huyanhvn

Latency Comparison Numbers
--------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

huyanhvn

# Create strong LUKS key
openssl genrsa -out /root/luks.key 4096
chmod 400 /root/luks.key

# Fill random data to the device
shred -v --iterations=1 /dev/xvdb 

# Format device
echo "YES" | cryptsetup luksFormat /dev/xvdb --key-file /root/luks.key 

huyanhvn

<?xml version="1.0" encoding="UTF-8"?>
<jmeterTestPlan version="1.2" properties="2.9" jmeter="3.0 r1743807">
  <hashTree>
    <TestPlan guiclass="TestPlanGui" testclass="TestPlan" testname="cic-proxy-latency-test" enabled="true">
      <stringProp name="TestPlan.comments"></stringProp>
      <boolProp name="TestPlan.functional_mode">false</boolProp>
      <boolProp name="TestPlan.serialize_threadgroups">false</boolProp>
      <elementProp name="TestPlan.user_defined_variables" elementType="Arguments" guiclass="ArgumentsPanel" testclass="Arguments" testname="User Defined Variables" enabled="true">
        <collectionProp name="Arguments.arguments"/>
      </elementProp>

huyanhvn

### SIZE OF S3 BUCKET
aws s3api list-objects --bucket BUCKETNAME --output json --query "[sum(Contents[].Size), length(Contents[])]”

### BUCKET POLICY FOR ENCRYPTED BUCKET
{
	"Version": "2012-10-17",
	"Id": "PutObjPolicy",
	"Statement": [
		{
			"Sid": "DenyUnEncryptedObjectUploads",

huyanhvn

### knife.rb:
knife[:vault_mode] = "client"
data_bag_path		"/Users/hnguyen/data_bags"

### Creating a Vault

Vault creation is very similar to data bag creation. Specify a Vault name, and Item name inside of that vault as well as the default JSON data to go into the vault. You can optionally specify a node search, and/or a list of Chef Server users who should have access to the vault.

knife vault create [vault] [item] '{}'
knife vault create [vault] [item] '{}' -S 'search' -A 'user1,user2'

huyanhvn

### USING DBM MAP
RewriteEngine On
RewriteMap some_map dbm=sdbm:/var/www/some_map.map

RewriteCond %{QUERY_STRING} some[iI]d=(\d+)
RewriteCond ${some_map:%1} !=""
RewriteRule ^/some/thing/view\.asp$ /some/thing/else/${some_map:%1}? [P]

huyanhvn

# tcpdump -i eth0 -A -s65535 port 8080
intecepts all packets goving over port 8080 on eth0  network interface.
-s means size of each packet. so it dumps first 65k of the packet. default is much short and will truncate long http responses.
-A means show packets as ascii on screen
-w filename

for non plain text protocol (e.g. LDAP), write to file and use wireshark.

https://danielmiessler.com/study/tcpdump/

huyanhvn

### berks ignore ssl
$ cat ~/.berkshelf/config.json 
{
	"ssl": {
		"verify": false
	}
}

### berks Faraday SSL error
export SSL_CERT_FILE=/etc/openssl/cert.pem

huyanhvn

[	
	{ "keys": ["ctrl+x"], "command": "cut" },
	{ "keys": ["ctrl+c"], "command": "copy" },
	{ "keys": ["ctrl+v"], "command": "paste" },
	{ "keys": ["ctrl+shift+v"], "command": "paste_and_indent" },
	{ "keys": ["ctrl+s"], "command": "save" },
	{ "keys": ["ctrl+z"], "command": "undo" },
	{ "keys": ["ctrl+shift+z"], "command": "redo" },
	{ "keys": ["ctrl+y"], "command": "redo_or_repeat" },
	{ "keys": ["ctrl+u"], "command": "soft_undo" },

huyanhvn

### Kill process and all its children
kill -- -$(ps -o pgid= $PID | grep -o '[0-9]*')   (signal TERM)
kill -9 -$(ps -o pgid= $PID | grep -o '[0-9]*')   (signal KILL)

### FIND TOP MEMORY USERS
ps aux | awk '{print $2, $4, $11}' | sort -k2rn | head -n 10

### SSH menu
~C