es. To interact with virtual ma- Pastwatch: A Distributed Version other branch, but that this had chines Ventana uses the NFS Control System rarely been observed in practice. protocol, which is understood by Alexander Yip, Benjie Chen, and Robert most operating systems. Ben Morris, MIT CSAIL FreeBSD Developer Summit concluded his talk by discussing several use cases, for example, In the last talk of the conference, and BSDCan how to use the branch hierarchy Alexander Yip presented Past- Summarized by Rik Farrow to apply a security patch effi- watch, a cvs-style version control ciently in multiple virtual ma- system that supports disconnect- On May 10, I headed off to Ot- chines. ed operation. In Pastwatch, users tawa, Canada, for a several-day do not have to be connected to adventure with the three BSD Olive: Distributed Point-in-Time a central server to commit communities. BSD, which start- Branching Storage for Real Systems changes; for example, a small ed off as the Berkeley Software group of developers can use it to Marcos K. Aguilera, Susan Spence, and Distribution when Bill Joy collaborate while on an airplane Alistair Veitch, HP Labs arranged to ship out nine-track and later merge their changes tapes containing assorted soft- The talk was given by Marcos into the main repository when ware (such as vi and csh, which Aguilera, who argued that a they are connected to the net- he wrote, and sendmail), has widening gap between storage work again. Of course, this can forked twice into three groups. capacity and transfer rates makes result in write conflicts if multi- FreeBSD, the largest community, it increasingly difficult to handle ple disconnected users modify focuses on building a main- large volumes of data. For exam- the same file. Pastwatch handles stream server/network operating ple, an administrator may want this by lazily creating branches, system, with multiprocessor sup- to archive a snapshot of a vol- which are visible to the users and port. NetBSD, the next largest ume for further reference, or run can be merged later. community, specializes in port- a “what if” installation of a new Each Pastwatch user maintains ing the BSD operating system to software package without affect- his or her own local copy of the as many target CPUs as possible. ing the main copy. Aguilera pre- repository, which is organized Currently, 59 CPU architectures sented Olive, a distributed and using a special data structure are supported. OpenBSD, a fork replicated storage system that called a revtree. The revtree from NetBSD, is best known for addresses these problems by structure is such that two reposi- its focus on improving security. providing an efficient branching tories can be synchronized sim- operation. By creating a new I caught the second day of the ply by forming the set-union of branch, the user obtains a sec- FreeBSD Developer Summit, an the revtree nodes. This allows ond copy of a volume which can invitation-only meeting of about updates to spread in an ad-hoc evolve independently from the 50 developers. Eight long talks manner and yet ensures eventual first. were packed into a long day, with consistency. Pastwatch has been a pub trip for lunch. Having a Aguilera pointed out that the in production use for over a year, pub break somewhat disturbed main technical challenge in and an implementation is avail- my note-taking ability, but I will Olive was to provide strong con- able for several major operating provide you with an overview of sistency, and he described the systems. More information is the talks, as well as some links if mechanisms Olive uses to available at http://pdos.csail.mit you want to search deeper. achieve this. Specifically, Olive .edu/pastwatch/. provides linearizability, which The Developer Summit is a In the Q&A session, Yip fielded implies that the state captured by chance for FreeBSD developers several questions regarding how a branch is one that could also to meet in person to catch up on Pastwatch handles write con- have resulted from a crash. the status of projects and plan flicts. Brad Karp asked how users Aguilera also presented evalua- for future work. Another key as- could find out about new tion results from an implementa- pect of the summit is the chance branches; the answer was that tion of Olive in the federated ar- for developers to meet each oth- Pastwatch displays an explicit ray of bricks; he showed that a er in person—something that’s warning during synchronization. new branch can be created in especially important given the Eric Eide asked what would hap- tens of milliseconds and that the limitations of electronic commu- pen if two users reconciled the per-branch metadata is small nication. same branches; the answer was enough to allow dozens of The morning began with Dario that Pastwatch would create an- branches. Freni and Scott Ullrich dis- 90 ;LO GIN: V OL. 31, NO. 4 cussing a LiveCD version of has become the authoritative peaters, virtual APs, and WDS FreeBSD, called FreeSBIE source of general IPv6 code. (Wireless Distribution System). (www.freesbie.org). You can use Robert Watson spoke for the Requests for someone to take FreeSBIE like Knoppix, a popu- first of many times. Watson responsibility for some part of lar Debian Linux–based LiveCD; (http://www.watson.org/~robert/) the kernel code were not uncom- that is, you can boot from the has added auditing capabilities mon during this conference. CD and use FreeBSD without in- to TrustedBSD, a version of Anyone can become a part of the stalling anything on your hard FreeBSD. The auditing support is FreeBSD community by con- drive. The developers described based on Apple’s audit imple- tributing patches, even for docu- how the image can be made mentation as found in Darwin, mentation. The more time and small enough to fit on a busi- and it uses the same format as useful patches or code you con- ness-card-sized CD (8 MB), us- Sun’s BSM, as there are already tribute, the more important you ing a new toolkit called sysutils/ tools available for perusing those become to the community. From freesbie, and to create other pur- audit records. Audit records of an outsider’s perspective, this pose-built CDs using FreeSbie. this type refer to secure operat- concept looks very appealing Next off, Colin Percival de- ing systems in the tradition of and straightforward. scribed his Update 2.0 project. the Orange Book, and now the Randall Stewart of Cisco spoke Percival recently became the Common Criteria. next about SCTP. SCTP appeared FreeBSD security officer. Updat- He has also decided to add over five years ago as an alterna- ing a FreeBSD system currently NFSv4-style ACLs to the existing tive to TCP, and Stewart wrote involves either collecting new POSIX.1.e-style in TrustedBSD, both a reference implementation sources and performing a make and he hopes that Kirk McKu- and a book about SCTP. SCTP world in /usr/src or installing sick will implement backup and sets out to solve many of the from scratch (which does ensure restore support for ACLs. The weaknesses of TCP and includes a clean upgrade). The Update 2.0 decision to retrofit/update the the ability to multiplex streams system supports installing binary MAC framework is based on four within a single connection. Al- security patches, making in- years of deployment experience, though there are five new system stalled FreeBSD systems easier to which ends up being mostly calls involved with SCTP (and maintain. For now, the system cleanup, since there are a num- kernel support also in Linux 2.6 only works with security patch- ber of companies shipping with and Solaris 10), there are cur- es. Apple and the Mozilla Foun- the framework and they are, in rently no FreeBSD man pages. dation use a version of Update fact, generally happy with it. But SCTP has been used in tele- v1. Part of making the binary up- phone applications in China, date system officially supported Watson also talked about need- ing to reduce the number of fire- Cisco BGP implementations (be- involves moving it to a formal cause it has protection against project infrastructure rather than walls supported in FreeBSD from four to three (really!). Ip6fw will RST attacks), SIP proxies, and using ad-hoc systems he’s assem- satellite communications. bled previously, and part is mak- be eliminated, as ipfw now has ing it a tool that can be reused by full IPv6 support. The other fire- Robert Watson took over at this administrators to deploy their walls supported in FreeBSD are point, covering a myriad of top- own updates, not just the securi- pf and ipfilter. ics very quickly. Besides his work ty updates. Sam Leffler picked up after in secure systems, Watson has been at the forefront in removing The KAME project involved the lunch. Leffler writes code for 802.11 infrastructure support for the Giant lock from the network- creation of a reference IPv6 and ing stack (see Michael Lucas’s ar- IPSec implementation for BSD various wireless devices. Al- though many of the devices are ticle in the October 2005 ;login:). operating systems in general. Watson explained where Giant KAME began with Japanese re- Linux-based, Leffler prefers to begin working in the FreeBSD had been removed, then men- searchers (http://www.kame.net tioned that there were device /project-overview.html), and the programming environment. Some of the work Leffler has drivers where Giant is still used IPv6/IPSec implementation has (which hurts SMP performance).