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#319 Cannot Access Any Flash Drive After Installing DrJava
After installing DrJava on my Apple Mac air early 2014, my computer does not acknowledge that I connect flash drives to it. I have a 64gb sans disk flash drive I last christmas and a very old 0.25GB ford flashdrive, I don't remember how it was aquired. Neither of these is recognized by the computer when I plug them in, but in the case of the Sans Disk drive, the light that shows it is connected does turn on. Also, when I attach a 500GB external hard drive I use for backing up my computer, it works just fine.
DrJava Version : drjava-20140826-r5761
DrJava Build Time: 20140826-0459
Yosemite 10.10.5 (14F27)
I recently tried to awaken my computer and it was frozen. Forcefully restarting it fixed the problem, both being frozen and being unable to see the flash drive.
Hi Kyle,
DrJava is not an executable program; it is a datafile containing "Java byte
code" that a Java Virtual Machine reads and executes. Java byte code is
ordinary data just like a text file containing numerals as far as Mac OS X
is concerned. The Mac OS X app that we distribute (which only works with
Apple Java 6 because Oracle who developed Java 7 and Java for Mac OS X uses
a different app launcher) tells Mac OS X to start a Java Virtual Machine
and start executing the byte code for DrJava (which constitutes most of the
data in the app). So DrJava cannot change any aspect of your computer
configuration. I can assure you that no code in DrJava tries to
manipulate any device configuration files; none of the input/output
performed by DrJava is device specific (other than keyboard input and
screen output as supported by the Java Virtual Machine). DrJava can write
to any file that the operating system mounts assuming that the file is not
protected against access by the account corresponding to the Java Virtual
Machine. It does so transparently using device independent file operations.
A Java Virtual Machine is a binary program but I would be astonished if it
affected the mounting of flash (USB) drives in any way. Typically
modifying the configuration files for devices (like USB drives) requires
permissions that a Java Virtual Machine would not have (unless it was
configured to run as root which may be possible; I have never tried
installing a JVM with such privileges and would not because many privileges
are reserved for root access which not provided by normal application
installations). I have not used Mac OS X in several years and I did not
mount any flash drives when I did use it. But Mac OS X is a flavor of Unix
so I suspect Apple provides at least as much security regarding
reconfiguring devices as my open source Ubuntu Linux systems. To change
the mount configuration for the file system, Ubuntu Linux requires "root"
status which ordinary accounts normally do not have. Most systems will
automount USB drives but the automounting protocol is governed by
configuration files that cannot be modified without root status.
As far as accessing USB drives is concerned, the file system formatted on
the drive affects which operating systems and applications can read them.
For example, flash drives that are formatted for Linux (typically ext4) are
not recognized when I try to read them on my wife's Windows 7 machine. I
am sure that Windows can be configured to access such drives with the
proper auxiliary software installed, but the Windows 7 machines in my house
will not read them. I had to reformat one of my drives from ext4 to ntfs
so that it could be read on our Windows machines. You may want to read the
documentation on formatting flash drives for Mac OS X and determine how
your drives are formatted. Common choices include ntfs (Windows), fat32
(an older Windows standard), ext4 (Linux), and htfs (Mac OS X). They are
all different and incompatible. But a particular OS can be
designed/configured to read all such formats. Most do not for various
reasons.
[I just saw your updated post. I decided to send my response anyway
because it may provide with some insight o why your flash drives may not
always behave as you expect.]
Best,
Robert "Corky" Cartwright
www.cs.rice.edu/~cork
On Wed, Sep 16, 2015 at 11:06 AM, Kyle Berman noekrb@users.sf.net wrote:
Related
Support Requests: #319