Older blog entries for etbe (starting at number 955)

Long Term Adverts

I’ve just seen a mailing list post from someone who needs an ancient printer to work with their old software. As the printer is no longer manufactured and changing the software is expensive this puts them in a difficult situation – which can be profitable for someone who happens to own an ancient printer that still works. This sort of thing is not uncommon at all.

Ebay is a nice auction and online store site but it doesn’t cater for long term personal adverts. I’ve got a lot of old computer equipment that I keep because it might be useful at some time and it’s a shame to throw away working equipment. I’d like to be able to list that stuff on a sale site and have the adverts stay online for years just in case someone wants to pay a decent amount of money for it. If there was such a site I would also list all the systems in my test network, I can test software just as well with different hardware if someone wants to pay decent money for what I’ve currently got.

Storage space is pretty cheap and searching for keywords isn’t that difficult either. The cost of running an online personal sale site for items that sell every few years isn’t going to be much greater than running one that sells items after 10 days. But the profit in many cases will be a lot greater, an old printer that sells for $10 on Ebay could go for $200 or more if the seller could wait for a buyer who had some enterprise software that absolutely depended on that particular printer.

Does anyone know of such an online sale site? If not does anyone want to start one?

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Syndicated 2012-03-19 02:24:35 from etbe - Russell Cokeretbe - Russell Coker

Airtasker – Outsourcing Small Jobs

Airtasker.com is a new company that is dedicated to outsourcing small jobs [1]. It’s still in a “beta” phase and has no way of making money – the worker is paid directly by the employer and there’s no facility for either of them to pay Airtasker, I would really like to know what the business model will be before considering whether to use it. It also doesn’t seem to operate outside of Sydney which seems quite strange, how hard can it be to have separate Google maps instances for each city in Australia?

The jobs that are advertised seem to be mostly household repair tasks and from the member list it appears that some people who already run small service businesses are trying to use Airtasker to get more work. There are also a lot of delivery tasks such as buying something from a shop and delivering it and driving a car from Melbourne to Sydney (good for someone who wants a subsidised interstate holiday). But there are some unusual tasks such as pretending to be someone’s girlfriend to make his mother stop nagging him.

It will be interesting to see whether this takes off. One thing that I might use it for is delivering computer equipment in the CBD. Some of my clients have no good parking near their office so I end up carrying computer gear from a tram stop or an inconvenient parking spot to their office. I’d rather have someone paid to do at least half the work in carrying the gear and the rates that are being discussed on Airtasker are well within the range that my clients would be happy to pay.

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Syndicated 2012-03-13 12:31:39 from etbe - Russell Cokeretbe - Russell Coker

USB Flash Storage

For some years I have had my Internet gateway/firewall system in a cupboard in my bedroom. While I don’t mind some computer noise (I’ve slept near a server for most of the last 22 years) it’s good to have it as quiet as possible so getting rid of the hard drive is desirable.

I considered buying an IDE flash drive, but I’d like to continue my trend of not paying for hardware so I chose to use some USB flash devices that HP was giving away at a seminar (thanks HP – as an aside the P3 system is an old Compaq Desktop system). So I’ve got one 4G USB device for root and one for Squid.

For the past few months I’ve had /var/spool/squid be a USB flash device. I considered using RAID-0 for that filesystem because the computer is a P3 and only has USB 1.2 and thus a maximum theoretical transfer rate of 1.5MB/s and a maximum real-world rate of about 1MB/s. But my ADSL connection doesn’t seem able to sustain much more than 1MB/s and Squid doesn’t write data synchronously so in all my tests the USB speed hasn’t affected HTTP performance.

One issue that has delayed my move to all USB is the difficulty of booting as the P3 system in question doesn’t support booting from USB. I considered creating a boot CD that loads the kernel from the USB device, but that seemed a little painful and also relies on the CD-ROM drive working – which isn’t a great idea for a system that runs 24*7 in a dusty cupboard. I ended up using GRUB on the IDE hard drive to load the kernel and initrd and then mount a USB device as root, this seems to work and the command “hdparm -S6 /dev/sda” in /etc/rc.local makes the hard drive go to sleep once the system is booted.

The only technical parts of the process were putting in the UUIDs of the filesystems in /etc/fstab (because I can’t be sure which USB device will be found first) and creating a new initramfs with modules for USB storage listed in /etc/initramfs-tools/modules so that a USB device could be the root filesystem.

The firewall system is now a bit quieter and based on my last tests of hard drive power use will probably dissipate about 5-7W less heat. The next thing to do is wait and see if it keeps running or falls over. ;)

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Syndicated 2012-03-11 11:58:27 from etbe - Russell Cokeretbe - Russell Coker

SE Linux Status in Debian 2012-03

I have just finished updating the user-space SE Linux code in Debian/Unstable to the version released on 2012-02-16. There were some changes to the build system from upstream which combined with the new Debian multi-arch support involved a fair bit of work for me. While I was at it I converted more of them to the new Quilt format to make it easier to send patches upstream. In the past I have been a bit slack about sending patches upstream, my aim for the next upstream release of user-space is to have at least half of my patches included upstream – this will make things easier for everyone.

Recently Mika Pflüger and Laurent Bigonville have started work on Debian SE Linux, they have done some good work converting the refpolicy source (which is used to build selinux-policy-default) to Quilt. Now it will be a lot easier to send policy patches upstream and porting them to newer versions of the upstream refpolicy.

Now the next significant thing that I want to do is to get systemd working correctly with SE Linux. But first I have to get it working correctly wit cryptsetup.

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Syndicated 2012-03-06 06:44:33 from etbe - Russell Cokeretbe - Russell Coker

LUV Hardware Library

What is it?

Last month I started what I am calling the LUV Hardware Library. It’s a briefcase full of computer parts that are free to LUV members which I plan to bring to all LUV meetings [1]. The issue is that there is a lot of hardware which has no great value to people and is often excess to requirements but which is still somewhat expensive or difficult to obtain and thus transferring it from the people who don’t need it to people who do provides a significant benefit to the recipient but no real cost to the donor.

Currently my briefcase has a range of different types of DIMM, some PCI cards, some assorted cables, a laptop SATA disk, and a bunch of other random things. Most of the stuff has been in my spare parts pile for a year or two, but some of it has been donated by other people.

What we Need

The next thing we need is more packaging, anti-static bags for RAM and PCI cards, sealable bags for screws, and some way of storing motherboard batteries.

In terms of hardware that can be donated one thing that would be really useful is SATA disks. I’m sure that there are lots of people who have upgraded the storage of their computer and kept the old drive with no real chance of using it. But there are lots of people who need such disks, for example I’ve been giving away a bunch of P4 systems which lack disks and are not cabled for IDE disks – a supply of SATA disks would make them a lot more usable.

Also any other random electronic stuff is of interest, including non-Linux things such as mobile phones (but only if not network locked).

If you have something that’s big or heavy to donate then contact me via email first.

Other Options

Computerbank does great work in rebuilding old PCs and selling them cheaply to worthy people [2], but most of the spare hardware I get is below the minimum specs that they will accept. I’m not planning to compete with Computerbank in any way, I just want to provide a useful service to LUV members who want to upgrade their PC for free.

I encourage other people to do the same at other LUG meetings!

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Syndicated 2012-03-05 10:33:13 from etbe - Russell Coker

Links February 2012

Sociological Images has an interesting article about the attempts to apply the word “Camping” to OWS and framing the issues [1].

Lester Macgurdy wrote an insightful article about “the snake”, a new technique for OWS protesters to beat riot police [2].

Ron Barassi suggests that “Australia Day” be celebrated on the 27th of May to commemorate the day in 1967 when the Australian constitution was amended to not be racist [3]. The current “Australia Day” is often referred to as “Invasion Day”. IMHO Ron deserves another “Best and Fairest” award.

Stefon Harris gave an entertaining TED talk about improv Jazz music titled “There Are No Mistakes on the Bandstand” [4]. It seems that his concepts can apply to some extent to many collaborative projects.

John Robb wrote an interesting article about the future of drone (UAV) warfare [5]. He suggests that having one person control each drone is a temporary thing and that the future is to have a cloud of cheap autonomous drones taking strategic control from one person. His comparison of Starcraft players to future drone fighters is interesting.

The OWS movement is branching out into other related areas, OccupyYourHomes.org is one of the latest ones [6]. When banks try to forclose on homes without good cause the OWS people are protesting.

Cory Doctorow wrote an important article for The Guardian about corporations using the Youtube ContentID system to pirate works that other people have uploaded [7].

Matt Taibbi’s description of Goldman Sachs as “a great vampire squid wrapped around the face of humanity, relentlessly jamming its blood funnel into anything that smells like money” will never die [8]. It has spawned many other creative descriptions of the evil and greed of Goldman Sachs and even Lloyd Blankfein of Goldman Sachs describes his company as having “burned down the Reichstag, shot the Archduke Ferdinand and fired on Fort Sumter” – he was trying to use satire, but I don’t think that Goldman Sachs people would act differently to Fritz Thyssen.

Keith Packard wrote an interesting article about the Calypso CalDAV system which he uses with Android [9]. He makes lots of good points about how to improve calendaring and contacts on Android, unfortunately I lack time to fiddle with such things at the moment so I’ll stick with Google in spite of the risks.

Asheesh Laroia wrote a great article about the problems with short (32bit) GPG keys [10]. It seems that creating keys with matching ID numbers isn’t particularly difficult and that GPG doesn’t handle them as well as we would like giving the possibility of at best annoying DoS attacks and at worse security problems due to using the wrong key.

Sociological Images has an interesting article about when game show audiences are trustworthy [11]. It seems that French people don’t want an undeserving person to win so they will intentionally advocate the wrong answer if the contestant should know it.

Paul Wayper gave a great lecture titled “SE Linux for Everyone” [12]. He covers the basics of SE Linux in a user-friendly way and explains some simple solutions to common problems which don’t involve compromising system security.

Paul Tassi wrote an insightful article for Forbes about piracy [13]. His conclusion is that the media companies should make it cheaper and easier to be a customer and not spend insane amounts of money on low quality products.

The Reid Report has an interesting article about Ron Paul’s racism [14]. Ron Paul is generally well regarded outside the US because he wants the US government to stop meddling in the affairs of other countries, but while he’s less bad than other US politicians in terms of foreign policy that doesn’t make him a good person.

Anonymous hacked some mailboxes belonging to a neo-Nazi group and found links to Ron Paul [15]. I’ve always been suspicious of the way Ron Paul wanted to avoid anti-racism legislation on supposed Libertarian principles.

The Reid Report has an interesting summary of Ron Paul news plus some criticism of Glenn Greenwald and others who associate with him [16].

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Syndicated 2012-02-15 15:19:51 from etbe - Russell Coker

Cooling a Thinkpad

Late last year I wrote about the way that modern laptops suck [1]. One of the problems that inspired that post was the excessive heat generated by my Thinkpad T61.

There is a partial solution to this, Fool Control explains how the kernel option pcie_aspm=force can be used on kernels from 2.6.38 onwards to solve a heat regression problem [2]. I applied this to my Thinkpad T61 and the result was that on a cool evening (ambient temperature about 24C) the temperature changed from 85C to 66C on the NVidia video card, and for the “virtual devices” it changed from 80C and 78C to 60C and 61C. I’m not sure exactly what each of those measurements refers to, but it seems that the change was somewhere between 17C and 20C.

This changes the system from being almost unbearable to use to being merely annoyingly warm.

I’m not going to make my laptop be my primary computing device again though, the combination of a desktop system with a 27″ monitor and an Android phone is working quite well for me [3]. But I haven’t yet got version control systems working for all my software. Also Wouter suggested using NBD which is something I haven’t got working yet and probably won’t until I can swap on it and therefore have a diskless workstation. Finally I still haven’t got the “Chrome to Phone” browser extension working such that a page I’m viewing at home can be loaded on my phone.

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Syndicated 2012-02-13 04:14:06 from etbe - Russell Coker

Magic entries for BTRFS and Software RAID

I’ve just discovered that the magic database for the file(1) command in Debian/Unstable has no support for Linux Software RAID and that it’s support for BTRFS is lacking (no reporting of space used, number of devices, or the UUID). Below is my first draft of a change to fix these problems. I would appreciate it if someone with a big-endian system could test these out and let me know how they go, I suspect that I will have to change the “lelong” types to “long” but I’m not sure.

4096 lelong 0xa92b4efc Linux Software RAID
>4100 lelong x version 1.2 (%d)
>4112 belong x UUID=%8x:
>4116 belong x \b%8x:
>4120 belong x \b%8x:
>4124 belong x \b%8x
>4128 string x name=%s
>4168 lelong x level=%d
>4188 lelong x disks=%d

0 lelong 0xa92b4efc Linux Software RAID
>4 lelong x version 1.1 (%d)
>16 belong x UUID=%8x:
>20 belong x \b%8x:
>24 belong x \b%8x:
>28 belong x \b%8x
>32 string x name=%s
>72 lelong x level=%d
>92 lelong x disks=%d

0×10040 string _BHRfS_M BTRFS Filesystem
>0x1012b string >\0 label "%s",
>0×10090 lelong x sectorsize %d,
>0×10094 lelong x nodesize %d,
>0×10098 lelong x leafsize %d,
>0×10020 belong x UUID=%8x-
>0×10024 beshort x \b%4x-
>0×10026 beshort x \b%4x-
>0×10028 beshort x \b%4x-
>0x1002a beshort x \b%4x
>0x1002c belong x \b%8x,
>0×10078 lequad x %lld/
>0×10070 lequad x \b%lld bytes used,
>0×10088 lequad x %lld devices

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Syndicated 2012-02-11 07:21:07 from etbe - Russell Coker

Starting with BTRFS

Based on my investigation of RAID reliability [1] I have determined that BTRFS [2] is the Linux storage technology that has the best potential to increase data integrity without costing a lot of money. Basically a BTRFS internal RAID-1 should offer equal or greater data protection than RAID-6.

As BTRFS is so important and so very different to any prior technology for Linux it’s not something that can be easily deployed in the same way as other filesystems. It is possible to easily switch between filesystems such as Ext4 and XFS because they work in much the same way, you have a single block device which the filesystem uses to create a single mount-point. While BTRFS supports internal RAID so it may have multiple block devices and it may offer multiple mountable filesystems and snapshots. Much of the functionality of Linux Software RAID and LVM is covered by BTRFS. So the sensible way to deploy BTRFS is to give it all your storage and not make use of any other RAID or LVM.

So I decided to do a test installation. I started with a Debian install CD that was made shortly before the release of Squeeze (it was first to hand) and installed with BTRFS for the root filesystem, I then upgraded to Debian/Unstable to get the latest kernel as BTRFS is developing rapidly. The system failed on the first boot after upgrading to Unstable because the /etc/fstab entry for the root filesystem had the FSCK pass number set to 1 – which wasn’t going to work as no FSCK program has been written. I changed that number to 0 and it then worked.

The initial install was on a desktop system that had a single IDE drive and a CD-ROM drive. For /boot I used a degraded RAID-1 and then after completing the installation I removed the CD-ROM drive and installed a second hard drive, after that it was easy to add the other device to the RAID-1. Then I tried to add a new device to the BTRFS group with the command “btrfs device add /dev/sdb2 /dev/sda2” and was informed that it can’t do that to a mounted filesystem! That will decrease the possibilities for using BTRFS on systems with hot-swap drives, I hope that the developers regard it as a bug.

Then I booted with an ext3 filesystem for root and tried the “btrfs device add /dev/sdb2 /dev/sda2” again but got the error message “btrfs: sending ioctl 5000940a to a partition!” which is not even found by Google.

The next thing that I wanted to do was to put a swap file on BTRFS, the benefits for having redundancy and checksums on swap space seem obvious – and other BTRFS features such as compression might give a benefit too. So I created a file by using dd to take take from /dev/zero, ran mkswap on it and then tried to run swapon. But I was told that the file has holes and can’t be used. Automatically making zero blocks into holes is a useful feature in many situations, but not in this case.

So far my experience with BTRFS is that all the basic things work (IE storing files, directories, etc). But the advanced functions I wanted from BTRFS (mirroring and making a reliable swap space) failed. This is a bit disappointing, but BTRFS isn’t described as being ready for production yet.

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Syndicated 2012-02-10 09:52:16 from etbe - Russell Coker

More DRBD Performance tests

I’ve previously written Some Notes on DRBD [1] and a post about DRBD Benchmarking [2].

Previously I had determined that replication protocol C gives the best performance for DRBD, that the batch-time parameters for Ext4 aren’t worth touching for a single IDE disk, that barrier=0 gives a massive performance boost, and that DRBD gives a significant performance hit even when the secondary is not connected. Below are the results of some more tests of delivering mail from my Postal benchmark to my LMTP server which uses the Dovecot delivery agent to write it to disk, the rates are in messages per minute where each message is an average of 70K in size. The ext4 filesystem is used for all tests and the filesystem features list is “has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize“.

Default Ext4 1663
barrier=0 2875
DRBD no secondary al-extents=7 645
DRBD no secondary default 2409
DRBD no secondary al-extents=1024 2513
DRBD no secondary al-extents=3389 2650
DRBD connected 1575
DRBD connected al-extents=1024 1560
DRBD connected al-extents=1024 Gig-E 1544

The al-extents option determines the size of the dirty areas that need to be resynced when a failed node rejoins the cluster. The default is 127 extents of 4M each for a block size of 508MB to be synchronised. The maximum is 3389 for a synchronisation block size of just over 13G. Even with fast disks and gigabit Ethernet it’s going to take a while to synchronise things if dirty zones are 13GB in size. In my tests using the maximum size of al-extents gives a 10% performance benefit in disconnected mode while a size of 1024 gives a 4% performance boost. Changing the al-extents size seems to make no significant difference for a connected DRBD device.

All the tests on connected DRBD devices were done with 100baseT apart from the last one which was a separate Gigabit Ethernet cable connecting the two systems.


For the level of traffic that I’m using it seems that Gigabit Ethernet provides no performance benefit, the fact that it gave a slightly lower result is not relevant as the difference is within the margin of error.

Increasing the al-extents value helps with disconnected performance, a value of 1024 gives a 4% performance boost. I’m not sure that a value of 3389 is a good idea though.

The ext4 barriers are disabled by DRBD so a disconnected DRBD device gives performance that is closer to a barrier=0 mount than a regular ext4 mount. With the significant performance difference between connected and disconnected modes it seems possible that for some usage scenarios it could be useful to disable the DRBD secondary at times of peak load – it depends on whether DRBD is used as a really current backup or a strict mirror.

Future Tests

I plan to do some tests of DRBD over Linux software RAID-1 and tests to compare RAID-1 with and without bitmap support. I also plan to do some tests with the BTRFS filesystem, I know it’s not ready for production but it would still be nice to know what the performance is like.

But I won’t use the same systems, they don’t have enough CPU power. In my previous tests I established that a 1.5GHz P4 isn’t capable of driving the 20G IDE disk to it’s maximum capacity and I’m not sure that the 2.8GHz P4 is capable of running a RAID to it’s capacity. So I will use a dual-core 64bit system with a pair of SATA disks for future tests. The difference in performance between 20G IDE disks and 160G SATA disks should be a lot less than the performance difference between a 2.8GHz P4 and a dual-core 64bit CPU.

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Syndicated 2012-02-08 13:24:03 from etbe - Russell Coker

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