Category: Administration

Everything related to system administration.

How to find network device using it’s manufacturer name?

I’ve previously posted a note about finding Raspberry Pi without knowing it’s ip address. Well, basically it’s the same… Only you need to change MAC prefix to find other manufacturer. To wrap this is up, this is a command to find device by MAC prefix:

sudo nmap -sP 192.168.100.0/24 | awk '/^Nmap/{ip=$NF}/00:D0:23/{print ip}'

And here you can find actual MAC information (use CTRL+F).

Of course you need Nmap to do that! And sudo is necessary!

Beware that sometimes there might be many prefixes for one manufacturer. Also check company name precisely, for example HP is Hewlett Packard but it also can be ProCurve Networking by HP.

PHP reading problem with files larger than 2 GB

If you’ll ever have problem with opening (fopen) and reading (fread) files larger than 2 GB in your PHP script. Check your version of scripting engine. In my case switching to 64 bit solved the problem. Please mind that this error is very hard to debug because PHP does not log anything (same as MS IIS) in such case. It simply resets client connection…

Cryptic error 0x1 in Windows™ Task Scheduler

In case you ever wondered why your task returns 0x1 in Last Run Result instead of 0x0. Check if your task is trying to create any files, if it does, you must tick “Run with highest privileges” in General tab of your task properties. I’ve spent some precious time to uncover that because I’m not a native Winblows administrator 🙂

How to list all PostgreSQL databases and their sizes in MB

You must provide proper database name and user:


File: gistfile1.txt
-------------------

psql -c "SELECT pg_database.datname, pg_database_size(pg_database.datname), pg_size_pretty(pg_database_size(pg_database.datname)) FROM pg_database ORDER BY pg_database_size DESC;" -d

How to find Raspberry Pi using MAC address

When you want to find your headless but networked Raspberry Pi and you’re lazy like me use nmap:

sudo nmap -sP 192.168.1.0/24 | awk '/^Nmap/{ip=$NF}/B8:27:EB/{print ip}'

Mask /24 means that addresses from 192.168.1.0 to 192.168.1.254 will be searched. You can extend that to /16 if you don’t know subnet of your device.