1. System wide command aliases are defined in /etc/bashrc
2. User level command aliases are defined in ~/.bashrc
3. Eg. to create a short cut for cd to /home/httpd/cgi-bin
# vi /etc/bashrc
add
alias cdcgi='cd /home/httpd/cgi-bin'
3. The alias will be effective at next logon for all users.
[UPDATE]
System wide aliases are defined inside the respective initialisation scripts in /etc/profile.d
e.g.
# cat /etc/profile.d/java.sh
alias java='java -Xms8m -Xmx64m'
alias javac='javac -client'
alias jar='jar -client'
alias javadoc='javadoc -client'
alias javah='javah -client'
alias javap='javap -client'
alias javaws='javaws -client'
User specific aliases can be defined inside ~/.bashrc or ~/.bash_profile