• [1] http://securecon.unimelb.edu.au/


• [2] http://en.wikipedia.org/wiki/Mac_mini

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$ mount   grep tmpfs
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)

• The SysV IPC shared memory layer (ipc/shm.c) is a wrapper layer which manages IPC keys and internally plugs itself into the tmpfs code. Essentially creating a key with shmget() ends up calling ipc/shmem.c:newseg() which calls mm/shmem.c:shmem_file_setup() which then creates a struct file for the shared memory. This new file reuses the file operations from the tmpfs filesystem, but is not actually put into the file system (i.e. linked to the superblock). When shat() is called to attach to this memory the SysV IPC layer will internally translate this into a mmap of this file. This is what is used by the Shared Global Area of Oracle and some Java implementations, amongst many other things (see /proc/sysvipc/shm for a comprehensive list).
• The second common thing to do is an anonymous mmap. By default MAP_ANONYMOUS ignores the file-descriptor, but an analagous methodology is to explicitly map /dev/zero. If you look at the implementation of /dev/zero in drivers/char/mem.c you can see code such as

  static int mmap_zero(struct file * file, struct vm_area_struct * vma)
   
          int err;
          if (vma->vm_flags & VM_SHARED)
                  return shmem_zero_setup(vma);
  

  which ends up backing shared areas with tmpfs.
• The third way is actually mounting tmpfs and using it from userspace as a normal file system. glibc implements the POSIX shared memory call shm_open by creating and mmaping files on a tmpsfs mount (by default looking in /dev/shm). Other utilities also use the tmpfs semantics and mount it at other points; the obvious one of course being mounting /tmp on it!

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xen-resize-guest --hostname=foo.my.flat --increase=5Gb

• an introduction of apt-xapian-index;
• an example of how to query it;
• a way to add simple result filters to the query;
• a way to suggest keywords and tags to use to improve the query.
• a way to search for similar packages.
• a way to implement an adaptive cutoff on result quality.
• a smart way of querying tags

    def mainloop(self):
        while True:
            c = self.win.getch()
            self.line += chr(c)
            self.results.update(self.line)

        # Split the line in words
        args = self.splitline.split(line)
        # Convert the words into terms for the query
        terms = termsForSimpleQuery(args)

        # Since the last word can be partially typed, we add all words that
        # begin with the last one.
        terms.extend([x.term for x in db.allterms(args[-1])])

        # Build the query
        query = xapian.Query(xapian.Query.OP_OR, terms)

        # Retrieve as many results as we can show
        mset = enquire.get_mset(0, self.size - 1)

        # Redraw the window
        self.win.clear()
        # Header
        self.win.addstr(0, 0, "%i results found." % mset.get_matches_estimated(), curses.A_BOLD)
        # Results
        for y, m in enumerate(mset):
            # /var/lib/apt-xapian-index/README tells us that the Xapian document data
            # is the package name.
            name = m[xapian.MSET_DOCUMENT].get_data()
            # Get the package record out of the Apt cache, so we can retrieve the short
            # description
            pkg = cache[name]
            # Print the match, together with the short description
            self.win.addstr(y+1, 0, "%i%% %s - %s" % (m[xapian.MSET_PERCENT], name, pkg.summary))
        self.win.refresh()

• sudo -u root xen-manage create centos debian [permissive]
  
  Create an image, the parameter debian or centos specifies which
  distribution you want to use and the optional parameter permissive
  specifies that you want to use Permissive mode (no SE Linux access controls
  enforced).
  
  Note that creating an image will leave you at it’s console. Press ^]
  to escape from the console.


• sudo -u root xen-manage list
  
  Display the Xen formation on your DomU. Note that it doesn’t tell you whether
  you are using Debian or CentOS, you have to access the console to do that.


• sudo -u root xen-manage console
  
  Access the console.


• sudo -u root xen-manage destroy
  
  Destroy your Xen image - if it’s crashed and you want to restart it.

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• Flexibility. In theory any programming language that is turing-complete will allow one to write any imaginable program. In practice, some programming languages will require you 100 lines of code to do stuff which can be done in three lines in another language. A programming language that doesn't require you to turn your brain upside down three times to figure out how to get something done is a better language in my book than one that does. A language that provides multiple ways to do any given thing is very strong for this particular requirement; it allows you to pick the best way to do anything in order to prove readability. The alternative is for you to have to write some extra hairy code because the language requires you to jump through silly hoops.
  The Turing Machine utterly fails this criterion. Any language that lacks pointers or references or something similar fails it, too, though not in such a dramatic way. Perl is very good in this particular requirement.
• Compactness. I blame COBOL for this particular requirement, but it's still rather important, in my opinion: a programming language should not require me to write an entire novella for a simple 'hello world' program. Obviously COBOL utterly fails this requirement. Large parts of Java's libraries do, too. Perl and C are rather good at this particular requirement.
• Resembling english. COBOL fails this requirement, too—COBOL is english, not a programming language. Brainfuck fails, as well. Obviously. Mostly everything else passes. Except for windev, that is, which resembles French. Hah.