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Linux: Howto Fix “N: Repository ‘http://deb.debian.org/debian buster InRelease’ changed its ‘Version’ value from ‘10.9’ to ‘10.10’” error to resolve apt-get release update issue

Friday, August 13th, 2021

Linux's surprises and disorganization is continuously growing day by day and I start to realize it is becoming mostly impossible to support easily this piece of hackware bundled together.
Usually so far during the last 5 – 7 years, I rarely had any general issues with using:

 apt-get update && apt-get upgrade && apt-get dist-upgrade 

to raise a server's working stable Debian Linux version packages e.g. version X.Y to verzion X.Z (for example up the release from Debian Jessie from 8.1 to 8.2). 

Today I just tried to follow this well known and established procedure that, of course nowdays is better to be done with the newer "apt" command instead with the legacy "apt-get"
And the set of 
 

# apt-get update && apt-get upgrade && apt-get dist-upgrade

 

has triggered below shitty error:
 

root@zabbix:~# apt-get update && apt-get upgrade
Get:1 http://security.debian.org buster/updates InRelease [65.4 kB]
Get:2 http://deb.debian.org/debian buster InRelease [122 kB]
Get:3 http://security.debian.org buster/updates/non-free Sources [688 B]
Get:4 http://repo.zabbix.com/zabbix/5.0/debian buster InRelease [7096 B]
Get:5 http://security.debian.org buster/updates/main Sources [198 kB]
Get:6 http://security.debian.org buster/updates/main amd64 Packages [300 kB]
Get:7 http://security.debian.org buster/updates/main Translation-en [157 kB]
Get:8 http://security.debian.org buster/updates/non-free amd64 Packages [556 B]
Get:9 http://deb.debian.org/debian buster/main Sources [7836 kB]
Get:10 http://repo.zabbix.com/zabbix/5.0/debian buster/main Sources [1192 B]
Get:11 http://repo.zabbix.com/zabbix/5.0/debian buster/main amd64 Packages [4785 B]
Get:12 http://deb.debian.org/debian buster/non-free Sources [85.7 kB]
Get:13 http://deb.debian.org/debian buster/contrib Sources [42.5 kB]
Get:14 http://deb.debian.org/debian buster/main amd64 Packages [7907 kB]
Get:15 http://deb.debian.org/debian buster/main Translation-en [5968 kB]
Get:16 http://deb.debian.org/debian buster/main amd64 Contents (deb) [37.3 MB]
Get:17 http://deb.debian.org/debian buster/contrib amd64 Packages [50.1 kB]
Get:18 http://deb.debian.org/debian buster/non-free amd64 Packages [87.7 kB]
Get:19 http://deb.debian.org/debian buster/non-free Translation-en [88.9 kB]
Get:20 http://deb.debian.org/debian buster/non-free amd64 Contents (deb) [861 kB]
Fetched 61.1 MB in 22s (2774 kB/s)
Reading package lists… Done
N: Repository 'http://deb.debian.org/debian buster InRelease' changed its 'Version' value from '10.9' to '10.10'
…


As I used to realize nowdays, as Linux started originally as 'Hackers' operating system, its legacy is just one big hack and everything from simple maintenance up to the higher and more sophisticated things requires a workaround 'hack''.

 

This time the hack to resolve error:
 

N: Repository 'http://deb.debian.org/debian buster InRelease' changed its 'Version' value from '10.9' to '10.10'


is up to running cmd:
 

debian-server:~# apt-get update –allow-releaseinfo-change
Поп:1 http://ftp.de.debian.org/debian buster-backports InRelease
Поп:2 http://ftp.debian.org/debian stable InRelease
Поп:3 http://security.debian.org stable/updates InRelease
Изт:5 https://packages.sury.org/php buster InRelease [6837 B]
Изт:6 https://download.docker.com/linux/debian stretch InRelease [44,8 kB]
Изт:7 https://packages.sury.org/php buster/main amd64 Packages [317 kB]
Игн:4 https://attic.owncloud.org/download/repositories/production/Debian_10  InRelease
Изт:8 https://download.owncloud.org/download/repositories/production/Debian_10  Release [964 B]
Изт:9 https://packages.sury.org/php buster/main i386 Packages [314 kB]
Изт:10 https://download.owncloud.org/download/repositories/production/Debian_10  Release.gpg [481 B]
Грш:10 https://download.owncloud.org/download/repositories/production/Debian_10  Release.gpg
  Следните подписи са невалидни: DDA2C105C4B73A6649AD2BBD47AE7F72479BC94B
Грш:11 https://ookla.bintray.com/debian generic InRelease
  403  Forbidden [IP: 52.39.193.126 443]
Четене на списъците с пакети… Готово
N: Repository 'https://packages.sury.org/php buster InRelease' changed its 'Suite' value from '' to 'buster'
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://download.owncloud.org/download/repositories/production/Debian_10  Release: 
…

apt-get-update-allow-releaseinfo-change-debian-linux-screenshot

Onwards to upgrade the system up to the latest .deb packages, as usual run:

# apt-get -y update && apt-get upgrade -y
…

 

and updates should be applied as usual with some prompts on whether you prefer to keep or replace existing service configuration and some information on some general changes that might affect your installed services. In a few minutes and few prompts hopefully your Debian OS should be up to the latest stable.

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Posted in Linux, System Administration, Various | No Comments »

Create simple proxy http server with netcat ( nc ) based tiny shell script

Tuesday, January 26th, 2021

use-Netcat_proxy-picture

The need of proxy server is inevitable nowadays especially if you have servers located in a paranoid security environments. Where virtually all is being passed through some kind of a proxy server. In my work we have recently started a  CentOS Linux release 7.9.2009 on HP Proliant DL360e Gen8 (host named rhel-testing).

HP DL360e are quite old nowadays but since we have spare servers and we can refurnish them to use as a local testing internal server Hypervisor it is okay for us. The machine is attached to a Rack that is connected to a Secured Deimilitarized Zone LAN (DMZ Network) which is so much filtered that even simple access to the local company homebrew RPM repository is not accessible from the machine.
Thus to set and remove software from the machine we needed a way to make yum repositories be available, and it seems the only way was to use a proxy server (situated on another accessible server which we use as a jump host to access the testing machine).

Since opening additional firewall request was a time consuming non-sense and the machine is just for testing purposes, we had to come with a solution where we can somehow access a Local repository RPM storage server http://rpm-package-server-repo.com/ for which we have a separate /etc/yum.repos.d/custom-rpms.repo definition file created.

This is why we needed a simplistic way to run a proxy but as we did not have the easy way to install privoxy / squid / haproxy or apache webserver configured as a proxy (to install one of those of relatively giant piece of software need to copy many rpm packages and manually satisfy dependencies), we looked for a simplistic way to run a proxy server on jump-host machine host A.

A note to make here is jump-host that was about to serve as a proxy  had already HTTP access towards the RPM repositories http://rpm-package-server-repo.com and could normally fetch packages with curl or wget via it …

For to create a simple proxy server out of nothing, I've googled a bit thinking that it should be possible either with BASH's TCP/IP capabilities or some other small C written tool compiled as a static binary, just to find out that netcat swiss army knife as a proxy server bash script is capable of doing the trick.

Jump host machine which was about to be used as a proxy server for http traffic did not have enabled access to tcp/port 8888 (port's firewall policies were prohibiting access to it).Since 8888 was the port targetted to run the proxy to allow TCP/IP port 8888 accessibility from the testing RHEL machine towards jump host, we had to issue first on jump host:

[root@jump-host: ~ ]# firewall-cmd –permanent –zone=public –add-port=8888/tcp

To run the script once placed under /root/tcp-proxy.sh on jump-host we had to run a never ending loop in a GNU screen session to make sure it runs forever:

Original tcp-proxy.sh script used taken from above article is:
 

#!/bin/sh -e

 

if [ $# != 3 ]
then
    echo "usage: $0 <src-port> <dst-host> <dst-port>"
    exit 0
fi

TMP=`mktemp -d`
BACK=$TMP/pipe.back
SENT=$TMP/pipe.sent
RCVD=$TMP/pipe.rcvd
trap 'rm -rf "$TMP"' EXIT
mkfifo -m 0600 "$BACK" "$SENT" "$RCVD"
sed 's/^/ => /' <"$SENT" &
sed 's/^/<=  /' <"$RCVD" &
nc -l -p "$1" <"$BACK" | tee "$SENT" | nc "$2" "$3" | tee "$RCVD" >"$BACK"
 

Above tcp-proxy.sh script you can download here.

I've tested the script one time and it worked, the script syntax is:

 [root@jump-host: ~ ]#  sh tcp-proxy.sh
usage: tcp-proxy.sh <src-port> <dst-host> <dst-port>


To make it work for one time connection I've run it as so:

 

 [root@jump-host: ~ ]# sh tcp-proxy.sh 8888 rpm-package-server-repo.com 80

 

 

To make the script work all the time I had to use one small one liner infinite bash loop which goes like this:

[root@jump-host: ~ ]#  while [ 1 ]; do sh tcp-proxy.sh 8888 rpm-package-server-repo.com 80; done​

On rhel-testing we had to configure for yum and all applications to use a proxy temporary via
 

[root@rhel-tresting: ~ ]# export http_proxy=jump-host_machine_accessibleIP:8888


And then use the normal yum check-update && yum update to apply to rhel-testing machine latest RPM package security updates.

The nice stuff about the tcp-proxy.sh with netcat in a inifite loop is you will see the binary copy of traffic flowing on the script which will make you feel like in those notorious Hackers movies ! 🙂

The stupid stuff is that sometimes some connections and RPM database updates or RPMs could be cancelled due to some kind of network issues.

To make the connection issues that are occuring to the improvised proxy server go away we finally used a slightly modified version from the original netcat script, which read like this.
 

#!/bin/sh -e

 

if [ $# != 3 ]
then
    echo "usage: $0 <src-port> <dst-host> <dst-port>"
        exit 0
        fi

        TMP=`mktemp -d`
        BACK=$TMP/pipe.back
        SENT=$TMP/pipe.sent
        RCVD=$TMP/pipe.rcvd
        trap 'rm -rf "$TMP"' EXIT
        mkfifo -m 0600 "$BACK" "$SENT" "$RCVD"
        sed 's/^/ => /' <"$SENT" &
        sed 's/^/<=  /' <"$RCVD" &
        nc –proxy-type http -l -p "$1" <"$BACK" | tee "$SENT" | nc "$2" "$3" | tee "$RCVD" >"$BACK"


Modified version tcp-proxy1.sh with –proxy-type http argument passed to netcat script u can download here.

With –proxy-type http yum check-update works normal just like with any normal fully functional http_proxy configured.

Next step wasto make the configuration permanent you can either add to /root/.bashrc or /etc/bashrc (if you need the setting to be system wide for every user that logged in to Linux system).

[root@rhel-tresting: ~ ]#  echo "http_proxy=http://jump-host_machine_accessibleIP:8888/" > /etc/environment


If you need to set the new built netcat TCP proxy only for yum package update tool include proxy only in /etc/yum.conf:

[root@rhel-tresting: ~ ]# vi /etc/yum.conf
proxy=http_proxy=http://jump-host_machine_accessibleIP:8888/


That's all now you have a proxy out of nothing with just a simple netcat enjoy.

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Posted in Linux, Security, System Administration, Various, Web and CMS | No Comments »

Cracking zip protected password files on GNU/Linux and FreeBSD

Wednesday, October 5th, 2011

crack-zip-freebsd

Its not very common, but sometimes it happens you have to crack some downloaded file from thepiratebay.com or some other big torrent tracker. An example scenario would be downloading a huge words dictionary (a rainbow tables) dictionary etc., which was protected by the author with a password and zipped.

Fortunately Mark Lehmann developed a software called fcrackzip which is capable of brute forcing zip protected file passwords straight on UNIX like operating systems (GNU/Linux, FreeBSD).

fcrackzip is available from package repositories on Debian and Ubuntu Linuces to install via apt:

linux:~# apt-get install frackzip
...

fcrackzip is also available on FreeBSD via the ports tree and can be installed with:

freebsd# cd /usr/ports/security/fcrackzip
freebsd# make install cleam

On Debian it's worthy to have a quick look on the README file:

linux:~# cat /usr/share/doc/fcrackzip/READMESee fcrackzip.txt (which is derived from the manpage), or fcrackzip.html

There is a web page with more information at
http://lehmann.home.ml.org/fcrackzip.html or
http://www.goof.com/pcg/marc/fcrackzip.html

A sample password-protected .zip file is included as "noradi.zip". It's
password has 6 lower case characters, and fcrackzip will find it (and a
number of false positives) with

fcrackzip -b -c a -p aaaaaa ./noradi.zip

which will take between one and thirty minutes on typical machines.

To find out which of these passwords is the right one either try them out
or use the –use-unzip option.

Marc

Cracking the noradi.zip password protected sample file on my dual core 1.8 ghz box with 2gb, it took 30 seconds.

linux:~# time fcrackzip -u -b -c a -p aaaaaa noradi.zip

PASSWORD FOUND!!!!: pw == noradi

real 0m29.627s
user 0m29.530s
sys 0m0.064s

Of course the sample set password for noradi.zip is pretty trivial and with more complex passwords, sometimes cracking the password can take up to 30 minutes or an hour and it all depends on the specific case, but at least now we the free software users have a new tool in the growing arsenal of free software programs 😉

Here are the options passed on to the above fcrackzip command:

-u – Try to decompress with the detected possible archive passwords using unzip (This is necessery to precisely find the archive password, otherwise it will just print out a number of possible matching archive passwords and you have to try each of the passwords one by one. Note that this option depends on a working unzip version installed.)

-c a – include all charsets to be tried with the generated passwords

-b – Select brute force mode – Tries all possible combinations of letters specified

-p aaaaaa – init-password string (Look up for a password between the password length 6 characters long)

FCrackZip is partly written in assembler and thus is generally works fast, to reduce the CPU load fcrackzip will put on the processor its also capable of using external words dictionary file by passing it the option:

-D – The file should be in a format one word per line and be preliminary alphabetically sorted with let's say sort

Also fcrackzip supports parallel file brute force, for example if you have 10 zip files protected with passwords it can paralelly try to brute force the pwds.

As of time of writting frackzip reached version 1.0 and seems to be pretty stable. Happy cracking.
Just to make sure fcrackzip's source is not lost somewhere in the line in the long future to come, I've created a fcrackzip download mirror here

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Posted in Computer Security, Hacks, System Administration | 1 Comment »

Monitor General Server / Desktop system health in console on Linux and FreeBSD

Tuesday, October 4th, 2011

slurm-output-monitoring-networking
saidar is a text based ncurses program to display live statistics about general system health.

It displays in one refreshable screen (similar to top) statistics about server state of:
CPU, Load, Memory, Swap, Network, I/O disk operations
Besides that saidar supports a ncurses console colors, which makes it more funny to look at.
Saidar extracts the statistics for system state based on libgstrap cross platform statistics library about pc system health.

On Debian, Ubuntu, Fedora, CentOS Linuxes saider is available for install straight from distribution repositories.
On Debian and Ubuntu saidar is installed with cmd:

debian:~# apt-get install saidar
...

On CentOS and Fedora saidar is bundled as a part of statgrab-tools rpm package.
Installing it on 64 bit CentOS with yum is with command:

[root@centos ~]# yum install statgrab-tools.x86_64

Saidar is also available on FreeBSD as a part of the /usr/ports/devel/libgstrab, hence to use on my FreeBSD I had to install the libgstrab port:

freebsd# cd /usr/ports/devel/libstatgrab
freebsd# make install clean

Here is saidar running on my Desktop Debian on Thinkpad in color output:

debian:~# saidar -c

Saidar Linux General statistics Screenshot

I've seen many people, who use various shell scripts to output system monitoring information, this scripts however are often written to just run without efficiency in mind and they put some let's say 1% extra load on the system CPU. This is not the case with saidar which is written in C and hence the program is optimized well for what it does.

Update: Next to saidar I recommend you check out Slurm (Real Time Network Interface Monitor) it can visualizes network interface traffic using ascii graph such as on top of the article. On Debian and Ubuntu Slurm is available and easily installable via simple:
 

apt-get install –yes slurm

 

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Posted in FreeBSD, Linux, Monitoring, Networking, System Administration | 1 Comment »

Create SVN (Subversion) web statistics on Debian Lenny Linux with mpy-svn-stats and svnstats.sh

Monday, July 5th, 2010

I’ve recently desired to have a visualized statistics on how many commits, imports, people who commit into subversion’s repositories,graphs showing up the most active comitters, commits into the all subversion repositories grouped by month, week etc.
This kind of valuable information can give you insight, on a projects code life cycle. It can also help you to find out who takes most active participation into a certain project code development etc. and therefore could play a vital role in finding out about the work efficiency within your IT company or IT department.

There are plenty of softwares that can generate you some shiny statistics on how often and by whom are commits into your repositories as well as general statistics concerning your repositories accessibility.

Some of the projects suggested by most Linux users online, who had to resolve the same task e.g. (find some decent software to generate them good statistics on the svn use.) are:

1. statsvn

Here is a description on what statsvn is directly taken from its website:

StatSVN retrieves information from a Subversion repository and generates various tables and charts describing the project development, e.g.

StatSVN looks really promising, however what I find personally repulsive about it is that it depends on a Sun Java virtual machine
I have a bad taste for third party software that depends on java and therefore the software uses an XML dump generated from svn log –xml -v path/to/repos > svn-logfile.xml after which it’s necessary to pass the generated svn-logfile.xml file to statsvn, for instance:

statsvn [options] svn-logfile.xml path/to/repos

though a debian of statsvn is available and packaged for Debian in /usr/share/doc/statsvn/README.Debian we read:

Notes to Debian users:

* the jtreemap-based report has been disabled as jtreemap is currently
not packaged for Debian, and Debian cannot ship the applet without
its sources (not included in statsvn’s sources).

— Vincent Fourmond <fourmond@debian.org>, Tue, 4 Mar 2008 21:14:14 +0100

What I understood from statsvn documentation is that jtreemap is absolutely necessary in order to have a running statsvn, regardless if you have or you don’t have a java vm installed.

To take a general idea on what kind of Repo Roadmap does svnstat generates with jtreemap check out the following link

Since jtreemap is not available prepackaged for Debian I decided not to use svnstats though it looked quite superb.

Some further research on the kind of softwares available online able to generate me some statistics from cvs or subversion source repositories led me to,

2. svnplot

svnplot stroke me with it’s perfect looking many graphics generated on the Lines of Code commited, contribution of different authors to the repository, File count, avarage commit file sizes, common activity, author commit activity etc. etc.

I think tt’s worthy to check out some example statistics about a sample repository statistics generated by svnplot to get a better idea what to expect if you choose to install it on your server.

Even though svnplot looked also promising It wasn’t actually my choice because I think it’s not really mature enough as a software, the second reason which hold me back from installing it on my debian server was that I find it too much as a work in progress still.

Since neither svnstast nor svnplot didn’t well match my expectation and lacked a debian package I finally choose:

3. mpy svn stats as a solution to generate and graph information about svn usage

There are few reasons I finally took svn-mpy-stats to be the solution of choice.

1. It is available as a package in Debian Linux and easily installable via apt-get
2. It is written in Python and therefore doesn’t require a java virtual machine or some extra cosmetics to make it work3. It’s really simple and straight forward to configure and already tested and reported that it works well in Debian GNU/Linux

So here is the few simple steps I took to install mpy-svn-stats on Debian Lenny (in Debian Sid / Squeeze I suppose the procedure would be analogous.

– Install mpy-svn-stats via apt-get or aptitude

debian-server:~# apt-get install mpy-svn-stats

Run it for your svn repository with a command like:

debian-server:~# mkdir /var/www/svnstats
/usr/bin/mpy-svn-stats -o /var/www/svnstats/ file:///var/svn-repos/repository_name

In the above command substitute /var/www/svnstats/ and /var/svn-repos/repository_name with a directory of choice where you like to generate the html statistics for the svn usage as well as the full path and name of your repository.

Of course it’s a good idea to make mpy-svn-stats run periodically with for instance crontab or at or any other unix task cheduler available for your Linux system.

So far so good. You have probably already noticed that it’s rather inconvenient because you have to execute mpy-svn-stats command to each of your svn repositories individually.
This is absolute madness if your company is creating new svn source repository projects often, like let’s say everyday, because you will have to generate statistics for each of the repositories either manually or add new repositories manually to a script which will be later invoked by a crontab rule.

To get around this constrain, I’ve come up with a tiny shell script svnstats.sh which takes care for everything on it’s own.

It automatically will loop in your main subversion repositories directory through all the sub-repositories and generate individual html statistics in a separate automatically created directory by the script.

So to make your life easier and automate the process of generating stats with mpy-svn-stats consider downloading svnstats.sh and installing it as a separate rule like so:

debian-server:~# crontab -u root -e

Include therein the following:

# generate svn statistics everyday in 05:20 a.m.20 5 * * * /usr/sbin/svnstats.sh >/dev/null >>&1

Now everyday at 05:20 your mpy-svn-stats will generate a nice graphs and statistics for your subversion repository usage in /var/www/svstats, if you consider generating the data into a different location consider editting the head of mpy-svn-stats svnstats.sh script and change according to your likings.

Now let’s create an Alias in Apache to enable the (mpy-svn-stats generated by svnstats.sh) to be visualized via web:

– Edit VirtualHost configuration file of choice and put there, something like:

Alias /svnstats/ /var/www/svnstats/

Lastly it might be a good idea to use htaccess to protect your url with a password, afterwards you can enjoy your mpy svn statistics.

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Posted in Linux, System Administration | 2 Comments »

Quick way to access remotely your GNU / Linux Desktop – Access Linux Desktop from Mac and Windows 7

Tuesday, August 5th, 2014

how-to-access-linux-host-from-microsoft-windows-or-mac-client-xrdp-tightvnc-native-way-logo
For M$ Windows users its always handy to have remote access to your home PC or notebook via Remote Desktop (RDP) protocol.

However in GNU / Linux, there is no native implementation of RDP protocol. So if you're using Linux as your Desktop like me you will probably want to be able to access the Linux system remotely not only via terminal with SSH using (Putty) or MobaXTerm all in one tabbed Windows terminal program but also be able to use your Linux GNOME / KDE Graphical environment from anywhere on the Internet.

This will make you ponder – Is it possible to access Linux Desktop via proprietary RDP protocol and if not how you can achieve remote GUI access to Linux?

1. Using Linux Xorg and Xming Xserver for Windows

Most people should already know of Linux ability to start multiple Xserver sessions remotely which is the native way to access between two Linux hosts or access remotely Linux from other Linux UNIX like OS. It is also possible to use xinit / startx / xhost commands to establish remotely connection to new or running Linux (Xorg) Xserver by using them in combination with XMing – XServer for Windows running on the Windows host and Debian package (x11-xserver-utils) – providing xhost cmd, however this method is a bit complicated and not so convenient.

I used to be using this method XMing (whose mirror is here), earlier in my university years to use remotely my Debian Linux from  Windows 98 and this works perfectly fine.

2. Using RDP emulation with XRDP server

in order to be able to access your desk from any friend or computer club in the world using standard available in MS Windows Remote Desktop client (mstsc.exe).
There is also another alternative way by using Windows Desktop sharing RDP experimental server xrdp:
 

apt-cache show xrdp |grep -i descr -A 3
Description: Remote Desktop Protocol (RDP) server
 Based on research work by the rdesktop project, xrdp uses the Remote
 Desktop Protocol to present a graphical login to a remote client.
 xrdp can connect to a VNC server or another RDP server.

To make your Linux host accessible via RDP:

On Debian / Ubuntu etc. deb based Linux:

 

apt-get update
apt-get install xrdp
 
$ /etc/init.d/xrdp status
Checking status of Remote Desktop Protocol server xrdp                                             [ OK ]
Checking status of RDP Session Manager sesman

/etc/init.d/xrdp start

On  Fedora Linux:
 

yum -y install xrdp
systemctl enable xrdp.service
systemctl start xrdp.service
systemctl enable xrdp-sesman.service
systemctl start xrdp-sesman.service


It is possible to access remote Linux host using xrdp RDP server, but this will only work in older releases of mstsc.exe (Windows XP / Vista / 2003) and will not work on Windows 7 / 8, because in MS Windows 7 and onwards RDP proto version has changed and the client no longer has compatability with older mstsc releases. There is a work around for this for anyone who stubbornly want to use RDP protocol to access Linux host. If you want to connect to xrdp from Windows 7 you have to copy the old RDP client (mstsc.exe and mstscax.dll) from a WinXP install to the Windows 7 box and run it independently, from the default installed ones, anyways this method is time consuming and not really worthy …

3. Using the VNC withTightVNC server / client

 

Taking above in consideration, for me personally best way to access Linux host from Windows and Mac is to use simply the good old VNC protocol with TightVNC.

TightVNC is cross-platform free and open source remote Desktop client it uses RFB protocol to control another computer screen remotely.

To use tightvnc to access remote Debian / Ubuntu – deb based Linux screen, tightvncserver package has to be installed:

apt-cache show tightvncserver|grep -i desc -A 7
Description-en: virtual network computing server software
 VNC stands for Virtual Network Computing. It is, in essence, a remote
 display system which allows you to view a computing `desktop' environment
 not only on the machine where it is running, but from anywhere on the
 Internet and from a wide variety of machine architectures.
 .
 This package provides a server to which X clients can connect and the
 server generates a display that can be viewed with a vncviewer.
—
 

apt-get –yes install tightvncserver
…


TightVNCserver package is also available in default repositories of Fedora / CentOS / RHEL and most other RPM based distros, to install there:
 

yum -y install tightvnc-server
…


Once it is installed to make tightvncserver running you have to start it (preferrably with non-root user), usually this is the user with which you're using the system:

tightvncserver

You will require a password to access your desktops.

Password:
Verify:   
Would you like to enter a view-only password (y/n)? n

New 'X' desktop is rublev:4

Creating default startup script /home/hipo/.vnc/xstartup
Starting applications specified in /home/hipo/.vnc/xstartup
Log file is /home/hipo/.vnc/rublev:4.log

 

tightvncserver-running-in-gnome-terminal-debian-gnu-linux-wheezy-screenshot

To access now TightVncserver on the Linux host Download and Install TightVNC Viewer client

note that you need to download TightVNC Java Viewer JAR in ZIP archive – don't install 32 / 64 bit installer for Windows, as this will install and setup TightVNCServer on your Windows – and you probably don't want that (and – yes you will need to have Oracle Java VM installed) …
 

tightvnc-viewer-java-client-running-on-microsoft-windows-7-screenshot

Once unzipped run tightvnc-jviewer.jar and type in the IP address of remote Linux host and screen, where TightVNC is listening, as you can see in prior screenshot my screen is :4, because I run tightvnc to listen for connections in multiple X sessions. once you're connected you will be prompted for password, asker earlier when you run  tightvncserver cmd on Linux host.

If you happen to be on a Windows PC without Java installed or Java use is prohibited you can use TightVNC Viewer Portable Binary (mirrored here)

/images/tightvnc-viewer-portable-windows-7-desktop-screenshot

If you have troubles with connection, on Linux host check the exact port on which TightVncServer is running:
 

ps ax |grep -i Tightvnc

 8630 pts/8    S      0:02 Xtightvnc :4 -desktop X -auth /var/run/gdm3/auth-for-hipo-7dpscj/database -geometry 1024×768 -depth 24 -rfbwait 120000 -rfbauth /home/hipo/.vnc/passwd -rfbport 5904 -fp /usr/share/fonts/X11/misc/,/usr/share/fonts/X11/Type1/,/usr/share/fonts/X11/75dpi/,/usr/share/fonts/X11/100dpi/ -co /etc/X11/rgb

Then to check, whether the machine you're trying to connect from doesn't have firewall rules preventing the connection use (telnet) – if installed on the Windows host:
 

telnet www.pc-ferak.net 5904
Trying 192.168.56.101…
Connected to 192.168.56.101.
Escape character is '^]'.
RFB 003.008

telnet> quit
Connection closed.

remote-connection-via-tightvnc-to-linux-host-from-windows-7-using-tightvnc-java-client-screenshot
 

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Posted in Everyday Life, Linux and FreeBSD Desktop, Remote System Administration, System Administration | 3 Comments »

How to take multiple screenshots with scrot and ImageMagick import commands in terminal on GNU / Linux and FreeBSD

Friday, January 13th, 2012

scrot and import are two commands, which can be used to take screenshot in terminal on Linux and FreeBSD:

To use scrot cmd to take screenshots on Ubuntu and Debian the scrot package has to be installed:

noah:~# apt-get install scrot
...

scrot should also be available on most other Linux distributions in the main repositories, I'll be glad to hear if someone has used it on Fedora, SUSE etc.

On FreeBSD, there is a port called scrot , to install on FreeBSD:

freebsd# cd /usr/ports/graphics/scrot
freebsd# make install clean
...

Scrot has plenty of nice arguments one can use to make a screenshot. Maybe the most handy one in my view is after a preliminary set delay before screenshot is taken.

To take screenshot with it after lets say 5 seconds delay before the screenshot:

hipo@noah:~/Desktop$ scrot -t 20 -d 5

Screenshot scrot my debian Linux gnome-termina

To put an year, month and day and year followed by screen resolution with scrot :

hipo@noah:~$ scrot '%Y-%m-%d_$wx$h.png'

Another way to take a screenshot of screen with command is by using ImageMagick's – import image manipulation package.
To take screenshot of the current screen via terminal using import , type in xterm, gnome-termina or Gnome's Run Application (ALT+F2)

hipo@noah:~$ import -window root ScreenShot.png

To make import command to save the taken screenshot in a format (minute:hour:day:month:year)i :

hipo@noah:~$ import -window root $screenshot_dir/screenshot-$(date +%M_%k_%d_%m_%Y|sed -e 's/^ *//').png

Taking a delayed screenshot is also possible via The GIMP via menus File -> Create -> Screenshot

GIMP Screenshot 15 seconds delay GIMP window screenshot

Now here is an interesting question, what if I would like to take periodic screenshots of what I do on my Desktop to take random movie scenes from a movie I watch with totem or vlc??

This task is quite easily achiavable with a little bash shell script, I wrote:

screenshot_dir='Screenshots';
seconds='60';
if [ ! -d "$screenshot_dir" ]; then
mkdir $screenshot_dir;
fi
while [ 1 ]; do
sleep $seconds;
(import -window root $screenshot_dir/screenshot-$(date +%M_%k_%d_%m_%Y|sed -e 's/^ *//').png) &
done

This script will take screenshot automatically to Screenshots/ directory every (1 min – 60 seconds)
You can also my downloads take_screenshot_every_60_secs_import.sh here

To use take_screenshot_every_60_secs_import.sh just issue the script inside xterm or gnome-terminal, after that simply use your computer as you normally would.
The script will take snapshots every minute and store all taken screenshots in Screenshots dir.

If you prefer to use scrot to take automatically the screenshots every lets say 5 minutes, you can use a script like:

screenshot_dir='Screenshots';
# 300 secs (5 mins)seconds='300';
if [ ! -d "$screenshot_dir" ]; then
mkdir $screenshot_dir;
fi
while [ 1 ]; do
sleep $seconds;
(scrot $screenshot_dir/'%Y-%m-%d_$wx$h.png') &
done

You can fetch take_screenshot_every_60_secs_scrot.sh here

The script using scrot is better in terms of efficiency, the system load scrot will put on your machine will be less.
Using some of this scripts will be handy if you need screenshots to Movies, Programs and favourite Free Software games.
Hope this is educative to someone 😉

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Posted in FreeBSD, Linux, Linux and FreeBSD Desktop, System Administration, Various | No Comments »

Debian Linux: Installing and monitoring servers with Icanga (Nagios fork soft)

Monday, June 3rd, 2013

icinga-monitoring-processes-and-servers-linux-logo

There is plenty of software for monitoring how server performs and whether servers are correctly up and running. There is probably no Debian Linux admin who didn't already worked or at least tried Nagios and Mointor to monitor and notify whether server is unreachable or how server services operate. Nagios and Munin are play well together to prevent possible upcoming problems with Web / Db / E-mail services or get notify whether they are completely inaccessible. One similar "next-generation" and less known software is Icanga.
The reason, why to use Icinga  instead of Nagios is  more features a list of what does Icinga supports more than Nagios is on its site here
I recently heard of it and decided to try it myself. To try Icanga I followed Icanga's install tutorial on Wiki.Icanga.Org here
In Debian Wheezy, Icinga is already part of official repositories so installing it like in Squeeze and Lenny does not require use of external Debian BackPorts repositories.

1. Install Icinga pre-requirement packages

debian:# apt-get --yes install php5 php5-cli php-pear php5-xmlrpc php5-xsl php5-gd php5-ldap php5-mysql

2. Install Icanga-web package

debian:~# apt-get --yes install icinga-web

Here you will be prompted a number of times to answer few dialog questions important for security, as well as fill in MySQL server root user / password as well as SQL password that will icinga_web mySQL user use.

icinga-choosing-database-type

configuring-icinga-web-debian-linux-configuring-database-shot

debian-config-screenshot-configuring-icinga-idoutils

icinga-password-confirmation-debian-linux
….

Setting up icinga-idoutils (1.7.1-6) …
dbconfig-common: writing config to /etc/dbconfig-common/icinga-idoutils.conf
granting access to database icinga for icinga-idoutils@localhost: success.
verifying access for icinga-idoutils@localhost: success.
creating database icinga: success.
verifying database icinga exists: success.
populating database via sql…  done.
dbconfig-common: flushing administrative password
Setting up icinga-web (1.7.1+dfsg2-6) …
dbconfig-common: writing config to /etc/dbconfig-common/icinga-web.conf

Creating config file /etc/dbconfig-common/icinga-web.conf with new version
granting access to database icinga_web for icinga_web@localhost: success.
verifying access for icinga_web@localhost: success.
creating database icinga_web: success.
verifying database icinga_web exists: success.
populating database via sql…  done.
dbconfig-common: flushing administrative password

Creating config file /etc/icinga-web/conf.d/database-web.xml with new version
database config successful: /etc/icinga-web/conf.d/database-web.xml

Creating config file /etc/icinga-web/conf.d/database-ido.xml with new version
database config successful: /etc/icinga-web/conf.d/database-ido.xml
enabling config for webserver apache2…
Enabling module rewrite.
To activate the new configuration, you need to run:
  service apache2 restart
`/etc/apache2/conf.d/icinga-web.conf' -> `../../icinga-web/apache2.conf'
[ ok ] Reloading web server config: apache2 not running.
root password updates successfully!
Basedir: /usr Cachedir: /var/cache/icinga-web
Cache already purged!

3. Enable Apache mod_rewrite
 

 

debian:~# a2enmod rewrite
debian:~# /etc/init.d/apache2 restart


4. Icinga documentation files

Some key hints on Enabling some more nice Icinga features are mentioned in Icinga README files, check out, all docs files included with Icinga separate packs are into:
 

debian:~# ls -ld *icinga*/
drwxr-xr-x 3 root root 4096 Jun  3 10:48 icinga-common/
drwxr-xr-x 3 root root 4096 Jun  3 10:48 icinga-core/
drwxr-xr-x 3 root root 4096 Jun  3 10:48 icinga-idoutils/
drwxr-xr-x 2 root root 4096 Jun  3 10:48 icinga-web/

debian:~# less /usr/share/doc/icinga-web/README.Debian debian:~# less /usr/share/doc/icinga-idoutils/README.Debian

5. Configuring Icinga

Icinga configurations are separated in two directories:

debian:~# ls -ld *icinga*

drwxr-xr-x 4 root root 4096 Jun  3 10:50 icinga
drwxr-xr-x 3 root root 4096 Jun  3 11:07 icinga-web

>

etc/icinga/ – (contains configurations files for on exact icinga backend server behavior)

 

/etc/icinga-web – (contains all kind of Icinga Apache configurations)
Main configuration worthy to look in after install is /etc/icinga/icinga.cfg.

6. Accessing newly installed Icinga via web

To access just installed Icinga, open in browser URL – htp://localhost/icinga-web

icinga web login screen in browser debian gnu linux

logged in inside Icinga / Icinga web view and control frontend

 

7. Monitoring host services with Icinga (NRPE)

As fork of Nagios. Icinga has similar modular architecture and uses number of external plugins to Monitor external host services list of existing plugins is on Icinga's wiki here.
Just like Nagios Icinga supports NRPE protocol (Nagios Remote Plugin Executor). To setup NRPE, nrpe plugin from nagios is used (nagios-nrpe-server). 

To install NRPE on any of the nodes to be tracked;
debian: ~# apt-get install –yes nagios-nrpe-server
…

 Then to configure NRPE edit /etc/nagios/nrpe_local.cfg 

 

Once NRPE is supported in Icinga, you can install on Windows or Linux hosts NRPE clients like in Nagios to report on server processes state and easily monitor if server disk space / load or service is in critical state.

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Posted in Everyday Life, Linux, Monitoring, System Administration, Various | 1 Comment »

How to install Google Chrome web browser on Debian 7 Wheezy Linux

Wednesday, September 4th, 2013

How to install Google Chrome web browser on Debian Gnu Linux Chrome and tux logo
Just installed Debian 7 Linux and wondered how to install Google Chrome Browser on Debian Wheezy. It took me a while until I figure it out, as direct download from Google after searching for Chrome Linux had library requirements which are missing from Debian 7 Wheezy repositories.
Here is how;

1. Add  Wheezy Backports and Google's Chrome Repository to /etc/apt/sources.list

echo 'deb http://ftp.debian.org/debian/ wheezy-backports main contrib non-free' >> /etc/apt/sources.list
echo 'deb http://dl.google.com/linux/chrome/deb/ stable main' >> /etc/apt/sources.list

2. Install Google Chrome with apt-get

Here you have few options install Google Chrome Beta (whether you prefer you're an innovator), install unstable – if you prefer latest functionality and don't count on stability or install stable version.

a) Install Google Chrome Beta

apt-get install --yes google-chrome-beta
b) Install Google Chrome Unstable

apt-get install --yes google-chrome-unstable
c) Install Google Stable

apt-get install --yes google-chrome-stable
I personally prefer always to keep stable so prefer to install google-chrome-stable.

Only reason I need Google-Chrome is for testing how websites looks with it. Otherwise I don't recommend this browser to anyone who cares for his security. Obviously as Chrome is product of Google it is almost certainly it keeps complete surveillance on what you do on the net.

That's all happy web development with Chrome on Debian 🙂
 

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Posted in Linux, Linux and FreeBSD Desktop, Various | No Comments »

Install xmame from source on Debian Linux 7.0 (Wheezy) to play for better MAME (Arcade Games Emulation)

Thursday, May 30th, 2013

xmame logo install xmame on latest stable debian

Whether you're keen on playing old school arcade games. And you just updated or installed latest stable Debian 7 Wheezy. You will find out current installable Mame (Arcade Emulator) package cannot play many of the hot Games, even though game rom files are okay and you might have played those games in some previous versions of Debian with now obsolete but apparently better working emu  xmame.

As playing Captain Command, Xain'D Sleena, Cadillac & Dinosaurs and Punisher Classic Arcades is one of my great entertainments when I have some free time. I took the time to find out if xmame is still installable either by deb package or from source.

Unfortunately xmame for latest Debian releases is not available from unofficial repositories, so I proceeded with installing it from source. Thanksfully source install was successful. Hence, below is explained how to install xmame from source on Debian Wheezy and Debian testing/unstable.
First before compiling install a bunch of development packages necessary for proper compilation:

# apt-get install --yes zlib1g-dev
# apt-get install --yes libexpat1-dev
# apt-get install --yes libghc-x11-dev
# apt-get install --yes x11proto-video-dev
# apt-get install --yes libxv-dev
Download xmame 0.103 source archive (xmame-0.103.tar.bz2)

Tar archive doesn't have configure script so to compile it just run make ;

# cd /usr/local/src
# tar -jxvvf xmame-0.103.tar.bz2
# su hipo
$  cd xmame-0.103
$ make
...
....
$ exit
# make install
.....


In case some header .h file is still missing and compile fails, as it happened to me on few occasions. You can install and use apt-file;

One important note is xmame's build will take very long on my machine with 2Gb of Memory and Dual Core 1.8 Ghz it took about 1,.30 or 2 hours. 

# apt-get –yes install apt-file
# apt-file update

To find from which package the the missing .h file can be installed

# apt-file search Header-Name.h

Then just install package which will provide needed header.

Next step is to create xmame config file:
# mkdir /usr/local/share/xmame/
xmame-0.103$ cp -rpf ./src/unix/doc/xmamerc.dist /usr/local/share/xmame/xmamerc
In xmamerc set proper location for Mame ROM files:

# vim /usr/local/share/xmame/xmamerc
 Find line;

rompath                 /usr/local/share/xmame/roms

and change it to whether Rom files are located. In my case they're in /disk/Games/Mames/roms, so change rompath to;
 

rompath                 /disk/Games/Mames/roms

There are some other configurations which you might want to tune. A well configured xmamerc that works fine for me is here

Finally link xmame.x11 to /usr/bin/xmame

# ln -sf /usr/local/bin/xmame.x11 /usr/bin/xmame

After having properly configured XMamE'S roms Directory to launch a game, for example punisher.zip or captcomm.zip:

$ xmame punisher
....
 $ xmame captcom
....
captain_commando_arcade-game-logo running on xmame Linux

I've build xmame from source on Debian but I suppose same guide should be working okay on Ubuntu, Mint and rest of Debian distributions. I'll be happy to get feedback if someone succeeded running xmame on other distro. If you do please drop me a comment with distro name and specifics or problems faced.

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Posted in Entertainment, Everyday Life, Games Linux | No Comments »

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