boltblog

Save and restore partition tables with sfdisk

In my raid setup, I set up the partitions a certain way for running several mdadm raids on the same drive.

My server currently boots off of two drives, sda and sdb, where sda1 and sdb1 are the root file system in raid 1 (mirror) and sda2 and sdb2 are (encrypted) swap in raid 0 (striped). This is useful to have the redundancy of raid for booting, but none of that redundancy for the volatile swap partition. Instead I get higher write speed, which is always a bonus.

Note: Most Linux distros would actually stripe the swap anyway, given two swap partitions with equal priority, but I chose to do it this way.

Anyway, when one of the drives went for a one-way trip to electronic oblivion, the need arose to configure my new drive exactly as the old ones. Mind you, mdadm can actually handle non-equal partition sizes in a raid, but I'm kind of anal about this.

sfdisk to the rescue!

First, of course, I replaced the faulty drive (sdb) with one of the same brand and equal size. You don't necessarily need the same brand, but that's what I had.

Then, to export and save the partition table from sda (which was still working)
sfdisk -d /dev/sda > sda_partitions
..and save it to the replaced sdb
sfdisk /dev/sdb < sda_partitions
You can also do it all in one go
sfdisk -d /dev/sda | sfdisk /dev/sdb
As usual, RTM for more options

sudo without a password

Note, this is not something I recommend doing. In fact, the only reason why I'm documenting it is that I am removing this solution from the last box I used to have it on.

Anyway, edit the /etc/sudoers file (with visudo, as root), then add lines under the default one for root, like this:

# User privilege specification
root	ALL=(ALL) ALL
bolt    ALL=(ALL) ALL
bolt    ALL=NOPASSWD: ALL

(replace "bolt" with your own username)

If you would rather want to not type a password only for specific commands, specify them like this:

bolt	ALL=NOPASSWD: /sbin/shutdown, /bin/mount, /bin/umount

(replacing the username and commands with the ones you want)

Using Flags and Arguments in Bash

Here's a simple example script, showing how to deal with different inputs depending on the flag preceding them:

#!/bin/bash
USAGE="Usage: Enter a noun after either -p (polite) or -i (insulting)."

while getopts ":p:i:" OPTIONS; do
  case $OPTIONS in
    p ) polite=$OPTARG;;
    i ) insulting=$OPTARG;;
    h ) echo $USAGE;;
    \? ) echo $USAGE
         exit 1;;
    * ) echo $usage
        exit 1;;
  esac

if [ $polite ];then echo "Your $polite smells good."; fi
if [ $insulting ];then echo "Your $insulting smells bad."; fi
done

Stolen from http://www.okboot.org/2010/04/using-flags-and-arguments-in-bash.html

exim4 smarthost smtp password

Note to self:

To use a smarthost you have to authenticate to with exim4, edit /etc/exim4/passwd.client

# password file used when the local exim is authenticating to a remote
# host as a client.
#
# see exim4_passwd_client(5) for more documentation
#
# Example:
### target.mail.server.example:login:password
*:myusername:myawfullylongpassword

Here I added a username and password for all target mail servers (*) because this host sends everything through the smarthost.

If yours does not, you have to be more specific (like the example).

Surprisingly, there is no need to reload or restart exim4 after modifying the passwd.client file.

Use OpenDNS with Smoothwall Express 3.x

If you're using DHCP to get your public IP, Smoothwall doesn't allow you to override the DNS addresses given by your ISP through the DHCP protocol. Time to override Smoothwall

Edit /etc/rc.d/rc.updatered, and add "DNSMASQ_DNS1=208.67.222.222" and "DNSMASQ_DNS2=208.67.220.220" at the bottom of the DHCP section, making the file look like this:

#!/bin/sh

. /var/smoothwall/ethernet/settings

if [ "$RED_TYPE" = "DHCP" ]; then
 DNSMASQ_DNS1=`/usr/bin/smoothwall/getdnsfromdhcpc.pl 1`
 DNSMASQ_DNS2=`/usr/bin/smoothwall/getdnsfromdhcpc.pl 2`
 . /var/lib/dhcpc/dhcpcd-${RED_DEV}.info
 echo "$IPADDR" >/var/smoothwall/red/local-ipaddress
 echo "$GATEWAY" >/var/smoothwall/red/remote-ipaddress
 DNSMASQ_DNS1=208.67.222.222
 DNSMASQ_DNS2=208.67.220.220
elif [ "$RED_TYPE" = "STATIC" ]; then
 DNSMASQ_DNS1=$DNS1
 DNSMASQ_DNS2=$DNS2
 echo "$RED_ADDRESS" >/var/smoothwall/red/local-ipaddress
 echo "$DEFAULT_GATEWAY" >/var/smoothwall/red/remote-ipaddress
fi

echo -n "$RED_DEV" >/var/smoothwall/red/iface
touch /var/smoothwall/red/active
echo "$DNSMASQ_DNS1" >/var/smoothwall/red/dns1
echo "$DNSMASQ_DNS2" >/var/smoothwall/red/dns2

/usr/bin/smoothcom dnsproxyrestart $DNSMASQ_DNS1 $DNSMASQ_DNS2

/usr/bin/smoothcom setxtaccess
/usr/bin/smoothcom setincoming
/usr/bin/smoothcom snortrestart
/usr/bin/smoothcom upnpdrestart
/usr/bin/smoothcom trafficrestart

/usr/bin/smoothwall/setddns.pl
/usr/bin/smoothwall/updatelists.pl

/etc/rc.d/rc.vpn.up
/etc/rc.d/rc.machineregister

The next time you Smoothwall connects, the setting you just put will override the ones from your ISP. Reboot or reconnect to apply.

Switching alsa sound cards around

Short reference on switching around alsa sound cards, making another one the default.
Needed to do this since my computer has 3 sound cards (M-Audio, SoundBlaster and the G35 headset)

List alsa modules:

cat /proc/asound/modules
0 snd_ice1724
1 snd_ctxfi
2 snd_usb_audio

Edit /etc/modprobe.d/alsa-base.conf, adding the following lines (note the underscores from above are now dashes):

options snd-ctxfi index=-2
options snd-usb-audio index=-2
options snd-ice1724 index=-1

Done.
If you're reading this, and you're not me, customize the above to match your settings, and the priorities you want for your modules.

Hide join/part messages in XChat

To do this, type /set irc_conf_mode 1

To re-enable join/part messages do /set irc_conf_mode 0

The setting is automagically remembered by XChat

XFCE: Unable to perform shutdown

To fix this issue, add the following lines between <config .....> and </config> in /etc/PolicyKit/PolicyKit.conf

<match action="org.freedesktop.hal.storage.mount-removable">
<return result="yes"/>
</match>
<match action="org.freedesktop.hal.power-management.shutdown">
<return result="yes"/>
</match>
<match action="org.freedesktop.hal.power-management.reboot">
<return result="yes"/>
</match>