Drew's Blog » HowTo http://drewdahl.com A Barrage of Liquid Awesome in Geek Form Thu, 26 May 2011 08:43:41 +0000 en hourly 1 http://wordpress.org/?v= Using NetworkManager to run scripts after connecting http://drewdahl.com/2011/05/03/using-networkmanager-to-run-scripts-after-connecting/ http://drewdahl.com/2011/05/03/using-networkmanager-to-run-scripts-after-connecting/#comments Tue, 03 May 2011 23:14:01 +0000 Drew Dahl http://drewdahl.com/?p=651 For years now, I’ve had to run vpnc after connecting my school’s wireless. Truly, it never bothered me; however, at my new job, I need to run route after I connect to their wireless. For whatever reason, that got to me. I didn’t really want to run route when I wasn’t on their network (it likely wouldn’t have screwed anything up, but still…). So, I went about putting a quick bit in /etc/sysconfig/network-scripts/ifup-wireless, and it didn’t work… =\ So, after some digging, I’ve found another way using NetworkManager. Here’s what I did:

Because I hate hacking up scripts that services use, I wrote a quick script and put it in /usr/local/bin/wireless.sh:

#!/bin/bash

if iwconfig|grep -c MY-WORK-ESSID
then
        route add -net 111.111.111.111/22 gw 222.222.222.222
fi

if iwconfig|grep -c msum-wireless
then
        vpnc
fi

Once that was done, I ran:

chmod +x /usr/local/bin/wireless.sh

and added the line:

/usr/local/bin/wireless.sh

to the file /etc/NetworkManager/dispatcher.d/00-netreport right before the exit.

And that’s it! It would be neat if NetworkManager added in similar functionality through the GUI, but until that day, this should work fine. Also, to note, those scripts are run as root, so be careful!

Update!

Upon upgrading from Fedora 14 to 15, the file 00-netreport was overwritten. I’ve done updates to NetworkManager, so that had nothing to do with it. In any case, if you end up upgrading your distro, there’s a chance that’ll get overwritten. In the event it does, you’ll just have to paste the line to the script again. (Another good reason to use a script!)

There may be a better way than what I’m doing above, but it works for me, so I’m not going to bother looking for another way. Hope this helps!

]]> http://drewdahl.com/2011/05/03/using-networkmanager-to-run-scripts-after-connecting/feed/ 0 Using Ruby to run commands on a lab of Linux machines http://drewdahl.com/2011/02/24/using-ruby-to-run-commands-on-a-lab-of-linux-machines/ http://drewdahl.com/2011/02/24/using-ruby-to-run-commands-on-a-lab-of-linux-machines/#comments Fri, 25 Feb 2011 03:19:20 +0000 Drew Dahl http://drewdahl.com/?p=645 Lately, I’ve been getting acquainted with Rails development at work. It’s been a pretty steep learning curve (for that matter, I guess it still is), but I’ve enjoyed it thus far. So, with my new found Ruby skills (or, I guess more-so my new found need to learn Ruby), I wrote a script that uses SSH to iteratively connect to every computer in a lab and update them. This could be used for just about anything, but for my instance it was updating a lab. There was a bit more to my script as I needed to recompile some device drivers when there was a new kernel, but for simplicities sake, I’ve ripped them out. Hope this helps someone else!

First, you’ll need to install the ruby-ssh library.

sudo gem install net-ssh
sudo gem install highline

And, the script is:

#!/usr/bin/ruby

require 'rubygems'
require 'net/ssh'
require 'highline/import'

hosts=[ "host1",
            "host2" ]

cmds = ["yum -y update",
             "init 6"]

username = "root"

# Assuming that all hosts have the same password
password = ask("Enter Password: ") { |q| q.echo = false }

hosts.each do |host|
    Net::SSH.start( host , username, :password => password) do |ssh|
        puts "Connected to #{host}"
        cmds.each do |cmd|
            puts "Performing #{cmd} on #{host}"
            output = ssh.exec! cmd do |ch, stream, data|
                if stream == :stderr
                    puts "Error: #{data}"
                else
                    puts data
                end
            end
        end
    end
end

And, that’s all there is to it! There’s a real lack of comments, but I feel it’s pretty self-explanatory. Enjoy!

]]> http://drewdahl.com/2011/02/24/using-ruby-to-run-commands-on-a-lab-of-linux-machines/feed/ 2 Simple Shell in C http://drewdahl.com/2010/12/02/simple-shell-in-c/ http://drewdahl.com/2010/12/02/simple-shell-in-c/#comments Thu, 02 Dec 2010 10:15:31 +0000 Drew Dahl http://drewdahl.com/?p=619 Well, life has been a 24/7 hell for the last few months. As an example of how much free time I’ve had, I haven’t seen a couple of my really good friends since July or August. Hopefully they haven’t forgotten about me ;-)

In any case, I wrote a pretty good simple shell in C for my Operating Systems class. I finished it back in October, but haven’t posted it until now as several students just recently finished theirs.  Wouldn’t want them to cheat. ;-)

Less rambling.  The reason I’m posting this is that I think it is a really good example of using some basic system calls, such as malloc(), printf(), fgets(), strtok(), strcmp(), strcpy(), sprintf(), free(), chdir(), fork(), execpe(), opendir(), and wait(). Hopefully someone finds this useful :-)

#include <stdio .h>
#include <stdlib .h>
#include <unistd .h>
#include <string .h>
#include <sys /types.h>
#include <dirent .h>

const int SIZE=100;
const int ARGSIZE=10;

void cd(char *dir)
{
    int ret = 0;

    //Check to see if directory argument is blank
    if(dir == '\0')
        dir = getenv("HOME");
    //Check to see if directory argument starts with ~ and replace it with $HOME
    else if(dir[0] == '~')
    {
        char* temp = malloc(SIZE);
        strcpy(temp,dir+1);
        sprintf(dir,"%s%s",getenv("HOME"),temp);
        free(temp);
    }

    //Change Directory
    ret = chdir(dir);
           
    if(ret != 0)
        fprintf(stderr,"Failed to enter directory: %s\n",dir);
    else
        printf("%s\n",dir);
}

void ls(char *dir)
{
    DIR* open_dir;
    struct dirent* drent;

    if(dir == '\0') //See if dir is valid, if not set it to current directory
        dir = (char*)".";

    if((open_dir = opendir(dir)) != NULL) //open dir
    {
        while((drent = readdir(open_dir)) != NULL) //get contents of directory
        {
            printf("%s\n",drent->d_name); //print contents
        }
   
        closedir(open_dir); //close dir
    }
}

void execute(char *args[])
{
    int status;
    pid_t pid;

    //fork and execute the command   
    if((pid = fork()) == 0)
    {
        execvp(args[0],args);
        //execvp should only return if there was an error

        fprintf(stderr,"Unknown command\n");
        exit(0);
    }
    else if(pid < 0)
    {
        fprintf(stderr,"Failed to fork(): %s\n", args[0]);
        status = -1;
    }
    //Wait for child so stdin and stdout aren't fighting for use   
    else
        while(wait(&status) != pid)
           continue;
}

int main(int argc, char *argv[], char *envp[])
{
    char *temp;
    char *line;
    char *args[ARGSIZE];
    char argIndex = 0;

    for(;;)
    {
        line = malloc(SIZE); //Allocate memory for line
        argIndex = 0; //Initialize argIndex

        printf("\n[SHELL ] ");

        fgets(line, SIZE, stdin); //Get Input

        temp = strtok(line, " \n"); //Get input into an array to use w/ execve

        while(temp != NULL)
        {
            args[argIndex] = temp;
            argIndex++;
            temp = strtok(NULL, " \n");
        }

        args[argIndex] = (char*) 0; //Set the end of the arguments list

        if(strcmp(args[0], "quit") == 0 || strcmp(args[0], "exit") == 0)
            break; //break out for for(;;) loop

        if(line== "\n")
            printf("[SHELL ] ");
        else if ((strcmp(args[0], "ls") ==0))
            ls(args[1]); //run ls
        else if ((strcmp(args[0], "cd") == 0))
            cd(args[1]); //run cd
        else
            execute(args); //Fork and Execute command

        free(line); //Free memory from line
    }

    printf("\n");
    return 0;
}

And, in case you want a Makefile (I know I do!):

CC = gcc
OBJECTS =
PROC = shell

CFLAGS =
LFLAGS =

$(PROC):
$(CC) $(CFLAGS) simpleshell.c -o $(PROC) $(LFLAGS)
all:
$(CC) $(CFLAGS) simpleshell.c -o $(PROC) $(LFLAGS)
clean:
rm -rf *.o *.c~ $(PROC)

Enjoy!

(P.S… Todoist-for-Android updates will follow! I promise! The holidays are coming after all! :-] )

]]> http://drewdahl.com/2010/12/02/simple-shell-in-c/feed/ 2 HowTo Setup Authenticated Postfix http://drewdahl.com/2010/05/15/howto-setup-authenticated-postfix/ http://drewdahl.com/2010/05/15/howto-setup-authenticated-postfix/#comments Sun, 16 May 2010 00:54:01 +0000 Drew Dahl http://drewdahl.com/?p=478 I recently had the experience of setting up Postfix. It works really well, in my opinion; however, setting it up wasn’t the simplest for what I wanted. But, at least it was simpler than sendmail :-)

Reading through several articles on the Internet, everyone was giving steps on how to setup postfix to handle e-mail for any FQDN (Fully-Qualified Domain Name). Well, we don’t want to be handling someone else’s e-mail, so we decided to set it up with authentication. All of the guides on setting up Postfix with SASL authentication are great and all; however, they don’t address the issue of, what if you want to receive mail as well. That’s a simple fix, but moreover, what if you have a service like mailman running? Mailman isn’t easily configured to authenticate against the SMTP server to send mail. So, the following are the configurations that I’ve come up with to solve all of these problems:

For the file /etc/postfix/main.cf

<strong>queue_directory = /var/spool/postfix
command_directory = /usr/sbin
daemon_directory = /usr/libexec/postfix
data_directory = /var/lib/postfix
mail_owner = postfix
myhostname = hostname.domain.tld
mydomain = domain.tld
myorigin = $mydomain
inet_interfaces = all
inet_protocols = all
mydestination = $myhostname, localhost.$mydomain, localhost, localhost.localdomain, $mydomain
unknown_local_recipient_reject_code = 550
mynetworks = 192.168.0.0/24, 127.0.0.1/32
relay_domains = $mydestination
smtpd_sasl_auth_enable = yes
smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated, reject_unauth_destination
broken_sasl_auth_clients = yes
alias_maps = hash:/etc/aliases, hash:/etc/mailman/aliases
alias_database = hash:/etc/aliases
recipient_delimiter = +
debug_peer_level = 2
debugger_command =
         PATH=/bin:/usr/bin:/usr/local/bin:/usr/X11R6/bin
         ddd $daemon_directory/$process_name $process_id & sleep 5
sendmail_path = /usr/sbin/sendmail.postfix
newaliases_path = /usr/bin/newaliases.postfix
mailq_path = /usr/bin/mailq.postfix
setgid_group = postdrop
html_directory = no
manpage_directory = /usr/share/man
sample_directory = /usr/share/doc/postfix-2.6.5/samples
readme_directory = /usr/share/doc/postfix-2.6.5/README_FILES</strong>

Now keep in mind, your values for some of the above WILL be different. This configuration is on a machine that’s running mailman as well (thus the /etc/mailman/aliases file).

And lastly, for SASL auth, edit the file: /usr/lib64/sasl2/smtpd.conf

<strong>pwcheck_method: saslauthd
mech_list: plain login</strong>

Your lib64 directory may just be lib, depending on the architecture of your box. All of these edits were made a 64-bit Fedora 12 machine, but they should work for every machine.

And last note. After all of the edits have been made, make sure to restart postfix and restart saslauthd with the following:

/etc/init.d/postfix restart
/etc/init.d/saslauthd restart

For questions on what some of the postfix settings mean, you can check out one of the following:

postconf man-page by running “man postconf” or visit http://www.postfix.org/postconf.5.html

Postfix Documentation at: http://www.postfix.org/documentation.html

Postfix HowTo’s at: http://www.postfix.org/docs.html

Postfix is definition the easiest MTA I’ve ever had the pleasure of working with, as far as configuration goes. I hope this helps :-)

]]> http://drewdahl.com/2010/05/15/howto-setup-authenticated-postfix/feed/ 0 Forefront Client Security – MOM Installation Failure http://drewdahl.com/2010/05/02/forefront-client-security-mom-installation-failure/ http://drewdahl.com/2010/05/02/forefront-client-security-mom-installation-failure/#comments Sun, 02 May 2010 05:38:19 +0000 Drew Dahl http://drewdahl.com/?p=476 Well, I’m working on installing Forefront Client Security at my work and after configuring all of the prerequisites, nobody could figure out why it wasn’t installing. So, I setup a test machine and started playing with it. After about an hour of searching google, it seems nobody really has an answer for why MOM fails to install… but, I just figured it out!

If you check the installation logs in C:\Program Files\Microsoft Forefront\Client Security\Logs\MOMDB.log, you should notice there’s a line in there about an error running a query that results in an ERROR 112. The error is something like “There is not enough space on disk.” Well, in my case I had 60GB free on the disk, so this can’t be right… The database to be created was only 1GB in size.

Well, turns out the Quota on the disk was preventing the file from being created. To change the Quota (or in my case, turn it off for the duration of the install) go to Computer -> Right click on the drive you’re installing on -> Select “Properties” -> Click on the “Quota” tab. Once here you can either uncheck “Enable Quota Management” to completely disable it, or just select the radio button that reads “Do not limit disk usage”.

This should hopefully solve the problem :-)

]]> http://drewdahl.com/2010/05/02/forefront-client-security-mom-installation-failure/feed/ 0 Setup sendmail to use Gmail’s SMTP server http://drewdahl.com/2010/02/18/setup-sendmail-to-use-gmails-smtp-server/ http://drewdahl.com/2010/02/18/setup-sendmail-to-use-gmails-smtp-server/#comments Thu, 18 Feb 2010 09:14:12 +0000 Drew Dahl http://drewdahl.com/?p=341 Well, I did this on Fedora 12, so I’ll be basing everything off of Fedora packages and yum; however, this should work on any distro.

Things you’ll need: sendmail, sendmail-cf, cyrus-sasl

Might need something more, but if so, I’ve overlooked it…

The first thing we’re going to do is setup our authinfo. Do the following:

mkdir /etc/mail/auth/
cd /etc/mail/auth/
vim client-info

In the client-info file you’ve open in your text editor, insert the following line:

AuthInfo:smtp.gmail.com “U:root” “I:username@gmail.com” “P:password” “M:PLAIN”
AuthInfo:smtp.gmail.com:587 “U:root” “I:username@gmail.com” “P:password” “M:PLAIN”

Now, save it, quit your editor, and run the following in the same directory.

makemap -r hash client-info.db < client-info
chmod 600 *
cd ../
chmod 700 auth

Now, let’s move on to making our certs. Do the following:

mkdir /etc/mail/certs/
cd /etc/mail/certs/
openssl req -new -x509 -keyout cakey.pem -out cacert.pem -days 3650
openssl req -nodes -new -x509 -keyout sendmail.pem -out sendmail.pem -days 3650
cp  /etc/pki/tls/certs/ca-bundle.crt /etc/mail/certs

And finally, let's edit our sendmail.mc. Do the following:

cd /etc/mail/
vim sendmail.mc

And, add the following to sendmail.mc:

FEATURE(`authinfo’,`hash /etc/mail/auth/client-info.db’)dnl
define(`SMART_HOST’,`smtp.gmail.com’)dnl
define(`RELAY_MAILER_ARGS’, `TCP $h 587′)
define(`ESMTP_MAILER_ARGS’, `TCP $h 587′)
define(`CERT_DIR’, `/etc/mail/certs’)
define(`confCACERT_PATH’, `CERT_DIR’)
define(`confCACERT’, `CERT_DIR/ca-bundle.crt’)
define(`confCRL’, `CERT_DIR/ca-bundle.crt’)
define(`confSERVER_CERT’, `CERT_DIR/sendmail.pem’)
define(`confSERVER_KEY’, `CERT_DIR/sendmail.pem’)
define(`confCLIENT_CERT’, `CERT_DIR/sendmail.pem’)
define(`confCLIENT_KEY’, `CERT_DIR/sendmail.pem’)
define(`confAUTH_MECHANISMS’, `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN’)
TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN’)

Now run:

m4 sendmail.mc > sendmail.cf
/etc/init.d/sendmail restart

I think it's all self explanatory for the most part. Happy mailing :-)

-=EDIT=-06/02/2010

In the above configuration files, a user reported having issues while copying the above information into their config files. The issue was regarding the quotes around various options. So, if you experience any trouble, please try replacing the quotes. (e.g. delete the ones that are there and add them back within your text editor)

]]> http://drewdahl.com/2010/02/18/setup-sendmail-to-use-gmails-smtp-server/feed/ 10 Quick Overview of SELinux and Apache http://drewdahl.com/2010/01/17/quick-overview-of-selinux-and-apache/ http://drewdahl.com/2010/01/17/quick-overview-of-selinux-and-apache/#comments Sun, 17 Jan 2010 20:07:07 +0000 Drew Dahl http://drewdahl.com/?p=329 I found this link on-line and found it to be quite useful.

http://www.beginlinux.com/server_training/web-server/976-apache-and-selinux

I refer to it often as I forget some of the commands once in a while when I add new files for Apache to serve.

]]> http://drewdahl.com/2010/01/17/quick-overview-of-selinux-and-apache/feed/ 0 Make it snow http://drewdahl.com/2010/01/17/make-it-snow/ http://drewdahl.com/2010/01/17/make-it-snow/#comments Mon, 18 Jan 2010 01:53:10 +0000 Drew Dahl http://drewdahl.com/?p=319 A friend of mine set this up on his page for Christmas. I thought it was kind of cool, so I thought I’d post it here.

You can download the code from my site directly here. (Right click or option-click the link and choose “Save As…” to download this file.)

]]> http://drewdahl.com/2010/01/17/make-it-snow/feed/ 0 DBDesigner 4 on Fedora 12 http://drewdahl.com/2010/01/17/dbdesigner-4-on-fedora-12/ http://drewdahl.com/2010/01/17/dbdesigner-4-on-fedora-12/#comments Sun, 17 Jan 2010 19:46:07 +0000 Drew Dahl http://drewdahl.com/?p=317 I found this very useful article on running DBDesigner 4 on Fedora 8, here. I followed the directions and found it to work on Fedora 11 and Fedora 12. I’m sure it’ll work for just about any distro, so I’m just reposting the directions here as I find it to be a very useful program.

Do not use the original DBDesigner4 download available on the fabForce.net website. Instead download the dbdesigner-fork package from here:

http://sourceforge.net/projects/dbdesigner-fork/

Once you have unpacked it. Edit the bin/startdbd_using_kernel2.6 script and remove the assume kernel 2.4.1 text:

Original file contents: LD_ASSUME_KERNEL=2.4.1 LANG=en_US.ISO8859-1 LD_LIBRARY_PATH=./Linuxlib/ ./DBDesignerFork

Edited contents: LANG=en_US.ISO8859-1 LD_LIBRARY_PATH=./Linuxlib/ ./DBDesignerFork

Save it and run it. It should all work as expected on Linux Fedora 8 or indeed any other modern distribution like Ubuntu, etc.

]]> http://drewdahl.com/2010/01/17/dbdesigner-4-on-fedora-12/feed/ 0 Visual Studio 6 – Scroll Wheel http://drewdahl.com/2010/01/07/visual-studio-6-scroll-wheel/ http://drewdahl.com/2010/01/07/visual-studio-6-scroll-wheel/#comments Thu, 07 Jan 2010 07:18:45 +0000 Drew Dahl http://drewdahl.com/?p=310 The last time I used Visual Studio 6… Not having a scroll wheel drove my bonkers. Well, this time around, I was lucky enough to find this:

http://joebott.com/vb6scrollwheel.htm

Just run it in the background, and it’ll take care of everything. Much love to this one <3 It’s saved me much pain.

(Also, before you go off on me as to why the hell I’m using VS6… Well, I have to for work. We have software that has to be maintained that was originally made in VS6 and I can’t get the projects to migrate to any of the *newer* Visual Studios… not that they are any better >.> )

]]> http://drewdahl.com/2010/01/07/visual-studio-6-scroll-wheel/feed/ 0