Xenserver does not reclaim space after deleting VDI or Snapshot

In most cases removing old snapshots and then initiating a scan of the SR has resolved this for me.

vhd-util scan -f -m “VHD-*” -l “VG_XenStorage-<uuid_of_SR>” –p





NetSPI – SQL Injection Wiki


This wiki’s mission is to be a one stop resource for fully identifying, exploiting, and escalating SQL injection vulnerabilities across various Database Management Systems (DBMS).

Below is an outline of the wiki’s structure, laid out in the order of a normal escalation path. Certain queries may be version specific.

Step 1: Injection Detection
Step 2: DBMS Identification
Step 3: Injection Types
Step 4: Injection Techniques
Step 5: Attack Queries


PDFsam – OpenSource PDF Utility

PDFsam https://pdfsam.org/ is a free and open source desktop application to split, merge, extract pages, rotate and mix PDF files.

There are 3 products, PDFsam Basic, PDFsam Enhanced and PDFsam Visual:

PDFsam Basic

  • Merge
    Merge PDF files, select the pages, merge bookmarks and interactive forms
  • Split
    Split a PDF file at given page numbers, at given bookmarks level or in files of a given size
  • Extract from PDF
    Extract pages from PDF files
  • Rotate
    Rotate PDF files, every page or just the selected pages
  • Mix
    Merge PDF files together taking pages alternatively from one and the other. The perfect tool if you have a single-sided scanner

PDFsam Enhanced

  • Edit
    Modify the PDF content without the need to export it or copy to another format
  • Insert
    Insert pages or hyperlinks and update page numbers once you are done
  • Convert
    Convert PDF files to a number of popular formats like doc, docx, xls, xlsx and many others
  • Review
    Collaborate with your peers by adding notes, highlighting text and drawing on your document with the pencil
  • Forms
    Create fillable forms from scratch or pre designed, import and export data, add actions to print the document, send it by email and other
  • Security
    Protect PDF files with 256 bits AES encryption, set permissions on them and add a digital signature
  • OCR
    An Optical Character Recognition module to extract text from images

PDFsam Visual

  • Combine and Reorder
    Visually reorder pages, move them, rotate them or combine PDF files dragging and dropping pages from multiple documents
  • Split by text
    Split PDF files at pages where text in a selected area changes
  • Crop
    Crop PDF files by drawing the rectangular area you want to keep
  • Split
    Split PDF files visually selecting pages to split at, or split at given bookmarks level or in files of a given size
  • Protect and Unprotect
    Add permissions and encrypt PDF files using AES 256bits or 128bits. Decrypt PDF files supplying a password and create an unprotected version
  • Extract
    Visually select the pages you want to extract from a PDF file
  • More
    Mix PDF files, Rotate PDF files, Merge PDF files…


Amazon Time Sync Service

The Amazon Time Sync Service provides a highly accurate and reliable time reference that is natively accessible from Amazon EC2 instances.

Built on Amazon’s proven network infrastructure, the service utilises a fleet of redundant satellite-connected and atomic reference clocks in AWS regions to deliver current time readings of the Coordinated Universal Time (UTC) global standard. The service is designed to be highly available with a continuously monitored time infrastructure and provides a low variance reference time source. Leap seconds are known to cause application errors, and can be a concern for developers and system administrators. The Amazon Time Sync Service automatically smooths out (smears) leap seconds that are periodically added to UTC, so that customers do not have to worry about application errors due to their addition.

Setting the Time for Your Linux Instance


The Amazon Time Sync Service is available through NTP at the IP address for any instance running in a VPC. Your instance does not require access to the internet, and you do not have to configure your security group rules or your network ACL rules to allow access. Use the following procedures to configure the Amazon Time Sync Service on your instance using the chrony client.

To configure your Ubuntu or Debian derivative instance to use the Amazon Time Sync Service

Connect to your instance and use apt to install the chrony package.

ubuntu:~$ sudo apt install chrony 
If necessary, update your instance first by running sudo apt update.

Open the /etc/chrony/chrony.conf file using a text editor (such as vim or nano). Add the following line after any other server or pool statements that are already present in the file, and save your changes:

 server prefer iburst 

Restart the chrony service.

 ubuntu:~$ sudo /etc/init.d/chrony restart
[ ok ] Restarting chrony (via systemctl): chrony.service.

Verify that chrony is using the IP address to synchronize the time.

 ubuntu:~$ chronyc sources -v
210 Number of sources = 7

.-- Source mode '^' = server, '=' = peer, '#' = local clock.
/ .- Source state '*' = current synced, '+' = combined , '-' = not combined,
| / '?' = unreachable, 'x' = time may be in error, '~' = time too variable.
|| .- xxxx [ yyyy ] +/- zzzz
|| Reachability register (octal) -. | xxxx = adjusted offset,
|| Log2(Polling interval) --. | | yyyy = measured offset,
|| \ | | zzzz = estimated error.
|| | | \
MS Name/IP address Stratum Poll Reach LastRx Last sample
^* 3 6 17 12 +15us[ +57us] +/- 320us
^- tbag.heanet.ie 1 6 17 13 -3488us[-3446us] +/- 1779us
^- ec2-12-34-231-12.eu-west- 2 6 17 13 +893us[ +935us] +/- 7710us
^? 2a05:d018:c43:e312:ce77:6 0 6 0 10y +0ns[ +0ns] +/- 0ns
^? 2a05:d018:d34:9000:d8c6:5 0 6 0 10y +0ns[ +0ns] +/- 0ns
^? tshirt.heanet.ie 0 6 0 10y +0ns[ +0ns] +/- 0ns
^? bray.walcz.net 0 6 0 10y +0ns[ +0ns] +/- 0ns 

In the output that’s returned, ^* indicates the preferred time source. Verify the time synchronization metrics that are reported by chrony.

 ubuntu:~$ chronyc tracking
Reference ID : (
Stratum : 4
Ref time (UTC) : Wed Nov 29 07:41:57 2017
System time : 0.000000011 seconds slow of NTP time
Last offset : +0.000041659 seconds
RMS offset : 0.000041659 seconds
Frequency : 10.141 ppm slow
Residual freq : +7.557 ppm
Skew : 2.329 ppm
Root delay : 0.000544 seconds
Root dispersion : 0.000631 seconds
Update interval : 2.0 seconds
Leap status : Normal 

Setting the Time for a Windows Instance