Disable Ping on Linux Server - Quick HOWTO

How do you disable ping to Linux server? Here is the quick steps:

 To disable ping:

echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all

To enable ping:

echo 0 > /proc/sys/net/ipv4/icmp_echo_ignore_all

That's all..! 

Change Username Max Length in AIX - Quick HOWTO

In AIX 5.3,

To change the default length of username:

# chdev -l sys0 -a max_logname=9
sys0 changed

To check the current length of username:

# lsattr -El sys0 -a max_logname
max_logname 9 Maximum login name length at boot time True
# getconf LOGIN_NAME_MAX 21

Hope this quick tip helps someone..!