usefulgeek » tips

Lock and Unlock Linux accounts

jonmoore — Thu, 22 Apr 2010 13:37:06 +0000

Using passwd it is possible to quickly lock and unlock Linux accounts. To lock an account. passwd -l username To unlock an account. passwd -u username Related posts:Quick install of Tomcat5 on CentOS At the office, we’re in the process of doing some... Related posts brought to you by Yet Another Related Posts Plugin. Related posts:

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Using telnet to test POP server

jonmoore — Wed, 21 Apr 2010 14:52:28 +0000

Using telnet (or putty) it’s possible to some simple tests against a POP server. By no means exhaustive, it can give you insights in where to start troubleshooting.

First, using telnet and open a connection the remote POP server

telnet mailserver 110

Where mailserver is the mail server you want to connect to. Note that port 110 is the default port for POP, but could be different depending on your servers settings.

Once connected, use USER and PASS to login.

[root@ms1 ~] # telnet localhost 110
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
+OK POP3 localhost v2001.78rh server ready
USER username
+OK User name accepted, password please
PASS password
+OK Mailbox open, 1 messages
QUIT
+OK Sayonara
Connection closed by foreign host.

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Linux IPv6 Neighbor Discovery

jonmoore — Tue, 20 Apr 2010 21:37:54 +0000

Using ping6 and ip neigh it’s possible to discover other IPv6 hosts on your local network using the link-local addresses.
First, use ping6 to ping all hosts on the local network using the IPv6 link-local address

ping6 -c 2 -I eth0 ff02::1

Then, use ip neigh to show a list of IPv6 enable hosts on the local network

ip -f inet6 neigh

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Rewrite incoming CallerID

jonmoore — Fri, 26 Feb 2010 21:38:27 +0000

We’re using asterisk, and as part of the dial plan, a 9 is required before the number to make calls out to the PSTN. Since our phones have a incoming call log, it would be very convient to have asterisk rewrite the CallerID value on calls from the PSTN to include this leading digit. I found this was rather easy to accomplish. Adding something similar to the following to whatever extension handles your incoming calls, all CallerID numbers will have a 9 added to the front.
exten => s,1,Set(CALLERID(num)=9${CALLERID(num)})
And proceed with your normal call routing logic. Change the preceding digit to whatever matches your system. If you have several extensions this is going to be used with, you could benefit from using a global variable for the leading digit.

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Asterisk GotoIf Application

jonmoore — Fri, 22 Jan 2010 15:12:20 +0000

The description from asterisk for this is GotoIf(condition?[labeliftrue]:[labeliffalse]), however for me (being somewhat new to asterisk, and not fully understanding all the little bits, this was a bit confusing. A better way of describing this, at least for those of use new to asterisk, might be GotoIf(condition?[context,priority,labeliftrue]:[context,priority,labeliffalse]).
I have not used labels in the dial plan before, and when starting out with this application I read label to be a context. This lead me to write my dial plan similar to this..

[default]
exten => 100,1,GoToIf(condition?true,false)
[true]
exten => s,1,...
[false]
exten => s,1,...

In retrospect, it’s obvious what the documentation is saying, but as I said, not being familiar with labels, I was a bit lost.

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Quick install of Tomcat5 on CentOS

jonmoore — Wed, 18 Nov 2009 19:19:27 +0000

At the office, we’re in the process of doing some work where we need a tomcat server. Without having to get into things to much, I found this simple method for getting tomcat5 up and running pretty quickly. I’m sure I’ve left out some important things, and I’m doubtful as to how production ready this is, but for our testing, it’s working out fine.

I’m using CentOS 5.3 for all of this, but I’m sure it will work with CentOS 5.4

yum install tomcat5 tomcat5-admin-webapps tomcat5-webapps

After this, you need to edit the tomcat-users.xml file to create a new user.Using the above, this file ends up in /etc/tomcat5/tomcat5-users.xml and all that needs to be added is a line similar to the following..

user username="admin" password="p@ssw0rd" roles="admin,manager"

I can’t get wordpress to work with me on this, so you’ll need to wrap the above in angle brackets, the same as all the other lines in that file.
You can set username and password to whatever you’d like. After this, restart tomcat (not sure if this is needed) with service tomcat5 restart and off you go.

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Launch Google Chrome and external links with incognito mode.

drale — Mon, 02 Nov 2009 03:19:50 +0000

The instructions floating around are to place the --incognito switch (single – works fine for me) in your desktop shortcut. But sometimes you may be in an application like Tweek Deck, etc that links to webpages. These pages don’t launch in incognito if you only fix your desktop shortcut. Here is how to do both. Google Chrome is set as the default browser in this case.

(These instructions are based off of Windows XP)

Right-click on your Chrome shortcut. Choose Properties. Add -incognito to the end:

chrome.exe" --incognito

To launch all web shortcuts and links from your system:
Control Panel > Folder Options > File Types
Select the File Type URL:HyperText Transfer Protocol and choose Advanced
Select action open and edit.
Just like before add the switch to the end like this:

chrome.exe" --incognito -- "%1"

Edit: After more digging in Google I found this tip mentioned in Google Code Chromium issues (Comment 3).

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Remove bonded interface in OpenFiler

jonmoore — Mon, 26 Oct 2009 13:45:42 +0000

I decided to try and use NIC bonding in OpenFiler and while things seemed to go well at first, I did run into some issues over time. I’m still in the process of testing, and I think most of the issues are “user error” and not so much problems with NIC bonding or OpenFiler itself. More on that later.

I was able to configure a bonded interface, and add both interfaces to it. However, after the issues started, I wanted to remove the bond. There is no way of doing this from within the Web UI it seems. Easiest solution, login to the console, and delete /etc/sysconfig/network-scripts/ifcfg-bond0 if you’re using the first bond interface.

After this file is deleted, service network restart should get you going again.

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Find Text and Find/Replace Easier Than You Think in Linux

drale — Sat, 24 Oct 2009 09:37:49 +0000

How to search all files for a text string:

grep -lr string ./ > results.txt

-l will print only the path and file names of the matches.

Search all files of a certain name for a certain string:

grep -lr string ./ | grep filename

Yes, do specify ./ if you are doing all directories within current.

(source and more info)

Find an replace a string in files:
Searching for a way to do this usually leads me to finding fancy scripts that don’t work right, are scary (create temp files, etc) or aren’t recursive. Just have backups at hand and test the following combination of find and sed before unleashing it, because it works great! You can test it by replacing sed with grep

find ./ -type f -exec sed -i ’s/string1/string2/’ {} \;

Within specific file names/extentions…

find ./ -iname \*.htm\* -exec sed -i 's/\-2005/\-2007/g' {} \;

Don’t forget to use escape \ as seen above. And if your strings contain forward slash / just use a different delimiter such as pipe | or escape it.

You can also install rpl, as shown in the source pdf, for even cleaner line of code for executing your find and replace.

(source and more info) A nice pdf to keep by your side.

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Installing Dropbox on Ubuntu (and others)

jonmoore — Wed, 21 Oct 2009 13:12:27 +0000

I’ve been using dropbox to sync and share files between my various computers for quite some time, and overall have been very pleased. However, one area things are not so great… documentation for installation on Linux. After having to reinstall on my notebook, I decided to somewhat document the hidden part of the process.

After downloading the .deb (or other package) and installing, dropbox instructions leave you hanging. There is no dropbox folder, there is no daemon running, nothing. The next step is simply to run dropbox start -i to install the daemon and launch the process to move forward. It’s simple, easy and poorly documented. Maybe dropbox should add this to the end of their install instructions?

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