26 Sep 09 Shrinking/Resizing ext3 Partitions

Shrinking or expanding an ext3 partition is easy but is not without it’s risks. Before starting, you NEED to take a backup of your data. There’s a strong possibility that it will all disappear and your filesystem will become permenantly broken, as with any disk or filesystem procedure.

Please note:

1. The steps below are the RAW STEPS required to resize your partition. This is a potentially dangerous procedure that could easily destroy/ruin/damage your partition, data, filesystem or other partitions on the same disk.
2. DO NOT perform these steps on a live/production machine
3. DO NOT perform these steps unless you have a full backup of your data/disk
4. These steps are really for theoretical purposes only. They should work just fine, but tools such as gparted will do this for you.

ns3:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             9.4G  6.8G  2.2G  77% /
tmpfs                 443M     0  443M   0% /lib/init/rw
udev                   10M   92K   10M   1% /dev
tmpfs                 443M     0  443M   0% /dev/shm
/dev/sdb1              20G  9.8G  9.0G  52% /email

In my example, I’m going to resize /dev/sdb1 which is my /email partition. /dev/sdb1 is a partition residing on device /dev/sdb

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Tags: df, ext3, fdisk, fsck, resize, resize2fs, tune2fs

08 Mar 09 How to create a simple disk image formatted to ext3

We want a 48MB image, formatted to ext3

ns3:/tmp# dd if=/dev/zero of=./disk.img bs=1MiB count=48
48+0 records in
48+0 records out
50331648 bytes (50 MB) copied, 0.301372 s, 167 MB/s
ns3:/tmp# mkfs.ext3 ./disk.img
mke2fs 1.41.3 (12-Oct-2008)
./disk.img is not a block special device.
Proceed anyway? (y,n) y

ns3:/tmp# mkdir disk

ns3:/tmp# mount -oloop ./disk.img ./disk
ns3:/tmp# df -h ./disk
Filesystem            Size  Used Avail Use% Mounted on
/tmp/disk.img          47M  4.8M   40M  11% /tmp/disk

That’s it – now we can copy our content to ./disk before unmounting it, then use dd to write it to our target medium (such as a CF card or similar)

ns3:/tmp# umount ./disk

Tags: CF, df, disk image, ext3, loop, mkfs.ext3, mount, umount

27 Sep 08 Linux Benchmark, IO statistics and system statistics with dstat

There are a number of common command line tools that we can use to monitor system resources. We have df for disk space, free for RAM usage, top for processes, bmon for network usage, etc. Quite often though, I find it useful to monitor them all simultaneously, and constantly switching commands or using ‘watch’ with free/df is annoying.

I came across dstat recently that gives a nice colorful overview of a choice of statistics. Here are some useful command line options from the man page:

You can also output to CSV with –csv and disable color with –nocolor.
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Tags: bandwidth usage, bmon, df, disk space, dstat, free, io statistics, linux benchmark, linux statistics, monitor, network usage, process, processes, RAM usage, system statistics, top