Page 260 - DCAP602_NETWORK_OPERATING_SYSTEMS_I

Network Operating Systems-I

notes A lot of systems give some information about how to use the
system when you login, look for that after you have typed

the password (some of those messages will not be shown if
you use a - as the first character in your password, some
people need this because the system won’t recognize them
otherwise. If you have problems logging into a site, try
a - as the first character).

Different systems have different organizations for their files,
and the above example is the way most archives have set it up.
By looking around other systems, you can learn how their files

are arranged and move around much faster. Note, however,
that FTP will not allow you outside the FTP ‘root’ directory.
Moving about the entire system is not permitted. You will
get ‘Permission denied’ messages (or plainly not receiving any
message and still not be able to change to the directory).

Usually, files are grouped in archive files, so you don’t have
to get many small files separately. The most common archival
file formats for the Internet are tar and zip. Occasionally,
people use shell archives (shar) instead. Tar files are basically

a bunch of files ‘glued’ together. Tar archives can be unpacked
by running the ‘tar’ command on a Unix system (tar exists also
for DOS, VMS and a whole bunch of other Operating Systems) --
you may want to first do a ‘tar t’ on the file to see what it
contains before unpacking it. This means typing: ‘tar t filename.tar’

or ‘tar tf filename.tar’ and looking what the output shows. To unpack
the .tar file, type: ‘tar xvf filename.tar’, this will create a
directory called filename with the unpacked archive in it (no quotes
again).

Be careful when unpacking shell archives since they have to be
run through the Bourne shell to unpack them. (The simplest
way is to use the unshar command).

Files are often stored compressed, because they take up less
space that way -- for Unix, the most common compression ‘scheme’

254 LoveLy professionaL university