See IDE disk settings (must be root)

hdparm /dev/hd? (hda, hdb, etc.)

Set DMA for IDE disks (must be root)

hdparm -d1 /dev/hd? (hda, hdb, etc.)
Usually big performance gains, especially for DVD drives.

Tune additional IDE disk settings (must be root)

hdparm -d1 -c3 -m16 /dev/hd? (hda, hdb, etc.)
The -c3 option turns on the 32-bit EIDE interface. The -m16 option sets the read ahead buffer to 16 sectors. Fairly non-agressive settings for modern EIDE disk.

More aggressive IDE disk settings (must be root)

hdparm -d1 -c1 -m16 /dev/hd? (hda, hdb, etc.)
The -c1 option has less overhead than -c3 but works with fewer chipsets. Newer drives should work fine with -c1.

Aggressive IDE disk settings with multiple disks (must be root)

hdparm -d1 -c1 -m16 -u1 /dev/hd? (hda, hdb, etc.)
The -u1 option permits the driver to unmask other interrupts during a disk interrupt. With multiple drives/controllers, this can dramatically increase performance. However, quoting the man page, some drive/controller combinations do not tolerate the increased I/O latencies possible when this feature is enabled, resulting in massive filesystem corruption. Use with extreme caution.

Test IDE disk performance (must be root)

hdparm -tT /dev/hd? (hda, hdb, etc.)

General

The Linux kernel stores all hardware settings in the virtual directory /proc.

See IO ports

cat /proc/ioports

See IRQs

cat /proc/interrupts

See PCI devices

cat /proc/pci
also
/sbin/lspci

See USB hubs and devices

cat /proc/bus/usb/devices
also
usbview (gui program)

See IDE disk settings (must be root)

hdparm /dev/hd? (hda, hdb, etc.)

View serial ports/multi-port boards (must be root)

setserial /dev/ttyS0 setserial /dev/ttyS1

Active network cards

/sbin/ifconfig
also
/sbin/ip addr

Boot time hardware detection messages (kernel ring buffer)

dmesg | less

To update the local cache from apt repositories

apt-get update

To download and install a package (including dependencies):

apt-get install package-name

To install a single .deb package:

dpkg --install package.deb

To remove a package:

apt-get remove package-name

To find all available packages that match a pattern:

apt-cache search pattern

apt-cache searches the package names and descriptions.

To display package information:

apt-cache show package-name

To show all installed packages:

dpkg --list

To show all files that belong to a package:

dpkg --listfile package-name