Hacktopia

You might be saying that IPv6 is the bees knees, and I must be crazy for wanting to disable it.  Well that is partially true.  In this case I need to disable it because my machinne is on a network that can only handle IPv4 packets.  It also slowed down connections on the machine because of how the network was set up.  So basically it was necessary in order to speed up the networking on the server.

add the “options single-request” to the /etc/resolv.conf file

nameserver 4.2.2.1
nameserver 4.2.2.2
options single-request

add “NETWORKING_IPV6=off” to /etc/sysconfig/network

NETWORKING_IPV6=off

next edit the /etc/modprobe.d/ECS.conf file and add “alias ipv6 off” and “net-pf-10″

alias ipv6 off
alias net-pf-10 off

remove the running module

# rmmod ipv6

Then restart network by

# service network restart

or reboot to box to make sure it works after a reboot with

# reboot

To test to make sure that the changes have worked, you should not get anything returned

# lsmod | grep ipv6

You can also run “ifconfig -a” and make sure you do not see the fowling

lo        Link encap:Local Loopback
inet addr:127.0.0.1  Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING  MTU:16436  Metric:1

should see

lo        Link encap:Local Loopback
inet addr:127.0.0.1  Mask:255.0.0.0
UP LOOPBACK RUNNING  MTU:16436  Metric:1

For some reason my new CentOS install has a working ssh but I could not find any scp.

So the package that contains openssh-clients

[root@localhost ~]# whereis scp
scp:
[root@localhost ~]# yum install openssh-clients
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: mirrors.seas.harvard.edu
* epel: mirror.cogentco.com
* extras: centos.mirror.nac.net
* updates: mirrors.seas.harvard.edu
Setting up Install Process
Resolving Dependencies
–> Running transaction check
—> Package openssh-clients.x86_64 0:5.3p1-20.el6_0.3 set to be updated
–> Processing Dependency: libedit.so.0()(64bit) for package: openssh-clients-5.3p1-20.el6_0.3.x86_64
–> Running transaction check
—> Package libedit.x86_64 0:2.11-4.20080712cvs.1.el6 set to be updated
–> Finished Dependency Resolution

Dependencies Resolved

===================================================================================================================================================================================
Package                                      Arch                                Version                                               Repository                            Size
===================================================================================================================================================================================
Installing:
openssh-clients                              x86_64                              5.3p1-20.el6_0.3                                      updates                              351 k
Installing for dependencies:
libedit                                      x86_64                              2.11-4.20080712cvs.1.el6                              base                                  74 k

Transaction Summary
===================================================================================================================================================================================
Install       2 Package(s)
Upgrade       0 Package(s)

Total download size: 425 k
Installed size: 1.2 M
Is this ok [y/N]: y
Downloading Packages:
(1/2): libedit-2.11-4.20080712cvs.1.el6.x86_64.rpm                                                                                                          |  74 kB     00:00
(2/2): openssh-clients-5.3p1-20.el6_0.3.x86_64.rpm                                                                                                          | 351 kB     00:00
———————————————————————————————————————————————————————————–
Total                                                                                                                                              1.0 MB/s | 425 kB     00:00
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
Installing     : libedit-2.11-4.20080712cvs.1.el6.x86_64                                                                                                                     1/2
Installing     : openssh-clients-5.3p1-20.el6_0.3.x86_64                                                                                                                     2/2

Installed:
openssh-clients.x86_64 0:5.3p1-20.el6_0.3

Dependency Installed:
libedit.x86_64 0:2.11-4.20080712cvs.1.el6

Complete!
[root@localhost ~]# whereis scp
scp: /usr/bin/scp /usr/share/man/man1/scp.1.gz

So your system is acting screwy and you are tying to figure out what is going wrong.  Listing the processes in order to determine who the CPU or memory hogs are.

List how much CPU percent and time each process is uing

ps -e -o pcpu,cpu,nice,state,cputime,args –sort pcpu | sed ‘/^ 0.0 /d’

In order to list the process with how much memory each process is using, listed from lease to most memory hogs.

ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS