I compressed a backup with various tools:

1606M original tarfile
1226M bzip2 –best
1.3G gzip –best (sorry, no exact MB)
1152M lzma -7 (default)
1131M lzma -8

LZMA (7-zip) is definitly a algorithm heavy on cpu and memory, but achieved great compression.
This shouldn’t be a benchmark (as I didn’t measure time), only a perception in this specific use case.

There exists a really lame problem on X (X11,XFree86,Xorg,…): The authentification or identification mechanism when a new application wants to connect to the X server (read: show a window) works over the hostname.

This is fine if you live in 1990, but wireless network have dhcp and dhcp server can send a hostname to your machine making your X session stop working: You can’t start any programs anymore.

NetworkManager (what also make the little icon on GNOME/KDE desktops, pre-installed on Ubuntus et.al., developed by RedHat) uses dhclient to retrieve a hostname.

The magic words to add to your dhclient.conf are:

send host-name "hoot";
supersede host-name "hoot";

If you use pump (instead of dhclient), you shouldn’t have this problem, as it doesn’t set the hostname (see the man page).

A mailing list entry on this topic starts here: http://lists.freedesktop.org/archives/xorg/2004-August/002772.html

I already knew that the linux man pages contain documentation for a lot of the C-functions.

But I just found the info pages for glibc and using yelp (gnome help), entering

yelp file:///usr/share/info/libc.info.bz2

gives the C reference manual I always wanted!
Awesome.

For not getting confused with my emails, I use filters obviously.
For blocking Spam I use spamassassin. http://wiki.apache.org/spamassassin/
Both are integrated really nice in KMail, my favorite mail application.

Spamassessin is nice ’cause it’s actually software meant for mail servers. Thus I think the bayes and other stuff is quite good. Coolest thing is, I can also fine tune it:

The spam rating is based on scores given for the different tests run on the incoming email. As a user, you can create new test and set the scores for existant tests. If the sum hits a maximum (5 for me), it is flagged as spam. Cool feature in Kmail: You can see the spaminess (Spam score given by spamassessin)

My .spamassassin/user_prefs:

score DATE_IN_FUTURE_12_24      5
score HTML_MESSAGE              3.3
score MIME_HTML_ONLY            5
score MULTIPART_ALT_NON_TEXT    3
score GAPPY_SUBJECT             5
score FROM_EXCESS_BASE64        3
score FROM_HAS_ULINE_NUMS       3
score UPPERCASE_25_50           3
score UPPERCASE_50_75           4
score SUBJ_ALL_CAPS             2
body EVIL_WORDS         /(software|petroleum|casino|kurs|profit|symbol)/i
score EVIL_WORDS                2
describe EVIL_WORDS     evil_words
body EVIL_WORDS2        /(price|oil|bonus|prognose|borse|preis)/i
score EVIL_WORDS2               2
describe EVIL_WORDS2    evil_words2
body DOLLAR_SIGN        /[\$]/
score DOLLAR_SIGN       3
body PERCENT_SIGN       /[\%]/
score PERCENT_SIGN      3

The 25_50 stands always for percent.

Introduction: I’m talking about the weird things after opening a shell on stud4

stud4 has a ugly configuration. If you connect, you get a minimal shell. the locale is set wrong, so you see the following all the time:

 Warning! One or more of your selected locales are not available.
Please invoke the commands "locale" and "locale -a" to verify your
selections and the available locales.
Continuing processing using the "C" locale.

Also, vi is no fun, and vim doesn’t accept the extended keyboard (delete, end).

Here I want to provide some info how you can improve your comfort.

1: start bash. Way better than the default shell.

bash

2: set your locale (language and localization). This is also in which language the error messages for example are.

export LC_ALL="en_US.utf8"
#export LC_ALL="de_DE.utf8"

For example:

[e0123456@stud4:~]$ export LC_ALL="en_US.utf8"
[e0123456@stud4:~]$ man
Usage: man [-M path] [-T macro-package] [ section ] name ...
or: man -k keyword ...
or: man -f file ...
[e0123456@stud4:~]$ export LC_ALL="de_DE.utf8"
[e0123456@stud4:~]$ man
Syntax: man [-M Pfad] [-T Makro-Paket] [ Sektion ] Befehlsname ...
oder: man -k Schlüsselwort ...
oder: man -f Datei ...
[e0123456@stud4:~]$

3: allow backspace

stty erase "^?"

4: get a informative prompt (second is with color)

PS1="[\u@\h \W]\\$ "
PS1="\e[0;34m[${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~}]$ \e[m"

Example:

bash-2.04$ PS1="\e[0;34m[${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~}]$ \e[m"
[e0123456@stud4:~]$

List of colors and manual

If you want that in your startup, write the following into your .bashrc

#!/bin/bash
export LC_ALL="en_US.utf8"
#export LC_ALL="de_DE.utf8"
stty erase "^?"
PS1="\e[0;34m[${USER}@${HOSTNAME%%.*}:${PWD/#$HOME/~}]$ \e[m"

Now you may wonder, how can I write that easily in the freaking file?

pico .bashrc

To set pico, vim, xemacs or whatever your default editor (so "crontab -e" and other commands call it), use:

export EDITOR=pico

Another funny thing is XForwarding. Try this:

ssh e0123456@stud4.tuwien.ac.at -X
bash
xemacs

Ta-daa! A fat graphical editor. Of course only if you use X.
Also funny commands you can play with: xload, xbiff++, xclock, etc.

Really useful on the stud4 server is the script quotax:

[e0123456@stud4:~]$ quotax
Disk space limits on stud4:
---------------------------
Total disk space in home directory:   200 MB
Minimal free space for mail delivery:  10 MB
Maximal capacity of inbox folder:      50 MB
Disk usage summary for user e0123456:
-------------------------------------
Used disk space in home directory:  186.0 MB [93.0 %]
Free disk space in home directory:   13.9 MB [ 7.0 %]
Number of messages in inbox folder:  213
Size of inbox folder:                 2.0 MB [ 4.0 %]
Free space for incoming messages:     3.9 MB
WARNING: Remaining disk space in home directory is very low.
-------> There is not much space left for files and incoming mails.

At the end, some useful bash and vim tips for these crippled terminals:

bash:
Ctrl-A: begin of line
Ctrl-E: end of line
Ctrl-W: delete last word
vim: (watch out if you are in edit or command mode)
:dl      Delete letter
:dw    Delete word
:dd     Delete line
:wq    Write & quit
:q!      Quit without writing or anything

It is always worthy reading the according manuals (probably not on HP-UX, but on a linux machine or man-pages on the internet).

That’s it. Try things, don’t break things, and have fun.

Everyone says, backups are important, but how do you backup? And have you ever tried replaying a backup?

My backup plan:
- Working copy on my laptop
- Compressed archive is created every week. I delete old backups infrequently.
- Infrequent rsync of working copy (filtered) to USB stick.
- rsync of working copy (filtered) to the university servers.
- Compressed archive copied to the university server.

I would say I’m quite secure …

Crontab entry: 0 */4 * * * cd backup && sh backup2.sh

#!/bin/bash
PARENT=/mnt/daten/Daten/
DIR=Studium/
SELDOMCHANGE='*.zip *.ps *.pdf *.rar *.tar.* *.jpg *.gif *.png'
BORING='*.log *.out *.xac *~'
LARGESERVER=a0123456@login.unet.univie.ac.at
SMALLSERVER=e0123456@stud4.tuwien.ac.at
SERVERS="$LARGESERVER $SMALLSERVER"
cd $PARENT
# part A:
# compress some file types that change seldom and send them over once a month
# that would be zip, ps, pdf, rar, tars, images,
FILENAME=Sicherungen/Full/seldom-changed-types-$(date +%W).tar.bz2
TARGETSERVERDIR=$LARGESERVER:Sicherungen/Full/
# create archive if it doesn't exist yet
[ -s $FILENAME ] || \
echo 'creating weekly archive' &&
find Studium -type f $( for i in $SELDOMCHANGE ; do echo "-iname" "$i" "-or"; done) -false | \
tar --create --bzip2 "--verbose" "--files-from=-" "--file=$FILENAME"
# lets sync that to the server
# commented out: files ~ 500MB :-(
#echo 'rsyncing weekly archive to server'
#rsync $FILENAME $TARGETSERVERDIR
# part b
# rsync the others
#
for SERVER in $SERVERS
do
echo 'rsyncing with ' $SERVER
TARGETSERVERDIR=$SERVER:Sicherungen/Studium/
for i in $SELDOMCHANGE $BORING; do echo "- $i"; done | \
rsync -az --checksum --delete-excluded --exclude-from=- $PARENT/$DIR $TARGETSERVERDIR
done
echo 'backup done.'