1. Open ssh_config / sshd_config – the first file is the configuration file for the client, the second is for the daemon (SSH server).
2. Uncomment Ciphers section and leave it as:
This will ensure that only aes128 and aes256-cbc ciphers will be used.
3. Add the following line:
This will ensure that this will be the only supported key exchange method.
4. To drop SSH packets with certain size you can always use the good old iptables:
iptables -A INPUT -p tcp -m length --length 1400:1500 --dport 22 -j DROP
This will drop all incoming packets with size between 1400 and 1500 for port 22 (the SSH port).
mysql -hhostname -uusername -ppassword db_name -e 'query to execute;'
- hostname – the host on which MySQL is installed
- username – the MySQL user that has the necessary privileges over the database
- passsword – the MySQL user password
- db_name – the name of the MySQL database that you want to query
- -e – MySQL option which will execute the statement and quit
- query to execute; – the MySQL query you want to execute enclosed in single quotes
apg is a handy utility for creating random passwords / strings. To install it run:
apt-get install apg
The below for loop will create 300 random usernames / email addresses in the format firstname.lastname@example.org. You can always replace “domain” with “$i” , then you’ll have addresses in the format email@example.com.
-M – specifies that mode will be used
L – use small letters only mode
-n – number of passwords/random strings, in this case 300
for i in $(apg -M L -n 300); do echo $firstname.lastname@example.org >> fileToSaveResult ; done
Quickly create a list of email addresses / usernames in the format usernameprefixNumber@domain.name
if [ $# -ne 4 ]; then
echo Insufficient arguments:
echo "Usage: $0 userprefix numberofusers domainname filetosave"
echo " - enter user prefix, e.g. demo"
echo " - enter number of users,e.g. 100"
echo " - enter domain/hostname, e.g. some-hostname.domain.com"
echo " - file to save the result in"
touch $4 ;
while [[ $counter -le $numberofusers ]];
do echo Creating User $counter;
echo "$userprefix$counter@$domain" >> $4;
let "counter += 1";
apt-get update; apt-get install sysstat
The sysstat package contains several utilities for monitoring system performance. To enable performance data collection edit
/etc/init.d/sysstat restart. If necessary edit the cronjob which will collect the statistics and make sure to setup a logrotate entry in order to avoid large logs.
apt-get update; apt-get install dnsutils
The dnsutils (could be bind-utils for non-Debian based distros) package contains the host, dig, nslookup and nsupdate commands – used for DNS querying and update
This will add the common slash / at the end of each line in the text file and save it. If you want just to see the result use ‘ -e ‘ instead of ‘ -i ‘.
sed -i "s/.*/&\//" filename
What it does: The script will create certain number of files with certain size. It takes two arguments – first is the number of files and the second is the size of each file ( in kilobytes ).
Usage: ./script.sh 100 1
(this will create 100 files 1MB each)
while [[ $counter -le $filecount ]];
do echo Copying $counter;
dd if=/dev/zero of=filename$counter bs=$2k count=1024
let "counter +=1";