Repair Linux Boot failures in Grub 2 rescue mode

As GRUB 2’s ability to fix boot problems is greatly improved over the original GRUB bootloader. This article provides the you with information on options available for repairing GRUB 2 boot issues and specific instructions on how to use the GRUB 2 terminal. The instructions are written for GRUB 2.

How it looks?

There are basically three messages or error or screen mode whatever you say, when grub fails to boot.

grub: This is the screen mode you see when grub has found everything ecept the configurationn file. This file probably will be grub.conf.

grub rescue: This is the mode when GRUB 2 is unable to find the grub folder or its contents are missing/corrupted. The GRUB 2 folder contains the menu, modules and stored environmental data.

GRUB: Just “GRUB” nothing else indicates GRUB 2 failed to find even the most basic information needed to boot the system.

This is are the basic errors that we se on the boot. Althought there are few more errors that can be seen on the screen like frozen splash screen, Busybox or Initramfs: GRUB 2 began….
But each of the GRUB 2 failure modes can be corrected either from GRUB 2 terminal or the Live boot CD or DVD of the distro , there are also 3rd party rescue tools available out there.

Basic Commands available.

This are the commands that can be used when when you enter the GRUB 2 terminl mode by pressing “c”.

boot (Initiate the boot, also F10 or CTRL-x)

cat (view the contents of config or txt files; cat (hd0,1)/boot/grub/grub.cfg)

configfile (Load a GRUB 2 configuration file such as grub.cfg; configfile (hd0,5)/boot/grub/grub.cfg.)

initrd (Loads the initrd.img, necessary for booting; initrd (hd0,5)/initrd.img.)

insmod (Loads a module; insmod (hd0,5)/boot/grub/normal.mod, or insmod normal.)

linux (Loads the kernel; insmod /vmlinuz root=(hd0,5) ro.)

loop (Mount a file as a device; loopback loop (hd0,2)/iso/my.iso.)

ls (lists the contents of a partition/folder; ls, ls /boot/grub, ls (hd0,5)/, ls (hd0,5)/boot.)

lsmod (List loaded modules.)

normal (Activate the normal module, if loaded.)

search (Search for a device. Type help search for the available options.)

set (Review current settings, or set XXX to set a variable such as colors, prefix, root.)

vbeinfo (Display GRUB 2 available resolutions.)

The Rescue Shell.

If you get a rescue shell, this usually means that GRUB failed to load the “normal” module for some reason. It may be possible to work around this temporarily: for instance, if the reason for the failure is that “prefix” is wrong (perhaps it refers to the wrong device, or perhaps the path to “/boot/grub” was not correctly made relative to the device), then you can correct this and enter normal mode manually: Inspect the current prefix (and other preset variables):


You will probably have an output more or less like this:

Your output may differ but you get the information required. Find out which devices are available:


Set to the correct value, which might be something like this:

set prefix=(hd0,1)/grub

(this has to be done according to your own drive name)

set root=(hd0,1)

(this has to be performed according to your own drive name.)

insmod normal

The above commands will get you out of the rescue mode to the normal terminal mode. In the terminal mode you have more commands and with increased functionality.
After the above commands you can go ahead and start the rest of the settings.

insmod linux
* linux /vmlinuz root=/dev/sdXY ro

(if this doesn’t work try this)

linux /boot/vmlinuz-3.2.0-14-generic root=/dev/sda1 ro


initrd /initrd.img

(Selects the initrd image.)


After Booting in to the system.

Update the grub config file.

sudo update-grub

Reinstallation of grub on the device:

sudo grub-install /dev/sdX

This should the thing for the rescue part and your system should be good and running. If not you can save all your trouble by using Boot Repair. This is the tool used to repair your complete boot menu. It can be downloaded directly and used as a Live Boot CD or DVD. Here is the download link.


How to whitelist an IP in Fail2ban on Debian Wheezy

How to whitelist an IP in Fail2ban on Debian Wheezy

Fail2Ban is used to protect servers against brute force attacks. Fail2ban uses iptables to block attackers, so, if we want to add permanent IP address and never be blocked, we must add it in the config file.

First, edit the config file :

vi /etc/fail2ban/jail.conf

Then, check the line :

ignoreip =

Add now add all ip you want. Each IP or range IP must be placed here with a space. Ex:

Save. And restart Fail2Ban:

service fail2ban restart

That’s all.


How to create a jailed ssh user with Jailkit on Debian Wheezy

How to create a jailed ssh user with Jailkit on Debian Wheezy


This document describes how to install and configure Jailkit in Debian Wheezy Server.  Jailkit is a set of utilities to limit user accounts to specific files using chroot() and or specific commands. Setting up a chroot shell, a shell limited to some specific command, or a daemon inside a chroot jail is a lot easier and can be automated using these utilities.

Jailkit is known to be used in network security appliances from several leading IT security firms, internet servers from several large enterprise organizations, internet servers from internet service providers, as well as many smaller companies and private users that need to secure cvs, sftp, shell or daemon processes.

1 Preliminary Note

This tutorial is based on Debian 7.6 server, so you should set up a basic Debian 7.6 server installation before you continue with this tutorial. The system should have a static IP address. I use as my IP address in this tutorial and as the hostname.

2 Install Jailkit

We will first download and install the Jailkit. At present time of writing this guide the latest available version of Jailkit is 2.17. I will download it and install it as follows:

cd /tmp
tar xvfz jailkit-2.17.tar.gz
cd jailkit-2.17

Jailkit requires some packages before its installation, we will install them as follows:

apt-get install build-essential autoconf automake1.9 libtool flex bison debhelper binutils-gold python

Now our system is ready to install the Jailkit, install it as follows:

./debian/rules binary
cd ..
dpkg -i jailkit_2.17-1_amd64.deb

It will install the Jailkit in Debian Server, we can remove the extra packages from /tmp:

rm -rf /tmp/jailkit*

3 Jailing a user

Now we will create  a user which will be jailed using Jailkit as:

adduser srijan

root@server1:~#adduser srijan
Adding user `srijan’ …
Adding new group `srijan’ (1001) …
Adding new user `srijan’ (1001) with group `srijan’ …
Creating home directory `/home/srijan’ …
Copying files from `/etc/skel’ …
Enter new UNIX password: –password
Retype new UNIX password:–password
passwd: password updated successfully
Changing the user information for srijan
Enter the new value, or press ENTER for the default
Full Name []: –ENTER
Room Number []:–ENTER
Work Phone []:–ENTER
Home Phone []:–ENTER
Other []:–ENTER
Is the information correct? [Y/n] –Y

In my case I am creating the user srijan, you can use any name.

Next we will check the information about user srijan in /etc/passwd as:

egrep srijan /etc/passwd

root@server1:/tmp# egrep srijan /etc/passwd

Next we will jail the created user. Create a directory /jail for Jail environment:

mkdir /jail

Now we will provide the Jail with some of the default programs environment as:

jk_init -v /opt/jail netutils basicshell jk_lsh openvpn ssh sftp

We can give other values also, the complete list of the Jail environment can be checked in the file

nano /etc/jailkit/jk_init.ini

Now Jail is ready, just add the user inside the environment:

jk_jailuser -m -j /jail/ srijan

Again check the values in /etc/passwd for user srijan:

egrep srijan /etc/passwd

root@server1:/tmp# egrep srijan /etc/passwd

Now our user have been added in the Jailed environment. I will connect the Debian server with bash terminal with its IP

ssh srijan@

root@server1:~$ ssh srijan@
The authenticity of host ‘ (’ can’t be established.
ECDSA key fingerprint is 3d:ca:91:67:96:39:15:b4:0f:6e:c8:2c:92:ef:25:d7.
Are you sure you want to continue connecting (yes/no)? yes
srijan@’s password:
Linux server1 3.2.0-4-amd64 #1 SMP Debian 3.2.60-1+deb7u3 x86_64The programs included with the Debian GNU/Linux system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.
Connection to closed.

Connection is getting closed as the user don’t have logging shell, lets add it in the configuration file for Jail:

nano /jail/etc/passwd


It will add the bash prompt for the jailed user srijan.  Now again try the ssh login with srijan user and you will be able to login:

ssh srijan@

Now check the root directory content, you will notice that it have contents like this:

ls /

srijan@server1:~$ ls /
bin  dev  etc  home  lib  lib64  usr

4 Running services and commands in Jailed environment

Jail can be used to run services in Jailed environment. Suppose we want to run any service in Jailed environment then we will use jk_chrootlaunch command for that:

jk_chrootlaunch -j /jail -u srijan -x ‘service apache2 start’

Here I am starting the service of Apache, similarly you can run any service or daemon with it in Jailed environment.

Suppose we want to run a particular command in Jail environment then we will use jk_cp. Lets test it in Jailed environment when we will run cal then it shows as follows:


srijan@server1:~$ cal
bash: cal: command not found

It means Jail environment don’t knows the cal command, now I will add it in Debian Server as follows:

jk_cp  -v -j /jail/ /usr/bin/cal

root@server1:~# jk_cp  -v -j /jail/ /usr/bin/cal
Creating symlink /jail/usr/bin/cal to ncal
Copying /usr/bin/ncal to /jail/usr/bin/ncal
Creating symlink /jail/lib/x86_64-linux-gnu/ to
Copying /lib/x86_64-linux-gnu/ to /jail/lib/x86_64-linux-gnu/
/jail/lib/x86_64-linux-gnu/ already exists, will not touch it
/jail/lib/x86_64-linux-gnu/ already exists, will not touch it
/jail/lib/x86_64-linux-gnu/ already exists, will not touch it
/jail/lib64/ already exists, will not touch it
/jail/lib/x86_64-linux-gnu/ already exists, will not touch it
/jail/lib/x86_64-linux-gnu/ already exists, will not touch it
/jail/lib/x86_64-linux-gnu/ already exists, will not touch it
/jail/lib64/ already exists, will not touch it

Again run the cal command in Jailed environment:


srijan@server1:~$ cal
September 2014
Su Mo Tu We Th Fr Sa
1  2  3  4  5  6
7  8  9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30


So we have added the command for the Jailed environment. Congratulations! Now we have successfully configured Jail environment in Debian Wheezy 🙂

5 Links

How To Build PHP 5.6 (PHP-FPM & FastCGI) with Zend OPcache And APCu For ISPConfig 3 On Debian 7 (Wheezy)

How To Build PHP 5.6 (PHP-FPM FastCGI) with Zend OPcache And APCu For ISPConfig 3 On Debian 7 (Wheezy)


ISPConfig 3 has a builtin feature to support multiple PHP versions on one server and select the optimal PHP version for a website. This feature works with PHP-FPM and FastCGI. This tutorial shows how to build PHP 5.6 as a PHP-FPM and a FastCGI version on a Debian Wheezy server. These PHP 5.5 builds include Zend OPcache, and APCu.


1 Preliminary Note

I will install PHP 5.6.0, the latest PHP 5 version at the time of this writing. I will also show how to build some additional PHP extensions such as APCu and memcache. The ioncube loader is not available for php 5.6 at this time, so I will leave out that step.

Please note that PHP-FPM can be used on both Apache and nginx servers, while FastCGI is available only for Apache servers.

PHP-FPM and FastCGI are mutually exclusive in PHP 5.6, that’s why I show two ways of building PHP, one for PHP-FPM, one for FastCGI, however you can compile PHP twice to get both, one time with –enable-fpm and one time with –enable-cgi (make sure to use different base directories, such as /opt/php-5.6.0 for PHP-FPM and /opt/phpfcgi-5.6.0 for FastCGI).


2 Building PHP 5.6.0 (PHP-FPM)

Download and extract PHP 5.6.0:

mkdir /opt/php-5.6.0
mkdir /usr/local/src/php5-build
cd /usr/local/src/php5-build
wget -O php-5.6.0.tar.bz2
tar jxf php-5.6.0.tar.bz2

cd php-5.6.0/

Install the prerequisites for building PHP5:

apt-get install build-essential

apt-get build-dep php5

apt-get install libfcgi-dev libfcgi0ldbl libjpeg62-dbg libmcrypt-dev libssl-dev libc-client2007e libc-client2007e-dev

ln -s /usr/lib/libc-client.a /usr/lib/x86_64-linux-gnu/libc-client.a

(The last command is needed if you build PHP with –with-imap, because otherwise ./configure will stop with the following error:

checking for crypt in -lcrypt… yes
configure: error: Cannot find imap library (libc-client.a). Please check your c-client installation.


Configure and build PHP 5.6.0 as follows (you can adjust the ./configure command to your needs, take a look at

./configure –help

to see all available options; if you use a different ./configure command, it is possible that additional libraries are required, or the build process will fail):

./configure –prefix=/opt/php-5.6.0 –with-pdo-pgsql –with-zlib-dir –with-freetype-dir –enable-mbstring –with-libxml-dir=/usr –enable-soap –enable-calendar –with-curl –with-mcrypt –with-zlib –with-gd –with-pgsql –disable-rpath –enable-inline-optimization –with-bz2 –with-zlib –enable-sockets –enable-sysvsem –enable-sysvshm –enable-pcntl –enable-mbregex –enable-exif –enable-bcmath –with-mhash –enable-zip –with-pcre-regex –with-mysql –with-pdo-mysql –with-mysqli –with-jpeg-dir=/usr –with-png-dir=/usr –enable-gd-native-ttf –with-openssl –with-fpm-user=www-data –with-fpm-group=www-data –with-libdir=/lib/x86_64-linux-gnu –enable-ftp –with-imap –with-imap-ssl –with-kerberos –with-gettext –with-xmlrpc –with-xsl –enable-opcache –enable-fpm

The last switch (–enable-fpm) makes sure this PHP version will work with PHP-FPM.

make install

Copy php.ini and php-fpm.conf to the correct locations:

cp /usr/local/src/php5-build/php-5.6.0/php.ini-production /opt/php-5.6.0/lib/php.ini

cp /opt/php-5.6.0/etc/php-fpm.conf.default /opt/php-5.6.0/etc/php-fpm.conf

Open /opt/php-5.6.0/etc/php-fpm.conf and adjust the following settings – in the listen line you must use an unused port (e.g. 8999; port 9000 might be in use by Debian’s default PHP-FPM already), and you must add the line include=/opt/php-5.6.0/etc/pool.d/*.conf at the end:

vi /opt/php-5.6.0/etc/php-fpm.conf

pid = run/
user = www-data
group = www-data
listen =

Create the pool directory for PHP-FPM:

mkdir /opt/php-5.6.0/etc/pool.d

Next create an init script for PHP-FPM:

vi /etc/init.d/php-5.6.0-fpm

#! /bin/sh
# Provides:          php-5.6.0-fpm
# Required-Start:    $all
# Required-Stop:     $all
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: starts php-5.6.0-fpm
# Description:       starts the PHP FastCGI Process Manager daemon
php_opts="--fpm-config $php_fpm_CONF"
wait_for_pid () {
        while test $try -lt 35 ; do
                case "$1" in
                        if [ -f "$2" ] ; then
                        if [ ! -f "$2" ] ; then
                echo -n .
                try=`expr $try + 1`
                sleep 1
case "$1" in
                echo -n "Starting php-fpm "
                $php_fpm_BIN $php_opts
                if [ "$?" != 0 ] ; then
                        echo " failed"
                        exit 1
                wait_for_pid created $php_fpm_PID
                if [ -n "$try" ] ; then
                        echo " failed"
                        exit 1
                        echo " done"
                echo -n "Gracefully shutting down php-fpm "
                if [ ! -r $php_fpm_PID ] ; then
                        echo "warning, no pid file found - php-fpm is not running ?"
                        exit 1
                kill -QUIT `cat $php_fpm_PID`
                wait_for_pid removed $php_fpm_PID
                if [ -n "$try" ] ; then
                        echo " failed. Use force-exit"
                        exit 1
                        echo " done"
                       echo " done"
                echo -n "Terminating php-fpm "
                if [ ! -r $php_fpm_PID ] ; then
                        echo "warning, no pid file found - php-fpm is not running ?"
                        exit 1
                kill -TERM `cat $php_fpm_PID`
                wait_for_pid removed $php_fpm_PID
                if [ -n "$try" ] ; then
                        echo " failed"
                        exit 1
                        echo " done"
                $0 stop
                $0 start
                echo -n "Reload service php-fpm "
                if [ ! -r $php_fpm_PID ] ; then
                        echo "warning, no pid file found - php-fpm is not running ?"
                        exit 1
                kill -USR2 `cat $php_fpm_PID`
                echo " done"
                echo "Usage: $0 {start|stop|force-quit|restart|reload}"
                exit 1

Make the init script executable and create the system startup links:

chmod 755 /etc/init.d/php-5.6.0-fpm
insserv php-5.6.0-fpm

Finally start PHP-FPM:

/etc/init.d/php-5.6.0-fpm start

As long as there are no pools in /opt/php-5.6.0/etc/pool.d, you will get this warning which you can ignore:

root@server1:/usr/local/src/php5-build/php-5.6.0# /etc/init.d/php-5.6.0-fpm start
Starting php-fpm [29-Aug-2014 13:21:12] WARNING: Nothing matches the include pattern ‘/opt/php-5.6.0/etc/pool.d/*.conf’ from /opt/php-5.6.0/etc/php-fpm.conf at line 528.

To enable the Zend OPcache, open /opt/php-5.6.0/lib/php.ini

vi /opt/php-5.6.0/lib/php.ini

… and add the following line at the end:


That’s it – if you like, you can now install some additional modules like APCu, memcache, memcached, and ioncube.

The APCu, memcache, and memcached modules can be installed through PEAR which we must install and initialize first:

apt-get -y install php-pear

cd /opt/php-5.6.0/etc

pecl -C ./pear.conf update-channels

APCu can now be installed as follows:

pecl -C ./pear.conf install channel://

Accept all default values. Afterwards, open /opt/php-5.6.0/lib/php.ini

vi /opt/php-5.6.0/lib/php.ini

… and add the line at the end of the file (you can also configure some additional APCu settings):

;apc.shm_segments = 5

The memcache extension can be installed as follows:

pecl -C ./pear.conf install memcache

Open /opt/php-5.6.0/lib/php.ini

vi /opt/php-5.6.0/lib/php.ini

… and add the line at the end of the file:


Reload PHP-FPM afterwards:

/etc/init.d/php-5.6.0-fpm reload

In ISPConfig 3.0.5, you can configure the new PHP version under System Additional PHP Versions. On the Name tab, you just fill in a name for the PHP version (e.g. PHP 5.6.0) – this PHP version will be listed under this name in the website settings in ISPConfig:

Go to the PHP-FPM Settings tab (the FastCGI Settings tab can be left empty) and fill out the fields as follows: