Inventory Your Machines with a One-liner

The command dmidecode dumps the DMI table from your machines BIOS in human readable text. Depending on your machine, this should contain some really useful info. Basically a total hardware profile on most machines, including info like service tags and model numbers. I recently needed to quickly inventory a bunch of Dell servers and came up with this one-liner that will production a CSV line of text for the machine it's run on. Combine these lines of text into one file and import into Excel, inventory done.

Format is:
'Hostname','Distro-Release Version','UUID','Service Tag','Model','Processor Version','Memory'

echo `hostname` , `cat /etc/*-release` , `dmidecode |egrep UUID |sed "s/\s\+UUID: //"` , `dmidecode -s system-serial-number` , `dmidecode -s system-product-name` , `dmidecode -s processor-version` , `dmesg |egrep Mem |awk '{ print $2; }'`

Now of course you'll need to modify this command for your own hardware, this won't even work for every Dell. But, the output of dmidecode is readable enough to just scan through it and figure out what you need. Also look in /proc/ for other info you might want to add to your inventory.

Add Up a Column of Data with Awk

When you pipe a line of text to awk, every "word" (string of non-white space) shows up in $n, where n is equal to the order for which it appears in the line of text. For example;

>echo this is a test | awk '{print $2};'
prints
is

If you have a column of numbers, say from the output of a command or a log file, you can do math with these numbers like this

ps aux | awk '{ t =+ $6}; END { print t};'

This will give you the total for the sixth column of the output from the command ps aux. In another example, lets say I wanted to see the total number of clients with active and inactive connections on my LVS server. The command to see this info is


[root@lvs~]#ipvsadm -L
IP Virtual Server version 1.2.1 (size=4096)
Prot LocalAddress:Port Scheduler Flags
-> RemoteAddress:Port Forward Weight ActiveConn InActConn
TCP www:https sed
-> webapp06:https Route 110 54 86
-> webapp01:https Route 70 36 46
-> webapp04:https Route 300 148 207
-> webapp03:https Route 300 146 307
-> webapp02:https Route 120 58 77
-> webapp05:https Route 300 142 183

That's nice, but you'll notice I don't get totals. The command doesn't have any syntax to give me totals either. So we'll let awk take care of it. First we need to grep just the lines that we want to add up. In this case they all have the text 'webapp0' in them, and that string of text doesn't appear on any lines we don't want to add up.

[root@lvs~]#ipvsadm -L |grep webapp0
-> webapp06:https Route 110 72 80
-> webapp01:https Route 70 45 53
-> webapp04:https Route 300 198 267
-> webapp03:https Route 300 196 268
-> webapp02:https Route 120 79 105
-> webapp05:https Route 300 199 240

Now the two columns we'd like to add up are the 5th and the 6th.

[root@lvs~]#ipvsadm -L |grep webapp0|awk '{s += $5; i += $6} END { print s,i; };'
846 1066

Now lets say instead of wanting a total, we wanted an average? 'NR' is equal to the number of rows we sent awk.

[root@lvs~]#ipvsadm -L |grep webapp0|awk '{s += $5; i += $6} END { print s/NR,i/NR; };'
68.5833 88.4167

MaxClients in Apache with Preforking MPM

The advice for figuring out what your MaxClients setting should be in Apache with the Preforking MPM is pretty straight forward. First figure out the average amount of RAM each Apache process uses. Then divide the amount of RAM your system has, minus a little for other processes, by the average amount of RAM the average Apache process uses. In CentOS the following command should give you that number.

ps -ylC httpd |awk "{ s += \$8 } END { m = `cat /proc/meminfo|grep MemTotal|awk '{print $2}'`; printf \"MaxClients: %i\\n\", (m-(m*.15))/(s/NR) }"