Posted in Linux, Uncategorized

I have a bunch of sites in /var/www and need individual user logins with access to their respective sites. In this tutorial I’ll go over how to create a user, chroot jail them and allow access to specific folders (in our case web directories).

For reference I’m using a standard LAMP server on Ubuntu:

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sudo apt-get install -y tasksel
sudo tasksel install lamp-server

but this tutorial will work for any web server configuration.

 

1. Create User, Assign Web Group

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# Create the user setting group to www-data
sudo useradd -Ng www-data myuser
sudo passwd myuser
 
# Restrict login to SFTP only
sudo groupadd sftp-only
sudo usermod myuser -G sftp-only

 

Create their web directory and provide access

With the new user created, make a directory matching their website’s name and mount the real website folder to it:

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# Create chroot directory and set permissions
mkdir -p /home/myuser/mysite.com/html
chmod 755 /home/myuser/mysite.com/html
 
# Mount the destination directory at the directory we just created
mount --bind /var/www/mysite.com/html /home/myuser/mysite.com/html
 
# Add the above command to /etc/rc.local to mount it on boot
nano /etc/rc.local

 

Restrict the user to SFTP Only

We only want to allow SFTP access for this user. First open /etc/passwd and make sure the end of the line has /bin/false like so:

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tail -n1 /etc/passwd
# myuser:x:1001:33::/home/myuser:/bin/false

Now edit /etc/sshd/sshd_config to allow only SFTP myuser:

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Match User myuser
  ChrootDirectory /home/myuser
  ForceCommand internal-sftp
  AllowTcpForwarding no
  X11Forwarding no

Restart the SSHD service:

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sudo service sshd restart

Now when you try to SSH in with this user you’ll get the error:

This service allows sftp connections only.

 

That’s it! They should now be able to SFTP in and will only have a mysite.com directory with access to their web files.

 

Further Reading

mihai.ile’s post on Stack Overflow – How can I chroot sftp-only SSH users into their homes?

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Posted in Database

When doing a

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mysqldump --all-databases -uUSER -p > dump.sql

I was getting the error

mysqldump: Got error: 1017: Can’t find file: ‘./dbname/tablename.frm’ (errno: 13 – Permission denied) when using LOCK TABLES

The error was caused by the table files in my MySQL data directory being owned by the wrong user so MySQL couldn’t properly read them. The solution is simple.

Find your MySQL Data Directory, Fix Permissions

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$ mysql -uroot -p -e 'SHOW VARIABLES WHERE Variable_Name="datadir"'
 
+---------------+-----------------------+
| Variable_name | Value                 |
+---------------+-----------------------+
| datadir       | /usr/local/var/mysql/ |
+---------------+-----------------------+
 
# Check owner of each file
$ ls -lh /usr/local/var/mysql/
 
# Update to correct owner
$ sudo chown -R _mysql:admin /usr/local/var/mysql/*

After fixing the permissions on all files in this directory, I was able to mysqldump correctly.

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Posted (Updated ) in Javascript, PHP

Dropzone is a really nice lightweight javascript upload library with drag drop support and a high level of customisability. The documentation for direct uploads to Amazon S3 with a PHP backend are entirely lacking though so I’ve whipped up a complete tutorial on how to make it happen. For this tutorial I’ll be using Laravel but the script is very simple and any PHP backend will work.

 

What You’ll Need

  • AWS Access Key
  • AWS Secret Key
  • AWS Region
  • AWS Bucket Name

As part of Laravel I’m using dotenv to store these values and retrieving them with getenv() but they can be stored as config variables or any other method you like.

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Posted in Uncategorized

Occasionally after running a brew update && brew upgrade I’ll attempt to start apache with sudo apachectl start and get the error


[Thu Jan 25 08:53:02.769633 2018] [core:warn] [pid 41502] AH00111: Config variable ${APACHE_LOG_DIR} is not defined
[Thu Jan 25 08:53:02.769654 2018] [core:warn] [pid 41502] AH00111: Config variable ${APACHE_LOG_DIR} is not defined
AH00543: httpd: bad user name ${APACHE_RUN_USER}

I also notice OSX’s built in apache is running instead of homebrews. But where should the envvars file go?

 

The Fix

Firstly disable OSX’s built in apache:

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sudo launchctl unload -w /System/Library/LaunchDaemons/org.apache.httpd.plist

Drop your envvars file in /usr/local/Cellar/httpd/2.4.*/bin folder replacing the * with your version number.

You should now be able to sudo apachectl start again.

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Posted in Uncategorized

For a while now I’ve been having an issue where when I plug my headphones into the headphone jack of my Logitech 5.1 PC speakers, some YouTube and Facebook videos wouldn’t have sound, but most would.

I found this Reddit thread on the topic however the best solution seemed to be:

Hopefully everyone has fixed this by now, however I fixed this by changing my Realtek settings from 7.1 to stereo. – VeryRedChris

I went poking around in my sound settings (Windows 10) and made the following adjustment: Sound – Playback Devices – Speakers (Realtek High Definition Audio) – Properties – Spatial Sound and set Spatial sound format to Windows Sonic for Headphones and made sure Turn on 7.1 virtual surround sound checkbox was checked. This fixed the issue! If you have Chrome open, restart it and any other existing audio apps for the changes to take affect.

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Posted in Linux

I’ve been trying to clone a private git repository from BitBucket and getting the response:

$ git clone git@bitbucket.org:my/repo.git
Cloning into ‘repo’…
Permission denied (publickey).
fatal: Could not read from remote repository.

There are two things that need to be done to fix this.

 

Add your SSH Key to BitBucket

Firstly, make sure your git server has your SSH key. I’m using BitBucket so as per their documentation:

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ssh-keygen
cat ~/.ssh/id_rsa.pub

Copy and add your key to Settings – SSH Keys area in BitBucket.

 

Add your Key to the SSH Agent

If this still isn’t enough to fix the above error you may need to add your new key to your machines SSH agent.

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# Make sure SSH agent is running
eval `ssh-agent -s`
 
# Add your key to the agent
ssh-add ~/.ssh/id_rsa

 

Give it a try now and you should be all good. Thanks to Srikanth Kondaparthy and user456814 for their helpful posts on Stack Overflow.

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Posted in Uncategorized

Our firewall at work restricts us to only port 80 and no access to SSH – which as you can imagine for a web developer is a pretty big issue. Below I’ll describe the various methods of routing around this crap.

 

Create a SOCKS5 Proxy with SSH

If your firewall restricts which sites you can visit but you have access through SSH to a remote server, route your browser and other traffic through that server with a SOCKS5 proxy. This is called Dynamic Port Forwarding:

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ssh -f -N -D 1080 remote-server

The above command creates a SOCKS5 proxy server on port 1080 of your machine which sends all traffic through remote-server. 

Use it with you browser:

Now use the server in Firefox:

  • go to Edit -> Preferences -> Advanced -> Network -> Connection -> Settings…
  • check “Manual proxy configuration”
  • make sure “Use this proxy server for all protocols” is cleared
  • clear “HTTP Proxy”, “SSL Proxy”, “FTP Proxy”, and “Gopher Proxy” fields
  • enter “127.0.0.1” for “SOCKS Host”
  • enter “1080” (or whatever port you chose) for Port.

Use it with git:

You can also configure SSH git origins to work with your proxy:

Open ~/.ssh/config and add

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Host bitbucket.org
    User git
    ProxyCommand nc -x localhost:1080 %h %p

Now you can just clone/push/pull as normal. See here for more information.

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Posted (Updated ) in Uncategorized

Recording a gif on OSX is fairly easy but you’ll need a few tools to make it happen – especially if you want a nice, small filesize for online viewing.

 

Step 1 – Record a video

You can use anything for this – I was recording a window on my screen so I used Screenium but Quicktime works fine. The output was a 15 second 1.1MB MOV file of resolution 1184×738. I saved the file as demo.mov on my desktop.

 

Step 2 – Convert to a Slideshow of PNGs

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    brew install ffmpeg #if you don't already have it
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    mkdir output
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    ffmpeg -i demo.mov -vf scale=iw:ih -r 10 output/ffout%3d.png
    • ‘scale=iw:ih’ – Don’t change the input scale. You can also set this to specific values or ‘320:-1’ to rescale down for example
    • ‘-r 10’ – Set to 10 FPS
    • ‘output/ffout%3d.png’ output slideshow of pngs in output folder

 

Step 3 – Convert the Slideshow to a GIF

From our PNG slideshow we can generate a (huge) gif. Don’t worry, we’ll fix the filesize later.

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    brew install imagemagick #if you don't already have it
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    convert -delay 8 -loop 0 output/ffout*.png output/demo.gif
    • ‘convert’ is the command-line tool from ImageMagick
    • ‘-dalay’ is the delay of 8, you would get a FPS=100/8=12.5
    • ‘-loop’ adds Netscape loop extension to your GIF animation
    • ‘output/ffout*.png’ is the directory and file names going into the GIF
    • ‘output/animation.gif’ is the final location and GIF output

 

Step 4 – Optimise your GIF with Photoshop

  • Drag your new gif into Photoshop. Here you can make any changes such as removing frames. Turning on Window – Timeline will help here.
  • File – Save for Web and select GIF from the image type drop down at the top right
  • Tweak your Image Size and Colors values until you get the filesize you want (shown at bottom left). You can preview the GIF in realtime using the media buttons at the bottom right.
  • If the filesize is still too large, return to step 2 and lower your gifs FPS by lowering the r value.
  • Optimising your GIF with Photoshop

 

References

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Posted in PHP

Say you’re pooling requests in Guzzle and want the responses to have access to data such as the request URL. Guzzle doesn’t currently allow for this but that’s all fixed with the help of a simple middleware class.

 

Usage

When requesting a URL with GuzzleHttp\Client, pass a RESPONSE_META array in your requests second argument like so:

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$client->get($url, [
    'RESPONSE_META' => [
        'url' => $url,
        'some_data' => 'foo',
    ],
]);

The data is attached as a header to the response. Access it like so: (Remembering to prepend X-GUZZLE-META- to your key)

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$some_data = $response->getHeaderLine('X-GUZZLE-META-some_data');

 

Complete Example

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$names = ['Alpha', 'Beta', 'Charlie', 'Delta'];
$stack = GuzzleHttp\HandlerStack::create();
$stack->push(GuzzleResponseMetaMiddleware::middleware());$client = new GuzzleHttp\Client([
    'handler' => $stack]);
$requests = function() use ($client, $names) {
    foreach ( $names as $name )
    {
        $url = "Http://mydomain.com/?name=".$name;
 
        yield function() use ($client, $url, $name) {
            return $client->getAsync($url, [
                'RESPONSE_META' => [                    'url' => $url,                    'name' => $name,                ],            ]);
        };
    }
};
$pool = new GuzzleHttp\Pool($client, $requests(), [
    'concurrency' => 5,
    'fulfilled' => function (Psr\Http\Message\ResponseInterface $response, $index) {
        $url = $response->getHeaderLine('X-GUZZLE-META-url');        $name = $response->getHeaderLine('X-GUZZLE-META-name'); 
        // do something with this info
    },
]);
 
// Initiate the transfers and create a promise
$promise = $pool->promise();
 
// Force the pool of requests to complete.
$promise->wait();

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Posted in Database

This post will be a short and sweet one. Copying/cloning a database between mysql hosts in a single command can be done with:

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mysqldump -h old_host -u old_user -p old_password old_db_name | mysql -h new_host -u new_user -p new_password new_db_name

Note that this will dump the entire database down to your machine before re-uploading it to the new machine.

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