Probing for hardware information
lsscsi
Many people imagine that SCSI drives are obsolete, but, in fact, both hard drives and solid state drives, as well as DVD drives, continue to use SCSI, although in a highly modified standard. For help, lsscsi
has an info file, but not a man file. Adding --list
(-L
), --long
(-l
), and --verbose
(-v
) to the command all give more information, while --classic
(-c
) is the equivalent of:
cat /proc/scsi/scsi
If you want the names of devices, add --generic
(g
) (Figure 7).

dmesg
dmesg
reads the kernel ring buffer where messages about a system's startup messages are stored, including information about the initialization of device drivers or kernel modules. Although the results can often be hit or miss, dmesg
is sometimes an ideal place to start troubleshooting. With the bare command, you can scroll through startup messages, but in most cases, it is more efficient to search instead. For instance, to find messages about USB devices, enter:
dmesg | grep -i usb | less
in which the -i
option ignores letter cases. Note that dmesg
must be run as root. As an alternative to dmesg
, you can read the file /var/log/dmesg
in a text editor (Figure 8).

/proc
The pseudo filesystem /proc
contains information from the kernel. It contains one subdirectory for each process. The names of the subdirectories are usually self-explanatory, such as cpu
, cwd
(current working directory), environ
, and so on. You can view detailed information using a text viewer such as cat
or less
, or sysctl
to read the contents, but be careful not to edit in case you crash the system (Figure 9).

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