas up to the recent one via ftp from the sites listed below. Sizes are:
Larger ctm updates are rare, though, usually occurring only after a major import of something like binutils, perl, gcc, etc.
There are several mailing lists related to ctm. There is a list for updates to the CVS tree, a list for the source tree, a list for the X11 part of both, and one for the ports tree, plus a list for log messages from the ctm delta generation runs.
The following commands will subscribe you to the appropriate lists:
For the CVS tree (without the X11 part):
echo subscribe OpenBSD-cvs | mail majordomo@OpenBSD.orgFor the X11 part of the CVS tree:
echo subscribe OpenBSD-cvs-x11 | mail majordomo@OpenBSD.orgFor the source tree (without the X11 part):
echo subscribe OpenBSD-src | mail majordomo@OpenBSD.orgFor the X11 part of the source tree:
echo subscribe OpenBSD-src-x11 | mail majordomo@OpenBSD.orgFor the ports tree:
echo subscribe OpenBSD-ports-ctm | mail majordomo@OpenBSD.orgFor the ctm log list:
echo subscribe ctm-log | mail majordomo@OpenBSD.org
cat split/OpenBSD-cvs.1500A.gz.* > OpenBSD-cvs.1500A.gz cd target ctm -v -v -v .../OpenBSD-cvs.1500A.gz
cat split/OpenBSD-cvs.1500.tar.gz.* > OpenBSD-cvs.1500.tar.gz cd target tar -xzvf .../OpenBSD-cvs.1500.tar.gz
where split is the directory in which you have placed the files you downloaded and target is the place you have chosen for the source set.
It is not necessary to keep these files around, if you're sure you've got a complete tree. But you can keep the base set file(s) for backup purposes. However, be sure to note the number of the base set before continuing.
cd target ctm -v -v -v deltas/OpenBSD-cvs.*
where target is the directory where your source set tree is, and deltas is where you have stored the deltas.
ctm_rmail -p /tmp -d deltas -b target folder
where folder is the mail folder containing the delta mail. This will decode the ctm delta and save it in the deltas directory. The delta will be a file of the form OpenBSD-cvs.XXXX.gz, where XXXX is the number of the delta. Then the delta will be applied to the directory tree located at target, the place where you unpacked the base delta.
Repeat this last step every time you receive a delta from the mailing list. If you like you can automate this step using procmail or any similar program.
The addresses for the deltas are:
NOTE: I'm very interested in finding other sites around the world that would like to mirror these deltas.
This depends on your diskspace, among other factors. Since ctm doesn't deal with files which have been modified locally, the "better" choice is probably the CVS tree. You then can check out your working source tree from your CVS tree, and keep your local modifications in your source tree, because cvs is smart enough to merge in your local changes.
The drawback, however, is the amount of diskspace it takes. A checked-out source tree takes about 350MB or so, but if you have your own cvs tree you need about 1Gb for it, plus another 350MB for the checked out tree.
This doesn't count the 100MB or more (depending on the architecture) you will need to do a build, i.e. compile the sources.
If you just get the source tree, you will need to deal with local modifications. One way to do this is to use the union filesystem, although there have been reports that the union filesystem can be unstable if both the upper and lower layers reside on the same physical filesystem. If you place your upper and lower layers on separate filesystems you should have no problems. A sample of this is as follows:
Suppose your ctm-updated tree is in /usr/src-ctm, and your real source tree, the one you make your modifications to and do your builds from, is in /usr/src. /usr/src should be initially an empty directory. The following command will set up the union mount:
mount -t union -o -b /usr/src-ctm /usr/src
Modifications made to files in /usr/src will become a file contained within /usr/src, hiding the one in src-ctm. If changes are made via ctm to the underlying src-ctm tree, those changes will not be seen if there is a file in the upper layer hiding it.
You should periodically unmount the union and search for files which are local to the union filesystem.
umount /usr/src find /usr/src -type f
The commands ls -W and rm -W will be useful too, as objects named "whiteouts" in /usr/src will also hide files in src-ctm.
If you get the CVS tree, you can use the cvs checkout command to check out a source tree from it, and each time you update with ctm you can use the cvs update command to update your source tree.
To get an initial src tree:
cd /usr cvs -qd YOUR_CVS_TREE checkout -A src
and after each ctm update:
cd /usr/src cvs -q update -PAd
Important notes and announcements about ctm will be posted to:
For any problems, suggestions, reports and questions regarding ctm contact the ctm maintainer Hans Günter Weigand.
OpenBSD/CTM logo designed for the OpenBSD Project by Phillip F Knaack.