- luv-main - example.com

WiFi transfer rates (Linux->Linux)
by Toby Corkindale 21 Aug '12

21 Aug '12

Hi, Wifi is not something I consider myself an expert upon. I understand the security problems with WEP, WPS, WPA and WPA2 fairly well, and I've read some docs on fragmentation, RTS thresholds, and channel width. I don't consider myself a newbie here either. Try as I might, I just can't seem to get decent performance out of my home network. It's a 802.11n network, theoretically 300 mbit/s, however testing with iperf between a Linux wireless laptop and a wired linux server results in 60-70 mbits reported in either direction. I tried fiddling with a few options on the router, such as: * disabling a/b/g support. (no effect) * disabling pre-spec-N support. (no effect) * lowering RTS threshold slightly (lower throughput) * lowering fragment threshold (no effect at small changes; perf slightly increases (~5mbit) as fragments decrease for a while, then after a point (around ~2000 bytes) performance just drops as you decrease size.) * WMM no-ack mode (totally wrecked performance) I'm using a Broadcom chipset in the laptop, which seems to have reasonable Linux support. I'm using the opensource brcmsmac driver on a 3.2.0 kernel. The AP is an Asus RT-N15, which also runs Linux, although I'm still on the vendors firmware. So, no matter what I've done, I can't get more than 75 mbits, and on default settings its more like 65 mbits between these two Linux devices. However a friend with an Apple Mac laptop and an Apple airport AP can push about 200 mbit/s according to iperf! So.. I just wondered if anyone has some hints about how to improve wifi performance? I also wondered what sort of bitrates you see? And if someone is getting good speeds, can you report your hardware (incl. chipset) and configuration options? thanks! Toby

7 12

MySQL Help needed [Scanned]
by Christopher M. Bailey 17 Aug '12

17 Aug '12

Hi All, Just looking for guidance, I have had a server crash, HDD failure, luckily I have good backups through Backup Exec 2012. What I need to know is what files do I need to restore to a basic install of the same distro (CentOS 5.8) to get our MySQL databases running again with the same security permissions? TIA Chris -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.

5 6

caching USB
by Russell Coker 16 Aug '12

16 Aug '12

sda is a regular SATA disk and sdd is a USB attached SATA disk. Why isn't sdd cached? # dd if=/dev/sdd of=/dev/zero bs=1024k count=100 100+0 records in 100+0 records out 104857600 bytes (105 MB) copied, 3.00316 s, 34.9 MB/s # dd if=/dev/sdd of=/dev/zero bs=1024k count=100 100+0 records in 100+0 records out 104857600 bytes (105 MB) copied, 2.98833 s, 35.1 MB/s # dd if=/dev/sda of=/dev/zero bs=1024k count=100 100+0 records in 100+0 records out 104857600 bytes (105 MB) copied, 1.29493 s, 81.0 MB/s # dd if=/dev/sda of=/dev/zero bs=1024k count=100 100+0 records in 100+0 records out 104857600 bytes (105 MB) copied, 0.0669201 s, 1.6 GB/s -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/

1 0

USB Hard disk / Linux
by Brian May 14 Aug '12

14 Aug '12

Hello, I have a USB hard disk that I use to make backups of my system. Previously it has worked just fine. In fact it still does work fine on my work computer. Unfortunately, it is my home computer I am trying to backup, not my work computer. When I plug it it, it detects it fine. Then I try to mount the filesystem. The mount process hangs. Neither dmesg or /var/log/kern.log logs anything unusual. I can kill the mount process with ctrl-c, and the file system isn't mounted. I can then unplug the USB device if I so desire. Nothing is logged. However at this point the computer is "crashed", as if I type in "sync", the sync process hangs for ever too. If I wait long enough I get CPU x hung type messages. Shutdown won't work, I have to hard reboot the system. My working theory I have is that USB support on my motherboard may be dodgy. However this doesn't explain how the same drive has worked in the past, for the same computer, but suddenly doesn't work any more. Alternatively, maybe the entire motherboard is an unreliable piece of rubbish, and I should ditch it. Any ideas? This is running Ubuntu 12.04 64 bit. Thanks -- Brian May <brian(a)microcomaustralia.com.au>

6 8

Custom battery charging levels
by Toby Corkindale 14 Aug '12

14 Aug '12

Hi, When I boot my ThinkPad into Windows, I can set the battery to operate in long-life mode. It then only charges up to 90% capacity, and won't start charging until it has dropped below 80% capacity. This is claimed to make the battery live longer -- and so far the battery HAS lasted much better than they have in previous laptops. (Of course, if I'm going to a conference, I can configure the battery to charge up to 100% again easily) I wondered if there is any way to achieve this behaviour in Linux? cheers, Toby

9 20

FTP from crashed computer to Laptop
by Andrew Greig 13 Aug '12

13 Aug '12

Hi, I had some trouble with my Notebook and desktop computers last week when Entangle stuffed the display files on both computers. I successfully rebuilt the Notebook because I had a separate /home partition. Unfortunately the desktop PC (Suse 12.1 64 bit) was a single partition, and it will not be quite so easy. How do I get the files I want from the desktop onto a dive attached to my notebook? Ctrl+Alt+F2 gives me a console in the desktop. The Notebook is running Gnome. Once I have my data tucked away, I get adventurous. Many thanks Andrew Greig

4 4

Re: Whom do I complain about from this traceroute
by Craig Sanders 13 Aug '12

13 Aug '12

cc-ed back to the list. please don't reply privately when the discussion belongs on the list. On Sat, Aug 04, 2012 at 08:14:26PM +1000, Mark Trickett wrote: > On Sat, 2012-08-04 at 08:59 +1000, Craig Sanders wrote: > > On Fri, Aug 03, 2012 at 09:45:57PM +1000, Allan Duncan wrote: > > > It won't help you with your download problem, but it helps explain > > > strange numbers when MPLS gets invovled. > > > > well spotted. > > But since I am not an Internode customer, I cannot get to that page. I I meant well-spotted RE the fact of MPLS, not the particular web page. MPLS is something that is easily googled, whether you have access to one ISP's customer-only web pages or not. someone there will likely know wvdial and modem pppd configuration a lot better than I remember it (i haven't used a modem connection for over 10 years). > > I think Mark has mentioned problems downloading the Linux Journal > > before. Makes me wonder what the MTU and MRU on his PPP interface is > > and whether he (or Telstra) is blocking ICMP packets (in particular ICMP > > Fragmentation Required msgs). > > Tell me where to look, and how to set, and I will try. you need to mru and mtu values in the pppd config file for your connection. e.g. /etc/ppp/peers/provider. the exact filename depends on your distro and what method you used to configure pppd in the first place (e.g. gui config, dialog text mode config, or just a text editor) see the man page for pppd and the network configuration documentation for your distro for details. you'll want to add lines like: mtu 600 mru 600 > I am currently using wvdial, and want to know what options are passed > to pppd. no idea. i've never used wvdial. > I am also looking to migrate to a desktop running Debian 6, and would > very appreciate some pointers to making use of "pon" and "poff", > particularly just what is the minimal necessary to configure. IIRC debian has a curses/dialog pppconfig tool for managing ppp configuration. dunno if they have a gui or not. the abominable gnome Network Manager may do ghastly things in the name of configuring pppd. dunno. vi has always been my configuration tool of choice. > I would also appreciate pointers to more advanced configuration. I > need the modem link to be the default route, rather than any Ethernet > interface. 1. don't have a gateway line in your ethernet configuration - that tells ifup that you want a default route pointing at the gateway mentioned. 2. add "defaultroute" to your ppp configuration. same place as you add the mtu and mru. > As commented, a little advice would be appreciated. I would also > appreciate comments about how wvdial invokes pppd, and why when I use > wget, I need to use the --no-proxy option to get anywhere at all. no idea about wvdial but if you need to specify --no-proxy, that means you have a proxy set in either your environment (type: 'set | grep -i proxy' to check. use 'unset foo_proxy' to remove for the current running shell, edit your bashrc/bash_profile/etc files to remove permanently), or in your wget config. check ~/.wgetrc and maybe /etc/wgetrc. craig -- craig sanders <cas(a)taz.net.au>

10 11

initramfs and bcache
by James Harper 13 Aug '12

13 Aug '12

I'm doing some testing with bcache on my Debian system, with the block devices layered like: sd[ab] md0 /boot (because grub doesn't understand bcache superblocks) md1 bcache lvm / And it almost works except that my bcache initramfs script runs after lvm. I told bcache to prereq on mdadm, so that much works, but unless I change the system provided lvm initramfs script, I can't get bcache to run before it, so I need to intervene at boot time to get it moving. Any suggestions? Thanks James

2 1

rsync crashes on me - confused
by Carl Turney 11 Aug '12

11 Aug '12

Hi All, I'm using rsync (version 3.0.7-1ubuntu1.1 on my Ubuntu 10.4 system) in a shell script to perform local backups of my system on to removable hard disks. (FYI: It's a bit kludgy, but I'm VERY happy with it. Been doing it for a few years. Normally works great. It's extremely fast at creating up-to-date immediately-bootable clones/mirrors (?) of my system. I always store backups in different locations from my office. So, I'm not hogging up bandwidth, or exposing my data to others, by using the internet to do my backups.) My system is a dual boot, sharing Ubuntu with WinXP, for when I (rarely) HAVE to genuinely do something in Win. (Thanks, but no thanks. I don't want to do a virtual machine.) Are there any rsync wizards out there? My problem is this: Lately, when rsync updates my WinXP partition (by this command)... rsync -Hvxrlt --delete /mnt/tempWindows/ /mnt/backupWindows ... I get the following error messages ... > *sending incremental file list* > > *pagefile.sys* > > *rsync: writefd_unbuffered failed to write 4 bytes to socket [sender]: > Broken pipe (32)* > > *deleting Documents and Settings/etc. ... > * > > *((Here, it seems to remove various deleted WinXP files from the > target partition.)) * > > *deleting Documents and Settings/etc. ...* > > *rsync: write failed on “/mnt/backupWindows/pagefile.sys”: No space > left on device (28)* > > *rsync error: error in file IO (code 11) at receiver.c(302) > [receiver=3.0.7]* > > *rsync: connection unexpectedly closed (28 bytes received so far) > [sender]* > > *rsync error: error in rsync protocol data stream (code 12) at > io.c(601) [sender=3.0.7]* > I'm confused by this, as I'm not a CLI wizard by any means. So if you offer advice, please try to dumb it down to the newbie level. You'll get an understanding of my comprehension level by the following comments... Booting into each of the two WinXP partitions proves that the clone/mirror partition is "out of date" compared to the master partition. I used ls to find out that the pagefile.sys files on both WinXP partitions are exactly the same size: 2,145,386,496 bytes. I used df to find out that (at this point in time) the source WinXP partition has 468,400 1KB blocks available, while the target WinXP partition has 2,015,600 1KB blocks available. df also informed me that the source WinXP partition is only 10,472,136 1KB blocks in total size, while the target partition is =larger=, at 10,985,712 1KB blocks. My guess is that the target can only run out of space is if rsync (1) copies an updated file into the free space of the target partition using a temp filename, (2) deletes the original file at the target partition, and (3) renames the newly-copied file to the original name. Any other explanation for that? Any suggested work-arounds? I'm thinking about cutting the Win swap file size in half, and seeing if that removes the problem at rsync time. Then limping along with that setup until I rebuild my system (when Ubuntu 12.4.1 comes out in a few weeks), with a larger partition for my "bare bones" WinXP. Thanks in advance for any help. Cheers, Carl Turney Bayswater Mobile 0427 024 735

4 6

sed and matching braces in the source string
by James Harper 09 Aug '12

09 Aug '12

I have a string in the following format: ALTER TABLE QuestionnaireCategory ADD CONSTRAINT DF_QuestionaireCategory_QuestionaireCategoryID DEFAULT ("123") FOR QuestionnaireCategoryID That I need to convert to: ALTER TABLE QuestionnaireCategory ALTER QuestionnaireCategoryID SET DEFAULT ("123") The former being MSSQL format and the latter being postgresql. I have a sed script that does it and works great except for when the DEFAULT value itself contains braces, eg: DEFAULT (newid()) The problem is that my sed script says to start at the "(" and then read up until a ")", but I really mean to say read up until a matching ")". Can I do this with sed or should I be using something else? Thanks James

5 7