Category Archives: linux base

Alexander Leidinger » FreeBSD 2012-04-15 18:43:03

This weekend I made some progress in the linuxulator:

  • I MFCed the reporting of some linux-syscalls to 9-stable and 8-stable.
  • I updated my linuxulator-dtrace patch to a recent -current. I already compiled it on i386 and arundel@ has it compiled on amd64. I counted more than 500 new DTrace probes. Now that DTrace rescans for SDT probes when a kernel module is loaded, there is no kernel panic anymore when the linux module is loaded after the DTrace modules and you want to use DTrace. I try to commit this at a morning of a day where I can fix things during the day in case some problems show up which I did not notice during my testing.
  • I created a PR for portmgr@ to repocopy a new linux_base port.
  • I set the expiration date of linux_base-fc4 (only used by 7.x and upstream way past its EoL) and all dependent ports. It is set to the EoL of the last 7.x release, which can not use a later linux_base port. I also added a comment which explains that the date is the EoL of the last 7.x release.

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New CentOS linux_base for testing soonish

It seems my HOWTO create a new linux_base port was not too bad. There is now a PR for a CentOS 6 based linux_base port. I had a quick look at it and it seems that it is nearly usable to include into the Ports Collection (the SRPMs need to be added, but that can be done within some minutes).

When FreeBSD 8.3 is released and the Ports Collection open for sweeping commits again, I will ask portmgr to do a repo-copy for the new port and commit it. This is just the linux_base port, not the complete infrastructure which is needed to completely replace the current default linuxulator userland. This is just a start. The process of switching to a more recent linux_base port is a long process, and in this case depends upon enough support in the supported FreeBSD releases.

Attention: Anyone installing the port from the PR should be aware that using it is a highly experimental task. You need to change the linuxulator to impersonate himself as a linux 2.6.18 kernel (described in the pkg-message of the port), and the code in FreeBSD is far from supporting this. Anyone who wants to try it is welcome, but you have to run FreeBSD-current as of at least the last weekend, and watch out for kernel messages about unsupported syscalls. Reports to [email protected] please, not here on the webpage.

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New opportunities in the linuxulator

Last weekend I committed some dummy-syscalls to the linuxulator in FreeBSD-current. I also added some comments to syscalls.master which should give a hint which linux kernel had them for the first time (if the linux man–page I looked this up in is correct). So if someone wants to experiment with a higher compat.linux.osrelease than 2.6.16 (as it is needed for a CentOS based linux_base), he should now get some kernel messages about unimplemented syscalls instead of a silent failure.

There may be some low-hanging fruits in there, but I did not really verify this by checking what the dummy syscalls are supposed to do in linux and if we can easily map this to existing FreeBSD features. In case someone has a look, please send an email to emulation@FreeBSD.org.

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HOWTO add linux-infrastructure ports for a new linux_base port

In my last blog-post I described how to create a new linux_base port. This blog-post is about the other Linux–ports which make up the Linux–infrastructure in the FreeBSD Ports Collection for a given Linux-release.

What are linux-infrastructure ports?

A linux_base port contains as much as possible and at the same time as little as possible to make up a useful Linux-compatibility-experience in FreeBSD. I know, this is not a descriptive explanation. And it is not on purpose. There are no fixed rules what has to be inside or what not. It “matured� into the current shape. A practical example is, that there is no GUI-stuff in the linux_base. While you need the GUI parts like GTK or QT for software like Skype and acroread, you do not need them for headless game servers. While you may need various libraries for game servers, you may not need those for Skype or acroread. As such some standard parts are in separate ports which are named linux–LINUX_DIST_SUFFIX-NAME. For GTK and the Fedora 10 release this results in linux-f10-gtk2. Such generic ports which depend upon a specific Linux-release make up the Linux-infrastructure in the FreeBSD Ports Collection. Those ports are referenced in port-Makefiles via the USE_LINUX_APPS variable, e.g. USE_LINUX_APPS=gtk2.

If you created a new linux_base port, you need most standard infrastructure ports in a version for the Linux-release used in the linux_base port, to have the Linux-application ports in the FreeBSD Ports Collection working (if you are unlucky, some ports do not play well with the Linux-release you have chosen, but this is out of the scope of this HOWTO).

Updating Mk/bsd.linux-apps.mk

 First we need to set the LINUX_DIST_SUFFIX variable to a value suitable to the new Linux-release. This is done in the conditional which checks the OVERRIDE_LINUX_NONBASE_PORTS variable for valid values. Add an appropriate conditional, and do not forget to add the new valid value to the IGNORE line in the last else branch of the conditional.

The next step is to check the _LINUX_APPS_ALL and _LINUX_26_APPS variables. If there are some infrastructure ports which are not available for the new Linux-release, the conditional which checks the availability of a given infrastructure port for a given Linux-release needs to be modified. If at a later step you notice that there are some additional infrastructure ports necessary for the new Linux-release, _LINUX_APPS_ALL and the check-logic needs to be modified too (e.g. add a new variable for your Linux-release, add the content of the variable to _LINUX_APPS_ALL, and change the check to do the right thing).

After that two tedious parts need to be done.

For each infrastructure port there is a set of variables. The name_PORT variable contains the location of the port in the Ports Collection. Typically you do not have to change it (if you really want to change it, do not do it, fix the naming of the infrastructure port instead), because we use a naming convention here which includes the LINUX_DIST_SUFFIX. The name_DETECT variable is an internal variable, do not change it (if you create a new infrastructure port, copy it from somewhere else and make sure the name in value of the variable matches the port name in the name of the variable). Then there are several name_suffix_FILE variables. Leave the existing ones alone, and add a new one with the correct suffix for your new Linux-release. The value of the variable needs to be an important file which is installed by the infrastructure port in question. FYI: The content of the name_suffix_FILE variables are used to set the name_DETECT variables, depending on the Linux-relase the name_DETECT variables are used to check if the port is already installed. Ideally the name_suffix_FILE variable points to a library in the port. The name_DEPENDS variable lists dependencies of this infrastructure port. If the dependencies changed in your Linux-release, you need to add a conditional to change the dependency if LINUX_DIST_SUFFIX is set to your Linux-release.

Normally this is all what needs to be done in PORTSDIR/Mk/bsd.linux-apps.mk, the rest of the file is code to check dependencies and some correctness checks.

The second tedious part is to actually create all those infrastructure ports. Normally you can copy an existing infrastructure port, rename it, adjust the PORTNAME, PORTVERSION, PORTREVISION, MASTER_SITES, PKGNAMEPREFIX, DISTFILES, CONFLICTS (also in all other Linux-release versions of this infrastructure port), LINUX_DIST_VER, RPMVERSION (if set/neccesary) and SRC_DISTFILE variables, generate the distfile checksums (make makesum), and fix the plist. I suggest to script parts of this work (as of this writing Freshports counts 68 ports where the portname starts with linux-f10-).

Adding new infrastructure ports, or removing infrastructure ports for a given Linux-release

If your Linux-release does not come with a package for an existing infrastructure port, just do not create a corresponding name_suffix_FILE line. You still need to do the right thing regarding dependencies of ports which depend upon this non-existing infrastructure port (if your Linux-release comes with packages for them).

To add a new infrastructure port, copy an existing block, rename the variables, set them correctly, add a new variable for your Linux-release in the first _LINUX_APPS_ALL section, add the content of this variable to _LINUX_APPS_ALL, and change the check-logic as described above.

Final words

If you have something which installs and deinstalls correctly, feel free to provide it on [email protected] for review/testing. If you have questions during the porting, feel also free to send a mail there.

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HOWTO create a new linux_base port

FreeBSD is in need of a new linux_base port. It is on my TODO list since a long time, but I do not get the time to create one. I still do not have the time to work on a new one, but when you read this, I managed to get the time to create a HOWTO which describes what needs to be done to create a new linux_base port.

I will not describe how to create a new linux_base port from scratch, I will just describe how you can copy the last one and update it to something newer based upon the existing infrastructure for RPM packages.

Specific questions which come up during porting a new Linux release should be asked on [email protected],  there are more people which can answer questions than here in my blog. I will add useful information to this HOWTO if necessary.

In the easy case most of the work is searching the right RPMs and their dependencies to use, and to create the plist.

Why do we need a new linux_base port?

The current linux_base port is based upon Fedora 10, which is end of life since December 2009. Even Fedora 13 is already end of life. Fedora 16 is supposed to be released this year. From a support point of view, Fedora 15 or maybe even Fedora 16 would be a good target for the next linux_base port. Other alternatives would be to use an extended lifetime release of another RPM based distribution, like for example CentOS 6 (which seems to be based upon Fedora 12 with backports from Fedora 13 and 14). Using a Linux release which is told to be supported for at least 10 years, sounds nice from a FreeBSD point of view (only minor changes to the linux ports in such a case, instead of creating a complete new linux_base each N+2 releases like with Fedora), but it also means additional work if you want to create the first linux_base port for it.

The mysteries you have to conquer if you want to create a new linux_base port

What we do not know is, if Fedora 15/16, CentOS 6, or any other Linux release will work in a supported FreeBSD release. There are two ways to find this out.

The first one is to take an existing Linux system, chroot into it (either via NFS or after making a copy into a directory of a FreeBSD system), and to run a lot of programs (acroread, skype, shells, scripts, …). The LTP testsuite is not that much useful here, as it will test mostly kernel features, but we do not know which kernel features are mandatory for a given userland of a Linux release.

The second way of testing if a given Linux release works on FreeBSD is to actually create a new linux_base port for it and test it without chrooting.

The first way is faster, if you are only interested in testing if something works. The second way provides an easy to setup testbed for FreeBSD kernel developers to fix the Linuxulator so that it works with the new linux_base port. Both ways have their merits, but it is up to the person doing the work to decide which way to go.

The meat: HOWTO create a new linux_base port

First off, you need a system (or a jail) without any linux_base port installed. After that you can create a new linux_base port (= lbN), by just making a copy of the latest one (= lbO). In lbN you need to add lbO as a CONFLICT, and in all other existing linux_base ports, you need to add lbN as a conflict.

Change the PORTNAME, PORTVERSION, reset the PORTREVISION in lbN, and set LINUX_DIST_VER  to the new Linux-release version in the lbN Makefile (this is used in PORTSDIR/Mk/bsd.linux-rpm.mk and PORTSDIR/Mk/bsd.linux-apps.mk).

If you do not stay with Fedora, there is some more work to do before you can have a look at chosing RPMs for installation. You need to have a look at PORTSDIR/Mk/bsd.linux-rpm.mk and add some cases for the new LINUX_DIST you want to use. Do not forget to set LINUX_DIST in the lbN Makefile to the name of the distribution you use. You also need to augment the LINUX_DIST_VER check in PORTSDIR/Mk/bsd.linux-rpm.mk with some LINUX_DIST conditionals. If you are lucky, the directory structure for downloads is similar to the Fedora structure, and there is not a lot to do here.

When this is done, you can have a look at the BIN_DISTFILES variable in the lbN Makefile. Try to find similar RPMs for the new Linux release you want to port. Some may not be available, and it may also be the case that different ones are needed instead. I suggest to first work with the ones which are available (make makesum, test install and create plist). After that you need to find out what the replacement RPMs for non-existing ones are. You are on your own here. Search around the net, and/or have a look at the dependencies in the RPMs of lbO to determine if something was added as a dependency of something else or not (if not, forget about it ATM). When you managed to find replacement RPMs, you can now have a look at the dependencies of the RPMs in lbN. Do not add blindly all dependencies, not all are needed in FreeBSD (the linux_base ports are not supposed to create an environment which you can chroot into, they are supposed to augment the FreeBSD system to be able to run Linux programs in ports like they where FreeBSD native programs). What you need in the linux_base ports are libraries, config and data files which do not exist in FreeBSD or have a different syntax than in FreeBSD (those config or data files which are just in a different place, can be symlinked), and basic shell commands (which commands are needed or not… well… good question, in the past we made decisions what to include based upon problem reports from users). Now for the things which are not available and where not added as a dependency. Those are things which are either used during install, or where useful to have in the past. Find out by what it was replaced and have a look if this replacement can easily be used instead. If it can be used, add it. If not, well… bad luck, we (the FreeBSD community) will see how to handle this somehow.

If you think that you have all you need in BIN_DISTFILES, please update SRC_DISTFILES accordingly and generate the distfile via  make –DPACKAGE_BUILDING makesum to have the checksums of the sources (for legal reasons we need them on our mirrors).

The next step is to have a look at REMOVE_DIRS, REMOVE_FILES and ADD_DIRS if something needs to be modified. Most of them are there to fall back to the corresponding FreeBSD directories/files, or because they are not needed at all (REMOVE_*). Do not remove directories from ADD_DIRS, they are created here to fix some edge conditions (I do not remember exactly why we had to add them, and I do not take the time ATM to search in the CVS history).

If you are lucky, this is all (make sure the plist is correct). If you are not lucky and you need to make some modifications to files, have a look at the do-build target in the Makefile, this is the place where some changes are done to create a nice user experience.

If you arrive here while creating a new linux_base port, lean back and feel a bit proud. You managed to create a new linux_base port. It is not very well tested at this moment, and it is far from everything which needs to be done to have the complete Linux infrastructure for a given Linux release, but the most important part is done. Please notify [email protected] and call for testers.

What is missing?

The full Linuxulator infrastructure for the FreeBSD Ports Collection has some more ports around a linux_base port. Most of the infrastructure for this is handled in Mk/bsd.linux-apps.mk.

UPDATE: I got some time to write how to update the Linux-infrastructure ports.

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