Chapter 8. Disks and Filesystems
Ordinary Files
 What
is a file?
– a container for ordered data
– persistent (stays around) and accessible by name
 Unix
files
– regular Unix files are pretty simple
essentially a sequence of bytes
– Unix files are identified by a name in a directory
this name is actually used to resolve the hard disk
name/number, the cylinder number, the track
number, the sector, the block number
– you see none of this
it allows the file to be accessed
Files, Directories, Devices
 Unix
files come in other flavors as well, such
as
– Directories
a file containing pointers to other files
equivalent of a “folder” on a Mac or Windows
– Links
a pointer to another file
used like the file it points to
similar to “shortcuts” in Windows, but better
– Devices
access a device (like a soundcard, or mouse,
or ...) like it is a file
Figure 3-3
A Directory Hierarchy
System Directories

Some standard directories and files in a typical Unix
system
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/
/bin
/sbin
/lib
/dev
/etc
/usr
/tmp
the root
BINaries (executables) used to start system
System BINaries for Superuser
LIBraries used for startup
DEVices (peripherals) hardware interfaces
unique settings for system, config, passwds
Biggest filesystem, sys tools, X, apps
temp storage, good to separate partition
Typical System Directory Contents
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/usr
USeR stuff
/usr/bin
BINaries again
/usr/include
include files for compilers
/usr/lib
LIBraries of functions etc.
/usr/local local stuff for apps installed later
/usr/local/bin
local BINaries
/usr/local/lib
local LIBraries for apps
/usr/X11R6
X window stuff
/usr/sbin
sysadmin stuff
/usr/tmp
place for more TeMPorary files
/var
VARiable stuff—mail, print jobs, logfiles
/var/mail
the mail spool
/var/log
security info VERY IMPORTANT
The /proc filesystem

/proc is a virtual directory. in RAM rather than in HDD.

/proc contains info about your system’s state.
amount of free memory
processes running
external devices plugged in
remaing battery power if you are working in a laptop

You can, though, navigate around it with cd command
and list its contents with ls command or view some of its
file contents with cat command
The /proc file system
Numbers are directories representing each of the running
process on the system and contain all info related to it.
terra$ ls /proc/480/
auxv
cwd
exe maps mounts stat status wchan
cmdline
environ fd mem root statm task
For example:
cmdline contains the command the process started with
mem contains the amount of memory this process holds
 . /proc contains information about the hardware of the system
cat /proc/meminfo contains information about memory state
more /proc/ioports gives all the information about the
availability of I/O ports on the system and the hardware
device assigned to each.

Figure 3-8
Inodes
Each file on the disk has an inode
which keeps information about the
file, it’s address, etc