iotop

iotop is a very neat tool showing the processes which do the most i/o in a top-like manner. Again having fun with SLES: SLES-10: # rpm -i /tmp/iotop-0.3.2-1.1.x86_64.rpm warning: iotop-0.3.2-1.1.x86_64.rpm: Header V3 DSA signature: NOKEY, key ID ee454f98 error: Failed dependencies: python >= 2.5 is needed by iotop-0.3.2-1.1.x86_64 Goes off and installs SLES-11 SLES-11: # rpm -i warning: /tmp/iotop-0.3.2-1.1.x86_64.rpm: Header V3 DSA signature: NOKEY, key ID ee454f98 error: Failed dependencies: python < 2.
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Spot the problem

An unofficial rpm of e2fsprogs installed on a SLES 10 system: # ldd /sbin/e2fsck libdb-4.3.so => /usr/lib64/libdb-4.3.so (0x00002b5e004e2000) libpthread.so.0 => /lib64/libpthread.so.0 (0x00002b5e006d6000) libc.so.6 => /lib64/libc.so.6 (0x00002b5e007ef000) /lib64/ld-linux-x86-64.so.2 (0x00002b5e003c6000) Now guess what happens when you reboot?
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nss-ldap

The nss-ldap module allows you to have your user information in a LDAP server. Within the module you can select some options on how to connect to the LDAP server: hard, use an exponential back-off when connection, waiting up to 64 seconds before trying a different server. soft, when the server is not responding give up immediately. The problem is, both are insufficient… With soft you don’t have any benefits for your backup LDAP server.
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KPN Dongle with Ubuntu

Well, as I’m off to The Hague for the rest of the year, I need some kind of Internet in the evening. So off to KPN to get a umts card (or dongel as they call it). For late night gaming I’ve also bought a PSP :-) Well, to make a long story short: this stuff is hard to get working in Ubuntu. When you insert the dongle it is first seen as a cdrom…, only after you successfully install the Windows software it will become a modem.
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Monit and Munin

After trying out Zabbix, I’m back to munin and monit for my (small) monitoring needs. I think the beautiful rrd images of munin are just unbeatable and monit has never let me down; you can easily restart daemons - something I was still configuring in zabbix. And our Ubuntu Certified Professional Course also has a few slides on munin. This was the last push I needed. I was still a bit rusty so I just followed a howto to do the initial configuration.
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Ubuntu Karmic

Well, a lets-install-kernel-2.6.31-on-Ubuntu-Jaunty turned out to be a bad idea. The kernel install went OK, but my X went poef. No more bitmap fonts. Looks like some bad interaction between the X Intel driver and the new kernel mode settings. Anyhow, I figured why not upgrade to Karmic? 15 minutes later my desktop system was completely hosed and I was left staring at a GRUB 1.97 menu. I never knew that the GRUB command line allows you to type
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Remote commands with Zabbix actions

With monit services are restarted, ever since I’ve installed zabbix I wanted the same functionallity. Turns out this is possible, but it takes some configuration. Also see the zabbix manual, where it gets interesting from page 160 onwards. In zabbix go to Configuration->Actions. Add a new ‘Action Operation’ in which you want to run a remote command. Operation type: remote command Remote command: host:script in my (test) case elektron:/home/miekg/bin/zabbix_service {TRIGGER.NAME}: {STATUS} And zabbix_service is now a shell script which will echo its arguments to a file in /tmp.
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Brace yourself

The shell (in this case bash) is packed with features. So much so that you will probably never ever learn them all. Brace expansion is one of those things. What is it? In the bash manual it says: Brace Expansion Brace expansion is a mechanism by which arbitrary strings may be generated. This mechanism is similar to pathname expansion, but the filenames generated need not exist So what is it? You can make your shell generate strings, like so:
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EeePC Linux install

Just bought anothor EeePC, this time the 900HD variant. Installing Ubuntu as we speak and giving Windows the boot. The 4 minute encounter with Windows XP (which felt like 4 hours) gave me the impression of a fast machine. This was just a quick peek to see if the hardware was working. Going with Ubuntu 9.04 - then removing Pulseadio and (maybe) upgrading the kernel to 2.6.30.4. The trick is to disable the hardisk in the BIOS and to disable all quick boot stuff in there too.
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Git filtering

Excellent idea Ton! How to make a custom filter in git to expand the string $Hash$ to something more usefull, ala the $Id$ (which git already supports), but then with more info (committer, date, etc.). Which also helped in this case was the Pro Git book which is, as of now, a must buy. But as always is the case between Ton and me, I find his scripts too long :-) So I miekified his solution.
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Bash shell scripting and octal values

While rechecking my rdup test-suite one of the tests failed. On closer inspection it was due to the following line: DAY_BEFORE=$(( $(date +%d) - 1 )) When $(date +%d) is 10 this yields: $ DAY_BEFORE=$(( 10 - 1 )) $ echo $DAY_BEFORE 9 Also with octal values (those starting with a leading zero), it also works: $ DAY_BEFORE=$(( 06 - 1 )) $ echo $DAY_BEFORE 5 So when does this go wrong?
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Performance plotting with atop and Gnuplot

A customer wanted some performance figures for a ESX cluster we built. We used our own atop and the trusted workhorse of plotting Gnuplot to make some performance plots. Creating the data As said, we used atop for this, it has a nice data gathering mode which prints out lines like these: 13:40:07 cpu %usr %nice %sys %irq %softirq %steal %wait %idle 13:40:08 all 0 0 0 0 1 0 4 95 13:40:09 all 0 0 1 0 0 0 0 99 We were interested in the values of %usr, %sys, %irq + %softirq, %wait and %idle.
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How to mess up git

So you think you know git… today I found out something “funny”. In a git repository: $ git log $ fatal: object 1fcc8de9361c56e538ff35d8cc4b07a9c95b7bf3 is corrupted Okay, WTF? Lets look in the .git directory: $ cd .git/objects/1f $ ls -l total 4 -r--r--r-- 1 root root 1057 2009-06-23 19:03 03db070bcb47bff3f8106f2ec7028b3496aaa8 -r--r--r-- 1 root root 0 2009-08-03 21:41 cc8de9361c56e538ff35d8cc4b07a9c95b7bf3 Ah, 0 bytes, that explains it (probably due to the weird reboot of last night and ext4).
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Die Pulseaudio, die die die!!!

Finally made the switch to jackd which works so much better than Pulseaudio. Ubuntu did not make this easy, but with some perseverance it works. One of the things I really hate about Pulseaudio is that when I click on a new song in audacious it would take about 1 second before the audio stabilized. Also with flash audio would stutter for the first few seconds. First (if you don’t care about gnome-desktop):
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Ssh escape key

Yes, what a nice post on ssh escape keys. So you need to press <enter> and then ~ for the escape character to work!
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Case insensitive cd

Do I want this? % ls -ld Joe_Cocker_-_The_Definitive_Collection drwxr-xr-x 2 miekg admin 4.0K Jul 20 22:20 Joe_Cocker_-_The_Definitive_Collection/ % cd *joe* cd: no such file or directory: *joe* % unsetop case_glob % cd *joe* % pwd /shared/vol/music/J/Joe_Cocker_-_The_Definitive_Collection
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SRM with KVM and DRBD

Currently we are building a fairly rock solid high availability cluster for a client. This has the “usual” ingredients: two locations, two NetApps, two clusters of three vmware ESX servers and a bunch of virtual machines running on top of the ESX servers. Also included in the mix is a VDI (now called View) virtual desktop infrastructure for running virtual windows XP clients. This is all managed by SRM (site recovery manager) and it is almost working.
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ZFS and Oracle

I already knew (Open)Solaris sucks, but now Ton has also figured it out. ZFS definitely does not suck. Why not petition Oracle to GPL(v2) ZFS? Especially now Oracle wants to kill OpenSolaris?
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Kernel logs

So, there I am browsing my logs. BAM [650521.310292] INFO: task mysqld:2730 blocked for more than 120 seconds. [650521.310320] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [650521.310364] mysqld D 00000000 0 2730 2674 [650521.310367] f6183ce0 00000086 c06ef6cc 00000000 f61c8c70 7834922a 00000dc2 00020050 [650521.310373] 00000296 c0796fe0 c0796fe0 f61c8f04 c2c35fe0 00000003 9500b16e 00024f83 [650521.310379] 00000002 00000002 f66bb500 f6d02e40 c2bf2090 f6e2e680 f6183ce8 c050eb68 [650521.310384] Call Trace: [650521.310388] [<c050eb68>] schedule+0x8/0x20 [650521.310391] [<c0266701>] do_get_write_access+0x2a1/0x3d0 [650521.310395] [<c0127d93>] ?
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Playing with dhcpd

Yes! At work today we made dhcpd crash on a /etc/dhcpd.conf :) We were working towards the following (now working) setup: class "igel" { match if binary-to-ascii(16, 8, "-", substring (hardware, 0, 5)) = "1-0-e0-c5-67"; } pool { allow members of "igel"; range 192.84.30.161 192.84.30.170; # igel[0-9] } But while figuring this out, dhcpd went boom :) [root@vmaster cfengine]# dhcpd -d -f -cf hosts/vnet/etc/dhcpd.conf Internet Systems Consortium DHCP Server V3.0.5-RedHat Copyright 2004-2006 Internet Systems Consortium.
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Making a library

We (my wife and I) have a lot of books, currently some 637… $ sqlite3 biblio.db 'select count(*) from books' 637 But we seem to loose books occasionally because we lend them to people and forget about it. So Linux (and Perl) to the rescue. I already own a bar code reader to read the ISBN number of books and then I use Google to give the author, genre, etc. (fully automated of course).
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Full file system and I/O redirection

This is an English translation of a blog item I wrote for AT Computing While giving a course a student showed me the following: $ ps -ef > /tmp/file Where /tmp is 100% filled yields no errors and seems to have worked! Lets try to see what is going on here. Firstly, lets fill up a file system. We are going to use an fs mounted under /media/disk: $ cp /dev/zero /media/disk/HUGE $ cp: writing `/media/disk/HUGE': No space left on device Further we need a little program to test a few things:
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2.6.30 and Ubuntu Jaunty

Well, thanks to Ubuntu I’m now running the new (new!) 2.6.30 kernel on my systems. No ill effects as of yet… Btw, I’ve written the following script to download the latest kernels from Ubuntu: SYNOPSIS: latest 29.4, this will fetch 2.6.29.4 or latest 30 which will get 2.6.30. #!/bin/bash # download the latest ubuntu mainline kernels ubuntu="http://kernel.ubuntu.com/~kernel-ppa/mainline/" version="2.6.$1" # need 29.n as argument arch="i386" # or amd64 major=${version%.[0-9]} minor=${1%.[0-9]} patch=${version#2.6.*.} [ -z "$1" ] && { echo -e "Usage: $0 MINOR\n$0 29.
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Group policy in Linux

Suppose you want to limit access to some servers, only people member of a specific group (or multiple groups) may log in. The following is one way to tackle this. In this example I will configure ssh access in such a way that only people from the admin group can login. The nice thing is that this will work regardless of any Kerberos or LDAP usage. Preparation In /etc/pam.d find the “service” which you want to add a group policy to.
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Kerberos

Mental note to self Having a host listed in a listprincs output isn’t enough to have single-sign-on working. You have explicitly add it with ktadd host/your.host.com So in my case: # kdadmin.local .... kadmin.local: addprinc -randkey host/charm.atoom.net ... kadmin.local: quit And then you can do a (on charm.atoom.net): % kinit Password for miekg@ATOOM.NET: % slogin elektron.atoom.net And have a password-less login to my server.
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Zsh prompt updates

I wanted some git information in the prompt I currently have. While thinking and googling about this, a quote on Bart’s log got me thinking. I don’t need to see my current host, nor do I need to see my current user name. I always login under my own account (miekg) and if I do change accounts, I probably will be forced to use bash. So showing the current user name is quite useless.
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mkfs.ntfs /dev/sdc1

Oh my God — why?? This is a 250 GB disk with a USB2 interface, so I’m in for a long wait apparently. # mkfs.ntfs /dev/sdc1 Cluster size has been automatically set to 4096 bytes. Initializing device with zeroes: 4% It this the Windows-way or is mkfs.ntfs a little bit brain dead?
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New teletekst script

I’ve update the teletekst script a little. It now outputs utf8 and uses LWP::Simple so no external commands are called anymore. You can find it here.
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KDE XFCE rocks

I could not agree more with Christoph Haas. I’ve tried KDE briefly during the last 6 months or so, but it never really stuck. Some observations. I’ve bought an EeeBox (Dual Atom, with 1 GB of ram), boy, how slow is KDE. Do I really need a Vista capable machine to run KDE? I like my current (XFCE) desktop. Why? Because it’s nice and clean. I have no use for desktop icons.
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Resize RAID1 array without knowing which disk is which

I want to grow my RAID1 array from 2x250GB to 2x500GB. The following resource has helped my a lot. Update It all worked, allthough the kernel decided to crash during the offline ext4 resize. But I finally have my extra disk space % df -h | grep md6 before: /dev/md6 77G 67G 6.7G 91% /vol after: /dev/md6 306G 67G 224G 23% /vol Now to my problem/solution: On Linux you often have the following problem: You are looking or touching some piece of hardware and you are asking yourself: “is this card eth0 or eth1?
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