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Networking tweaks
ifconfig eth0 mtu 9000 txqueuelen 10000modprobe tcp_illinois
net.ipv4.tcp_congestion_control = illinois
Adding additional repository to yum
Repositories:More on YUM
Install yum-skip-broken such that you can add --skip-broken switch to yum. Find yum-skip-broken rpm from your favorite rpm search site.Configure options I used for various software
Configureipcs
The ipcs utility lists the opened semaphores.ipcs
To remove semaphores owned by the user "www"
ipcs|grep www|awk '{print $2}'|xargs -n 1 ipcrm -sFast way to add swap
Create a 1G swap filedd of=/.swap01 bs=1k count=0 seek=1M mkswap /.swap01 swapon /.swap01
rsync & ssh
rsync -avvxz -e ssh source_file root@1.2.3.4:/dest/dir
syn attack
Add more buffer to your kernel and reduce syn retries. It seems to be somewhat effective towards syn attacks when remote servers try to reduce the tcp window to 0 on the initial handshake.net.ipv4.tcp_synack_retries = 3 net.ipv4.tcp_syn_retries = 3 net.ipv4.tcp_max_syn_backlog = 4096
DST fix for Redhat 9
1. Downloaded the tzdata2007c.tar.gz file from /pub/ at elsie.nci.nih.gov. 2. Extracted the tar.gz file: 3. Used zic to create the new zoneinfo file: # zic -d zoneinfo northamerica # cd zoneinfo # cp -r * /usr/share/zoneinfo/ 3. Typed zdump -v `echo $TZ` | grep 2010 to confirm that the DST patch had been applied. Results:
US/Eastern Wed Nov 3 04:20:50 2010 UTC = Wed Nov 3 00:20:50 2010 EDT isdst=1
US/Eastern Sun Mar 14 06:59:59 2010 UTC = Sun Mar 14 01:59:59 2010 EST isdst=0
US/Eastern Sun Mar 14 07:00:00 2010 UTC = Sun Mar 14 03:00:00 2010 EDT isdst=1
US/Eastern Sun Nov 7 05:59:59 2010 UTC = Sun Nov 7 01:59:59 2010 EDT isdst=1
US/Eastern Sun Nov 7 06:00:00 2010 UTC = Sun Nov 7 01:00:00 2010 EST isdst=0
More information on zdump
zdump -v /etc/localtime EST5EDT | grep 2007
is what you would use for the U.S. Eastern time zone. If you're in the Central time zone, use CST6CDT; in the Mountain time zone use MST7MDT; and in the Pacific time zone, use PST8PDT. If your system is set up properly, it will return a display that starts with two lines containing "Sun Mar 11". If, instead, you see a pair of lines with "Sun Apr 1" within them, you'll need to do a manual update. === Static routes === On Redhat, create a file /etc/sysconfig/network-scripts/route-eth0 with the following content. Note: /etc/sysconfig/static-route no longer works.
192.168.7.0/24 via 192.168.1.254
Redhat says it should be this. http://kbase.redhat.com/faq/FAQ_45_9670.shtm
GATEWAY0=192.168.1.1
NETMASK0=255.255.255.0
ADDRESS0=10.10.10.0
GATEWAY1=192.168.1.1
NETMASK1=255.255.255.0
ADDRESS1=20.20.20.2
On FreeBSD, add a static route to network in rc.conf:
static_routes="rsite1"
route_rsite1="-net 192.168.7.0 192.168.1.254 255.255.255.0"
===MTU size=== Experiment with the ping -s option
ping -s 9000 1.2.3.4
===preload=== http://www.techthrob.com/tech/preload.php ===max arguments=== If you run into argument list too long, the following probably won't help you. Pipe your output to xargs.
# getconf ARG_MAX
2097152
# sysctl kern.argmax
kern.argmax=2097152
===find and xargs=== These are the tools that most linux administartors will be familiar with. Here are some interesting options: ""<table class="data" border=1> <tr><td>tool</td><td>option</td><td>meaning</td><td>default</td></tr> <tr><td>xargs </td><td> -n 99</td><td>number of arguments to pass at a time </td><td>na</td></tr> <tr><td>xargs </td><td>-P 99 </td><td>number of processes to spawn </td><td> 1</td></tr> </table>"" ===Capturing mouse / keyboard event under X=== use xev === Create ISO image === mkisofs -l -J -L -r -o output.iso file_list ===Schedule task with at===
atq - list at jobs
at -c <job number> - cat job
at 17:00 friday - schedule job at that time
%%
Plesk
It does not belong to anywhere so I'll just put it here.http://rackerhacker.com
