Bash Script Request (someone please!! :)

[notaloafer]

Right now I have a program that needs to be run at startup as a daemon process so I don't have to run it in a gnome terminal. Right now the commands to start it are:

su - jbls
(enterpasswords)
cd Desktop/JBLS
java -jar JBLS.jar

This program runs in a terminal text-only window. However I don't like running it on my gnome desktop.

I asked someone on MSN how to create a BASH script to auto-run at startup and he said the following:


Eric: it runs in terminal
Eric: is it easy to daemon-tize it so it auto runs when i start up my server
Tex: hmm
Eric: and so i dont have to run it in gnome? (i usually turn gnome off when im not using it)
Tex: you *might* be able to do that with a script
Tex: does the java app display something graphical?
Eric: nope
Eric: just runs text-base in terminal
Tex: hmm... then you could just make a bash script that contains the startup commands, then put your bash script in /etc/rc.local so that it's run at boot
Tex: that'd be easiest
Eric: hm
Eric: i found /etc/rc.local and opened it
Eric: and theres nothing in it
Eric: how do i go about making a bash script?
Tex: bash scripts are easy, and they look like this:
Tex: #!/bin/bash
cd /somedirectory
./somescript
Eric: ooh ok
Tex: just put the commands you usually run within that script
Tex: then make it executable:
Tex: chmod +x yourbashscript.sh
Tex: then put this in /etc/rc.local
Tex: /bin/bash /path/to/your/bashscript.sh
Eric: ah i see
Tex: good to go
Eric: thanks
Tex: well, if the java app hangs, there is a possibility that your bootup could hang :-/



I would do it myself but I have no idea how to make a BASH script or where to start with it... I also don't want to risk making my server un-bootable by a mis-configuration.

Thanks!
-Eric

[notaloafer]

Did i post this in the right forum?

[Railsbuntu]

First create a file inside /etc/init.d and make it executable:

sudo touch /etc/init.d/myscript && sudo chmod 755 /etc/init.d/myscript

You can open your favorite text editor, for instance vim, so at command prompt:
$ sudo vim /etc/initd.d/myscript
Then inside your edito type in the shell commands you would usually type to perform the wanted task. See how each script starts with the same declaration #!/bin/bash

So inside your editor you type:
#!/bin/sh
cd /somedirectory
ls -la

Save the file.

Then tell Ubuntu you want to add this script to the startup process:
$ sudo update-rc.d myscript defaults

EDIT: actually when running update-rc.d, the "defaults" parameter might be inappropriate. It depends on what you script does at each run level.

[jpkotta]

If you don't need to run it as root, you should use su to run it as your user.

su -c "command arg1 arg2" -- username

[Railsbuntu]

It seems Gutsy usesupstart, see for more info: http://upstart.ubuntu.com/index.html

[notaloafer]

First create a file inside /etc/init.d and make it executable:



You can open your favorite text editor, for instance vim, so at command prompt:
$ sudo vim /etc/initd.d/myscript
Then inside your edito type in the shell commands you would usually type to perform the wanted task. See how each script starts with the same declaration #!/bin/bash

So inside your editor you type:
#!/bin/sh
cd /somedirectory
ls -la

Save the file.

Then tell Ubuntu you want to add this script to the startup process:


EDIT: actually when running update-rc.d, the "defaults" parameter might be inappropriate. It depends on what you script does at each run level.


I think I understand this... but if I mess up (which I probably will; trial & error), will my server restart still or completely hang? If it hangs is there a ubuntu-version of a safemode?

-Eric

[notaloafer]

Here's what I've come up with so far:

1) Run command
sudo touch /etc/init.d/jbls && sudo chmod 755 /etc/init.d/jbls

2) Open it up in VIM: sudo vim /etc/init.d/jbls
3) add the following:
#!/bin/sh
su - jbls
hardcode password here
cd /home/jbls/Desktop/JBLS
java -jar JBLS.jar

4) Test to see if it works by running
sudo /etc/init.d/jbls start

I think I'm missing some key information here.. but the directory that the JAR file resides in is in /home/jbls/Desktop/JBLS ...

Do these steps seem right or even close?

Thanks so much for your guys' help!
-Eric

[Martje_001]

If your script fails it doesn't hang your computer. It will only give an error message.

[notaloafer]

Okay thanks for that assurance =). My other question: How does my script look that I posted above (as far as all the steps to creating it and the actual script content)?

Thanks!
-Eric

[Martje_001]

Looks OK to me.You don't have to type your password since your root at startup (correct me if i'm wrong).

[ddixonr]

What does the "!" do in [ #!/bin/bash ] or [#!/bin/sh ] ?

I am a complete noob in saving bash scripts, but I've managed to complete two that I needed. First one was to close a stuck Firefox:

#/bin/bash
killall firefox-bin

And the second was to quickly empty trash:

#/bin/bash
-rf ~/.Trash/*

These worked nicely for me. Saved them as .sh filenames, dragged them to the panel for accessibility and life is grand.

[WW]

The following quote is from http://tldp.org/LDP/abs/html/sha-bang.html:

The sha-bang ( #!) at the head of a script tells your system that this file is a set of commands to be fed to the command interpreter indicated. The #! is actually a two-byte magic number, a special marker that designates a file type, or in this case an executable shell script (type man magic for more details on this fascinating topic). Immediately following the sha-bang is a path name. This is the path to the program that interprets the commands in the script, whether it be a shell, a programming language, or a utility. This command interpreter then executes the commands in the script, starting at the top (line following the sha-bang line), ignoring comments.

Without the !, the first line of your scripts is just a comment.