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This article describes the advanced OpenSSH features, which can greatly simplify the lives of system administrators and programmers who would like to use Secure SHell. Unlike most manuals, which explain only keys and L/D/R options, I tried to gather all the interesting features, which SSH has to offer.

Warning: The article is very long, but I have decided not to cut it into the pieces.

Table of contents:

  • Key management
  • Copying files over SSH
  • Stream forwarding of I/O
  • Mounting a remote FS using SSH
  • Remote code execution
  • Aliases and options for connections to .ssh / config
  • Default options
  • X-server forwarding
  • SSH as a socks-proxy
  • Port forwarding - direct and reverse
  • Reverse socks-proxy
  • Tunneling L2/L3 traffic
  • Authorization agent forwarding
  • SSH through SSH tunnel
  • Untrusted server
Siera 29 august 2012, 13:09

How often do you have to see the Blue Screen of Death Windows (BSoD)? BSoD can occur in the different situations, for example, in the process of loading the operating system or during working with the OS. How do you determine what caused the occurrence of BSoD and fix this problem? The OS of Windows is capable to store a memory dump when an error occurs, and the system administrator can analyze the data dump and find the cause of BSoD.

There are two types of memory dumps, such as a minidump and a full dump. Depending on your operating system, it can store the full or small dumps, or take no actions when an error occurs.

The minidump is located in %systemroot%\minidump, and it has a name like Minixxxxxx-xx.dmp.
The full dump is located in %systemroot%, and it has a name like Memory.dmp.
Siera 24 april 2012, 15:07

IP-address (v4) is consisted of 32 bits. Any self-respecting administrator or IT specialist should answer correctly the question: "How many bits are in an IP-address?" Of course, It is desirable to know about IPv6: 128 bits.
Here is a first case. Theoretically IPv4-addresses can be:
232 =210*210*210*22 = 1024*1024*1024*4 ≈ 1000*1000*1000*4 = 4 billion
Below we could see that a lot of them are "eaten up" by any garbage.

I think everyone knows how IPv4-address is written. The four octets (it is the same as byte) in decimal with no leading zeros, separated by dots: “192.168.11.10”.
ZimerMan 19 march 2012, 13:20

Today we are happy to present you Ajenti 0.6.0 is in our studio.

image

We remind you that Ajenti is a web-based admin panel for servers.

First, we would like to thank all 560 users, who are with us despite the fact that the project was in beta-stage, as well as all our wonderful developers;)
Breaking news – we provide almost full support for the following systems:

imageFreeBSD 8.0 +


imageGentoo


imageCentOS 6
KlauS 2 december 2011, 16:45

The study of data recovery method from accidentally deleted database of MySQL.

Testing environment

Here are CentOS 5.6 x86_64 and mysql 5.0.77
There was created testing database with a couple of tables as MyISAM and InnoDB, as well as a couple of stored procedures to test their recovery:


DROP DATABASE prod;
CREATE DATABASE prod;
USE prod;
CREATE TABLE table1 (
id INTEGER,
v VARCHAR (50)
PRIMARY KEY (id)
) ENGINE = MyISAM;
Tags: backups, Mysql
Killer 7 october 2011, 16:43

imageWhen I opened a mail for the domain on Yandex, I decided to open a free registration for unauthorized users to the mailboxes on mine “fancy” domain. In addition, I enabled catch-all feature, which directs all incoming mail of nonexistent mailboxes of my domain to my main mailbox. I faced necessity to reserve all the “standard” names of mailboxes for myself in order to avoid confusion, when some name already has been reserved by another user, and all “service” mail goes to someone else. Of course, you can any time expropriate any mailbox that is under control of domain. I'm puzzled: what are the names of mailboxes standard and system-defined? Yandex technical support said that they reserve for themselves only the name of postmaster @ for each domain to keep track of complaints and problems with the mail. Further, the search of results on the Internet was a bit predictable.
(On the picture is: the famous black mailbox, a place of pilgrimage for UFO enthusiasts)

RFC

First, I wanted to find RFC, which is RFC 2142, MAILBOX NAMES FOR COMMON SERVICES, ROLES AND FUNCTIONS (mailbox names for the public services, roles and functions), which was last amended in 1997. Here is just interesting information for us. Based on the document, the following mailboxes should exist and have the following functions:
ZimerMan 6 october 2011, 19:56

A few days ago, one of the hard drives went down on the budget’s array of 16x1Tb drives. The array level: RAID 6. The situation got complicated by the fact that (as it turned out) previously had stood a cooler on the video card of the same server that was not previously noticed, and after HDD was replaced due to changes in cooling mode of the casing, and this became appear in the form of hanging during synchronization, which itself is very unpleasant. It turned out that an array stopped auto-building, and a few drives were marked as faulty, so I had to deal with it seriously, checking out with the wiki, manuals and forums (forums are the most useful, as they describe the experience of specific people in specific situations).

The structure of array:

16x1Tb HDD

Sections:
md0 - / root 8x1 Gb, RAID 6
md1 - / data: 16x999 Gb, RAID 6
Tags: linux, raid
MeLavi 5 october 2011, 18:10