Harddrive

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S.M.A.R.T.

apt-get install smartmontools

If you have already smartsuite, it will be removed first.
On my system, there was a bug in the pre-removal script and I had to help a bit to remove this package:

/etc/init.d/smartsuite stop
echo "exit 0" > /etc/init.d/smartsuite
dpkg -r smartsuite

Turn SMART on (only once in HD's life):

smartctl --smart=on --offlineauto=on --saveauto=on /dev/hdX

Enable the daemon:

Edit /etc/default/smartmontools and uncomment start_smartd=yes
Edit /etc/smartd.conf:
- DEVICESCAN -a -o on -S on -m root@teuwen.org -s (S/../.././02|L/../../6/03)

Selftests:

smartctl -t short /dev/hdX
smartctl -t long /dev/hdX

Interrupting self-test:

smartctl -X /dev/hdX

Read results:

smartctl -l selftest /dev/hdX

You can also run tests in captive mode:

smartctl -t long -C /dev/hdX

For SATA disks accessed with libata, use "-d ata /dev/sdX"

Repairing

Forcing sector reallocations:

badblocks -n -s -v /dev/hdXX
Destructive: badblocks -w -s -v /dev/hdXX

Rescuing

apt-get install ddrescue
If you have a knoppix, dd-rescue was probably installed.
This is an older version packaged only for the knoppix.
dpkg -r dd-rescue;apt-get install ddrescue
dd_rescue -A -a -v /dev/hdXX /rescue-hdXX
dd_rescue -h for other options

Rebuilding filesystem

For ReiserFS:

apt-get install reiserfsprogs
losetup /dev/loop0 rescue-hdXX
reiserfsck --rebuild-sb /dev/loop0
reiserfsck --rebuild-tree --scan-whole-partition --logfile rebuild.log /dev/loop0

Restoring from backuppc

Prepare the HD

delay backups on backuppc interface
boot on Knoppix
partition the HD
mount /dev/hdaX /mnt/hdaX

Make the computer accessible to backuppc as the computer to restore

attribute the correct IP
restore sshd keys on Knoppix ramdisk via tgz
/etc/init.d/ssh start
restore /root/.ssh/authorized_keys on Knoppix ramdisk

The big operation

restore all / on /mnt/hdaX via backuppc
check for errors (possibly failed restoration of some symlink and mknod...) and create them
- gawk '/symlink/{match($0, /"(.*)".*"(.*)"/, a); system("ln -s " a[2] " " a[1])}'

Last steps: MBR and missing dirs if they were excluded from the backup:

/etc/init.d/libdevmapper1.00 start
cp -a /dev /mnt/hdaX/dev
chroot /mnt/hdaX
mkdir /tmp; chmod go+w /tmp; chmod +t /tmp
mkdir /proc
mkdir /mnt; cat /etc/fstab | gawk '/mnt/{system("mkdir " $2)}'
mkdir -p /var/cache/apt/archives/partial
mount /proc /proc -t proc
lilo/grub-install /dev/hda
exit
umount /mnt/hdaX
reboot

If you want to change the filesystem type, you are free to do so but pay attention:

change /etc/fstab accordingly
recreate the initrd image
- mount /sys /sys -t sysfs
- dpkg-reconfigure linux-image-XXXXX (look for initrd completion messages)

Managing the swap

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Check memory usage

cat /proc/meminfo
cat /proc/swaps

Swap partition

Here are the steps to create and enable a swap partition:

fdisk... (create the partition of the proper size, partition type 82)
mkswap -c /dev/hdXX
swapon /dev/hdXX

Swap file

Here are the steps for making a (256M) swap file:

dd if=/dev/zero of=/swapfile bs=1024 count=262144
mkswap /swapfile
sync
swapon /swapfile

To have the swap enabled automatically at bootup, you have to include the appropriate entry into the file /etc/fstab, for example:

/dev/hdXX swap swap defaults 0 0
or
/swapfile swap swap defaults 0 0

If you ever need to disable the swap, you can do it with (as root):

swapoff /dev/hdXX
or
swapoff /swapfile

You may also want to see the nice info written by Linus Torvalds himself:

man mkswap

Simulating RAID 0 (striping) for the swap

Simply give the same priority to both swap partitions:
/dev/hda2 swap swap defaults,pri=1 0 0
/dev/hdc2 swap swap defaults,pri=1 0 0