Marc's Public Blog - Linux Hacking


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This page has a few of my blog entries about linux, but my main linux page is here
Picture of Linus

Here is a list of older linux event reports I made before my blog was started, then the rest are below
1996/11/18-21:Linux Pavillion Comdex Fall 1996 (photos only). I've been going since then to help at the linux pavillion.
1997/11/18-21: Linux Pavillion Comdex Fall 1997 (photos only)
1998/05/28-30: Linuxexpo 1998 (photos only)
1998/11/16-20: Linux Pavillion Comdex Fall 1998 (full report)
1998/11/11: Silicon Valley Tea Party (report with pictures)
1999/02/15: Windows Refund Day (report with pictures)
1999/03/20: SVLUG KTEH night (photos only)
1999/03/01-04: LinuxWorld Expo Winter 99 (complete report with many pictures)
1999/03/31: Mozilla Party one year anniversary (photos only)
1999/05/18-22: Linuxexpo 1999 (complete report with many pictures)
1999/06/07: June 99 Balug meeting with Linus
1999/08/09-12: LinuxWorld Expo Summer 99 (complete report with many pictures)
1999/11/15-19: Linux Business Show at Comdex Fall 1999 (full report with pictures)
2000/08/14-17: LinuxWorld Expo Summer 2000 (complete report with many pictures)
2001/01/17-20: Linux.conf.au/LCA 2001 (complete report with pictures)
2001/07/25-28: OLS 2001 (photos only)
2001/08/25: Linux 10th Anniversary (report with pictures)
2001/09/27-30: LinuxWorld Expo Summer 2001 report with pictures)
2001/11/05-10: ALS 2001 (photos only)
2002/06/26-29: OLS 2002 (photos only)
2003/01/20-25: LCA 2003 (photos only)
2003/07/23-26: OLS 2003 (photos only)
2004/01/12-17: LCA 2004 (photos only)
2004/07/21-24: OLS 2004 (photos only)
2005/04/18-23: LCA 2005 (photos only)
2006/01/24-28: LCA 2006 (photos only)
2007/01/17-21: LCA 2007 (photos only)

Here is a list of all the talks I've given:

And below are my blog posts:



Table of Content for linux:

More pages: July 2002 February 2004 March 2004 November 2004 April 2005 August 2005 January 2006 July 2006 August 2007 November 2007 January 2008 October 2008 November 2008 December 2008 January 2009 May 2009 July 2009 August 2009 September 2009 November 2009 December 2009 January 2010 March 2010 April 2010 June 2010 August 2010 October 2010 January 2011 July 2011 August 2011 December 2011 January 2012 March 2012 May 2012 August 2012 December 2012 January 2013 March 2013 May 2013 September 2013 November 2013 January 2014 March 2014 April 2014 May 2014 October 2014 January 2015 March 2015 May 2015 January 2016 February 2016 June 2016 July 2016 August 2016 October 2016 January 2017 September 2017 January 2018 March 2018 December 2018 January 2019 January 2020 May 2020 January 2021 September 2021 March 2023 April 2023 December 2023 June 2024



2012/12/05 Serial Console With WR703N
π 2012-12-05 01:01 in Linux
I was looking for a cheap one port serial console server I could use to monitor a server far away. Turns out they are quite expensive, so I looked at making my own.

I ended up being told to look at a WR703N which can be had for around $25, either from china, or sometimes a US location like amazon . Another option is the mostly identical TL-MR3020

Both have an openwrt distribution which you can get from http://wiki.openwrt.org/toh/tp-link/tl-wr703n and http://wiki.openwrt.org/toh/tp-link/tl-mr3020

One way to get serial could be to open the device and with a bit of soldering and a level converter, one is supposed to get a serial port off the bare chip. That was more time than I was willing to put in, so I just used the built in USB port and a PL2303 USB-serial converter.

Unfortunately, the USB support on those devices has a bug there full speed USB devices (i.e. USB1) do not work reliably and in the case of a serial converter, it'll hang after a minute of use or two.

This is described in a long thread at https://forum.openwrt.org/viewtopic.php?id=39956&p=4 but you can jump to post #84. Basically the fix is to use a passive high speed (USB2) hub, and plug your USB1 device into it. No USB power required, and a cheap $10 USB hub works fine.

Next, get an old USB key, format it with ext4 as explained below, and edit /etc/rc.local on the router to mount the USB stick. This allows logging the serial session without writing to the main flash of your device, since that's not replaceable.

Ok, so the end cost is between $40 and $50, but you get a super small linux capable router that acts as serial console server, can log the output and provide ssh access. Still not bad... (I used a free 64MB USB key I had lying around).

/etc/rc.local:

# Get the card ready with # mkfs.ext4 /dev/sdc1 # tune2fs -c0 -i0 -m0 /dev/sdc1 # opkg install kmod-fs-ext4 mount -o noatime,commit=600,data=writeback /dev/sda1 /mnt

cd /mnt # opkg install kmod-usb-serial-pl2303 # opkg install screen # This will dump serial logs in /mnt on your USB key screen -m -d -L /dev/ttyUSB0 115200

# If you don't want screen, you can try minicom or microcom # http://www.damnsmalllinux.org/f/topic-3-7-11379-0.html


More pages: July 2002 February 2004 March 2004 November 2004 April 2005 August 2005 January 2006 July 2006 August 2007 November 2007 January 2008 October 2008 November 2008 December 2008 January 2009 May 2009 July 2009 August 2009 September 2009 November 2009 December 2009 January 2010 March 2010 April 2010 June 2010 August 2010 October 2010 January 2011 July 2011 August 2011 December 2011 January 2012 March 2012 May 2012 August 2012 December 2012 January 2013 March 2013 May 2013 September 2013 November 2013 January 2014 March 2014 April 2014 May 2014 October 2014 January 2015 March 2015 May 2015 January 2016 February 2016 June 2016 July 2016 August 2016 October 2016 January 2017 September 2017 January 2018 March 2018 December 2018 January 2019 January 2020 May 2020 January 2021 September 2021 March 2023 April 2023 December 2023 June 2024

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