Archive for SerJo

Tcpdump usage examples

Tcpdump usage examples

In most cases you will need root permission to be able to capture packets on an interface. Using tcpdump (with root) to capture the packets and saving them to a file to analyze with Wireshark (using a regular account) is recommended over using Wireshark with a root account to capture packets on an «untrusted» interface. See the Wireshark security advisories for reasons why.

See the list of interfaces on which tcpdump can listen:

tcpdump -D

Listen on interface eth0:

tcpdump -i eth0
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Hardening Nginx SSL/TSL Configuration

Days ago I had to investigate a SSL issue in one of my customer’s servers, he installed a SSL certificate but the Nginx SSL configuration was not hardened at all, so he was getting a very poor grade while checking his site at SSL Server Test.

In the same case, if you have a grade lower than A, you should try to optimize your Nginx SSL configuration. Here are some tips to harden your Nginx SSL Configuration.
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CentOS 6 — Configure NFS Client

Configure NFS Client to mount directories provided from NFS Server.
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Use from command line

Wouldn’t it be nice to be able to test your upload/download speed from your VPS and share the “famous” picture from ? uses Flash to test upload/download speed which is a hassle on most VPS.
The long way to get this is to install VNC and run it from a browser, but that is no longer necessary.
We can now use Matt Martz python script speedtest-cli to accomplish this from the commandline.

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Как создать template из ruby_block в chef-opscode

Иногда нужно создать template во время исполнения ruby_block.
Вот как это можно сделать.
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How to run a template that creates a init.d script before the service is created in Chef

How to run a template that creates a init.d script before the service is created in Chef
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Install «android-tools» package (adb and fastboot) in Ubuntu 12.04, 11.10 or 11.04

A package called «android-tools», which comes with «adb» and «fastboot» command line utilities, has been uploaded to the Ubuntu 12.10 Quantal Quetzal repositories recently. I’ve got a request to upload this package in a PPA for older Ubuntu releases, so I’ve backported it to Ubuntu 12.04, 11.10 and 11.04.

«adb» (Android Debug Bridge) is a command line tool you can use to access the file system from an Android device; it can be used to send commands, transfer or receive files, install or uninstall applications and more.

«fastboot» is a command line tools that you can use to flash the filesystem on Android devices over USB.

These tools can be found in the Android SDK too; using the official package in Ubuntu 12.10 or the packages in our PPA is just an alternative and easier way I’d say, to install them in Ubuntu. Also, the packages in the PPA are available for both 32bit and 64bit, while the Android SDK provided by Google is only available for 32bit.
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Windows 7 не подключается к Windows 2000

Windows 7 client cannot access remote file share

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Contro l\Lsa\
Add new DWORD record LmCompatibilityLevel and value 2
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Востановление mdraid на переустановленной системе

apt-get install mdadm
mdadm --detail --scan --verbose | awk '/ARRAY/ {print}' >> /etc/mdadm/mdadm.conf

И поправить fstab

/dev/md1p1      /media/2TB      xfs     defaults        0 0

Linux: emergency reboot or shutdown with magic commands

Most linux distributions use some type of mechanism to gracefully stop daemons and unmount storage volumes during a reboot or shutdown. It’s most commonly done via scripts that will wait for each daemon to shut down gracefully before proceeding to the next daemon.

As we know, sometimes servers misbehave due to things put them through, and you can quickly end up in a situation where things are going badly. I’m talking about the type of situation where you’re connected via SSH to a server that controls phone lines for five million people and it sits in a tiny building 400 miles away from the nearest human being. We’re talking bad. If you issue a plain reboot command, it might not even make it that far. Once SSH stops running, you’re going to be out of luck.
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