Here is how to run a Python script from the Finder:
A couple years ago I did a detailed set of posts on turning an old laptop into a Ubuntu file, print, and web server. That laptop started having hardware problems so I decided to decommission it and replace it with another recently retired Dell Inspiron 1521 laptop. Here is a checklist of all the steps I did to convert the Windows Dell Inspiron 1521 laptop into a home file, print, and web server. If you are new to Linux you should read my original posts since this checklist assumes you have done stuff like this before.
auto eth0
iface eth0 inet static
address 10.10.10.123
netmask 255.255.255.0
gateway 10.10.10.1
I have a web app that uses jQuery UI buttons. I noticed that on my iPad the buttons worked fine in portrait orientation, but in landscape orientation the buttons, and even regular links in a table, would not work properly when pressed (a different button or link than the one pressed would fire). I determined that this problem was caused by the following tag in my HTML:<meta name='viewport' content='width=device-width' />
Using this tag causes Safari Mobile (the iPad browser) to zoom in on the page a bit in landscape orientation, making the fonts a bit bigger, which would be fine except that it apparently breaks link and button functionality in some cases. I got the buttons and links to work properly by using this tag instead:<meta name='viewport' content='width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no' />
This locks down the page so it doesn't (and can't) zoom in or out.
That fixed my broken buttons and links in landscape orientation, but I had really liked the way the fonts got bigger in landscape orientation. It gave me a way to have two different zoom levels in may app. If I wanted to see more content in a small font I used portrait; if I wanted to see less content in a bigger font I used landscape.
So, I figured out how to get the exact same effect using CSS "media queries." Here is some CSS that first sets styles for the iPad regardless of orientation and then specifies different styles for portrait and landscape orientation:
@media only screen and (max-device-width: 1024px)
{/* This block specifies CSS that only applies to an iPad
max-device-width: 1024px seems to only select the iPad*/
body
{margin-left: 0px;
margin-top: 0px;}
}
@media only screen and (max-device-width: 1024px) and (orientation: portrait)
{/* This block provides CSS that only applies to the iPad in portrait orientation */
body
{font-size: 16px;}
}
@media only screen and (max-device-width: 1024px) and (orientation: landscape)
{/* This CSS kicks in only when an iPad is in landscape mode. It makes the font bigger, the table rows taller, etc */
body
{font-size: 18px;}
}
You can put this block of CSS at the end of the regular stylesheet for a page and it will apply different CSS when the page is viewed on the iPad, allowing you to have a completely different layout on the iPad than you have on a regular browser. What is remarkable to me is how smoothly the styles change when I switch orientation on the iPad; I was afraid there would be lag while the page reformatted but I can't detect any.
Occasionally in Mac OS X I want to write the full path of a file in a Bash script or something. To avoid typing out the full path (and possibly making errors) just:
I have a web app where I use the jQuery .live() method to attach a click event handler to a table td element (to convert it into a input field when the user clicks the table cell and then post the input using ajax.) Everything worked properly on all the mainstream browsers (Firefox, Safari, Chrome) but nothing happened when I tapped the table cell when viewing the app on my iPad. Some Googling led me to this blog post:
jQuery’s live click handler on mobile Safari
This guy discovered that the .live() click event will fire on Mobile Safari (i.e. iPad, iPod Touch, iPhone) when it is attached to certain elements (like an anchor tag), but for some other elements it will only fire if you add onclick="" to the element tag.
I added onclick="" to my td tag for my table cell and voila, tapping on the table cell works now to convert it to an input field like it should.
Recently I decided to make a web app to keep track of a number of policies. There were a number of different policies, all of which had their provisions numbered and organized in an outline hierarchy that often went three or more layers deep.
The first thing I researched was how to structure SQL databases to handle hierarchical data like a product catalog with the products grouped into categories and subcategories. Or a org chart where employees are grouped into divisions and departments. I quickly learned that most people used either the adjacency list model or the nested set model, both of which are described in detail in an article on the MySQL website: Managing Hierarchical Data in MySQL. Another detailed article on both models is Storing Hierarchical Data in a Database.
With the adjacency list model you have a table which gives each record a unique ID number, and then you have a "Parent ID" field where you record the ID number of the record's parent in the hierarchy tree. If you were doing foods, you would have a record for "apples" and the parent ID for that record would be "fruits." Then when you need to generate an output of the whole hierarchy tree you do SQL that organizes all the records by connecting the various parent ID values. Some articles I found on this approach include Tree Drawing with the Adjacency List Model and Hierarchical SQL. The thing I didn't like about the adjacency list model was that the SQL required to generate a simple display of the data seemed unduly complicated (lots of recursion) and likely to consume a lot of database server processing power.
I never did really grasp the nested set model, so I won't try and explain it. Needless to say it also involved very complicated SQL that seemed likely to put a big drain on a server.
Then I found an article about a variation on the adjacency list model: More Trees and Hierarchies in SQL. The author's basic idea was to include a Lineage field in each record where you record the ID numbers of the full path to the record in the hierarchy with each ID number separated by a delimiter character. For example, if you had a product tree with the iPod in it, the Parent ID field would be "MP3 Players" and the Lineage field would be "Electronics/Audio Equipment/MP3 Players." This makes the SQL to output the basic tree much easier: you just do a simple SELECT and ORDER BY the Lineage field and you are done.
So here is the structure I ended up with using the lineage field model. For a hierarchy like this:
| Node | Lineage |
| Plants | / |
| Animals | / |
| Fruit | /Plants/ |
| Vegetables | /Plants/ |
| Poultry | /Animals/ |
| Meat | /Animals/ |
| Apples | /Plants/Fruits/ |
| Bananas | /Plants/Fruits/ |
| Peaches | /Plants/Fruits/ |
| Chicken | /Animals/Poultry/ |
| Turkey | /Animals/Poultry/ |
| Beef | /Animals/Meat/ |
| Pork | /Animals/Meat/ |
| Broccoli | /Plants/Vegetables/ |
| Asparagus | /Plants/Vegetables/ |
SELECT * FROM table_Foods ORDER BY concat(Lineage, Node)SELECT *
FROM Foods
WHERE concat( Lineage, Node ) LIKE '/Plants%'
ORDER BY concat( Lineage, Node )I have been using jQuery and jQuery UI for a while now and they make it really easy to add fancy features and layout to a web app. However, one thing I didn't like was that the default appearance jQuery UI buttons is too tall for my taste. The jQuery buttons have lots of space above and below the button text, making them look square and blocky to me.
After playing around with it for a while I figured out how to adjust the height of jQuery UI buttons. Simply add the following to your CSS style sheet:.ui-button-text-only .ui-button-text
{ padding-top: .1em;
padding-left: 1em;
padding-right: 1em;
padding-bottom: .2em; }
Just tweak the top and bottom padding until you like the way the buttons look. I had to make my bottom padding bigger than my top padding to make the button text look vertically centered.
I also had some buttons with little GIF images instead of text. jQuery had the images jammed up against the top of the button by default. To center the images I added this to my CSS stylesheet:img {margin-bottom: -.25em;}
I could get away with just changing my img tag styles because these little GIFs were the only img tags on the whole page. If you have other img tags on your page you would need to give the button img tags their own class and apply this style to just that class.
I was tearing my hair out because my jQuery UI code was working properly with Firefox and Safari but not with Google Chrome. When I looked at the Javascript console in Google Chrome I was getting an error like this:Uncaught TypeError: Object #
Because it was working in Safari and Firefox, but not in Google Chrome, and because the error message sounded like some problem in the jQuery code and/or my other Javascript I spent hours trying to troubleshoot the problem. However, in the end the problem turned out to be with my script tags to reference the jQuery libraries:<script src="/jquery-ui-1.8.5.custom/js/jquery-1.4.2.min.js" type="text/javascript"</script>
<script src="/jquery-ui-1.8.5.custom/js/jquery-ui-1.8.5.custom.min.js" type="text/javascript"</script>
Do you see the error in my syntax? I left off the right angle bracket after the type="text/javascript". For some reason Firefox and Safari don't care about that, but Google Chrome does. To make it even odder, Google Chrome didn't give me an error about problems loading a script, but instead an error about the execution of the script.
Apple has a thorough guide to developing web content for Safari on the iPhone, presumably most of it also applies to the iPad:
[iOS] Safari Web Content Guide
I haven't read all of this article yet but the title is promising:
The iPad Web Design and Development Toolbox
I recently set up a web app hosted on nearlyfreespeech.net that uses mysql_real_escape_string to to escape user input. I noticed the other day that an entry in that web app displayed an escaped single quote, which led me to suspect that nearlyfreespeech.net has PHP magic quotes turned on and my user input was being double escaped, which turned out to be correct.
Here is how I turned off magic quotes for web app on nearlyfreespeech.net:
nano .htaccess to create a .htaccess file
and open it in nano for editingphp_flag magic_quotes_gpc offI was working on a web app where I wanted the appearance to be very different on my iPad than it was on my laptop. After some research I found this article:
Detecting device size & orientation in CSS
That describes how you can include code in a CSS stylesheet that will apply designated rules only if the device screen (or browser viewing area) meets certain criteria. For example (from the article):
@media only screen and (max-width: 999px) { /* rules that only apply for canvases narrower than 1000px */}
@media only screen and (device-width: 768px) and (orientation: landscape) { /* rules for iPad in landscape orientation */}
@media only screen and (min-device-width: 320px) and (max-device-width: 480px) { /* iPhone, Android rules here */}
CSS put inside the brackets in these examples would only apply if the specified criteria are met. Also, the CSS rules apparently work on the fly, so if the user resizes their browser screen the appropriate rules will be applied without refreshing.
I also found a reference article on these "media queries" for Firefox. Much of what is in this article applies to other browsers since I believe it is derived from the CSS 3 specification.
Media Queries
Note that this article only uses these media queries to select an alternate style sheet but as far as I can tell you can also use them to apply a block of rules enclosed in curly brackets after the query as shown in the example above and the first article.
There is also an Apple article that includes a section on conditional CSS:
Optimizing Web Content
After doing some experimenting, it appears that once a CSS property is specified the only way to remove it using a media query is to specifically specify a new value for the property. In other words, if you specify a bunch of properties for the ".main" class in your style sheet, and then in your media query block just specify:
@media only screen and (max-width: 999px) { .main {;}}
Then all the rules you specified for .main are still going to apply even when the media criteria is met because they were not individually countermanded.
I experimented around with different media queries to distinguish between my iPad and my laptop and in the end this seemed to work so that the rules were only applied on my iPad, and the rules were applied regardless of my iPads orientation:
@media only screen and (max-device-width: 1024px)
{/*max-device-width: 1024px seems to only select the iPad*/}
I have a PHP web app that pulls data from an SQL Server database using the ODBC functions. Earlier I come up with a PHP function to escape single quotes in user input by adding a single quote to each single quote (a single quote is the character you use to escape a single quote) as defense against (inadvertent) SQL injection (the web app is behind a firewall).
The other day I accidentally discovered that including text inside a pair of square brackets [like this] in user input that was added to a LIKE clause of a WHERE clause resulted in a huge data dump being returned by SQL Server. I did some Googling and discovered that characters enclosed in square brackets have some special meaning in SQL Server (I don't remember what it was). I first tried updating my PHP function to escape square brackets with single quotes, but that didn't work for some reason. Then I did some more research and discovered that the way to escape a square bracket in SQL Server is to enclose it in square brackets like this [[]. So I updated my PHP function to do this on user input and it worked to stop the data dumps when a user included something like [fred] in their input.
Writing the PHP to do this was tricky because if you just do a straight str_replace on each square bracket the second replace replaces some of the square brackets you added with the first replace and messes it all up. The way I solved this was to write my function to:
I am working on an application that uses a sequence field to keep records in a specific order.
The first challenge was how to fill in a numbered sequence in the new sequence field without using auto-increment (the data table will contain a number of independent sequences for different sub-sets of records so I need to be able to multiple sequences in the same table). I found the answer on this blog post:
How to Sequence each Sub-set of Records by David Soussan
I won't repeat that post here, but here is the SQL that I ended up with based on Mr. Soussan's technique.
This first SQL query creates a Temp table with Prov_ID and sequence number.
CREATE TABLE Temp
SELECT
t1.Prov_ID, COUNT(t1.Prov_Sort_Num) AS sequence,
t1.Prov_Sort_Num >= t2.Prov_Sort_Num AS flg
FROM
tbl_Provisions AS t1
INNER JOIN
tbl_Provisions AS t2 ON t1.Doc_ID = t2.Doc_ID
WHERE
t1.Doc_ID = 1
GROUP BY
t1.Doc_ID,
t1.Prov_Sort_Num, flg
HAVING
flg = TRUE
ORDER BY
t1.Prov_Sort_Num
UPDATE
tbl_Provisions AS t1
JOIN
Temp AS t2 ON t1.Prov_ID = t2.Prov_ID
SET t1.Prov_Sequence = t2.sequence
SELECTThis returns a two column table with each row giving the beginning of a gap in the Start column and the end of that gap listed in the End column.
a.Prov_Sequence + 1 AS start,
MIN(b.Prov_Sequence) - 1 AS end
FROM
tbl_Provisions AS a,
tbl_Provisions AS b
WHERE
a.Prov_Sequence < b.Prov_Sequence
AND
a.Doc_ID=$Doc_ID
AND
b.DOC_ID=$Doc_ID
GROUP BY
a.Prov_Sequence
HAVING
start < MIN(b.Prov_Sequence)
Occasionally I need to scan a double sided document. For a short documents (1-4) I just scan the fronts of the pages and then the backs and then manually put them together using Preview in Mac OS X. However for longer documents the free PDF Split and Merge, or PDFsam, quickly merges these types of scans:
http://www.pdfsam.org/
Here are some articles I found about securing PHP web applications:
I have had an annoying problem for years. I have two external hard drives hooked up to my Ubuntu server that are encrypted with Truecrypt. In order to mount these Truecrypt volumes on the correct mountpoints after a reboot I had to figure out which external drive was mounted as /dev/sdb and which as /dev/sdc since Ubuntu doesn't necessarily mount the same external drive in the same place every time the system is restarted. For a long time I deduced which drive was mounted as /dev/sdb and which as /dev/sdc by running sudo fdisk -l which shows the sizes and mount points off all attached drives. However, I recently found directions written by Ubuntu Forums user B-Con on how to make a script to reliably mount each Truecrypt volume in the right place regardless of which /dev/sd* it gets:
http://ubuntuforums.org/showthread.php?t=468664
Basically, the script uses ls -l /dev/disk/by-id to get a listing of all of the attached drives that includes each drives unique id code and it's mount point, then it uses grep and cut to extract the mount point and put it in a variable, which can then be used with the Truecrypt mount command. In the example below you will have to change the part in quotes to be the unique id code of your drive.
#! /bin/bash
my_var=`ls -l /dev/disk/by-id | grep "scsi-1ATA_Maxtor_7H500F0_H81E4GAH-part1" | cut -d / -f 3`
vol_path="/dev/${my_var}"
# Use vol_path as the path for your drive, now.
I have had a lot of troubles getting Mac OS X "Shared Folders" to behave the way I want. This page is for notes on things I have figured out.
Issue: Users connecting to a Shared Folder as Guest cannot even browse subfolders of the shared folder.
Resolution: It turns out that in order for someone connected to a Shared Folder as Guest to be able to browse a subfolder the subfolder has to have the eXecute permission set for Others, i.e. when you run ls -l on the shared folder the subfolder permissions should look like this:
drwx---rwx 11 ownersname groupname 12 Dec 30 06:19 My Subfolder
with the important one being the last x. If the last permission is not x, then non-authenticated users will not be able to even browse the subfolder.
In order to set all permissions on all subfolders to allow Guest access I ran this from Terminal:
chmod -R o=rwx /SharedFolderPath
This recursively goes through every subfolder and file under /SharedFolderPath and sets permissions for "others" (aka everyone) to read, write, and execute. I am sure there are all kinds of security issues with this, but this is a machine behind a firewall on a home network so I think I don't care.
IRS PDF forms are "fillable" meaning you fill in values on screen and then save the form with the values you entered.
The IRS PDF forms do not format completely correctly if you use Mac OS X Preview (for example social security numbers are all bunched together instead of being spread out like the form intends), so the best bet is to just use Adobe Reader.
Once you open an IRS PDF form in Preview and then save it you can no longer open it in Adobe Reader in fillable format; it will tell you that you cannot save your changes. So it is best to just use Adobe Reader from the outset on IRS PDF forms.
The Arizona PDF 140 form has its permissions set so that you cannot save the form with the values you entered. However, if you open this form using the Foxit Reader instead of Adobe Reader you can save the form with your input.
Unfortunately, the Foxit Reader cannot print the saved form with the barcode on the front page which encodes all your input.
Fortunately, you can use Adobe Reader to open a form with saved values that you saved using Foxit Reader and then print it with the barcode on the front page.
Download and install Audacity (open source software for editing audo files) from http://audacity.sourceforge.net/
Download and install InfraRecorder (open source software for burning CDs) from http://sourceforge.net/projects/infrarecorder/
Record something using the Zoom H2 using MP3 recording format.
Connect the Zoom H2 to the Windows computer using USB cord and then put the Zoom H2 in Storage mode: Menu -> USB -> Storage.
Copy the MP3 file from the Zoom H2 to the Windows computer.
Use "Safely Remove Hardware" icon on Windows taskbar to dismount Zoom H2, disconnect USB cable, and exit USB mode by hitting Menu key on Zoom H2.
Start Audacity and then use File -> Open to open the MP3 file.
Edit the MP3 file as needed, and then export it to WAV file: File -> Export As WAV
Insert blank CD-R in computer
Start InfraRecorder
Click Audio Disc.
In the Explorer View window select the WAV file (one click) and then click the blue plus sign above the window. This should make the WAV file show up in the bottom window. Or you can just drag the WAV file from the top window to the bottom window.
Drag as many WAV files as you want on the CD to the bottom window, and put them in the order you want them to be on the CD.
When ready to burn CD, click Action -> Burn Compilation then select the lowest write speed and click OK.
This is just a rough outline of steps, not a how to!
Install Sun Virtualbox on Mac.
Download ISO of Mythbuntu
Create new Linux virtual machine in Virtualbox. I used 8 GB as the disk size (figuring I would store recordings on an external drive) and 500 MB RAM (no particular reason.
Change settings on the virtual machine's Details list:
The documentation for mjpg-streamer is kind of scattered about. I have dumped it all here for my own convenience.
Usage introduction
This example shows how to invoke mjpg-streamer from the command line
export LD_LIBRARY_PATH="$(pwd)"
./mjpg_streamer -o "output_http.so -w ./www"
export LD_LIBRARY_PATH=`pwd`
./mjpg_streamer -o "output_http.so -w `pwd`/www"
./mjpg_streamer --help
./mjpg_streamer --input "input_uvc.so --help"
./mjpg_streamer --output "output_file.so --help"
./mjpg_streamer --output "output_http.so --help"
./mjpg_streamer -i "input_uvc.so -d /dev/video2 -r 320x240 -f 10"
mkdir pics
./mjpg_streamer -o "output_http.so -w `pwd`/www" -o "output_file.so -f pics -d 15000"
./mjpg-streamer -o "output_http.so -w ./www -c UsErNaMe:SeCrEt"
./mjpg_streamer -i "./input_testpicture.so -r 320x240 -d 500" -o "./output_http.so -w www"
kill -9 `pidof mjpg_streamer`
mjpg_streamer -i "input_uvc.so d /dev/video1" -o "output_http.so"mjpg_streamer -i "input_uvc.so" -o "output_http.so -p 8090"
mjpg_streamer -i "input_uvc.so help"
tar xzvf mjpg-streamer.tgz
cd mjpg-streamer
make clean all
export LD_LIBRARY_PATH=.
./mjpg_streamer -o "output_http.so -w ./www"
So I used Macfusion to connect my Macbook to the NSLU2 as root and copied the tar.gz file over to the NSLU2. Then I ran the tar xzvf command, which created a directory called mjpg-streamer-r63. I went into that directory and ran make clean all, but that gave me a command not found error."In case of error: the input plugin "input_uvc.so" depends on libjpeg, make sure it is installed."So I tried aptitude install libjpeg, but that gave me an error saying there was no such package, but listed the names of some packages with similar names. I took a chance and installed libjpeg-dev, figuring that sounded the most promising. Aptitude then said it was installing a different package with 62 in the name.
./mjpg_streamer -o "output_http.so -w ./www"
MJPG Streamer Version.: 2.0
i: Using V4L2 device.: /dev/video0
i: Desired Resolution: 640 x 480
i: Frames Per Second.: 5
i: Format............: MJPEG
o: www-folder-path...: ./www/
o: HTTP TCP port.....: 8080
o: username:password.: disabled
o: commands..........: enabled
Unable to start capture: Cannot allocate memory
i: Error grabbing frames
I figured this meant there wasn't enough memory so I went to this web page I had found about Debian on the NSLU2:"If you are not using IPv6, you can prevent the module from being automatically loaded by adding the lineAnd then rebooted using "shutdown -r now"
blacklist ipv6
to /etc/modprobe.d/blacklist."
nano /etc/modprobe.d/blacklistand added "blacklist evdev" (no quotes) to the end of the file and rebooted. evdev no longer appears when I run lsmod.
mjpg_streamer -o "output_http.so -w /usr/www"
Note that all the mjpg_streamer commands below are for the way I manually installed it on my system. To get them to work on a machine where mjpg_streamer wasn't manually installed you will have to modify the command to match the syntax in the original instructions."there is an option in mjpg-streamer to launch it in background, use it as a daemon:It works! After I launched mjpg-streamer with the -b option it continues running after closing the SSH terminal session.
[-b | --background]...: fork to the background, daemon mode"
So this lets me keep using the ttyS0 terminal -
mjpg_streamer -i "input_uvc.so -r 960x720" -b -o "output_http.so -p 8080 -w /webcam_www"
Note:- to make mjpg-streamer exit cleanly, use -
kill -9 `pidof mjpg_streamer`"
kill -9 `pidof mjpg_streamer`
Usage: mjpg_streamerI am having a heck of a time finding any documentation on the syntax. I found this forum post:
-i | --input "[parameters]"
-o | --output "[parameters]"
[-h | --help ]........: display this help
[-v | --version ].....: display version information
[-b | --background]...: fork to the background, daemon mode
-----------------------------------------------------------------------
Example #1:
To open an UVC webcam "/dev/video1" and stream it via HTTP:
mjpg_streamer -i "input_uvc.so -d /dev/video1" -o "output_http.so"
-----------------------------------------------------------------------
Example #2:
To open an UVC webcam and stream via HTTP port 8090:
mjpg_streamer -i "input_uvc.so" -o "output_http.so -p 8090"
-----------------------------------------------------------------------
Example #3:
To get help for a certain input plugin:
mjpg_streamer -i "input_uvc.so --help"
-----------------------------------------------------------------------
In case the modules (=plugins) can not be found:
* Set the default search path for the modules with:
export LD_LIBRARY_PATH=/path/to/plugins,
* or put the plugins into the "/lib/" or "/usr/lib" folder,
* or instead of just providing the plugin file name, use a complete
path and filename:
mjpg_streamer -i "/path/to/modules/input_uvc.so"
mjpg_streamer -i "input_uvc.so -r 320x240 -f 6" -o "output_http.so -p 8080" -b
mjpg_streamer -i "input_uvc.so -r 320x240 -f 6" -o "output_http.so -w /usr/www" -b
mjpg_streamer -i "input_uvc.so -r 800x600 -f 20" -o "output_http.so -w /usr/www" -b
auto wlan0
iface wlan0 inet dhcp
wpa-ssid Chacala
wpa-psk mywirelesspassword
"If everything looks like it's working, don't just unplug your ethernet. use "ifconfig eth0 down" beforehand, otherwise you'll loose both connections."
"Actually there's a strange behavior of networkingon NSLU, when i boot without the ethernet cable plugged, in the wlan interface is also not working.
When i replug the ethernet cable, the wireless network also comes up. When i ifconfig eth0 down and unplug the ethernet cable the wlan does still work.
Strange, after some meditation on the interfaces file I noticed the commented line # The primary network interface and had the idea to just change the sections for the interfaces, so lets wlan0 be my primary interface and eth0 an additional one."
# The loopback network interface
auto lo
iface lo inet loopback
# The primary network interface
auto wlan0
iface wlan0 inet dhcp
wpa-ssid mywirelessnetworkname
wpa-psk mywirelesspassword
allow-hotplug eth0
iface eth0 inet dhcp
mjpg_streamer -o "output_http.so -w /usr/www
lsusb -v
mjpg_streamer -i "input_uvc.so -f 1 -r 1280x1024" -o "output_http.so -w /usr/www"And here is what I got:
MJPG Streamer Version.: 2.0The good news is that it didn't reject the resolution saying it wasn't found. The bad news is the memory error. On to troubleshooting the memory error. dmesg shows a log of error messages, starting off with:
i: Using V4L2 device.: /dev/video0
i: Desired Resolution: 1280 x 1024
i: Frames Per Second.: 1
i: Format............: MJPEG
o: www-folder-path...: /usr/www/
o: HTTP TCP port.....: 8080
o: username:password.: disabled
o: commands..........: enabled
Unable to start capture: Cannot allocate memory
i: Error grabbing frames
[42951766.100000] mjpg_streamer: page allocation failure. order:5, mode:0x1After a lot of googling it seems that this is some flavor of running out of memory, and one possible solution is to set overcommit to 2. Apparently you do that by running this command:
echo 2 > /proc/sys/vm/overcommit_memorySo I did. But I still got the Cannot allocate memory error when I tried to launch the streamer! Even after rebooting.
nano /etc/modprobe.d/blacklist
blacklist snd_usb_audioAfter I rebooted I checked lsmod and it looked like all the sound modules that had previously been loading were no longer loading, and free showed about 6 MB free memory with no use of swap. But still get a memory error trying to run mjpg-streamer!
mjpg_streamer -i "input_uvc.so -f 1 -r 1280x1024" -o "output_http.so -w /usr/www"The new USB 2.0 hub I ordered (Belkin USB 2.0 4-Port Ultra Mini Hub F5U407 Belkin USB 2.0 4-Port Ultra Mini Hub F5U407) arrived from Amazon. I bought this because it was under $10 and had good ratings on Amazon. I plugged it in, hooked the webcam and the wifi dongle up to it and rebooted. I hung on the first reboot, so I rebooted with nothing connected and then added the new USB hub by itself, then the webcam, and then the wifi dongle, and things worked that time.
I have been working on using Google Maps to show the routes of various hiking trails in my area. It can be done, but it's not very straightforward. Here are cursory notes on what I learned in the process (i.e. this is not a detailed how-to).
Initially I used Google "My Maps." Here are the characteristics of Google "My Maps" relevant to mapping hiking tails: