I can verify this, very simply. I'll use JFS as my example, and I'll use two hard drives, to make I/O monitoring simple.
First, create the file system with "mkfs.jfs -j/dev/sda2/dev/sdb2", with journal on sda2, and main FS on sdb2. Mount the filesystem (I'll assume at/mnt).
Create a large-ish file: "dd if=/dev/zero of=/mnt/zeros bs=1048576 count=96". Run "sync" to flush buffers.
Now, if anything about that file besides its own file data changes, it'll go to the journal first. That includes file relocation, which is a block map operation. The file data OTOH goes directly to the file system.
Run your favorite disk I/O monitor. I use gkrellm, but you may also use "procinfo -Dn1" or "iotop". Make sure it's something that lets you watch individual disks' activities, not just the sum total activity.
Run "shred -n25 -vu/mnt/zeros". Note the drive with the activity; it's the drive with the file system on it, not the journal. Since anything other than overwriting in place, would involve meta-data operations, ergo journal activity, the file is being over-written in place. QED.
XFS is the opposite; shred writes to the journal. Sigh.
Shred also works on drives. I shredded a Deskstar with a 25-pass wipe, which took over 16 hours. (And in a stroke of good timing, it started making the Deskstar "click of death" sounds less than 10 minutes after it finished.)
But about file system journals. It's a bit much to say "any file system" besides ext2 defeats shred. The concern is this: If file data is committed to the journal first, rather than the filesystem proper, the only way shredding is secure is to shred a file that's larger than the journal. Otherwise, multiple overwrites of file data are actually going to the journal, where they'll be analyzed, all but the last overwrite will be canceled, and the file data in the filesystem ends up with only a single overwrite.
Part of the purpose of shredding a file, is to overwrite the residual magnetic flux between tracks on a platter. Multiple overwrites on the platter will do this; shred used to do 25 overwrites by default, which was good enough for DoD secure erasure requirements. However, a FS journal would defeat this on a file that was less than 1/25 the size of the journal.
Ext3/4 can do this, but not by default; the default is "ordered" mode, where file data goes directly to the FS, and then its metadata goes to the journal. A mount option can change this temporarily, and "tune2fs" can change the mode persistently.
XFS and JFS journal only metadata, so shredding a file on those FS's is safe. You can verify this with an external journal on a different drive, then watch where the activity is during a shred. It isn't in the journal.
OTOH, log-structured file systems like Btrfs may or may not erase the data in place; if the data is part of a snapshot, then later overwrites don't remove the snapshot.
The percentage of people who are harmed by arsenic (100) vs. the percentage of people who are harmed by gluten (small).
For pure arsenic, that's true. It still has its uses in medicine, such as oncology where it works better than iodine for locating tumors.
Oh, and have you eaten fish lately? You probably consumed a milligram of arsenic. But, since you're reading this, I'll assume you're still alive and well.
The Therac-20 radiation therapy device worked reasonably well. Despite the
software flaws, the hardware safeties in place prevented any deadly accidents.
Problem is, because of the hardware safeties, nobody knew just how bad the
software was. It had never been formally verified.
Then some numbskull
decided, "Hey, let's let the software handle the safety interlocking, and we can
cut down on hardware manufacturing costs!" The result was the Therac-25, which maimed and
killed people.
After the machine was recalled, someone finally sat down
and did a real analysis of the code, and found a whole raft of problems and bad
assumptions. Nancy Leveson wrote the definitive report (PDF) on the
failures in the R&D processes that made the Therac-25 so
deadly.
Yet, armed with this warning (among many others), both
manufacturers and purchasers keep human lives as transactions on a double-entry
ledger. It simply comes down to, how many deaths per thousand uses are
"acceptable"? Manufacturers and medical facilities already have so many costs.
Is it worth it to add on the cost of formal code analysis?
But nobody
will ask the Therac-25 victims and their families.
I decided early on
in my I.T. career, that I didn't want the stress of people's lives depending on
my correct code. I hadn't had any training in formal verification. In hindsight,
I see my worries would have come from incompetent management, more than from
myself.
Andy Warhol and Debbie Harry
on
The Amiga Turns 25
·
· Score: 2, Interesting
It's on YouTube here. The raw history of the occasion makes up for the downbeat aspect.
And just a month and a half ago, I came into possession of an Amiga 2000, with all the parts and manuals. Unfortunately, it seems not to be in working order, as nothing appears on the screen after a power-on. Ah, someday, maybe...
I have no problem with working from home, nor do I have a problem with using a VPN to do it.
But I do have a problem with mandating Windows onto my home network. If they want me to work from home, they will either (1) set up their outside access to allow non-Windows systems to connect, so that my firewall can afford some protection, or (2) provide the Windows computer and the connectivity, so that Windows stays off my home net.
Steve Ballmer's suggestion to use a system at both home and work, reeks of hubris. As soon as someone carries an infection from work to home unwittingly (and it WILL happen, even with the best A-V and firewall), the chair thrower will have to hide behind the Windows EULA, rather than own up to his implied warranty.
In the meantime, the company and the employee will argue about who was infected first, the company will fix the tablet/netbook/whatever, but the employee will be stuck with the cost of fixing his home system(s). And Microsoft laughs all the way to the bank.
Use Microsoft at work and home? Not just "no," but "HELL no!". When people arrange their computing needs so as to be bound to such an insecure system as Microsoft Windows, despite being warned from every direction about the dangers of doing so, then I have no sympathy for them when their systems get pwnz0r3d. For example:
Person A works for company B. Company B mandates use of Windows for access from outside corp network. Typical.
Scenario 1: Person A picks up malware unknowingly, and transmits it to company B's servers. Two days later, every single desktop on the corp network powers off suddenly and without warning at 2:05pm. Tough noogies. (Before you ask, yes, I saw something very similar happen. Twice. In two different workplaces.)
Scenario 2: I am person A. I tell company B that any Windows-only policy of theirs concerning my personal equipment, including my home network, is null and void. If the company wants me to work from home, using only Windows, the company can provide and maintain the equipment and connection at their expense.
The warnings are out there, all over the place, and Microsoft still can't put together a secure system. People will lock their cars, lock their doors at night or when they leave home, but they'll use Windows, plug in stray thumb drives, and browse with Internet Excoriator. Maybe they're betting that fat criminals who hardly ever go outside will be easier for the cops to catch?
If, at 18 or older, she was incapable of being responsible for her actions, she should have been institutionalized as a danger to herself and the people around her. By that age, the "why" doesn't matter. Her parents had eighteen years to get her ready for adult responsibilities. Protecting her from them until the day before her 18th birthday did her no favors.
That college student was, in all likelihood, an adult, not a child. She had passed her 18th birthday, and so was legally responsible for her own behavior. If she didn't have the sense to not do stupid shit (and avoid the people who would pressure her into doing stupid shit), that isn't my problem.
Stop thinking of the children, and start thinking of the future adults.
With so many data collection points working for Google, that's roughly what, three days' worth of data collected? It might take lesser companies a couple weeks to collect that much.
Really, has Microsoft had a trend-setting new product (not an update or sequel) since Steve Ballmer took the helm? Everything new product line they've come up with since 2000, from Xbox to the Kin, has been an attempt catch-up with someone, rather than blaze new trails.
I made nothing up, nowhere did I contradict myself, and you know it. The only way you could claim that, was to put words in my mouth (keyboard).
And pharmacists don't go to med school, they go to pharmacy school, and they still get their doctorates, so they are still doctors. But you couldn't be bothered to do the slightest research, could you?
Tell me, do you also believe that people with lots of qualifications have no common sense?
Far from it. But people with qualifications but no common sense, tend to go farther than people with neither qualifications nor common sense. That's true in any hierarchical organization. And the ones that have gone far, without a lick of common sense, tend to make an impression.
So intentionally "throwing" an exam caused here interpersonal skills to soar?
Cart before the horse. She had the interpersonal skills, but had no desire for her instructors to recommend her for research positions. Throwing her exams kept her from standing out in her class, and kept her later interviewers from looking at her like, "If you're so outrageously smart, what're you doing here?". It's a field which tends to value research positions highly, but she didn't (and doesn't) want to be a faceless name from a laboratory. Working with people has always been her focus. And, being the daughter of a doctor, she had a fairly good idea of the job requirements.
No matter; the one who graduates last in his class in med school is still called "Doctor".
That's the whole point of TFA: the straight-A students are the ones who can't communicate with the "man on the street." They're so immersed in the science, they lose touch with the human aspect of their work.
As for my friend, she definitely could get straight A's, but chose not to. No matter; the one who graduates last in his class in med school is still called "Doctor".
On why she didn't want to excel too much in med school: "The straight-A students end up in research. The B and C students are the ones that work with patients."
Today, she has a very successful private medical practice.
Slashdot Mirror
You mean they won't tolerate dishonest behavior among officials in Tooele County, Utah?
Oh, you mean the people they do business with. So, does that mean they won't tolerate dishonest behavior from any of their customers?
Apple, our self-appointed Messiahs. That reality distortion field is a lot stronger than I thought.
Very informative, but pure page sharing doesn't work for most Windows variants, due to the fact that Windows binaries aren't position independent.
Is that also true for 64-bit Windows binaries? According to the docs I've read, position-independent binary code is preferred in 64-bits.
I tested shred against XFS, and found that it writes to the journal, rather than to the file data in-place. So shred is not safe to use on XFS.
I can verify this, very simply. I'll use JFS as my example, and I'll use two hard drives, to make I/O monitoring simple.
/dev/sda2 /dev/sdb2", with journal on sda2, and main FS on sdb2. Mount the filesystem (I'll assume at /mnt).
/mnt/zeros". Note the drive with the activity; it's the drive with the file system on it, not the journal. Since anything other than overwriting in place, would involve meta-data operations, ergo journal activity, the file is being over-written in place. QED.
First, create the file system with "mkfs.jfs -j
Create a large-ish file: "dd if=/dev/zero of=/mnt/zeros bs=1048576 count=96". Run "sync" to flush buffers.
Now, if anything about that file besides its own file data changes, it'll go to the journal first. That includes file relocation, which is a block map operation. The file data OTOH goes directly to the file system.
Run your favorite disk I/O monitor. I use gkrellm, but you may also use "procinfo -Dn1" or "iotop". Make sure it's something that lets you watch individual disks' activities, not just the sum total activity.
Run "shred -n25 -vu
XFS is the opposite; shred writes to the journal. Sigh.
Shred also works on drives. I shredded a Deskstar with a 25-pass wipe, which took over 16 hours. (And in a stroke of good timing, it started making the Deskstar "click of death" sounds less than 10 minutes after it finished.)
But about file system journals. It's a bit much to say "any file system" besides ext2 defeats shred. The concern is this: If file data is committed to the journal first, rather than the filesystem proper, the only way shredding is secure is to shred a file that's larger than the journal. Otherwise, multiple overwrites of file data are actually going to the journal, where they'll be analyzed, all but the last overwrite will be canceled, and the file data in the filesystem ends up with only a single overwrite.
Part of the purpose of shredding a file, is to overwrite the residual magnetic flux between tracks on a platter. Multiple overwrites on the platter will do this; shred used to do 25 overwrites by default, which was good enough for DoD secure erasure requirements. However, a FS journal would defeat this on a file that was less than 1/25 the size of the journal.
Ext3/4 can do this, but not by default; the default is "ordered" mode, where file data goes directly to the FS, and then its metadata goes to the journal. A mount option can change this temporarily, and "tune2fs" can change the mode persistently.
XFS and JFS journal only metadata, so shredding a file on those FS's is safe. You can verify this with an external journal on a different drive, then watch where the activity is during a shred. It isn't in the journal.
OTOH, log-structured file systems like Btrfs may or may not erase the data in place; if the data is part of a snapshot, then later overwrites don't remove the snapshot.
Yes, this is a lot to think about.
The percentage of people who are harmed by arsenic (100) vs. the percentage of people who are harmed by gluten (small).
For pure arsenic, that's true. It still has its uses in medicine, such as oncology where it works better than iodine for locating tumors.
Oh, and have you eaten fish lately? You probably consumed a milligram of arsenic. But, since you're reading this, I'll assume you're still alive and well.
You can't push coins or bills down an IP connection, no matter how fat or thin.
More like, refusing to do business with a convicted, unrepentant monopolist.
This is probably a beautiful photograph that I will never see because I choose not to surrender my PC to a convicted monopolist.
FTFY.
Someone re-captioned it, and Randall Munroe is hosting it.
I think they both work.
The Therac-20 radiation therapy device worked reasonably well. Despite the software flaws, the hardware safeties in place prevented any deadly accidents. Problem is, because of the hardware safeties, nobody knew just how bad the software was. It had never been formally verified.
Then some numbskull decided, "Hey, let's let the software handle the safety interlocking, and we can cut down on hardware manufacturing costs!" The result was the Therac-25, which maimed and killed people.
After the machine was recalled, someone finally sat down and did a real analysis of the code, and found a whole raft of problems and bad assumptions. Nancy Leveson wrote the definitive report (PDF) on the failures in the R&D processes that made the Therac-25 so deadly.
Yet, armed with this warning (among many others), both manufacturers and purchasers keep human lives as transactions on a double-entry ledger. It simply comes down to, how many deaths per thousand uses are "acceptable"? Manufacturers and medical facilities already have so many costs. Is it worth it to add on the cost of formal code analysis?
But nobody will ask the Therac-25 victims and their families.
I decided early on in my I.T. career, that I didn't want the stress of people's lives depending on my correct code. I hadn't had any training in formal verification. In hindsight, I see my worries would have come from incompetent management, more than from myself.
It's on YouTube here. The raw history of the occasion makes up for the downbeat aspect.
And just a month and a half ago, I came into possession of an Amiga 2000, with all the parts and manuals. Unfortunately, it seems not to be in working order, as nothing appears on the screen after a power-on. Ah, someday, maybe...
Next year's model will be the MaxiPad.
I have no problem with working from home, nor do I have a problem with using a VPN to do it.
But I do have a problem with mandating Windows onto my home network. If they want me to work from home, they will either (1) set up their outside access to allow non-Windows systems to connect, so that my firewall can afford some protection, or (2) provide the Windows computer and the connectivity, so that Windows stays off my home net.
Steve Ballmer's suggestion to use a system at both home and work, reeks of hubris. As soon as someone carries an infection from work to home unwittingly (and it WILL happen, even with the best A-V and firewall), the chair thrower will have to hide behind the Windows EULA, rather than own up to his implied warranty.
In the meantime, the company and the employee will argue about who was infected first, the company will fix the tablet/netbook/whatever, but the employee will be stuck with the cost of fixing his home system(s). And Microsoft laughs all the way to the bank.
Use Microsoft at work and home? Not just "no," but "HELL no!". When people arrange their computing needs so as to be bound to such an insecure system as Microsoft Windows, despite being warned from every direction about the dangers of doing so, then I have no sympathy for them when their systems get pwnz0r3d. For example:
Person A works for company B. Company B mandates use of Windows for access from outside corp network. Typical.
Scenario 1: Person A picks up malware unknowingly, and transmits it to company B's servers. Two days later, every single desktop on the corp network powers off suddenly and without warning at 2:05pm. Tough noogies. (Before you ask, yes, I saw something very similar happen. Twice. In two different workplaces.)
Scenario 2: I am person A. I tell company B that any Windows-only policy of theirs concerning my personal equipment, including my home network, is null and void. If the company wants me to work from home, using only Windows, the company can provide and maintain the equipment and connection at their expense.
The warnings are out there, all over the place, and Microsoft still can't put together a secure system. People will lock their cars, lock their doors at night or when they leave home, but they'll use Windows, plug in stray thumb drives, and browse with Internet Excoriator. Maybe they're betting that fat criminals who hardly ever go outside will be easier for the cops to catch?
No sympathy from this direction.
If, at 18 or older, she was incapable of being responsible for her actions, she should have been institutionalized as a danger to herself and the people around her. By that age, the "why" doesn't matter. Her parents had eighteen years to get her ready for adult responsibilities. Protecting her from them until the day before her 18th birthday did her no favors.
That college student was, in all likelihood, an adult, not a child. She had passed her 18th birthday, and so was legally responsible for her own behavior. If she didn't have the sense to not do stupid shit (and avoid the people who would pressure her into doing stupid shit), that isn't my problem.
Stop thinking of the children, and start thinking of the future adults.
With so many data collection points working for Google, that's roughly what, three days' worth of data collected? It might take lesser companies a couple weeks to collect that much.
Really, has Microsoft had a trend-setting new product (not an update or sequel) since Steve Ballmer took the helm? Everything new product line they've come up with since 2000, from Xbox to the Kin, has been an attempt catch-up with someone, rather than blaze new trails.
Here.
I made nothing up, nowhere did I contradict myself, and you know it. The only way you could claim that, was to put words in my mouth (keyboard).
And pharmacists don't go to med school, they go to pharmacy school, and they still get their doctorates, so they are still doctors. But you couldn't be bothered to do the slightest research, could you?
Tell me, do you also believe that people with lots of qualifications have no common sense?
Far from it. But people with qualifications but no common sense, tend to go farther than people with neither qualifications nor common sense. That's true in any hierarchical organization. And the ones that have gone far, without a lick of common sense, tend to make an impression.
So intentionally "throwing" an exam caused here interpersonal skills to soar?
Cart before the horse. She had the interpersonal skills, but had no desire for her instructors to recommend her for research positions. Throwing her exams kept her from standing out in her class, and kept her later interviewers from looking at her like, "If you're so outrageously smart, what're you doing here?". It's a field which tends to value research positions highly, but she didn't (and doesn't) want to be a faceless name from a laboratory. Working with people has always been her focus. And, being the daughter of a doctor, she had a fairly good idea of the job requirements.
A med student who needs to re-take some classes.
There's a serious analysis here, with some extra commentary by OS News here.
That's the whole point of TFA: the straight-A students are the ones who can't communicate with the "man on the street." They're so immersed in the science, they lose touch with the human aspect of their work.
As for my friend, she definitely could get straight A's, but chose not to. No matter; the one who graduates last in his class in med school is still called "Doctor".
On why she didn't want to excel too much in med school: "The straight-A students end up in research. The B and C students are the ones that work with patients."
Today, she has a very successful private medical practice.