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Old 10-24-2003, 07:34 PM   #1
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Location: Rochester, MN, U.S.A
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understanding exacutables

I am trying to understand executable files. Some of the files in my /etc/rc.d have permission of execute and others do not. Are only the ones with permission set for execute(-rwx--x--x) used at startup. Are all of the other shell scripts(-rw-r--r--) in there dormant, in the sence that they need to change their permissions to be used?

I asked this because I added a firewall script to /etc/rc.d that Guarddog created. Which seems to be working(firewall starts at bootup). I wasn't sure if making something exacutable was just about changing the permissions.

Last edited by shanenin; 10-24-2003 at 09:30 PM.
Old 10-24-2003, 08:00 PM   #2
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I think only files ending with .sh and having the executable bit set are executed in rc.d at startup - at least this is how things work in FreeBSD, and maybe in Linux, too.
Thus rc.d may contain sample scripts that are not executed at startup, since they do not end with .sh.
Old 10-24-2003, 08:06 PM   #3
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Sorry for misleading you, but I took a look at /etc/rc.d of my Linux machine, and I saw there virtually no files ending with .sh, so Linux works differently.
However, I am sure that only files having the executeablebit set are executed there.
Old 10-24-2003, 08:08 PM   #4
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.bin are executable also right? I think so.

Last edited by Edward78; 10-24-2003 at 08:09 PM.
Old 12-22-2003, 06:35 PM   #5
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Looking in my /etc/init.d and /etc/rc.d/rc5.d directories, all of the listed files have the executable bits set. The files that run on startup or shutdown are the links in the /etc/rc.d/rc<runlevel>.d directories. They will point to programs (scripts) in the /etc/init.d directory. The S<num> prefix will determine the order they will start.

A binary program or script needs the x bit set to run. The .bin extension is usually added to let you know that it is an executable. For example, the netscape install program ends with the .bin extension, to remind you to use chmod +x on the file after downloading it.

Unix/Linux file systems don't have the text/binary file type distinctions that MSDOS / Windows does.
Old 12-22-2003, 08:42 PM   #6
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Exactly - extensions are purely descriptive for the most part (though some programs are coded to look for certain ones) and the only files that will execute are those that have the executable bit. However, some configuration files will be read by an executable and have the *effect* of being commands. But, in essence, it's an on/off thing - chmod 600 a binary and it won't run. Chmod 700 a script and it will. Of course, if you chmod a grocery list to execute bash'll just spew a lot errors - but it will 'execute'.


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