2012年3月26日 星期一

Brooks's law

[wiki] Brooks's Law
http://en.wikipedia.org/wiki/Brooks's_law

Brooks's law is a principle in software development which says that "adding manpower to a late software project makes it later".[1] It was coined by Fred Brooks in his 1975 book The Mythical Man-Month. The corollary of Brooks's Law is that there is an incremental person who, when added to a project, makes it take more, not less time. Brooks adds that "Nine women can't make a baby in one month".


IEEE Software "From the Editor" Column by Steve McConnell
Brooks' Law Repealed?
http://www.stevemcconnell.com/ieeesoftware/eic08.htm

Changing Counterproductive Behaviors in Real Acquisitions - Brooks' Law
http://www.sei.cmu.edu/library/assets/brooks1.pdf

Brooks Law Is Applicable To Many Collaborative People Activities : Project Planning & Estimation
http://www.galorath.com/wp/brooks-law-is-applicable-to-many-collaborative-people-activities.php



极客须知十大定律 - 博客 - 伯乐在线
http://blog.jobbole.com/12158/

2012年3月15日 星期四

Generating config for new kernel from old kernel config

  1. In new kernel source,
    make allmodconfig KCONFIG_ALLCONFIG=/boot/config-of-old-kernel
    This will create a kernel config of the new kernel, and answered all with "m" based on the old config.

  2. Build the kernel and boot. Go on if it boot without issues.
  3. Disable all the modules not used currently in .config.
    make localmodconfig
  4. Have all modules (m) in .config become built-in (y)
    make localyesconfig
  5. Save the .config as minimal config to ./defconfig
    make savedefconfig


"make help" in kernel source:
localmodconfig - Update current config disabling modules not loaded
localyesconfig - Update current config converting local mods to core

savedefconfig - Save current config as ./defconfig (minimal config)

allnoconfig - New config where all options are answered with no
allyesconfig - New config where all options are accepted with yes
allmodconfig - New config selecting modules when possible
alldefconfig - New config with all symbols set to default
KCONFIG_ALLCONFIG
To specify a filename that contains config options that the user requires to be set to a specific value

2012年3月14日 星期三

[Debian] Documentation/lguest: No such file or directory

#638012 - error compiling(make: *** Documentation/lguest: No such file or directory. Stop) - Debian Bug report logs
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=638012

As a workaround simply linking the virtual/lguest/ directory from the Documentation folder of the source tree will solve the problem.
cd ./Documentation
ln -s virtual/lguest/

2012年3月8日 星期四

dpkg-reconfigure

[藍森林-自由軟件] - 關於dpkg-reconfigure,請大家接龍
http://www.lslnet.com/linux/f/docs1/i41/big5289530.htm

2012年3月2日 星期五

IPSec: Fragmentation/Reassemble

RFC 4303: IP Encapsulating Security Payload (ESP)
http://tools.ietf.org/html/rfc4303

3.3. Outbound Packet Processing
3.3.4. Fragmentation
If necessary, fragmentation is performed after ESP processing within an IPsec implementation. Thus, transport mode ESP is applied only to whole IP datagrams (not to IP fragments). An IP packet to which ESP has been applied may itself be fragmented by routers en route, and such fragments must be reassembled prior to ESP processing at a receiver. In tunnel mode, ESP is applied to an IP packet, which may be a fragment of an IP datagram. For example, a security gateway or a "bump-in-the-stack" or "bump-in-the-wire" IPsec implementation (as defined in the Security Architecture document) may apply tunnel mode ESP to such fragments.
(......)
Fragmentation, whether performed by an IPsec implementation or by routers along the path between IPsec peers, significantly reduces performance. Moreover, the requirement for an ESP receiver to accept fragments for reassembly creates denial of service vulnerabilities. Thus, an ESP implementation MAY choose to not support fragmentation and may mark transmitted packets with the DF bit, to facilitate Path MTU (PMTU) discovery. In any case, an ESP implementation MUST support generation of ICMP PMTU messages (or equivalent internal signaling for native host implementations) to minimize the likelihood of fragmentation. Details of the support required for MTU management are contained in the Security Architecture document.

3.4. Inbound Packet Processing
3.4.1. Reassembly

If required, reassembly is performed prior to ESP processing.