Linux Blog

Here are some tips for working in the shell that I use on a daily basis. These may be known to most veterans, please contribute your favorite shortcuts to the comments. But for the most part this is not for the uber leet Linux geek, this is for those new to the terminal.

TAB
- Gives you suggestions / completes stuff for you. Type a, Press it twice, it will make your life a lot easier.

ctrl+w
- Remove word behind cursor.

ctrl+u
- Undo / Erase everything from cursor to beginning of the line

!!
- Type out whatever you typed out last, can be combined with tools like sudo

alt+f
- Go forward to the end of the previous word

alt+b
- Move cursor back to the beginning of the previous word

ctrl+d
- You’re done? Press ctrl+d to logout. If you’re in a virtual terminal, it may also close the window.

ctrl+z
- Stop the current process. Say you run gvim, and then you want to spawn another process. Press ctrl+z, then type bg. Once you’re done with the “other” process, you may type fg to bring it back into the foreground.

So, this morning, when I got to work and booted up, I noticed something was wrong. My machine was not running as usual. It turns out, packagekit was sitting there being a general pain. I just wanted to look busy, so I killed the process. Turns out that wasn’t such a good idea, since it didn’t finish doing whatever it was doing and caused an ugly error like this:

rpmdb: Thread/process 28373/3077981888 failed: Thread died in Berkeley DB library
error: db4 error(-30975) from dbenv->failchk: DB_RUNRECOVERY: Fatal error, run database recovery
error: cannot open Packages index using db3 – (-30975)
error: cannot open Packages database in /var/lib/rpm
CRITICAL:yum.main:

Error: rpmdb open failed

rpmdb: Thread/process 28373/3077981888 failed: Thread died in Berkeley DB library
error: db4 error(-30975) from dbenv->failchk: DB_RUNRECOVERY: Fatal error, run database recovery
error: cannot open Packages index using db3 – (-30975)

Naturally, I tried using rpm, do try and fix things, since it indicated something to do with a database I tried:

[owen@linuxblog ~]$ sudo rpm –justdb
rpm: –justdb may only be specified during package installation and erasure
[owen@linuxblog ~]$ sudo rpm –rebuilddb
rpmdb: Thread/process 28373/3077981888 failed: Thread died in Berkeley DB library
error: db4 error(-30975) from dbenv->failchk: DB_RUNRECOVERY: Fatal error, run database recovery
error: cannot open Packages index using db3 – (-30975)

Well, it turns out that those options don’t work, and the rebuilddb gave an error about the db4 being corrupt. Well, I decided to go into /var/lib/rpm as the other error had that directory and found the db4 files. Running db45_recover sounded like it might work, so I gave it a shot.

[owen@linuxblog rpm]$ db45_recover -h /var/lib/rpm/
db45_recover: unlink: /var/lib/rpm/__db.003: Permission denied
db45_recover: unlink: /var/lib/rpm/__db.004: Permission denied
db45_recover: unlink: /var/lib/rpm/__db.000: Permission denied
db45_recover: unlink: /var/lib/rpm/__db.002: Permission denied
db45_recover: unlink: /var/lib/rpm/__db.001: Permission denied
db45_recover: /var/lib/rpm/log.0000000001: log file unreadable: Permission denied
db45_recover: PANIC: Permission denied
db45_recover: DB_ENV->log_newfh: 1: DB_RUNRECOVERY: Fatal error, run database recovery
db45_recover: dbenv->close: DB_RUNRECOVERY: Fatal error, run database recovery

That’s right,you need to be root for this bad boy:

[owen@linuxblog rpm]$ sudo db45_recover -h /var/lib/rpm/

The above seemed to fix it for now. I guess next time I’ll think about it more before I start slaying processes on a Monday morning.

At an average of around $20 per DVD* most can’t afford to have any of their DVDs lost, stolen or broken. Backing them up is a touchy subject depending on who you talk to, but here is how to do it anyway.

Backing up a DVD on Linux used to be much harder than it is with K9Copy. No more flaky DVD Shrink crashes under wine. K9Copy takes the hassles out of creating backups of your DVDs under Linux. As the name implies it is KDE software but works well under gnome provided you have the needed libraries installed.

It has many options to backup and really is pretty comparable in functionality to the infamous DVD Shrink for Windows. Take a look at the screenshots and give it a try yourself:

* 2007 US Entertainment Industry Report (www.mpaa.org/USEntertainmentIndustryMarketStats.pdf)

One of the things that has irritated me about the persistent USB thumb drive installs is the “Press Enter” to continue prompt on shutdown. Luckily, if you have persistent working correctly, the fix for this is easy.

Open up /etc/rc0.d/S89casper
Search for ENTER and the shutdown string “Please remove the disc and close the tray (if any) then press ENTER: ” > /dev/console”
For me, this was on line 89. Comment out, that line and the lines down to the ending bracket for the do_stop() routine.

Reboot, and see if you have that annoying message, if not you’re good to go.

For Halloween this year every department at work was asked to carve or decorate a pumpkin. Since I’m in IT I thought I’d take the task of decorating our pumpkin with something IT related that would scare the crap out of everyone. Most of our end users are actually Windows users, so this pumpkin should be especially scary to them.

I introduce the B.S.O.Dkin, yes it’s a B.S.O.D pumpkin

B.S.O.D Pumpkin.

I’d like to say it looks better in person, but it really doesn’t. I don’t really have an artsy knack for carving or painting pumpkins or I could have done something a lot better.

I guess my “Halloween Costume” is a blue Mexican wrestlers mask, blue t-shirt, and jeans to complete the B.S.O.D theme. With as much hate as I’ve been giving Microsoft recently I’m going to have to keep my fingers crossed for no kernel panics. Karma might bite me.

This is not really “shell scripting” but the end result is some more bash scripts in my bin directory so what the hell? It’s going in the shell script section because its Sunday. So what?

I like to listen to music on my Windows box while I work on my Linux box. Online radio and other sounds, just get in the way too much. One of the things I wanted to do for a while was remotely control my volume so I didn’t have to use my KVM to switch over to change the volume when ever anyone came in my office.

Its actually pretty easy to control your windows volume from Linux.

At first I thought, I’d create a dummy audio device, and some how map it over. Then I figured that was overkill and I’d try something a bit easier. I have SSH via Cygwin, so all I needed was a way to control the volume locally, and I could execute the command with SSH. Having no volume utilities jump at me when I looked through the Cygwin repositories I went to look for something else.

NirCmd is an awesome utility, giving me and other Windows users the ability to do things that Linux users may take for granted, you can read about it here: http://www.nirsoft.net/utils/nircmd.html after installing it, and making sure that my corporate AV didn’t throw a hissy, it was just a matter of dumping some scripts in my bin directory and chmodding them so they would run.

Here is what they look like:

Volume Down Script: ssh windowsbox -l owen -C “nir changesysvolume -2000″

Volume Up Script: ssh windowsbox -l owen -C “nir changesysvolume 2000″

Mute: ssh windowsbox -l owen -C “nir mutesysvolume 1″

Unmute: ssh windowsbox -l owen -c “nir mutesysvolume 0″

Real simple, and the mute/unmute really comes in handy for when some one walks into my office.

This is how I quickly set up the Red5 streaming server for testing and evaluation. It worked on Fedora 11 and older Fedoras, and it might work on other distributions, or it may not. Here’s how I did it.

Downloaded the latest Java JDK:

(Read on …)

I’m not normally one to just flat out bash Microsoft or trash them for their flaws, but sometimes I do enjoy a good Microsoft Joke.

Here are I know off the top of my head:

Q: How many Microsoft Engineers does it take to change a lightbulb?
A: None its obviously a hardware problem
—

A helicopter was flying around above Seattle when an electrical malfunction disabled all of the aircraft’s electronic
navigation and communications equipment.

Due to the clouds and haze, the pilot could not determine the helicopter’s position. The pilot saw a tall building,
flew toward it, circled, and held up a handwritten sign that said “WHERE AM I?” in large letters.

People in the tall building quickly responded to the aircraft, drew a large sign, and held it in a building window.
Their sign said “YOU ARE IN A HELICOPTER.”

The pilot smiled, waved, looked at his map, determined the course to steer to SEATAC airport, and landed safely. After
they were on the ground, the copilot asked the pilot how he had done it.

“I knew it had to be the Microsoft Building, because they gave me a technically correct but completely useless answer!”

They’re terrible I know… Terribly *FUNNY*. Post your favorite Microsoft Jokes in the comments or tweet them to @LinuxBlog and I’ll include them here.

Sometimes when using grep it’s nice to be able to search for more than one string in a file. It’s actually pretty easy to do, if you can remember the simple syntax. Basically, you pipe the terms together in double quotes and escape the pipe.

grep “gnome\|kde” install.log

The above example will search for gnome or KDE. It works for more more than one term, and also works with the invert match -v option, to exclude lines that include gnome or kde.

Todays article extra short, and late, but better late and short than none at all I guess.

Thanks MG for giving the tip on some free issues of BSDmag / Linux+. When I went to check them out they were older articles (Fedora 6) on Linux but some interesting topics and still some relevant information. The BSD issues were newer. If your interested in the articles, you can read the comment on the Tether iPhone through the cable, on Linux post, or hit the jump. Here is a list of the free issues:
(Read on …)

So you got an iPhone huh? perhaps you’ve got an SSH client and maybe you jailbroke your iPhone and have done some iPhone wifi tethering (That’s not the best way, and not free), but have you been able to use SSH through the cable? Me neither until a little while ago.

The benefits of connecting by the cable are slightly obvious to anyone who wants to do it:

BATTERY!
With your phone plugged in, you’ll get better battery life, or perhaps just prevent the battery from getting discharged any further.

No Wifi Setup
This was really the biggest problem for me, having to reconfigure wifi on my laptop then getting the laptop and phone to talk. Some times wireless connections mysteriously dropped or just acted plain funky. Any one who’s ever typed in a WEP key on the iPhone also knows what a pain it is, so not having to use Wifi is a plus.

Privacy
Since the cable is used, there should be no wireless network for others to fool around with.

Data Transfer Rates
I have not yet confirmed this, mostly because I’m lazy, partly because I don’t have the time to produce any stats but, 480Mbps with USB2.0 Vs. a theoretical 54Mbps on 802.11G

Enough already, how do I do it?
Thanks to Jing Su there is a LGPL’d piece of software called itunnel that can be found here. Installing itunnel will vary by distribution. It’s fairly straight forward on Fedora, provided you have the library libiphone installed you should be able to download, untar, make, and run.

Once you’ve installed itunnel, you run it by using:

sudo itunnel <port>

If you don’t specify a port it listens on port 3023.

Connect to localhost using your normal SSH Socks proxy method -D <port> and your username, default being mobile with your new port.

 ssh -D <yourport> -p 3023 mobile@localhost

Type “Yes” to accept the fingerprint (you may need to eventually change your fingerprint when you upgrade your phone) and then type in your password which should NOT be “alpine”, because you did change it right?

Once you’re SSH’d in, you can set up your browser to use the socks proxy as you would with Wifi tether version on the port you specified with -D.

There you have it, a way to Tether your iPhone through the cable on Linux! Rumor, (well not really a rumor, since I’ve used itunnel.exe) has it that this also works with a Windows box, just try to find a non-virus infected version of the iTunnel suite.

Happy Hacking!