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Name: Russell Coker
Member since: 2001-02-19 14:53:50
Last Login: 2009-02-24 04:55:31

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Homepage: http://etbe.coker.com.au/

Notes:

I do general Linux programming and sys-admin work. I am mostly known for my work on NSA Security Enhanced Linux.

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BTRFS Status Dec 2014

My last problem with BTRFS was in August [1]. BTRFS has been running mostly uneventfully for me for the last 4 months, that’s a good improvement but the fact that 4 months of no problems is noteworthy for something as important as a filesystem is a cause for ongoing concern.

A RAID-1 Array

A week ago I had a minor problem with my home file server, one of the 3TB disks in the BTRFS RAID-1 started giving read errors. That’s not a big deal, I bought a new disk and did a “btrfs replace” operation which was quick and easy. The first annoyance was that the output of “btrfs device stats” reported an error count for the new device, it seems that “btrfs device replace” copies everything from the old disk including the error count. The solution is to use “btrfs device stats -z” to reset the count after replacing a device.

I replaced the 3TB disk with a 4TB disk (with current prices it doesn’t make sense to buy a new 3TB disk). As I was running low on disk space I added a 1TB disk to give it 4TB of RAID-1 capacity, one of the nice features of BTRFS is that a RAID-1 filesystem can support any combination of disks and use them to store 2 copies of every block of data. I started running a btrfs balance to get BTRFS to try and use all the space before learning from the mailing list that I should have done “btrfs filesystem resize” to make it use all the space. So my balance operation had configured the filesystem to configure itself for 2*3TB+1*1TB disks which wasn’t the right configuration when the 4TB disk was fully used. To make it even more annoying the “btrfs filesystem resize” command takes a “devid” not a device name.

I think that when BTRFS is more stable it would be good to have the btrfs utility warn the user about such potential mistakes. When a replacement device is larger than the old one it will be very common to want to use that space. The btrfs utility could easily suggest the most likely “btrfs filesystem resize” to make things easier for the user.

In a disturbing coincidence a few days after replacing the first 3TB disk the other 3TB disk started giving read errors. So I replaced the second 3TB disk with a 4TB disk and removed the 1TB disk to give a 4TB RAID-1 array. This is when it would be handy to have the metadata duplication feature and copies= option of ZFS.

Ctree Corruption

2 weeks ago a basic workstation with a 120G SSD owned by a relative stopped booting, the most significant errors it gave were “BTRFS: log replay required on RO media” and “BTRFS: open_ctree failed”. The solution to this is to run the command “btrfs-zero-log”, but that initially didn’t work. I restored the system from a backup (which was 2 months old) and took the SSD home to work on it. A day later “btrfs-zero-log” worked correctly and I recovered all the data. Note that I didn’t even try mounting the filesystem in question read-write, I mounted it read-only to copy all the data off. While in theory the filesystem should have been OK I didn’t have a need to keep using it at that time (having already wiped the original device and restored from backup) and I don’t have confidence in BTRFS working correctly in that situation.

While it was nice to get all the data back it’s a concern when commands don’t operate consistently.

Debian and BTRFS

I was concerned when the Debian kernel team chose 3.16 as the kernel for Jessie (the next Debian release). Judging by the way development has been going I wasn’t confident that 3.16 would turn out to be stable enough for BTRFS. But 3.16 is working reasonably well on a number of systems so it seems that it’s likely to work well in practice.

But I’m still deploying more ZFS servers.

The Value of Anecdotal Evidence

When evaluating software based on reports from reliable sources (IE most readers will trust me to run systems well and only report genuine bugs) bad reports have a much higher weight than good reports. The fact that I’ve seen kernel 3.16 to work reasonably well on ~6 systems is nice but that doesn’t mean it will work well on thousands of other systems – although it does indicate that it will work well on more systems than some earlier Linux kernels which had common BTRFS failures.

But the annoyances I had with the 3TB array are repeatable and will annoy many other people. The ctree coruption problem MIGHT have been initially caused by a memory error (it’s a desktop machine without ECC RAM) but the recovery process was problematic and other users might expect problems in such situations.

Related posts:

  1. BTRFS Status March 2014 I’m currently using BTRFS on most systems that I can...
  2. BTRFS Status April 2014 Since my blog post about BTRFS in March [1] not...
  3. BTRFS Status July 2014 My last BTRFS status report was in April [1], it...

Syndicated 2014-12-05 08:09:27 from etbe - Russell Coker

Links October 2014

The Verge has an interesting article about Tim Cook (Apple CEO) coming out [1]. Tim says “if hearing that the CEO of Apple is gay can help someone struggling to come to terms with who he or she is, or bring comfort to anyone who feels alone, or inspire people to insist on their equality, then it’s worth the trade-off with my own privacy”.

Graydon2 wrote an insightful article about the right-wing libertarian sock-puppets of silicon valley [2].

George Monbiot wrote an insightful article for The Guardian about the way that double-speak facilitates killing people [3]. He is correct that the media should hold government accountable for such use of language instead of perpetuating it.

Anne Thériault wrote an insightful article for Vice about the presumption of innocence and sex crimes [4].

Dr Nerdlove wrote an interesting article about Gamergate as the “extinction burst” of “gamer culture” [5], we can only hope.

Shweta Narayan wrote an insightful article about Category Structure and Oppression [6]. I can’t summarise it because it’s a complex concept, read the article.

Some Debian users who don’t like Systemd have started a “Debian Fork” project [7], which so far just has a web site and nothing else. I expect that they will never write any code. But it would be good if they did, they would learn about how an OS works and maybe they wouldn’t disagree so much with the people who have experience in developing system software.

A GamerGate terrorist in Utah forces Anita Sarkeesian to cancel a lecture [8]. I expect that the reaction will be different when (not if) an Islamic group tries to get a lecture cancelled in a similar manner.

Model View Culture has an insightful article by Erika Lynn Abigail about Autistics in Silicon Valley [9].

Katie McDonough wrote an interesting article for Salon about Ed Champion and what to do about men who abuse women [10]. It’s worth reading that while thinking about the FOSS community…

Related posts:

  1. Links September 2014 Matt Palmer wrote a short but informative post about enabling...
  2. Links July 2014 Dave Johnson wrote an interesting article for Salon about companies...
  3. Links August 2014 Matt Palmer wrote a good overview of DNSSEC [1]. Sociological...

Syndicated 2014-10-31 13:55:52 from etbe - Russell Coker

Samsung Galaxy Note 3

In June last year I bought a Samsung Galaxy Note 2 [1]. Generally I was very happy with that phone, one problem I had is that less than a year after purchasing it the Ingress menus burned into the screen [2].

2 weeks ago I bought a new Galaxy Note 3. One of the reasons for getting it is the higher resolution screen, I never realised the benefits of a 1920*1080 screen on a phone until my wife got a Nexus 5 [3]. I had been idly considering a Galaxy Note 4, but $1000 is a lot of money to pay for a phone and I’m not sure that a 2560*1440 screen will offer much benefit in that size. Also the Note 3 and Note 4 both have 3G of RAM, as some applications use more RAM when you have a higher resolution screen the Note 4 will effectively have less usable RAM than the Note 3.

My first laptop cost me $3,800 in 1998, that’s probably more than $6,000 in today’s money. The benefits that I receive now from an Android phone are in many ways greater than I received from that laptop and that laptop was definitely good value for money for me. If the cheapest Android phone cost $6,000 then I’d pay that, but given that the Note 3 is only $550 (including postage) there’s no reason for me to buy something more expensive.

Another reason for getting a new phone is the limited storage space in the Note 2. 16G of internal storage is a limit when you have some big games installed. Also the recent Android update which prevented apps from writing to the SD card meant that it was no longer convenient to put TV shows on my SD card. 32G of internal storage in the Note 3 allows me to fit everything I want (including the music video collection I downloaded with youtube-dl). The Note 2 has 16G of internal storage and an 8G SD card (that I couldn’t fully use due to Android limitations) while the Note 3 has 32G (the 64G version wasn’t on sale at any of the cheap online stores). Also the Note 3 supports an SD card which will be good for my music video collection at some future time, this is a significant benefit over the Nexus 5.

In the past I’ve written about Android service life and concluded that storage is the main issue [4]. So it is a bit unfortunate that I couldn’t get a phone with 64G of storage at a reasonable price. But the upside is that getting a cheaper phone allows me to buy another one sooner and give the old phone to a relative who has less demanding requirements.

In the past I wrote about the warranty support for my wife’s Nexus 5 [5]. I should have followed up on that before, 3 days after that post we received a replacement phone. One good thing that Google does is to reserve money on a credit card to buy the new phone and then send you the new phone before you send the old one back. So if the customer doesn’t end up sending the broken phone they just get billed for the new phone, that avoids excessive delays in getting a replacement phone. So overall the process of Google warranty support is really good, if 2 products are equal in other ways then it would be best to buy from Google to get that level of support.

I considered getting a Nexus 5 as the hardware is reasonably good (not the greatest but quite good enough) and the price is also reasonably good. But one thing I really hate is the way they do the buttons. Having the home button appear on the main part of the display is really annoying. I much prefer the Samsung approach of having a hardware button for home and touch-screen buttons outside the viewable area for settings and back. Also the stylus on the Note devices is convenient on occasion.

The Note 3 has a fake-leather back. The concept of making fake leather is tacky, I believe that it’s much better to make honest plastic that doesn’t pretend to be something that it isn’t. However the texture of the back improves the grip. Also the fake stitches around the edge help with the grip too. It’s tacky but utilitarian.

The Note 3 is slightly smaller and lighter than the Note 2. This is a good technical achievement, but I’d rather they just gave it a bigger battery.

Update USB 3

One thing I initially forgot to mention is that the Note 3 has USB 3. This means that it has a larger socket which is less convenient when you try and plug it in at night. USB 3 seems unlikely to provide any benefit for me as I’ve never had any of my other phones transfer data at rates more than about 5MB/s. If the Note 3 happens to have storage that can handle speeds greater than the 32MB/s a typical USB 2 storage device can handle then I’m still not going to gain much benefit. USB 2 speeds would allow me to transfer the entire contents of a Note 3 in less than 20 minutes (if I needed to copy the entire storage contents). I can’t imagine myself having a real-world benefit from that.

The larger socket means more fumbling when charging my phone at night and it also means that the Note 3 cable can’t be used in any other phone I own. In a year or two my wife will have a phone with USB 3 support and that cable can be used for charging 2 phones. But at the moment the USB 3 cable isn’t useful as I don’t need to have a phone charger that can only charge one phone.

Conclusion

The Note 3 basically does everything I expected of it. It’s just like the Note 2 but a bit faster and with more storage. I’m happy with it.

Related posts:

  1. Samsung Galaxy Note 2 A few weeks ago I bought a new Samsung Galaxy...
  2. Samsung Galaxy S3 First Review with Power Case My new Samsung Galaxy S3 arrived a couple of days...
  3. Samsung Galaxy Camera – a Quick Review I recently had a chance to briefly play with the...

Syndicated 2014-10-31 13:40:25 from etbe - Russell Coker

Samsung Galaxy Note 3

In June last year I bought a Samsung Galaxy Note 2 [1]. Generally I was very happy with that phone, one problem I had is that less than a year after purchasing it the Ingress menus burned into the screen [2].

2 weeks ago I bought a new Galaxy Note 3. One of the reasons for getting it is the higher resolution screen, I never realised the benefits of a 1920*1080 screen on a phone until my wife got a Nexus 5 [3]. I had been idly considering a Galaxy Note 4, but $1000 is a lot of money to pay for a phone and I’m not sure that a 2560*1440 screen will offer much benefit in that size. Also the Note 3 and Note 4 both have 3G of RAM, as some applications use more RAM when you have a higher resolution screen the Note 4 will effectively have less usable RAM than the Note 3.

My first laptop cost me $3,800 in 1998, that’s probably more than $6,000 in today’s money. The benefits that I receive now from an Android phone are in many ways greater than I received from that laptop and that laptop was definitely good value for money for me. If the cheapest Android phone cost $6,000 then I’d pay that, but given that the Note 3 is only $550 (including postage) there’s no reason for me to buy something more expensive.

Another reason for getting a new phone is the limited storage space in the Note 2. 16G of internal storage is a limit when you have some big games installed. Also the recent Android update which prevented apps from writing to the SD card meant that it was no longer convenient to put TV shows on my SD card. 32G of internal storage in the Note 3 allows me to fit everything I want (including the music video collection I downloaded with youtube-dl). The Note 2 has 16G of internal storage and an 8G SD card (that I couldn’t fully use due to Android limitations) while the Note 3 has 32G (the 64G version wasn’t on sale at any of the cheap online stores). Also the Note 3 supports an SD card which will be good for my music video collection at some future time, this is a significant benefit over the Nexus 5.

In the past I’ve written about Android service life and concluded that storage is the main issue [4]. So it is a bit unfortunate that I couldn’t get a phone with 64G of storage at a reasonable price. But the upside is that getting a cheaper phone allows me to buy another one sooner and give the old phone to a relative who has less demanding requirements.

In the past I wrote about the warranty support for my wife’s Nexus 5 [5]. I should have followed up on that before, 3 days after that post we received a replacement phone. One good thing that Google does is to reserve money on a credit card to buy the new phone and then send you the new phone before you send the old one back. So if the customer doesn’t end up sending the broken phone they just get billed for the new phone, that avoids excessive delays in getting a replacement phone. So overall the process of Google warranty support is really good, if 2 products are equal in other ways then it would be best to buy from Google to get that level of support.

I considered getting a Nexus 5 as the hardware is reasonably good (not the greatest but quite good enough) and the price is also reasonably good. But one thing I really hate is the way they do the buttons. Having the home button appear on the main part of the display is really annoying. I much prefer the Samsung approach of having a hardware button for home and touch-screen buttons outside the viewable area for settings and back. Also the stylus on the Note devices is convenient on occasion.

The Note 3 has a fake-leather back. The concept of making fake leather is tacky, I believe that it’s much better to make honest plastic that doesn’t pretend to be something that it isn’t. However the texture of the back improves the grip. Also the fake stitches around the edge help with the grip too. It’s tacky but utilitarian.

The Note 3 is slightly smaller and lighter than the Note 2. This is a good technical achievement, but I’d rather they just gave it a bigger battery.

Conclusion

The Note 3 basically does everything I expected of it. It’s just like the Note 2 but a bit faster and with more storage. I’m happy with it.

Related posts:

  1. Samsung Galaxy Note 2 A few weeks ago I bought a new Samsung Galaxy...
  2. Samsung Galaxy S3 First Review with Power Case My new Samsung Galaxy S3 arrived a couple of days...
  3. Samsung Galaxy Camera – a Quick Review I recently had a chance to briefly play with the...

Syndicated 2014-10-31 12:55:25 from etbe - Russell Coker

Links September 2014

Matt Palmer wrote a short but informative post about enabling DNS in a zone [1]. I really should setup DNSSEC on my own zones.

Paul Wayper has some insightful comments about the Liberal party’s nasty policies towards the unemployed [2]. We really need a Basic Income in Australia.

Joseph Heath wrote an interesting and insightful article about the decline of the democratic process [3]. While most of his points are really good I’m dubious of his claims about twitter. When used skillfully twitter can provide short insights into topics and teasers for linked articles.

Sarah O wrote an insightful article about NotAllMen/YesAllWomen [4]. I can’t summarise it well in a paragraph, I recommend reading it all.

Betsy Haibel wrote an informative article about harassment by proxy on the Internet [5]. Everyone should learn about this before getting involved in discussions about “controversial” issues.

George Monbiot wrote an insightful and interesting article about the referendum for Scottish independence and the failures of the media [6].

Mychal Denzel Smith wrote an insightful article “How to know that you hate women” [7].

Sam Byford wrote an informative article about Google’s plans to develop and promote cheap Android phones for developing countries [8]. That’s a good investment in future market share by Google and good for the spread of knowledge among people all around the world. I hope that this research also leads to cheap and reliable Android devices for poor people in first-world countries.

Deb Chachra wrote an insightful and disturbing article about the culture of non-consent in the IT industry [9]. This is something we need to fix.

David Hill wrote an interesting and informative article about the way that computer game journalism works and how it relates to GamerGate [10].

Anita Sarkeesian shares the most radical thing that you can do to support women online [11]. Wow, the world sucks more badly than I realised.

Michael Daly wrote an article about the latest evil from the NRA [12]. The NRA continues to demonstrate that claims about “good people with guns” are lies, the NRA are evil people with guns.

Related posts:

  1. Links July 2014 Dave Johnson wrote an interesting article for Salon about companies...
  2. Links May 2014 Charmian Gooch gave an interesting TED talk about her efforts...
  3. Links September 2013 Matt Palmer wrote an insightful post about the use of...

Syndicated 2014-09-30 13:55:48 from etbe - Russell Coker

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