LinuxQuestions.org - [SOLVED] rc.httpd and rc.mysqld break startup scripts

- Slackware (https://www.linuxquestions.org/questions/slackware-14/)

- - rc.httpd and rc.mysqld break startup scripts (https://www.linuxquestions.org/questions/slackware-14/rc-httpd-and-rc-mysqld-break-startup-scripts-702087/)

Quote:

Originally Posted by GazL (Post 3434070)

In this case, the change is fairly self evident.

Code:

sed -e 's:\. /etc/rc.d/rc.:/bin/sh /etc/rc.d/rc.:g' /etc/rc.d/rc.M

I do not see what is your point here. What is the practical advantage of replacing scripts' sourcing by scripts' running ?

Quote:

Originally Posted by Didier Spaier (Post 3434100)

I do not see what is your point here. What is the practical advantage of replacing scripts' sourcing by scripts' running ?

The point is that some people may run customised rc scripts. The original poster is a case in point. He used non-standard rc.httpd which included a 'exit' which broke rc.M. By changing them all to run in their own shell process, you protect rc.M from customisations to the files it calls. It's a very minor change, but it's all about resiliency. If you run the standard rc.'s you have no problems with it as long as everything is stock, but I'm a belt and braces guy when it comes to things as important as system starup scripts.

Quote:

Originally Posted by GazL (Post 3434110)

The point is that some people may run customised rc scripts. The original poster is a case in point. He used non-standard rc.httpd which included a 'exit' which broke rc.M.

IMHO, if someone replaces or edit a startup script, he/she should be wise and skilled enough to prevent possible unwanted side effects of his/her changes.

Is that so difficult e.g. to type "grep rc.httpd /etc/rc.d/*" and check the output ?

Would you not have to replace all the /path/to/binary portions of the rc scripts with `exec /path/to/binary` to stop having a bajillion spawned shell processes?

Also spawning a new shell for everything would affect 'global' variables like PS1, PATH, etc, to the extent that they would never appear in any scope other than the one that was spawned (and has maybe since been exec'd away).

I sympathise with the OP that his rc.M broke, but it broke because of poor understanding of the startup mechanisms. Knowing that (by default) startup scripts are all sourced and modifying your custom scripts to match the default is surely a better method than rewriting the entire init procedure to match some generic scripts that have been written as an example. Likewise, knowing that you can change rc.M where you prefer your own scripts to the 'official' ones is also a valid approach, which has been applied successfully I think to solve the OP's original problem.

For discussions on source vs shell, maybe a new thread would be a plan get the best exposure?

- Piete

Quote:

Originally Posted by Didier Spaier (Post 3434100)

I do not see what is your point here. What is the practical advantage of replacing scripts' sourcing by scripts' running ?

1. To prevent namespace pollution. This one benifit is good enough.

2. More friendly to non-sh scripts. For example, "rc.udev" is a bash-only script. I myself would also like to use python, in which case "source" is nonsense. If everything is run directly, the calling command need not be changed even if the interpreter changed, or even if the script is replaced by an ELF program. I have both cases in my /etc/rc.d/

I usually write a new script with sh; then when it grows, if I find difficulty, I change to python; in the end, if I think the script needs no more change, I sometimes re-write it in C. Because I don't use "source", the "rc.*" scripts themselves need not be changed.

I think if you decide to mess with the Slackware default scripts, you should be prepared to change anything that prevents total disaster. If you change scripts and add "exit" statements, you are responsible for changing the source-ing to spawning an external shell for the script's execution. Using python during early bootup is certainly not recommended because of the library files it needs in /usr/ ... you can not be certain (when you write scripts to be used on many different computers) that the /usr directory is available that early. It may be on a separate partition which is only mounted later.

Slackware's rc scripts will likely remain as they are, since I have not heard a good reason why they should change. Spawning a subshell will make the boot stage's shell environment unavailable to the script. Variables set of changed inside the script would vanish once the script ends.

Eric

Quote:

Originally Posted by Alien Bob (Post 3434208)

It was not me who put "exit" into the script ... Nevertheless, you can see in newer versions of Slackware that many startup scripts are really sh-ed instead of source-ed.

I think it will be even better to omit the sh. "/etc/rc.d/SCRIPT_NAME" is enough because some scripts, e.g. "rc.udev", is not sh-compatible (rc.udev is bash-only).

Quote:

Using python during early bootup is certainly not recommended because of the library files it needs in /usr/ ... you can not be certain (when you write scripts to be used on many different computers) that the /usr directory is available that early. It may be on a separate partition which is only mounted later.

Yes. I can be quite sure "/usr" is mounted early enough. You can find a lot of things if you "grep -l /usr/sbin /etc/rc.d/rc.*".

Quote:

Slackware's rc scripts will likely remain as they are, since I have not heard a good reason why they should change. Spawning a subshell will make the boot stage's shell environment unavailable to the script.

Not true. The spawned shell will inherit the environment variables from the calling shell.

Quote:

Variables set of changed inside the script would vanish once the script ends.

Eric

What are these variables? I mean the "useful" ones, i.e. the ones will be used by subsequent scripts.

If you must export variables, I think it's better to do it this way:

Code:

# ******* This is /etc/rc.d/rc.M ********

if [ -x /etc/rc.d/rc.servars ]; then

  `/etc/rc.d/rc.setvars`

fi

Code:

#! /usr/bin/env python

# ******* This is /etc/rc.d/rc.servars *******

import sys, os

sys.stdout.write('export TMP_MAX=%u' % os.TMP_MAX)

sys.stderr.write('This is %s\n' % sys.argv[0])

Guanx, my guess is you won't convince Slackware team to make the changes you propose.

But nobody prevents you to fork Slackware -- you would not be the first, anyway.

Meanwhile I will stick to the original ;)

Cheers,

Quote:

Originally Posted by Didier Spaier (Post 3434239)

I am not talking about what they should do. I am simply suggesting which is better :P

Actually, Slackware has already changed many "source SCRIPT_NAME" commands in "rc.M" and alikes to "sh SCRIPT_NAME". This means there are not so may environment variables to export as Eric thought. Preventing namespace pollution is more important.

Now because the scripts are not source-ed generally, if I want to use python instead sh, I can write the script this way:

Code:

#! /bin/sh



"exec" "python" "$0" "$@"

print 'This is Python'

It works as long as you don't "source" it. Furthermore, if you run it directly without specifying the interpreter, this ugly trick can go away and the code will look more beautiful.

Quote:

Originally Posted by Alien Bob (Post 3434208)

I agree, one should expect people making customisations to get it right, but having a consistent approach, i.e. calling all the sub scripts in the same manner, will help them get it right. As was mentioned above some are currently sourced into the current shell of rc.M and some are run in a new shell. It's a mess. It works, but it's clearly not tidy!

Then you have the issue of fault tolerance. Expecting someone making customisations in sub scripts to get it right is reasonable enough, but what's so wrong with making rc.M able to cope with errors regardless. It's just sound design and good programming practice.

Actually, on reflection, I like guanx idea of not even prefixing them with the shell at all and letting the interpreter string identified within the script file determine what executable is used to run it.

Quote:

Originally Posted by Alien Bob (Post 3434208)

We're talking specifically about rc.M and the subsystem scripts such as rc.httpd called from it. Filesystems will have already been mounted by this point.

Quote:

Originally Posted by Alien Bob (Post 3434208)

The rc.whatever sub scripts are all designed to be run individually, so that subsystems can be stopped/started manually. So, passing environment variables back and forth shouldn't be an issue. Wouldn't any requirements to pass environment variables between several scripts break this functionality?

If you want to take the line that: it's 'good enough' as it is and doesn't need changing, then that's fair enough, but that doesn't mean that these suggestions are without merit.

I can see that guanx is on the same wavelength as I am here, I guess I'll have to settle for that.

I Have Slackware 12.1 running really fast and flawlessly on my new Dell laptop, I used the command above: mysql_install_db , and it got my mysql server working pretty much instantly. What script can I use to get the mysql server to boot when I boot the laptop up ?

Does Slackware have a command to run a process manager?

I haven't checked the init scripts in question, but I suspect that the fact that some are simply sourced while others are run in a separate proces (using sh)has to do with whether the called process runs as a backgrounded daemon or not. If you source a script which starts a process which does not background itelf, then the init process would hang right there. Such a process would have to be run with a separate process to allow the normal bott process to continue.

Quote:

Originally Posted by bsurfin (Post 3439353)

What script can I use to get the mysql server to boot when I boot the laptop up ?

Does Slackware have a command to run a process manager?

Slackware uses BSD-style process management. You manage boot processes primarily by setting the execute status of scripts in /etc/rc.d/, and possibly by edits of /etc/rc.d/rc.local.

To make MySQL start at boot simply make /etc/rc.d/rc.mysqld executable. As root...

Code:

chmod 755 /etc/rc.d/rc.mysqld

To 'turn off' any process...

Code:

chmod 644 /etc/rc.d/rc.script_name

...with the desired script name.