Debian 5.0
Java on Debian tip
The default Java environment installed by Debian is the GNU Compiler for Java, while GNU have made remarkable progress with this – anyone doing mainstream Java development will probably prefer to install the latest Sun Java environment on their system – even free software projects like Hadoop are primarily tested in this environment.
Most Linux distributions provide packages for Sun’s Java as well as GCJ and probably OpenJDK. When you install more than one package which provides similarly named commands, Debian’s Alternatives System comes into play – allowing you to select one command or another. When you install a different Java, you can of course manually update each Java command (java, javac, javadoc, jconsole, jmap,jps and so on) using the update-alternatives command, but if you want a quicker way, try the update-java-alternatives command from the java-common package. It will automatically update the paths to all provided Java commands in one go once you tell it which installed Java environment you wish to use, for example,
update-java-alternatives -s java-6-sun
Debian 5.0 (Lenny) install on Software RAID
As mentioned in previous posts, I’m a big fan of Linux Software RAID. Most of the Ubuntu servers I install these days are configured with two disks in a RAID1 configuration. Contrary to recommendations you’ll find elsewhere, I put all partitions on RAID1, not some (that includes swap, /boot and / – in fact I don’t normally create a separate /boot partition, leaving it on the same partition as /). I guess if you’re using RAID1, I think you should get the advantage of it for all of your data, not just the really, really important stuff on a single RAIDed partition.
When installing Ubuntu (certainly recent releases including 8.10 and 9.04) you can configure all of this through the standard installation process – creating your partitions first, flagged for use in RAID and then configuring software RAID and creating a number of software RAID volumes.
I was recently installing a Debian 5.0 server and wanted to go with a similar config to the following,
| Physical device | Size | Software RAID device | Filesystem | Description |
|---|---|---|---|---|
/dev/sda1 |
6GB | /dev/md0 |
swap | Double the system physical memory |
/dev/sdb1 |
6GB | |||
/dev/sda2 |
10GB | /dev/md1 |
ext3, / | You can split this into multiple partitions for /var, /home and so on |
/dev/sdb2 |
10GB | |||
/dev/sda3 |
40GB | /dev/md2 |
ext3, /data | Used for critical application data on this server |
/dev/sdb3 |
40GB |
When I followed a standard install of Debian using the above configuration, when it came to installing GRUB, it failed with an error. The error seemed to be related to the use of Software RAID. Searching the web for possible solutions mostly turned up suggestions to create a non-RAIDed /boot partition but since this works on Ubuntu I figured it should also work on Debian (from which Ubuntu is largely derived).
First, a little background to GRUB and Linux Software RAID. It seems that GRUB cannot read Linux software RAID devices (which it needs to do to start the boot process). What it can do, is read standard Linux partitions. Given that Linux software RAID1 places a standard copy of a Linux partition on each RAID device, you can simply configure GRUB against the Linux partition and, at a GRUB level, ignore the software RAID volume. This seems to be how the Ubuntu GRUB installer works. A GRUB configuration stanza like the following should thus work without problems,
title Debian GNU/Linux, kernel 2.6.26-2-amd64 root (hd0,1) kernel /boot/vmlinuz-2.6.26-2-amd64 root=/dev/md1 ro initrd /boot/initrd.img-2.6.26-2-amd64
When I tried a configuration like this on my first install of Debian on the new server, it failed with the aforementioned error. Comparing a similarly configured Ubuntu server with the newly installed Debian server, the only obvious difference I could see is that the partition table on the Ubuntu server uses the old msdos format while the partition table on the Debian server seems to be in GPT format. I can’t find any documentation on when this change was made in Debian (or indeed whether it was something in my configuration that specifically triggered the use of GPT) but it seems like this was the source of the problems for GRUB.
To circumvent the creation of a GPT partition table on both disks, I restarted the Debian installer in Expert mode and installed the optional parted partitioning module when prompted. Before proceeding to the partitioning disks stage of the Debian installation, I moved to a second virtual console (Alt-F2) and started parted against each disk and ran the mklabel command to create a new partition table. When prompted for the partition table type, I input msdos.
I then returned to the Debian installer (Alt-F1) and continued the installation in the normal way – the partitioner picks up that the disks already have an partition table and uses that rather than recreating it.
This time, when it came to the GRUB bootloader installation step, it proceeded without any errors and I completed the installation of a fully RAIDed system.
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