Author name: Tim van Kooten Niekerk

About me / Hey I’m Tim. I work as a systems integration specialist for a large educational institution in the Netherlands. A part of my free time I spend making and creating music.

Netwerk IPv4 Subnetting

/ Other / 
max aantal subnetten: 2^n (-2) // n = aantal masked bits *subnet* mask
max aantal hosts in subnet = 2^n -2 // n = ongemaskeerde bits

next multiple of 8 = next mult. of 8 greater or eq. to CIDR netmask not.
interesting value = (next multiple of 8) / 8

incremental value = 2^ (next multiple of 8 - CIDR netmask notation)

bijv. 192.168.10.50/27:
incremental value = 2^(32-27) = 2^5 = 32
interesting value = 32 / 8 = 4
netwerkadressen: 192.168.10.0, 192.168.10.32, 192.168.10.64, enz.
broadcastadressen: 192.168.10.31, 192.168.10.63, 192.168.10.95, enz.
netwerk 192.168.10.32
broadcast 192.168.1.63 (192.168.10.(64-1))

bijv. 10.6.127.255/14:
incremental value: 2^(16-14) = 2^2 = 4
interesting value = 16 / 8 = 2
netwerkadres: 10.4.0.0
broadcast: 10.7.255.255 ( 10.(8.0.0-1)

 

OpenSSL Certificate Commands & Examples

/ GNU/Linux /

Below script creates al selfgesigned certificate from a private key and removes the password from the key so you can you can use the key-pair in Apache.

# Create Key and Certificate Signing Request (option -des3 creates a triple des encrypted key)...
openssl genrsa -des3 -out server.key 4096
openssl req -new -key server.key -out server.csr

# Remove password from key and sign certificate with key... 
cp server.key server.key.org
openssl rsa -in server.key.org -out server.key
openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt

# Re-encrypt private key...
openssl rsa -des -in server.key.org -out server.key
openssl rsa -aes256 -in server.key.org -out server.key

For ease you can add all key and signing options to a config file. This way you can also add a subjectAlternate to the certificate.

>openssl req -new -config server.cnf -key server.key -out server.csr

# server.cnf #
[ req ]
default_bits = 4096
prompt = no
encrypt_key = no
distinguished_name = dn
req_extensions = req_ext

[ dn ]
C = NL
O = Totietoot
CN = examplefqdn.totietoot.nl

[ req_ext ]
subjectAltName = DNS:examplefqdn.totietoot.nl, DNS:examplealtname.totietoot.nl

Use the following command to convert the key-pair to pkcs12 format.

openssl pkcs12 -export -in server.crt -inkey server.key [-name tomcat] -out server.p12 -CAfile chain.pem -caname root -chain

Convert pkcs12 file to java keystore (jks):

keytool -importkeystore -deststorepass <password> -destkeypass <password> -destkeystore server.jks -srckeystore server.p12 -srcstoretype PKCS12 -srcstorepass <password> -alias <name>

Decode a certificate request or a x509 certificate:

openssl req -in server.csr -noout -text
openssl x509 -in server.crt -noout -text

Convert a PFX file to PEM-format (single file)…

openssl pkcs12 -in server.pfx -out key-n-certs.pem -nodes

Check certificate and connection using openssl…

openssl s_client -showcerts -connect f.q.d.n:1234
openssl s_client -starttls smtp -showcerts -connect f.q.d.n:25 -servername f.q.d.n

Convert certificate (PEM) to public key…

openssl x509 -inform pem -in certificate.cer -pubkey -noout > pubkey.pem

Add a (CA) certificate to the JAVA CACerts certificate truststore…

"C:\Java\jdk1.8.0_121\bin\keytool" -import -alias ADCERT-CA-1 -keystore "C:\Java\jdk1.8.0_121\jre\lib\security\cacerts" -trustcacerts -file ADCERT-CA-1.cer

Open-iSCSI Commands

/ GNU/Linux /

Discover, Login & Mount Drives

Display all iSCSI targets on give ip-address.

iscsiadm --mode discovery --type sendtargets --portal 192.168.1.250

Connect to a give target.  

iscsiadm --mode node --targetname iqn.1994-04.org.netbsd.iscsi-target:target0 --portal 192.168.1.250:3260 --login

Close connection to a iSCSI target.

iscsiadm --mode node --targetname iqn.1994-04.org.netbsd.iscsi-target:target0 --portal 192.168.1.250:3260 --logout

Mount a iSCSI disk with lable ISCSI-0 on directory ‘/mnt/iscsi-0’.

mount /dev/disk/by-label/ISCSI-0 /mnt/iscsi-0

 

Node records

Display node records.

iscsiadm --mode node
iscsiadm --mode node --targetname iqn.1994-04.org.netbsd.iscsi-target:target0 --portal 192.168.1.250:3260

 

MySQL basic queries en commands

/ MySQL Server /

Connect to a MySQL instance (commandline)

 Connect to A MySQL instance using named pipe sessies.

>mysql -u root -p

MySQL commands

Some examples to show database objects.

SHOW DATABASES;
SHOW TABLES;
SHOW COLUMNS FROM naam_van_table;
SHOW STATUS;
SHOW FULL PROCESSLIST;
SHOW PROCEDURE STATUS;

View a stored procedure.

SELECT ROUTINE_DEFINITION FROM information_schema.ROUTINES
WHERE SPECIFIC_NAME = '<procedure_name>'
AND ROUTINE_SCHEMA = '<database_name>;

Create, remove and select

CREATE DATABASE naam_van_database;
DROP DATABASE naam_van_database;
USE naam_van_database;

Create and alter tables

CREATE and ALTER table syntax.

CREATE TABLE naam_van_table (column0_id int(10) unsigned NOT NULL primary
key auto_increment,
column1 varchar(75) NOT NULL default '',
column2 varchar(75) NOT NULL default '',
column3 varchar(40) NOT NULL default '',
column4 int(10) unsigned default NULL) engine = InnoDB;
ALTER TABLE naam_van_table ADD COLUMN (column5 bool default 0);
ALTER TABLE naam_van_table ADD COLUMN column6 int unsigned AFTER column2;
ALTER TABLE naam_van_table DROP COLUMN column2;
ALTER TABLE naam_van_table ADD INDEX naam_van_index (naam_van_column);

Queries (Selectie, Insert and Update)

SELECT * FROM naam_van_table WHERE naam_van_column='text';
SELECT column1, column2 FROM naam_van_table WHERE column3='text';
SELECT COUNT(*) FROM naam_van_table;
INSERT INTO naam_van_table VALUES (1, 'Jan', 'Jansen', MD5('zaq123'), 'Docent');
INSERT INTO naam_van_table (voornaam, achternaam, pswd) VALUES
('Jan', 'Jansen', MD5('zaq123')),
('Piet', 'Pieterse', MD5('qaz321'));
UPDATE naam_van_table SET naam_van_column1 = 'X' WHERE naam_van_column2='Y';

Create users and set privileges

CREATE USER 'username'@'localhost' IDENTIFIED BY 'password';

GRANT Select ON databasename.tablename TO 'username'@'localhost';
GRANT ALL PRIVILEGES ON databasename.* TO 'username'@'%.domain.tld'; 

ALTER USER 'username'@'localhost' IDENTIFIED BY 'newpassword';
FLUSH PRIVILEGES;

Set file privileges

Add file_priv to account to make it possible to use a bulk import procedure.

USE MYSQL;
UPDATE user SET file_priv = 'Y' WHERE user='username';
FLUSH PRIVILEGES;