I believe every system administrator is used to open source by now. From Apache to Firefox or Linux, everyone uses it at least a little bit.
However, most open source developers are not good in marketing, so I know that there are hundreds of very good tools out there that very few people know.
To fill this gap, share your favorite open source tool that you use in your day-to-day work.
*I will post mine in the comments.
LyX - The Document Processor
nc: Along with dd it can do wonders in data transfers. We can cloned harddisks/partitions piping nc, gzip and dd together.
dvdisaster: It is really nice tool to create error correction code of CD/DVDs. The ecc occupies much less space then actual disk and even when both ecc and original disk are corrupted (a little) we can still get original data back.
htop: It is way cooler then top as it uses ncurses to show things in nice colors and supports mouse.
tcptrack: It can be used to see live tcp sessions as th4y are getting created and closed. It can sort connections by speed. So you can see where is most of the bandwidth going.
iptraf: It can be used to monitor lot of network interfaces at once to see how much they are being used.
fdupes: It can help in finding duplicate files.
mail-notification: It gives nice pop-up with sound near notification area when new email comes to any of the configured accounts.
kompare: It can give visual diff of two files. You will have to use it once on two similar text files to really understand what I mean by visual diff. My favorite is to compare zone files of primary and secondary DNS to ensure they are consistent.
convert: It is very useful in converting from one image type to another. Specially to eps for Latex documents.
dos2unix / unix2dos: These help in changing files ending with '\r\n' to '\n' and vice-versa. Life saver for cross-platform developers.
indent: If you use vim for coding and do not want to indent some code file by hand. This is really good.
Doxygen: For generating documentation if written in javadoc files for source file in any language.
gftp: This is graphical client for ftp, ssh, http file transfers. It allows resume and asks for conflicting files whether they should be overwritten, resumes, skipped etc.
FileZilla: Similar to gftp above. But it also allows parallel connections to various sites.
Wireshark: I cant say that it is not famous. But it is extremely useful tool that I have used many many times to debug network problems. It is a must for every network administrator.
phpMyAdmin: It can be used to manage MySQL database using web browser from any where very easily. Best part is export options to various formats and easy backup and restore options.
phpPgAdmin: Similar to phpMyAdmin, although not as powerful as phpMyAdmin but it does make life easier.
p7zip: Really nice compression and very helpful in case formats zip / rar are blocked for some reason.
k3b: Really good at burning CD/DVDs. We can burn ISO images or create multi-session data DVDs. We can control what OS support is necessary and whether to use extensions like joilet, rocket ridge etc.
kile: Really nice editor for LaTeX documents. It supports good shortcuts for making dvi, ps, pdf etc and compiling and previewing only selected portion of text
I'm afraid that mine are all not very famous and minimalistic, but I live happier since I use them:
Sup - mutt-like console e-mail written in Ruby
wmii - minimalist window manager controlled by a filesystem exported with 9P
Vimperator - firefox plugin to provide a vim-like web brower
MCabber - console mode jabber client
pwsafe - command-line password keeper
AfterGlow - graph-generation from CSV files (for security visualization)
tcptraceroute - traceroute implementation using TCP packets.
pdftk - If PDF is electronic paper, then pdftk is an electronic stapler-remover, hole-punch, binder, secret-decoder-ring, and X-Ray-glasses.
imapfilter - Delete, copy, move, flag, etc. messages residing in mailboxes at the same or different mail servers
PhpMyAdmin--a tool written in PHP intended to handle the administration of MySQL over the Web. Currently it can create and drop databases, create/drop/alter tables, delete/edit/add fields, execute any SQL statement, manage keys on fields.
Blat! - A neat little SMTP email sending util - write a script around it to send test emails etc
The Apache Foundation's ActiveMQ.
I replaced a commercial MQ with it two years ago. It is blazing fast, has lots of HA capabilities and an excellent features list. It is not always easy to configure, but the licensing on the commercial one was starting to look like a pretty decent salary. Time to go open source!
My favourites that haven't been mentioned yet:
And of course all of the unsung heroes of the *nix command-line world like grep, bash and of course man.
Subversion - THE best revision control system ever.
My favorite sysadmin tools are:
Many of the ones I use have been mentioned but amongst the list of things I always add to a new system:
m4 macro-processor makes adding boilerplate text to config files (and web pages) simple
tidy W3C tool to validate (X)HTML
and, though not in the 'not famous' category in its usual role, I'll risk adding this for its use not as a programmer's tool for software generation but for document and configuration management:
make to simplify maintaining documentation and configs: great with m4 and a good VC system: add an editor of your choice (and not forgetting awk and sed :-)
At home, everything is open source, but at work (a Microsoft shop) these are the tools I use on a regular basis...
Performance Analysis of Logs (PAL) Tool - powerful tool that reads in a performance monitor counter log (any known format) and analyzes it using complex, but known thresholds (provided).
PolyMon - monitoring solution that can be used to generate email alerts and analyze historical trends of monitor counters and monitor statuses. It is based on the .NET 2.0 framework and SQL Server 2005.(I like the Powershell support.)
WinSCP - SFTP client and FTP client for Windows.
TortoiseSVN - easy to use Revision control / version control / source control software for Windows. It is based on Subversion. TortoiseSVN provides a nice and easy user interface for Subversion.
WinMerge - differencing and merging tool for Windows. WinMerge can compare both folders and files, presenting differences in a visual text format that is easy to understand and handle.
AxCrypt - file encryption software that integrates seamlessly with Windows to compress, encrypt, decrypt, store, send and work with individual files.
Other favorites already mentioned; Notepad++, PuTTY, TrueCrypt, gVim, Wget, Blat, PDFCreator, Wireshark, Subversion.
Many tools that I am using on a daily basis were already mentioned. bwm-ng anyone ? It is little live bandwidth monitor.
I'm a huge Puppet fanboy myself, and Systemimager has made my life SIGNIFICANTLY less hateful since I started with it ~2 years ago. iperf is a nifty bandwidth-assessment/troubleshooting tool, and of course the venerable tcpdump!
Chef - a configuration management framework written in Ruby, using a Ruby DSL as a configuration language.
Great Groupware Suite !
For network monitoring and behavior analysis and forensics I would highly recommend Argus (http://www.qosient.com/argus/).
Anyone mentioned Scapy yet? Very cool packet manipulation in python (and perl, but haven't used ScaPerl).
It's a pain to set up, but once it's running it's incredibly useful for monitoring anything on your network over time. Unlike tools like Nagios which focus on showing you the status of your systems right now, Cacti is designed specifically for graphing historical data. This is very handy for noticing subtle trends (a slowly filling hard drive, or a gradually warming server room as the AC starts to struggle), or identifying what has changed, and when (this server's load has spiked every day at 2 PM ever since we installed that new software).
It can easily monitor any data that can be collected with SMTP, and with just a bit more work can monitor any data that can be collected by a script at more-or-less-regular intervals.
atop a top like system monitor, but much better.
It makes it easier to spot the bottleneck (hdd, mem, net or cpu).
For me it would be:
poedit - cross-platform gettext catalogs (.po files) editor
ncftp - a very nice ftp client
htop - an interactive process viewer for Linux
nmap - Security Scanner For Network Exploration & Hacking - invaluable detecting all these firewall problems
wireshark - network protocol analyser for Unix and Windows - fantastic tool to trouble shoot networking problems, to learn how protocols work or to recover some passwords, and much, much more
inkscape - a Vector Graphics Editor, that focuses on SVG Compliance
mtr - My Traceroute, included with most Linux distros but I keep running into folks who haven't heard about it. It's a traceroute/ping mashup, checking every hop of a traceroute continuously and giving you real time stats. You can spot packet-dropping routers and high-latency connections within seconds.
Courier - it's a bit of an also-ran in MTAs, but I think it deserves a higher profile. I find it much easier to configure than any of the others and seems to avoid most of the personality quirks of them, too (e.g. qmail's inability to locally relay).
Nice applications you have stated all, but you definitely need to take a look at this XINE-mplayer and SugarCRM the best collaborative and CRM app
screen - it makes a command line an entire world.
I'd like to mention:
bash Not obvious but (ls -la,ps auwxf,df -h,du -sh,..) are rather useful GPG Thunderbird Dovecot exim perl apache munin RRDtool bind ntpd clamAV SpamAssassin mySQL svn Asterisk pidgin (all the way back to Mark "Asterisk" Spencer) xmpp (ok it is a protocol, but it is open)
collectl is a very good utility similar to vmstat. But it offers much more options and even supports subsystems like InfiniBand or Lustre. Highly recommended!