Mongo DB Cheetsheet

CONSOLE COMMANDS

  help                show all the console commands (same as this section)
  show dbs            show database names
  show collections    show collections in current database
  show users          show users in current database
  show profile        show most recent system.profile entries with time >= 1ms
  use <db name>       set curent database to <db name>
  db.help()           help on DB methods
  db.foo.help()       help on collection methods
  db.foo.find()       list objects in collection foo
  db.foo.find({a:1})  list objects in foo where a == 1
  it                  result of last line evaluated; use to further iterate

DATABASE METHODS

  db.addUser(username, password)
  db.auth(username, password)
  db.cloneDatabase(fromhost)
  db.commandHelp(name) // returns the help for the command
  db.copyDatabase(fromdb, todb, fromhost)
  db.createCollection(name, { size : ..., capped : ..., max : ... } )
  db.currentOp() // displays the current operation in the db
  db.dropDatabase()
  db.eval(func, args) // run code server-side
  db.getCollection(cname) // same as db['cname'] or db.cname
  db.getCollectionNames()
  db.getLastError() // just returns the err msg string
  db.getLastErrorObj() // return full status object
  db.getMongo() // get the server connection object
  db.getMongo().setSlaveOk() // allow this connection to read from the nonmaster member of a replica pair
  db.getName()
  db.getPrevError()
  db.getProfilingLevel()
  db.getReplicationInfo()
  db.getSisterDB(name) // get the db at the same server as this onew
  db.killOp() // kills the current operation in the db
  db.printCollectionStats()
  db.printReplicationInfo()
  db.printSlaveReplicationInfo()
  db.printShardingStatus()
  db.removeUser(username)
  db.repairDatabase()
  db.resetError()
  db.runCommand(cmdObj) // run a database command. if cmdObj is a string, turns it into {cmdObj:1}
  db.setProfilingLevel(level) // 0=off 1=slow 2=all
  db.shutdownServer()
  db.version() // current version of the server

COLLECTION METHODS

  db.foo.count()
  db.foo.dataSize()
  db.foo.distinct( key ) // eg. db.foo.distinct( 'x' )
  db.foo.drop() // drop the collection
  db.foo.dropIndex(name)
  db.foo.dropIndexes()
  db.foo.ensureIndex(keypattern,options) // options should be an object with these possible fields: name, unique, dropDups
  db.foo.find( [query] , [fields]) // first parameter is an optional query filter.
                                   // second parameter is optional set of fields to return.
                                   // e.g. db.foo.find( { x : 77 } , { name : 1 , x : 1 } )
  db.foo.find(...).count()
  db.foo.find(...).limit(n)
  db.foo.find(...).skip(n)
  db.foo.find(...).sort(...)
  db.foo.findOne([query])
  db.foo.getDB() // get DB object associated with collection
  db.foo.getIndexes()
  db.foo.group( { key : ..., initial: ..., reduce : ...[, cond: ...] } )
  db.foo.mapReduce( mapFunction , reduceFunction , <optional params> )
  db.foo.remove(query)
  db.foo.renameCollection( newName ) // renames the collection
  db.foo.save(obj)
  db.foo.stats()
  db.foo.storageSize() // includes free space allocated to this collection
  db.foo.totalIndexSize() // size in bytes of all the indexes
  db.foo.totalSize() // storage allocated for all data and indexes
  db.foo.update(query, object[, upsert_bool, multi_record_bool])
  db.foo.validate() // SLOW
  db.foo.getShardVersion() // only for use with sharding

UTILITIES

  mongodump -d database_name -o /some/directory
  mongorestore -d database_name /some/directory

EXAMPLES

  Inserting Data
    > j = { name: "mongo"};
    {"name" : "mongo"}
    > t = { x : 3 };
    { "x" : 3  }
    > db.things.save(j);
    > db.things.save(t);

  Accessing Data from a Query
    var cursor = db.things.find();
    while (cursor.hasNext()) { print(tojson(cursor.next())); }

  Retrieving Data with Javascript functions
    db.things.find().forEach( function(x) { printjson(x);});

  select * from things where name="mongo"
    db.things.find({name:"mongo"}).forEach(printjson);

  select * from things where x=4
    db.things.find({x:4}).forEach(printjson);

  select j from things where x=4
    db.things.find({x:4}, {j:true}).forEach(printjson);

  order by
    db.things.find().sort({x:1})  // ascending
    db.things.find().sort({x:-1}) // descending

  limit 1
    var mongo = db.things.findOne({name:"mongo"});
    print(tojson(mongo));

  limit(x)
    db.things.find().limit(3);

  regex search
    db.things.find({x : /foo.*/i});

  search for type
    db.things.find({ x : { $type : 16 }});  // finds integer values in this field

  update users set api_token = 'snafu' where _id = "fubar";
    db.users.update( { "_id" : "fubar" }, { $set : { "api_token" : "snafu" } }, false );

  update or insert users set api_token = 'snafu' where _id = "fubar";
    db.users.update( { "_id" : "fubar" }, { $set : { "api_token" : "snafu" } }, true );

  Rename all fields in a collection
    db.users.update( {}, { $rename : {"old_field_name" : "new_field_name"}}, false, true);

Manage multiple Linux Users on Amazon EC2 Instance

Step 0. Login by default user, “ubuntu”:

1	ssh -i my_key.pem ubuntu@111.111.11.111

Step 1. Create a new user, we will call our new user “john”:

1	[ubuntu@ip-11-111-111-111 ~]$ sudo adduser gmsundar

Set password for “gmsundar” by:

1 2	[ubuntu@ip-11-111-111-111 ~]$ sudo su [root@ip-11-111-111-111 ec2-user]$ passwd gmsundar

Add “gmsundar” to sudoer’s list by:

1	[root@ip-11-111-111-111 ec2-user]$ visudo

and add this to the last line:

1	gmsundar   ALL = (ALL)    ALL

Alright! We have our new user created, now you need to generate the key file which will be needed to login, like we have my_key.pem in Step 0.

Now, exit and go back to ubuntu, out of root.

Step 2. Creating the public and private keys:

1	[ubuntu@ip-11-111-111-111 ~]$ su gmsundar

Enter the password you created for “gmsundar” in Step 1.

1 2 3 4 5 6 7

[gmsundar@ip-11-111-111-111 ec2-user]$ cd /home/gmsundar/ [gmsundar@ip-11-111-111-111 ~]$ ssh-keygen -b 1024 -f gmsundar -t dsa [gmsundar@ip-11-111-111-111 ~]$ mkdir .ssh [gmsundar@ip-11-111-111-111 ~]$ chmod 700 .ssh [gmsundar@ip-11-111-111-111 ~]$ cat gmsundar.pub > .ssh/authorized_keys [gmsundar@ip-11-111-111-111 ~]$ chmod 600 .ssh/authorized_keys [gmsundar@ip-11-111-111-111 ~]$ sudo chown gmsundar:ubuntu .ssh

In the above step, gmsundar is the user we created and ubuntu is the default user group.

1	[gmsundar@ip-11-111-111-111 ~]$ sudo chown gmsundar:ec2-user .ssh/authorized_keys

Step 3. Now you just need to download the key called “gmsundar”

1 2	[gmsundar@ip-11-111-111-111 ~]$ sudo cp gmsundar /home/ubuntu/ [gmsundar@ip-11-111-111-111 ~]$ sudo chmod 777 /home/ubuntu/gmsundar

Now come to local machine’s terminal, where you have my_key.pem file and do this:

1	scp -i my_key.pem ubuntu@111.111.11.111:/home/ubuntu/gmsundar gmsundar

The above command will copy the key “gmsundar” to the present working directory on your local machine. Once you have copied the key to your local machine, you should delete “/home/ubuntu/gmsundar”, since it’s a private key.

Now, one your local machine chmod gmsundar to 600.

1	chmod 600 john

Step 4. Time to test your key:

1	ssh -i gmsundar gmsundar@111.111.11.111

So, in this manner, you can setup multiple users to use one EC2 instance!!

On RHEL in FIPS Mode

Went to an excellent talk by Steve Grubb of Red Hat that went over some of the particulars of the security systems in Red Hat Enterprise Linux. This talk really collected together a lot of the information that I had been searching for. I guess it is a fairly niche market that is searching for auditing capabilities, FIPS mode, and the like, so information was fairly thin until his talk. You can find his slides here.

For me the most important information at the moment is the FIPS 140-2 mode for RHEL 5 platforms. I was aware there were efforts to make this happen, you can use the fipscheck program to verify select binary integrity on start up, OpenSSH was being built with a FIPS mode, and so on, but the slide on page 40 gave me the main command to bring this all together.

• mkinitrd –with-fips -f /boot/initrd-$(uname -r).img $(uname -r)
• Add “fips=1” to grub kernel boot line
• Reboot

Now two caveats that I know of so far: in order for fipscheck to work, prelinking must be disabled, otherwise the hashes will change every time prelinking is re-run (which happens nightly). So in order to disable prelinking on a system do the following:

• Edit /etc/sysconfing/prelink and set ‘PRELINKING=no’
• Execute ‘sudo prelink -ua’ to remove relinking, or just wait until the nightly prelinking is run and everything is cleaned up.

As well /boot has to be a separate partition on your system.

There is now a Red Hat Knowledge base article up that describes this process, sadly you have to be logged in now to see Red Hat knowledge base articles.

How to send SMS message in Android

In Android, you can use SmsManager API or device’s Built-in SMS application to send a SMS message. In this tutorial, we show you two basic examples to send SMS message :

1. SmsManager API

   SmsManager smsManager = SmsManager.getDefault();
    smsManager.sendTextMessage("phoneNo", null, "sms message", null, null);

2. Built-in SMS application

   Intent sendIntent = new Intent(Intent.ACTION_VIEW);
    sendIntent.putExtra("sms_body", "default content"); 
    sendIntent.setType("vnd.android-dir/mms-sms");
    startActivity(sendIntent);

Of course, both need SEND_SMS permission.

<uses-permission android:name="android.permission.SEND_SMS" />

P.S This project is developed in Eclipse 3.7, and tested with Samsung Galaxy S2 (Android 2.3.3).

Note
The Built-in SMS application solution is the easiest way, because you let device handle everything for you.

1. SmsManager Example

Android layout file to textboxes (phone no, sms message) and button to send the SMS message.

File : res/layout/main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/linearLayout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >
 
    <TextView
        android:id="@+id/textViewPhoneNo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Enter Phone Number : "
        android:textAppearance="?android:attr/textAppearanceLarge" />
 
    <EditText
        android:id="@+id/editTextPhoneNo"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:phoneNumber="true" >
    </EditText>
 
    <TextView
        android:id="@+id/textViewSMS"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Enter SMS Message : "
        android:textAppearance="?android:attr/textAppearanceLarge" />
 
    <EditText
        android:id="@+id/editTextSMS"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:inputType="textMultiLine"
        android:lines="5"
        android:gravity="top" />
 
    <Button
        android:id="@+id/buttonSend"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="Send" />
 
</LinearLayout>

File : SendSMSActivity.java – Activity to send SMS via SmsManager.

package com.mkyong.android;
 
import android.app.Activity;
import android.os.Bundle;
import android.telephony.SmsManager;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
 
public class SendSMSActivity extends Activity {
 
 Button buttonSend;
 EditText textPhoneNo;
 EditText textSMS;
 
 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);
 
  buttonSend = (Button) findViewById(R.id.buttonSend);
  textPhoneNo = (EditText) findViewById(R.id.editTextPhoneNo);
  textSMS = (EditText) findViewById(R.id.editTextSMS);
 
  buttonSend.setOnClickListener(new OnClickListener() {
 
   @Override
   public void onClick(View v) {
 
     String phoneNo = textPhoneNo.getText().toString();
     String sms = textSMS.getText().toString();
 
     try {
    SmsManager smsManager = SmsManager.getDefault();
    smsManager.sendTextMessage(phoneNo, null, sms, null, null);
    Toast.makeText(getApplicationContext(), "SMS Sent!",
       Toast.LENGTH_LONG).show();
     } catch (Exception e) {
    Toast.makeText(getApplicationContext(),
     "SMS faild, please try again later!",
     Toast.LENGTH_LONG).show();
    e.printStackTrace();
     }
 
   }
  });
 }
}

File : AndroidManifest.xml , need SEND_SMS permission.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.mkyong.android"
    android:versionCode="1"
    android:versionName="1.0" >
 
    <uses-sdk android:minSdkVersion="10" />
 
    <uses-permission android:name="android.permission.SEND_SMS" />
 
    <application
        android:debuggable="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:label="@string/app_name"
            android:name=".SendSMSActivity" >
            <intent-filter >
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>
 
</manifest>

See demo :

'via Blog this'

How to create a yum repository on RHEL/CentOS 5.x with CD/DVD or ISO images « Linux T&T

We need several packages to create yum repository, you can install them from CD/DVD disks or ISO images.

# yum install createrepo wget

# cd /mnt # createrepo .
Mount your CD/DVD or ISO images
DVD Disk or DVD ISO image

* If you have DVD disk, please mount dvd-rom first, and then create yum repository:

# mkdir /mnt/dvd/
# mount /dev/cdrom /mnt/dvd/

* If you use DVD iso, please copy it to the system, and then create yum repository:

# mkdir /mnt/dvd/
# mount -o loop /root/rhel5.1-dvd.iso /mnt/dvd

CD images

If you have multiple CD image files, you should mount all iso images and then create yum repository.

* Mount all iso images:

# mkdir -p /mnt/{1,2,3,4,5}
# mount -o loop rhel5.1-disc1.iso /mnt/1
# mount -o loop rhel5.1-disc2.iso /mnt/2
# mount -o loop rhel5.1-disc3.iso /mnt/3
# mount -o loop rhel5.1-disc4.iso /mnt/4
# mount -o loop rhel5.1-disc5.iso /mnt/5

Install necessary package

* Find and install ‘createrepo’ package in /mnt directory:

# find /mnt -iname ‘createrepo*’
/mnt/dvd/Server/createrepo-0.4.11-3.el5.noarch.rpm

# rpm -ivh /mnt/dvd/Server/createrepo-0.4.11-3.el5.noarch.rpm

Create yum repository
Create metadata

* Create yum repository:

# cd /mnt/
# createrepo .

Define yum repository

Create yum repository define file /etc/yum.repos.d/dvdiso.repo:

[MailRepo]
name=MailRepo
baseurl=file:///mnt/
enabled=1
gpgcheck=0

Test it

# yum clean all
# yum list

If ‘yum list’ list all packages in DVD/CD disks or ISO images, it works. 

Share the repo via NFS:

Copy the yum repository define file /etc/yum.repos.d/dvdiso.repo on the second machine:

scp server1:/etc/yum.repos.d/dvd.repo /etc/yum.repos.d/

[root@server1 ~]# echo "/mnt 192.168.1.0/24(ro,async)' >>/etc/exports
[root@server1 ~]# exportfs -r