Ubuntu 9.04

η τρίτη Alpha έκδοση του αναμενόμενου Ubuntu 9.04 (Jaunty Jackalope) και σύμφωνα με δοκιμές του softpedia θα είναι πάρα πολύ γρήγορο. Αυτό οφείλεται κυρίως στο νέο filesystem EXT4, που ανακοινώθηκε την παραμονή των Χριστουγέννων και πλέον είναι σταθερό και υποστηρίζεται από τον πυρήνα 2.6.28. Τα καλά νέα είναι ότι η επόμενη έκδοση του Ubuntu 9.04 θα υποστηρίζει το νέο αυτό σύστημα αρχείων μέσω του Ubuntu Installer, αν ο χρήστης επιλέξει manual partitioning κατά τη διάρκεια της εγκατάστασης.

Τα άσχημα νέα είναι ότι το EXT4 δεν θα είναι το προεπιλεγμένο σύστημα αρχείων μέχρι την έκδοση 9.10 που αναμένεται τον Οκτώβριο του 2009. Τα πλεονεκτήματα για τους χρήστες σε σχέση με το σύστημα αρχείων EXT3 είναι η γρηγορότερη εκκίνηση, η υποστήριξη μεγαλύτερων αρχείων (έως και 16TB)...

Large file system

The ext4 filesystem can support volumes with sizes up to 1 exabyte^[6] and files with sizes up to 16 terabyte.

Extents

Extents are introduced to replace the traditional block mapping scheme used by ext2/3 filesystems. An extent is a range of contiguous physical blocks, improving large file performance and reducing fragmentation. A single extent in ext4 can map up to 128MB of contiguous space with a 4KB block size.^[7]

Backward compatibility

The ext4 filesystem is backward compatible with ext3, making it possible to mount an ext3 filesystem as ext4.

Forward compatibility

The ext4 file system is partially forward compatible with ext3, that is, it can be mounted as an ext3 partition (using “ext3” as the filesystem type when mounting). However, if the ext4 partition uses extents (a major new feature of ext4), then the ability to mount the file system as ext3 is lost. Extents were enabled by default in the 2.6.23 kernel. Previously, the “extents” option was explicitly required (e.g. mount /dev/sda1 /mnt/point -t ext4dev -o extents).

Persistent pre-allocation

The ext4 filesystem allows for pre-allocation of on-disk space for a file. The current methodology for this on most file systems is to write the file full of 0's to reserve the space when the file is created (although XFS has an ioctl to allow for true pre-allocation as well). This method would no longer be required for ext4; instead, a new fallocate() system call was added to the linux kernel for use by filesystems, including ext4 and XFS, that have this capability. The space allocated for files such as these would be guaranteed and would likely be contiguous. This has applications for media streaming and databases.

Delayed allocation

Ext4 uses a filesystem performance technique called allocate-on-flush, also known as delayed allocation. It consists of delaying block allocation until the data is going to be written to the disk, unlike other file systems, which allocate the necessary blocks before that step. This improves performance and reduces fragmentation by improving block allocation decisions based on the actual file size.

Break 32,000 subdirectory limit

In ext3 the number of subdirectories that a directory can contain is limited to 32,000. This limit has been raised to 64,000 in ext4, and with the "dir_nlink" feature it can go beyond this (although it will stop increasing the link count on the parent). To allow for continued performance given the possibility of much larger directories, htree indexes (a specialized version of a B-tree) is turned on by default in ext4. This feature is implemented in Linux kernel 2.6.23. Htree is also available in ext3 when the dir_index feature is enabled.

Journal checksumming

Ext4 uses checksums in the journal to improve reliability, since the journal is one of the most used files of the disk. This feature has a side benefit; it can safely avoid a disk I/O wait during the journaling process, improving performance slightly. The technique of journal checksumming was inspired by a research paper from the University of Wisconsin titled IRON File Systems (specifically, section 6, called "transaction checksums").^[8]

Online defragmentation

Ext4 has an online defragmenter. Even with the various techniques used to avoid it, a long lived file system does tend to become fragmented over time. Ext4 will have a tool which can defragment individual files or entire file systems.

Faster file system checking

In ext4, unallocated block groups and sections of the inode table are marked as such. This enables e2fsck to skip them entirely on a check and greatly reduce the time it takes to check a file system of the size ext4 is built to support. This feature is implemented in version 2.6.24 of the Linux kernel.

Multiblock allocator

Ext4 allocates multiple blocks for a file in single operation, which reduces fragmentation by attempting to choose contiguous blocks on the disk. The multiblock allocator is active when using O_DIRECT or if delayed allocation is on. This allows the file to have many dirty blocks submitted for writes at the same time, unlike the existing kernel mechanism of submitting each block to the filesystem separately for allocation.

[edit] Improved timestamps

As computers become faster in general and specifically Linux becomes used more for mission critical applications, the granularity of second-based timestamps becomes insufficient. To solve this, ext4 will have timestamps measured in nanoseconds. This feature is currently implemented in 2.6.23. In addition, 2 bits of the expanded timestamp field are added to the most significant bits of the seconds field of the timestamps to defer the year 2038 problem for an additional 500 years.

Support for date-created timestamps is added in ext4. But as Theodore Ts'o points out, while adding an extra creation date field in the inode is easy (thus technically enabling support for date-created timestamps in ext4), modifying or adding the necessary system calls, like stat() (which would probably require a new version), and the various libraries that depend on them (like glibc) is not trivial and would require the coordination of many different projects^[9]. So even if ext4 developers implement initial support for creation-date timestamps, this feature will not be available to user programs for now.^[9]

BrainFuck

++++++++++[>+++++++>++++++++++>+++<<<-]>++.>+.+++++++
..+++.>++.<<+++++++++++++++.>.+++.------.--------.>+.


BRAINFUCK!!!

>>>>+>+++>+++>>>>>+++[
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<<[++[<+>--]>+<]>>>[<+>-]<<<<<<<< ]>>>>>++++++++++.>+[[-]<]<<<
]

Ο

Kυβερνιτικοί ιοι !!!

Η Ευρωπαϊκή Ένωση έδωσε την έγκριση της στις αστυνομικές δυνάμεις να κάνουν έρευνα εξ αποστάσεως στα pc των πολιτών. Ετσι,τα ο χάκινγκ από τη μεριά του κράτους παίρνει μια άλλη τροπή.

Μόλις το Συμβούλιο Υπουργών της Ευρωπαϊκής Ένωσης έδωσε τη συγκατάθεσή του Αγγλία και Γερμανία έσπευσαν να εφαρμόσουν το μέτρο.

Μέχρι σήμερα οι αστυνομίες των κρατών μελών χρειαζόντουσαν ειδικό ένταλμα έρευνας και κάποια στοιχεία που να στηρίζουν την ανάγκη έρευνας από απόσταση των υπολογιστών των πολιτών.Σήμερα,με την απόφαση αυτή, τους λύνονται κυριολεκτικά τα χέρια και μπορούν χωρίς καμία ειδική άδεια εκ των προτέρων,εντελώς ανώνυμα, ανενόχλητα και απροειδοποίητα να επιτηρούν τα αρχεία ενός «ύποπτου» από απόσταση.

«Δεν διαφέρει από το προηγούμενο καθεστώς όπου μπορούσαν να εισβάλλουν στο σπίτι κάποιου, να το ψάξουν και να πάρουν το σκληρό δίσκο του υπολογιστή του.Μόνο που τώρα ο «ύποπτος», αν μπορούμε ακόμα να τον ονομάζουμε έτσι, ούτε καν το μαθαίνει.

Εννοείται ότι για να εισβάλλει κάποιος σ’ ένα συγκεκριμένο υπολογιστή χρειάζεται και τη συμμετοχή και κάποιων άλλων. Θα δούμε λοιπόν να αποστέλλονται e-mail με κάποιο ιό από τη μεριά της αστυνομίας, και με ποιο τρόπο θα αντιδράσουν (αν αντιδράσουν) οι διάφοροι κατασκευαστές antivirus και ειδικών software προστασίας ,σ’ αυτό το νέο καθεστώς?

Θα υπάρξουν βέβαια και αυτοί που θα πούνε «Γιατί να φοβάμαι, εγώ δεν έχω τίποτα να κρύψω?»

Αυτοί, ας απαντήσουν, πέρα των άλλων, πώς είναι τόσο σίγουροι ότι δεν θα γίνει κατάχρηση της «φιλοξενίας» που θα προσφέρουν, χωρίς τη συγκατάθεσή τους, στις δυνάμεις «ασφαλείας». Λίγα έχουνε δει τα μάτια μας?

Linux Τώρα!!!!!!!!

FREE GAZA

It's a tragedy that the Israelis - a people who must understand better than almost anybody the horrors of oppression - are now acting as oppressors. As the great Jewish writer Primo Levi once remarked "Everybody has their Jews, and for the Israelis it's the Palestinians". By creating a middle Eastern version of the Warsaw ghetto they are recapitulating their own history as though they've forgotten it. And by trying to paint an equivalence between the Palestinians - with their homemade rockets and stone-throwing teenagers - and themselves - with one of the most sophisticated military machines in the world - they sacrifice all credibility.

The Israelis are a gifted and resourceful people who fully deserve the right to live in peace, but who seem intent on squandering every chance to allow that to happen. It's difficult to avoid the conclusion that this conflict serves the political and economic purposes of Israel so well that they have every interest in maintaining it.

While there is fighting they can continue to build illegal settlements. While there is fighting they continue to receive huge quantities of military aid from the United States. And while there is fighting they can avoid looking candidly at themselves and the ruthlessness into which they are descending.

Gaza is now an experiment in provocation. Stuff one and a half million people into a tiny space, stifle their access to water, electricity, food and medical treatment, destroy their livelihoods, and humiliate them regularly...and, surprise, surprise - they turn hostile.

Now why would you want to make that experiment? Because the hostility you provoke is the whole point. Now 'under attack' you can cast yourself as the victim, and call out the helicopter gunships and the F16 attack fighters and the heavy tanks and the guided missiles, and destroy yet more of the pathetic remains of infrastructure that the Palestinian state still has left. And then you can point to it as a hopeless case, unfit to govern itself, a terrorist state, a state with which you couldn't possibly reach an accommodation. And then you can carry on with business as usual, quietly stealing their homeland.

Brian Eno.

ΚΑΤΙ ΑΚΟΜΑ για τον Eno :

The Microsoft Sound

In 1994 Microsoft corporation designers Mark Malamud and Erik Gavriluk approached Brian Eno to compose music for the Windows 95 project. The result – composed by Eno on an Apple MacIntosh computer – was the six-second start-up music-sound of the Windows 95 operating system, the The Microsoft Sound. In the San Francisco Chronicle he said: ^[15]

“

The idea came up at the time when I was completely bereft of ideas. I'd been working on my own music for a while, and was quite lost, actually, and I really appreciated someone coming along and saying, "Here's a specific problem — Solve it!" The thing from the agency said, "We want a piece of music that is inspiring, universal, blah-blah, da-da-da, optimistic, futuristic, sentimental, emotional", this whole list of adjectives, and then, at the bottom, it said: "and it must be 3¼ seconds long". I thought this was so funny, and an amazing thought, to actually try to make a little piece of music. It's like making a tiny little jewel. In fact, I made eighty-four pieces. I got completely into this world of tiny, tiny, little pieces of music. I was so sensitive to microseconds, at the end of this, that it really broke a logjam in my own work. Then, when I'd finished that and I went back to working with pieces that were, like, three minutes long, it seemed like oceans of time.