Wednesday, June 28, 2017

System information: Adding colors to Shell script

# Sample script written for Part 4 of the RHCE series
# This script will return the following set of system information:
# -Hostname information:
echo -e "\e[31;43m***** HOSTNAME INFORMATION *****\e[0m"
echo ""
# -File system disk space usage:
echo -e "\e[31;43m***** FILE SYSTEM DISK SPACE USAGE *****\e[0m"
df -h
echo ""
# -Free and used memory in the system:
echo -e "\e[31;43m ***** FREE AND USED MEMORY *****\e[0m"
echo ""
# -System uptime and load:
echo -e "\e[31;43m***** SYSTEM UPTIME AND LOAD *****\e[0m"
echo ""
# -Logged-in users:
echo -e "\e[31;43m***** CURRENTLY LOGGED-IN USERS *****\e[0m"
echo ""
# -Top 5 processes as far as memory usage is concerned
echo -e "\e[31;43m***** TOP 5 MEMORY-CONSUMING PROCESSES *****\e[0m"
ps -eo %mem,%cpu,comm --sort=-%mem | head -n 6
echo ""
echo -e "\e[1;32mDone.\e[0m"
Run this script in bash shell and you will get an output similar below.

Note that the headers of each section are shown in color for better visualization:
That functionality is provided by this command:
echo -e "\e[COLOR1;COLOR2m<YOUR TEXT HERE>\e[0m"
Where COLOR1 and COLOR2 are the foreground and background colors, respectively (more info and options are explained in this entry from the Arch Linux Wiki) and <YOUR TEXT HERE> is the string that you want to show in color.

Wednesday, June 7, 2017

Enable direct ssh access to EC2 instance without .pem key

Enable password authentication by editing /etc/ssh/sshd_config: change PasswordAuthentication no to PasswordAuthentication yes

Restart ssh:

sudo /etc/init.d/ssh restart

systemctl  restart sshd (for RHEL7)