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\renewcommand*{\subject}{Operating Systems and Systems Integration}

\newcommand*{\labTitle}{Lab 2, 3 Linux Study Guide 2 Supplement}

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\begin{document}

\section{Exercise (1)}
\label{sec:exercise-1}


\begin{enumerate}
\item What command will determine the version number of your kernel?
  \begin{explanation}
    Look at the list of commands on the last slide labelled ``Basic
    commands (27)''; it's one of those:
    \begin{itemize}
    \item \texttt{which}
    \item \texttt{uname -a}
    \item \texttt{hostname}
    \item \texttt{date}
    \item \texttt{date +\%Y\%m\%d\%H\%M\%S}
    \item \texttt{df -k}
    \item \texttt{du -sk dir\_pathname}
    \item \texttt{who}
    \item \texttt{whoami}
    \item \texttt{su}
    \end{itemize}
  \end{explanation}
  
\item How could you find the percentage of your root partition
  that is used?
  \begin{explanation}
    It is also one of the commands listed above.
  \end{explanation}
\item Use \texttt{sudo} to \texttt{find} files under the \texttt{/etc}
  directory that match the following criteria:
  \begin{itemize}
  \item Filename starting with \texttt{ta}
  \item Filename starting with \texttt{ta} and filesize smaller than
    100\,bytes
  \item Filename starting with \texttt{a} and file type is link
  \item Filename starting with \texttt{a} and file owner is ``\texttt{news}''
  \end{itemize}
  \begin{explanation}
    Use the \texttt{find} command.  Add the \texttt{-ls} option to
    print details of files found so that you can check whether your
    search worked properly or not.

    Read the manual page for \texttt{find}; discuss with your
    neighbour how to tackle each part of this.
  \end{explanation}
\end{enumerate}

\section{Exercise (2) --- 1}
\label{sec:exercise-2-1}

\begin{enumerate}
\item Find out the detailed file type (more than the 4 types) of
  following files: \sloppypar\texttt{/bin/vi}, \texttt{/bin/view},
  \texttt{/etc/passwd}, \texttt{/dev/fd0}, \texttt{/dev/hda},
  \texttt{/dev/isdn1}, \texttt{/bin/}, \texttt{/etc/rc.d/init.d/crond},
  \texttt{/boot/vmlinuz-2.4.18-14},
  \texttt{/boot/initrd-2.4.18-14.img}?
  \begin{explanation}
    Hint: read about the \texttt{file} command: \texttt{man file}.
  \end{explanation}
\item Create a subdirectory, named \texttt{lab2\_3}, under your home
  directory.  Copy the scripts \texttt{student\_cp} and
  \texttt{at\_cron} from the network directory at
  \texttt{/home/nfs/ossi-part-time/scripts} to
  \texttt{\$HOME/lab2\_3/}:
  \begin{alltt}
$ \texttt{cd}
$ \textbf{mkdir lab2_3}
$ \textbf{cp -a /home/nfs/ossi-part-time/scripts/student_cp lab2_3}
# Now press the up-arrow key and edit the above command line so it
# looks like this: 
$ \textbf{cp -a /home/nfs/ossi-part-time/scripts/at_cron lab2_3}
  \end{alltt}

  Run the script \texttt{student\_cp}.
  This script will copy all files (except \texttt{/bin/},
  \texttt{/dev/fd0}, \texttt{/dev/hda}, \texttt{/dev/isdn1}) in part a
  to directory \texttt{\$HOME/lab2\_3}.
  
\item after copying, how could you use one command to know the sum of
  filesizes of all files in \texttt{\$HOME/lab2\_3/}?
  \begin{explanation}
    Hint: See section~\vref{sec:exercise-1}; it's one of the commands
    listed there.
  \end{explanation}
\end{enumerate}


\section{Exercise (2) --- 2}
\label{sec:exercise-2-2}

\begin{enumerate}
\item \texttt{\$HOME/lab2\_3/passwd} is a file containing information
  of each user account with the following format:
\begin{alltt}
Username:password:uid:gid:comment:home-dir:shell-type 
\end{alltt}


\item How can you check for the existence of the usernames of the users
  ``\texttt{root}'', ``\texttt{bin}'', ``\texttt{daemon},'' and find
  out what their their uid and home directory are?
  \begin{explanation}
    Hint: you might consider using the commands \texttt{grep} and \texttt{cut}.
  \end{explanation}

\item What command can easily find the total number of accounts in
  file \texttt{\$HOME/lab2\_3/passwd}?
  \begin{explanation}
    Hint: what command can count lines?
  \end{explanation}
  
\item Copy \texttt{\$HOME/lab2\_3/passwd} to
  \texttt{\$HOME/lab2\_3/passwd.new} and compare these 2 files
  
\item \label{ste:part-g}modify the first and second lines of file
  \texttt{\$HOME/lab2\_3/passwd.new} with any editor and compare these
  2 files again.
  
\item How could you generate a new file
  \texttt{\$HOME/lab2\_3/passwd\_2} which contains only username, uid,
  home-dir fields, separated by a vertical bar ``\verb+|+'', for each
  account?
  
\item How could you generate another file \texttt{\$HOME/lab2\_3/passwd\_3}
  which is sorted by value of uid of file in part~\ref{ste:part-g}?
\end{enumerate}

\section{Exercise (3)}
\label{sec:exercise-3}

\begin{enumerate}
\item Archive all files in directory \texttt{\$HOME/lab2\_3/} into a single
  file, named ``\texttt{tarfile.tar}'', without compression.

\item How would you list what files are archived in ``\texttt{tarfile.tar}''?
  
\item Create a directory \texttt{\$HOME/lab2\_3/extract/} and extract all
  files in ``\texttt{tarfile.tar}'' into this new directory.

\item Compress all files in \texttt{\$HOME/lab2\_3/extract/}

\end{enumerate}

\section{Exercise (4)}
\label{sec:exercise-4}
\begin{enumerate}
\item What is done by the script \texttt{at\_cron}?
  \begin{enumerate}
  \item create a new file \texttt{\$HOME/lab2\_3/filesize} if this
    file does not exist.
  \item Then append ``\texttt{Hello...\bs n}'' to this file.
  \end{enumerate}
  
\item \label{ste:part-a}Schedule script
  \texttt{\$HOME/lab2\_3/at\_cron.ksh} to run at one minute later
  once.  What is the result?

\item Redo part \ref{ste:part-a}, but schedule to run at 9:10\,p.m.
  What is the value of the job id?
  
\item \label{ste:part-c}Schedule script
  \texttt{\$HOME/lab2\_3/a\t\_cron.ksh} to run every one minute and
  observe the result 2 minutes later.

\item Un-schedule what you did in part \ref{ste:part-c}. 
\end{enumerate}

\end{document}