While trying to install Grub on some old freebsd (6.2-RELEASE) I encountered following problem:

[root@host /usr/ports/sysutils/grub]# grub-install hd0
Probing devices to guess BIOS drives. This may take a long time.
/dev/twed0s1a does not have any corresponding BIOS drive.

Anyway, grub still can be installed there using following commands:

grub> device (hd0) /dev/twed0

grub> root (hd0,a)
 Filesystem type is ufs2, partition type 0xa5

grub> setup --stage2=/boot/grub/stage2 (hd0) 
 Checking if "/boot/grub/stage1" exists... yes
 Checking if "/boot/grub/stage2" exists... yes
 Checking if "/boot/grub/ufs2_stage1_5" exists... yes
 Running "embed /boot/grub/ufs2_stage1_5 (hd0)"...  16 sectors are embedded.
succeeded
 Running "install --stage2=/boot/grub/stage2 /boot/grub/stage1 (hd0) (hd0)1+16 p (hd0,0,a)/boot/grub/stage2 /boot/grub/menu.lst"... succeeded
Done.

grub>

I use CFengine for automation of different taks like copying config files from one place to nodes, reloading services after this, etc. And recently i configured it to check and install packages for different boxes depending on their role. For example, if box acts as web node, following packages need to be installed: apache2, apache2-mpm-prefork, libapache2-mod-php5, etc

So i added into control: section following lines:

    debian|ubuntu::
        DefaultPkgMgr = ( dpkg )
        DPKGInstallCommand = ( "/usr/bin/apt-get -y install %s" )
        DPKGRemoveCommand = ( "/usr/bin/apt-get -y purge %s" )
    gentoo::
        DefaultPkgMgr = ( portage )
        PortageInstallCommand = ( "/usr/bin/emerge --nocolor %s" )
    centos::
        DefaultPkgMgr = ( rpm )
        DPKGInstallCommand = ( "/usr/bin/yum -y install %s" )

Not sure about gentoo/centos though. And after that, listed required packages in packages: section:

    nodes.(debian|ubuntu)::
        apache2 action=install
        apache2-mpm-prefork action=install
        libapache2-mod-geoip action=install
        libapache2-mod-php5 action=install
        php5 action=install
        php5-curl action=install
        ...

Now cfengine should install packages if box is either ubuntu or debian and class nodes is defined. But there's one little problem: if you copy config file for some of those packages, or for some reason it resides on the box, apt-get/dpkg will ask you what to do with old/new config (use old or install new version). And '-y' option won't help in this situation.

I noticed that packages use ucf - Update Configuration File. And this tool respects following variables:
UCF_FORCE_CONFFNEW - if set, forces the new file to always overwrite the installed destination file
UCF_FORCE_CONFFOLD - if set silently retains the installed file
So, i changed definition of DPKGInstallCommand:

DPKGInstallCommand = ( "/usr/bin/env UCF_FORCE_CONFFOLD=1 /usr/bin/apt-get -y install %s" )

And it worked. But as i found later, not all packages seem use ucf for handling config files. So the final version of DPKGInstallCommand looks like this:

DPKGInstallCommand = ( "/usr/bin/env UCF_FORCE_CONFFOLD=1 /usr/bin/apt-get -y -o 'Dpkg::Options::=' '--force-confold' install %s" )

A few days ago I met a small html snippet with an image embedded in it. As it turns out, any data can be embedded this way:

<img src="data:image/gif;base64,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" />

And here's how it looks in html:

Besides images, any other data can be embedded this way. The general schema is:

data:[<mediatype>][;base64],<data>

If ;base64 is omited, data octets should be represented using ascii encoding or using %xx hex notation. Details can be found in rfc2397

I noticed that my jabber client crashes (segmentation fault) whenever i try to close last chat tab or try to open Appearance tab in Options. Version of psi is 0.11-3.

Seems like it has to do with new Qt version. There's a bug reported already. But it's not fixed yet. Fortunely, there's a fixed version available in Debian/unstable: 0.11-8.

If you run e.g. two dns servers and one goes down, some applications start to work slower. This happens because they pick one dns server in order to resolve some address, and if this server is down, you'll have to wait untill timeout. Then they try the other(s).

All this may lead to a number of unpleasunt situations, like:

• High load on servers
• High number of connections to the server
• Insufficient resources b/c of former and so on..

To prevent such situations when 1 of dns servers goes down, we decided to run DNS service under keepalived. So that if one dns server goes down, keepalived on the other server brings ip of the gone dns server up. Dns servers are setup on IPVS directors (where keepalived servers running on). Typical keepalived config for dns may look like this:

[...]
vrrp_instance DNS1 {
    state MASTER
    virtual_router_id 1
    interface eth0
    priority 150
    authentication {
        auth_type PASS
        auth_pass s3cr3t
    }
    virtual_ipaddress {
        10.1.1.1
    }
    smtp_alert
}

vrrp_instance DNS2 {
    state BACKUP
    virtual_router_id 2
    interface eth0
    priority 100
    authentication {
        auth_type PASS
        auth_pass s3cr3t
    }
    virtual_ipaddress {
       10.1.1.2
    }
    smtp_alert
}
[...]

And vise versa on the other director.

We use powerdns in our setup. Unfortunely it cannot bind to ``all`` ip's on box. Actually it can, but there's no guarantee the you'll get the answer from ip you was quering. Because of this you have to bind to concrete ip's. This is not a problem at all unless you need to bind to different ip's automaticly if the other server goes down. In the begining i was trying to use some scripts to change pdns' config with notify_master/notify_backup. But recently i found a much more simple solution. All you need to do is to specify all ip's in every pdn's config on every dns server. And just to let pdn bind to ip's the box doesnt own, simply do:

# sysctl -w net.ipv4.ip_nonlocal_bind=1

This lets pdns to bind to all ip's and if the other server goes down, the one that alive will serve all queries to all ip's.