start-stop-daemon: help for start, stop, create pidfile for your command that doesn't have pidfile

You have a command to start a long running process but it doesn't create a pidfile for you to write a script to start/stop it. start-stop-daemon could help that.

This is a document of the command.

Example:

start-stop-daemon -d dir_want_to_run_on -b -m -p pidfile.pid --start --startas command

start-stop-daemon -p pidfile.pid --stop

-b : background

-m : make file (need to use with -p)

-p : pid file name (need to use with -m)

Light Table: Stop the execution

Use `Eval: Cancel evaluation for the current client` or `Editor: Disconnect clients attached to editor` from the command bar

credit: How to interrupt eval?

Solved a different cause of SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed (OpenSSL::SSL::SSLError)

You get SSL_connect returned=1 errno=0 state=SSLv3 read server certificate B: certificate verify failed (OpenSSL::SSL::SSLError) or similar error when trying to request to a https endpoint but no any other people solutions you have found through googling seems to be able to fix it.

What I have found is that those blog posts and stackoverflow answers led me to the wrong direction. The problem is neither Ruby's false nor you misconfigured it. Instead, missing intermediate CA certificate is the cause of the problem.

To verify that you are having the same cause of problem that I had, try running these command and compare the results

$ ruby -rnet/http -e "puts Net::HTTP.get(URI('https://github.com'))"

$ ruby -rnet/http -e "puts Net::HTTP.get(URI('https://your_webserver'))"

If you get back proper result for the first command and get the same error for the second command. That's the same problem I had. If you get errors on both commands, this post won't help solving you problem.

What's happening is that Ruby doesn't have a certificate of the intermediate CA that is used to issue certificate of the server you are requesting to

Compare Certificate chain section of the result of these 2 commands

$ openssl s_client -connect github.com:443

$ openssl s_client -connect your_webserver.com:443

In github's server case, you will get 0 and 1. On the other hand, in your web server case, you probably get only 0. SSL certificate chains section of this nginx documentation page has a good explanation of the chain.

If you own that web server or has an access to it, go fix that and your ssl issue should be resolved. For nginx web server, the fix is described in the previous link.

Good luck.

Unix/Linux log script outputs to a file

In any scripts that print something out, the simplest way to capture those printed stuffs is to append with

>> logfilename.log 2>&1 

All the outputs (stdout, stderr) will be redirect to file logfilename.log. To learn this in details, search for something like "unix stdout redirection"

Installing Ruby: cannot load such file -- [ openssl | zlib ]

If you like me, installed Ruby by compiling from source code manually, and found that this 2 errors when trying to install bundler

• cannot load such file -- openssl
• cannot load such file -- zlib

You missed configure make to compile with those 2 libraries. Follow these steps to fix this issue.

1. Remove the installed Ruby with make clean
2. Install libssl-dev with your OS's package manager of choice. E.g. apt-get install libssl-dev
3. Install zlib1g-dev with your OS's package manager of choice. E.g. apt-get install zlib1g-dev
4. Config make file to include openssl by go to ext/openssl and run ruby extconf.rb
5. Config make file to include zlib by go to ext/zlib and run ruby extconf.rb
6. Go back to ruby source code directory run make && make install
7. You should be able to successfully run gem install bundler

You can also do the same thing for readline. Install libreadline-dev and run extconf.rb in ext/readline

Tested with ruby 2.0.0p247

Credit:

• http://askubuntu.com/questions/261914/install-ruby-2-0-with-openssl-and-readline-support
• http://stackoverflow.com/questions/769496/ubuntu-noob-rails-install-fails-on-zlib

Download file from S3 via HTTP

You need to have s3cmd installed. This command should return all your buckets

s3cmd ls 

First make the file you want to download be public accessible with command setacl

s3cmd setacl --acl-public s3://bucket-name/path-to-file/filname

 Then you can download from this path

http://bucket-name.s3.amazonaws.com/path-to-file/filename

(You can download with many connection in parallel with axel)

Don't forget to set permission back to private with

 s3cmd setacl --acl-private s3://bucket-name/path-to-file/filname

Credit:  a comment in s3tool.org

FATAL: Chef::Exceptions::ChildConvergeError: Chef run process exited unsuccessfully (exit code 1)

This error message from chef is not very useful

FATAL: Chef::Exceptions::ChildConvergeError: Chef run process exited unsuccessfully (exit code 1)

I took me a few hours to dig in to chef source code to figure out what's really happening. It turned out for me that chef doesn't like ~ (home) that I used in path declarations in the solo.rb file.

As I skimmed through the code, I have a feeling that any errors that occurs during fork process will cause this error message which does not explain anything. If your cause is not the same as me, unfortunately your only option is to go digging through chef source code. :(

Gem: Chef
Version: 11.6.0