damonparker.org » Technical

Debugging Wifi Connectivity and Routing

damonp — Fri, 11 Jun 2010 21:33:32 +0000

Sometimes wifi connectivity issues can be massaged a little by getting a little pushy with it… turn your internal airport card off. Leave it off for a minute then turn it back on and see if by forcing it to attempt to re-connect to your local network. Oftentimes this will clear up minor issues.

Check your routing tables:

netstat -nr

Get just the default route:

netstat -nr | grep default

In action:

[root@howie ~]$ netstat -nr | grep default
5:default 192.168.1.1 UGSc 11 5 en1

Enable Sendmail for PHP mail() in OSX

damonp — Thu, 25 Feb 2010 22:05:41 +0000

Since this didn’t dawn on me for thirty minutes while I pursued other avenues…

In /etc/hostconfig add/edit a line like:

MAILSERVER=-YES-

Note to self: Look for more OSX server administration clients.

Apache Log Grepping

damonp — Mon, 14 Sep 2009 18:34:51 +0000

Nothing beats a full stats package, but with a little grepping and a logfile and we can figure out some quick statistics.

Get only hits coming from Google.com/search:

grep 'google.com/search' access_log | head -1

Extract only the referrer field:

grep 'google.com/search' access_log | head -1 | awk '{print $11}'

Get the search terms only:

grep 'google.com/search' access_log | \
head -1 | \
awk '{print $11}' | \
cut -d\? -f2 | cut -d\& -f1 | \
sed 's/+/ /g;s/%22/"/g;s/q=//'

Here’s a little script that puts it all together. It finds the unique search terms, cleans out the trash, sorts them and list the top twenty five in order of descending hit count.

#!/bin/sh
LOG="/var/logs/httpd/access_log"
grep 'google.com/search' $LOG | \
awk '{print $11}' | \
cut -d\? -f2 | cut -d\& -f1 | \
sed 's/+/ /g;s/%22/"/g;s/q=//' | \
sed 's/%[0-9a-fA-F][0-9a-fA-F]/ /g;s/"//g' | \
grep -v '=' | sort | uniq -c | sort -rn | head -25

To see them all remove the | head -25 statement at the end of the command.

Thanks to an article at Linux Journal for the examples.

Find setuid root Files

damonp — Fri, 11 Sep 2009 04:29:20 +0000

Find all setuid / setgid files owned by root:

find / -user root -type f $ -perm -4000 -o -perm -2000 $ -exec ls -ld '{}' \;

Find all setuid / setgid files owned by any user:

find / -type f $ -perm -4000 -o -perm -2000 $ -exec ls -ld '{}' \;

Debugging HTTP Headers with cURL

damonp — Mon, 31 Aug 2009 16:05:39 +0000

curl -I http://damonparker.org

More info on cURL

DNS, Lookupd and OS X

damonp — Thu, 15 Nov 2007 19:27:30 +0000

Pre-Leopard the command to force OS X to flush and reload it’s DNS cache was:

sudo lookupd -flushcache

In Leopard, lookupd no longer exists. Instead force a DNS cache refresh with:

sudo dscacheutil -flushcache

OSX Scrollbars Top and Bottom

damonp — Mon, 05 Nov 2007 22:00:16 +0000

In Terminal:

defaults write "Apple Global Domain" AppleScrollBarVariant DoubleBoth

MailAnnounce Applescript Source

damonp — Tue, 09 Oct 2007 13:49:41 +0000

I have received several requests for the source of my MailAnnounce script that is able to speak the subject of mails using Mail.app and Applescript.

Source for version 1 of the script is now available.

rpmdb: unable to join the environment

damonp — Mon, 10 Sep 2007 17:03:15 +0000

This weekend I was contacted by a client regarding a server that had run out of room on the main hard drive. Among the things that were corrupted by the drive filling up was the RPM database.

When trying to query of upgrade any package, the error message

rpmdb: unable to join the environment
error: db4 error(11) from dbenv->open: Resource temporarily unavailable
error: cannot open Packages index using db3 - Resource temporarily unavailable (11)
error: cannot open Packages database in /var/lib/rpm
warning: /root/webmin-1.360-1.noarch.rpm: V3 DSA signature: NOKEY, key ID 11f63c51
rpmdb: unable to join the environment
error: db4 error(11) from dbenv->open: Resource temporarily unavailable
error: cannot open Packages database in /var/lib/rpm
rpmdb: unable to join the environment
error: db4 error(11) from dbenv->open: Resource temporarily unavailable
error: cannot open Packages database in /var/lib/rpm

A search turned up this howto on repairing the db.

These two commands made quick work of the fix. First remove any old lock files:

rm -f /var/lib/rpm/__db*

Then rebuild the RPM database:

rpm -vv --rebuilddb

Quickly Copy MySQL Database to Remote Host

damonp — Fri, 31 Aug 2007 16:29:50 +0000

Copy an entire database:

mysqldump LOCAL_DBNAME | ssh USER@REMOTE_HOST mysql -p REMOTE_DBNAME

Copy a single table:

mysqldump LOCAL_DBNAME LOCAL_TABLE | ssh USER@REMOTE_HOST -p REMOTE_DBNAME REMOTE_TABLE

This shortcut only works if you can access the local DB without a password. If you have to login to both local and remote MySQL servers, the MySQL password prompts get mashed together. You could specify the password on the command line like

-pPASSWORD

but your shell may keep the password in its history so that anyone with access to your account could pick through your shell history and retrieve the password. Using the MySQL password prompt doesn’t do this.