Notes from 20020328
pbarker at barker.dropbear.id.au
Tue Apr 2 19:43:45 EST 2002
I forgot to put these up earlier....
You may have noticed the lack of attributions for some of these
talks. That's because I don't know everyone's face - it may be a good idea
to mention your name if you want it in these notes :-)
CLUG notes 28th March, 2002
- clustering, Ed Lang
- for CBiS
- Standard stuff, cheap machines etc etc
- dual 1800+ Athlons
- 3*1.6T file servers
- RAID 5-0, one spare
- ~ 100MB/second
- 15 processing nodes, 100GB scratch storage on each
- separate login/auth server
- Sun's gridengine
- descendant of PCM, DQS
- Problems so far
- dense unit, not much room....
- lack of funding
- modular, slot more stuff in
- hope the WD-120s don't fail!
- pghistory with Drake Diedrich
- audit trails for PostgreSQL databases
- with one of the above file servers
- want to know who's changing what and when in postgres
- retrieve previous values
- databases which may need history
- machine records,
- major equipment tables
- anything to do with money
- what do you need for auditting?
- triggers, rules, views
- start with two tables
- test, test_old
- sequence number on old table
- functions to insert into "old" table
- deleted flag
- triggers copy old values out of table before inserting new data
- use views to look at old data ("history views")
- shell(?) wrapper to generate all of these tables, functions and views
- something to convert old schemas as well
- using postgresql from corporate desktops OK
- e.g. JCSMR licencing tables
- 9 tables
- 7 under auditting control
- no ref. integrity on old table
- a lot like the old temporal and time-travel features of postgres
- An old program, interface to apt called "console-apt" or "deity"
- graphical interface
- list of packages down the page
- a number of revisions
- now a C++ program linking against the apt library
- very similar to dselect
- in look and feel
- tree structure organisation of packages
- full recursive dependency listing
- filtering of package names
- searching etc etc
- similar functionality to apt-get, to get dependencies recursively
- but includes a tetris game to keep you occupied
- source of fsck (file system check) tetris?
- not enabled by default.
- not working too actively on it
- GTK interface, too
- lacks tetris, though
- uses threads
- continue doing stuff while it is downloading...
- progress bars etc
- multiple listings screens
- flick between them
- select actual version you want to install
- dselect uses 18M of memory while running... at least
- diety at 6M
- aptitude 8.1M
- problems getting debian to change away to another package manager
- doesn't have the ability to "hold" packages
- XDM themes?
- xdm is ugly
- as it should be
- when X starts, there are 8 steps
- XDM starts
- runs an xsetup file (as root) e.g. an x csonsole
- x startup (as root)
- x reset script (as root)
- hacking xsetup
- shell script
- before login prompt
- xsetroot etc etc
- call into themes directories
- e.g. themes/foo/Xstartup
- change symlink to change theme
- packaging advice is to put these under /usr/share(?)
- just not under /etc...
- xtheme chooser
- choose random theme
- control the login box with xresources
- random images
- waiting for alpha in xfree86
- transparency behing the login elements
- Brad Hards, Zeroconf networking
- not about functional programming
- no air guitar
- even though it was written with emacs
- networking with no admin staff
- ad hoc networking
- no-control-element networking
- IETF working group
- four protocol elements
- IP interface cinfiguration
- user group networking algorithm
- seed random number generator with MAC
- pick a random IP based on it...
- ARP for the IP
- If you get an arp response, choose another random number
- do a few gratuitous arps to try to claim the IP address
- wait for someone else to try to claim it
- defend it if you need to
- have a real IP address and zeroconf IP address
- windows already does all this (98...)
- with issues
- strong defence in Windows 2000...
- hammers other servers
- will not cede an IP address
- for when you join two networks
- MacOS does it...
- if DHCP fails
- translation between hostname and IP
- service discover
- SMB does it naturally
- e.g. random NFS file server
- Service Location Protocol (rfc2608)
- no central server....
- multicast DNS (mDNS)
- internet draft
- might be in Bind 9.x
- link-local multicast name resolution (LLMNR)
- uses 220.127.116.11, port 5353
- naturally susceiptible to DOS attacks
- use a sep. cache for "normal" DNS
- don't normally use it
- useful for things like just plugging a USB cable thingy in and having it work.
- uses multicast address
- each machine can claim to provide certain services
- "looks reasonably mature"
- requests like "Who has home directories for fred and john"?
- shell interface to futexes, Rusty
- Fast Userspace Mutexes
-no contention, no talking to kernel
- for fcntl locks, sysv semaphores etc
- a few older implementaations...
- linux threw the stuff in, went on holidays
- this thing called POSIX threading....
- doesn't work on futexes
- e.g. mysql
- reimplementing it... 6% slower, but...
- e.g. counters going to one... put yourself on a wait queue
- lots of nasty race conditions, solved in dodgy manners
- put yourself on the waitqueue, see if you needed to, ...
- two system calls
- half as fast
- Paulus suggests a single-call-for-most-common-case solution
- is it this value?? Then cool...
- read/write locks in userspace
- backending to two futexes in the kernel
- standard multiple readers/writers problem
- next generation POSIX threading
- researchy stuff in linux
- no longer chasing other unixes....
- fast read or grab userspace
- Hotplug CPU, again with Rusty
- nice machines allow hotplugging memory and CPUs
- Rusty said at some conference that it shouldn't be too hard to do
- ... and then pizza happened...
With the zeroconf stuff - did anyone catch how you determine a gateway
for the network you're - kind of - on?
Peter Barker | N _--_|\ /---- Barham, Vic
Programmer,Sysadmin,Geek | W + E / /\
pbarker at barker.dropbear.id.au | S \_,--?_*<-- Canberra
You need a bigger hammer. | v [35S, 149E]
qq%I've never heard of it or used it, apart from finding it in the Camel
book and saying "Oh god".% -- Onceler
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