Mounting a Samba Share From Linux Client to Linux Samba Server

Posted on by rchapin

In order to be able to access a Samba share on a remote client as a mounted file system execute the following command, as root on the client:

mount -t cifs -o user=<user-on-samba-share>,uid=<uid-on-local-macheine>,gid=<gid-on-local-machine>,rw,workgroup=<your-workgroup> //ip/share /mnt/mount-point-dir

You will be prompted for the password for the user defined on the Samba server.

If you are able to authenticate, and then get the following error:

ls: reading directory .: Permission denied

Check the SELinux context type of the directory on the samba share.  It should be samba_share_t

Mocking Static Methods That Return void in Java

Posted on by rchapin

This is one of those things that I tend to do on a regular basis . . . but unfortunately don’t remember the details each time, so I am adding it for future reference.

Often, developers will want to mock static methods that return void.  The Mockito and PowerMockito frameworks provide for this, but the syntax isn’t immediately obvious.

Following is an example.

public class SomeClass {
    public static void doSomething(String arg1, int arg2) {
        // Method that does something...
    }
}
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PowerMockIgnore;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

/*
 * The RunWith and PrepareForTest annotations are following annotations are
 * necessary to mock the static methods in the SomeClass class. The RunWith
 * enables the class to be run via PowerMock, and the PrepareForTest is an array
 * of the classes with static members that we want to mock.
 *
 * The PowerMockIgnore annotation tells PowerMock to defer the loading of
 * classes with the names supplied to the system classloader.  This will vary
 * depending on the dependency tree that you are using/testing.  It is also
 * not necessary, but here for example purposes.
 */
@RunWith(PowerMockRunner.class)
@PowerMockIgnore({
    "javax.management.*",
    "javax.net.ssl.*",
    "org.apache.log4j.*"
})
@PrepareForTest({ SomeClass.class })
public class SomeTestClass {
@Test
    public void shouldDoSomethingExpected() throws Exception {
         // Set up the SomeClass's static members for mocking
        PowerMockito.mockStatic(SomeClass.class);

        // Configure the mock for the method in question.
        // The following syntax is what is key here
        PowerMockito.doNothing()
            .when(
                SomeClass.class,
                "doSomething",
                Mockito.anyString(),
                Mockito.anyInt());
    }
}

   

       

       

Solution for Executing Native Process from Java that Requires sudo

Posted on by rchapin

If you are building a Java program that requires the ability to execute native commands on the machine which require sudo it requires some additional considerations other than just writing the Java code.

The problem is that sudo, by default, requires a tty for executing sudo such that a password can entered.  Even if you configure sudoers to grant NOPASSWD access to a specific command you will still get the following error

sudo: sorry, you must have a tty to run sudo

In my case, I was writing a set of integration tests in Java that needed to be able to start and stop a service to run a test.

I settled on adding an additional sudoers config file in /etc/sudoers.d.  This ended up be the cleanest and most encapsulated change that did not then require any special considerations in the Java code.

The change simply involved adding a file with the following contents to /etc/sudoers.d which indicates that running sudo for the rchapin user does NOT require a tty and then grants access to the specific commands.

Defaults:rchapin !requiretty
rchapin ALL=(root) NOPASSWD: /bin/systemctl stop rabbitmq-server.service
rchapin ALL=(root) NOPASSWD: /bin/systemctl start rabbitmq-server.service

[SOLVED] Ambari There are no DataNodes to do rolling restarts when there are DataNodes that do need a restart

Posted on by rchapin

When maintaining a Hadoop cluster, you will need to restart various service from time-to-time when/if you update Hadoop configurations.

I ran into a problem today with Ambari where I wanted to do a rollling restart of all of my DataNodes, but when I clicked on the “Restart DataNodes” entry in the “Restart” drop down the dialog indicated “There are no DataNodes to do rolling restarts”.

This was clearly incorrect.

It did not take me too long to figure out that I had already put HDFS into Maintenance Mode.  As a result, Ambari does not see that there are any DataNodes that need to be restarted.

Taking HDFS out of Maintenance mode allowed me to then execute a rolling restart through Ambari.

[SOLVED] Unable to Connect to ambari-metrics-collector Issues

Posted on by rchapin

I was having some issues with the ambari-metrics family of services on a ‘pseudo-distributed’ cluster that I have installed on my workstation.

The symptoms were:

1.  Ambari indicated the following CRITICAL errors in the Ambari Dashboard under the Ambari Metrics section

Connection failed: [Errno 111] Connection refused to rchapin-wrkstn:6188

2.  After attempting to restart the ambari-metrics-collector via either the Ambari Dashboard or through the commandline (# ambari-metrics-collector [stop|start]) you see the following (similar) messages in the ambari-metrics-collector.log

2016-09-02 12:15:37,505 INFO org.apache.zookeeper.ZooKeeper: Client environment:java.library.path=/usr/lib/ams-hbase/lib/hadoop-native -XX:+UseConcMarkSweepGC -verbose:gc -XX:+PrintGCDetails -XX:+PrintGCDateStam
ps -Xloggc:/var/log/ambari-metrics-collector/collector-gc.log-201609021215
2016-09-02 12:15:37,505 INFO org.apache.zookeeper.ZooKeeper: Client environment:java.io.tmpdir=/tmp
2016-09-02 12:15:37,505 INFO org.apache.zookeeper.ZooKeeper: Client environment:java.compiler=<NA>
2016-09-02 12:15:37,505 INFO org.apache.zookeeper.ZooKeeper: Client environment:os.name=Linux
2016-09-02 12:15:37,505 INFO org.apache.zookeeper.ZooKeeper: Client environment:os.arch=amd64
2016-09-02 12:15:37,505 INFO org.apache.zookeeper.ZooKeeper: Client environment:os.version=3.10.0-327.10.1.el7.x86_64
2016-09-02 12:15:37,505 INFO org.apache.zookeeper.ZooKeeper: Client environment:user.name=ams
2016-09-02 12:15:37,505 INFO org.apache.zookeeper.ZooKeeper: Client environment:user.home=/home/ams
2016-09-02 12:15:37,505 INFO org.apache.zookeeper.ZooKeeper: Client environment:user.dir=/home/ams
2016-09-02 12:15:37,506 INFO org.apache.zookeeper.ZooKeeper: Initiating client connection, connectString=rchapin-wrkstn:2181 sessionTimeout=120000 watcher=hconnection-0x5524cca10x0, quorum=rchapin-wrkstn:2181, b
aseZNode=/ams-hbase-unsecure
2016-09-02 12:15:37,523 INFO org.apache.zookeeper.ClientCnxn: Opening socket connection to server rchapin-wrkstn/172.19.64.2:2181. Will not attempt to authenticate using SASL (unknown error)
2016-09-02 12:15:37,531 INFO org.apache.zookeeper.ClientCnxn: Socket connection established to rchapin-wrkstn/172.19.64.2:2181, initiating session
2016-09-02 12:15:37,536 INFO org.apache.zookeeper.ClientCnxn: Session establishment complete on server rchapin-wrkstn/172.19.64.2:2181, sessionid = 0x155eefbab613617, negotiated timeout = 40000
2016-09-02 12:15:37,582 WARN org.apache.hadoop.hbase.io.util.HeapMemorySizeUtil: hbase.regionserver.global.memstore.upperLimit is deprecated by hbase.regionserver.global.memstore.size
2016-09-02 12:15:38,044 WARN org.apache.hadoop.hdfs.shortcircuit.DomainSocketFactory: The short-circuit local reads feature cannot be used because libhadoop cannot be loaded.
2016-09-02 12:15:38,089 INFO org.apache.phoenix.metrics.Metrics: Initializing metrics system: phoenix
2016-09-02 12:15:38,112 WARN org.apache.hadoop.metrics2.impl.MetricsConfig: Cannot locate configuration: tried hadoop-metrics2-phoenix.properties,hadoop-metrics2.properties
2016-09-02 12:15:38,167 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Scheduled snapshot period at 10 second(s).
2016-09-02 12:15:38,168 INFO org.apache.hadoop.metrics2.impl.MetricsSystemImpl: phoenix metrics system started
2016-09-02 12:15:38,362 WARN org.apache.hadoop.hbase.io.util.HeapMemorySizeUtil: hbase.regionserver.global.memstore.upperLimit is deprecated by hbase.regionserver.global.memstore.size
2016-09-02 12:15:38,494 WARN org.apache.hadoop.hbase.io.util.HeapMemorySizeUtil: hbase.regionserver.global.memstore.upperLimit is deprecated by hbase.regionserver.global.memstore.size
2016-09-02 12:15:38,627 INFO org.apache.hadoop.hbase.zookeeper.RecoverableZooKeeper: Process identifier=hconnection-0x48d7ad8b connecting to ZooKeeper ensemble=rchapin-wrkstn:2181
2016-09-02 12:15:38,627 INFO org.apache.zookeeper.ZooKeeper: Initiating client connection, connectString=rchapin-wrkstn:2181 sessionTimeout=120000 watcher=hconnection-0x48d7ad8b0x0, quorum=rchapin-wrkstn:2181, b
aseZNode=/ams-hbase-unsecure
2016-09-02 12:15:38,629 INFO org.apache.zookeeper.ClientCnxn: Opening socket connection to server rchapin-wrkstn/172.19.64.2:2181. Will not attempt to authenticate using SASL (unknown error)
2016-09-02 12:15:38,629 INFO org.apache.zookeeper.ClientCnxn: Socket connection established to rchapin-wrkstn/172.19.64.2:2181, initiating session
2016-09-02 12:15:38,633 INFO org.apache.zookeeper.ClientCnxn: Session establishment complete on server rchapin-wrkstn/172.19.64.2:2181, sessionid = 0x155eefbab613618, negotiated timeout = 40000
2016-09-02 12:16:27,001 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=10, retries=35, started=48362 ms ago, cancelled=false, msg=
2016-09-02 12:16:47,033 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=11, retries=35, started=68394 ms ago, cancelled=false, msg=
2016-09-02 12:17:07,148 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=12, retries=35, started=88509 ms ago, cancelled=false, msg=
2016-09-02 12:17:27,257 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=13, retries=35, started=108618 ms ago, cancelled=false, msg=
2016-09-02 12:17:47,276 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=14, retries=35, started=128637 ms ago, cancelled=false, msg=
2016-09-02 12:18:07,333 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=15, retries=35, started=148694 ms ago, cancelled=false, msg=
2016-09-02 12:18:27,397 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=16, retries=35, started=168758 ms ago, cancelled=false, msg=
2016-09-02 12:18:47,410 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=17, retries=35, started=188771 ms ago, cancelled=false, msg=
2016-09-02 12:19:07,555 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=18, retries=35, started=208916 ms ago, cancelled=false, msg=
2016-09-02 12:19:27,732 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=19, retries=35, started=229093 ms ago, cancelled=false, msg=
2016-09-02 12:19:47,923 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=20, retries=35, started=249284 ms ago, cancelled=false, msg=
2016-09-02 12:20:07,950 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=21, retries=35, started=269311 ms ago, cancelled=false, msg=
2016-09-02 12:20:28,051 INFO org.apache.hadoop.hbase.client.RpcRetryingCaller: Call exception, tries=22, retries=35, started=289412 ms ago, cancelled=false, msg=
2016-09-02 12:20:48,230 WARN org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation: Checking master connection
com.google.protobuf.ServiceException: org.apache.hadoop.hbase.exceptions.ConnectionClosingException: Call to rchapin-wrkstn/172.19.64.2:61300 failed on local exception: org.apache.hadoop.hbase.exceptions.Connect
ionClosingException: Connection to rchapin-wrkstn/172.19.64.2:61300 is closing. Call id=46, waitTime=1
        at org.apache.hadoop.hbase.ipc.AbstractRpcClient.callBlockingMethod(AbstractRpcClient.java:223)
        at org.apache.hadoop.hbase.ipc.AbstractRpcClient$BlockingRpcChannelImplementation.callBlockingMethod(AbstractRpcClient.java:287)
        at org.apache.hadoop.hbase.protobuf.generated.MasterProtos$MasterService$BlockingStub.isMasterRunning(MasterProtos.java:55824)
        at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation$MasterServiceState.isMasterRunning(ConnectionManager.java:1444)
        at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation.isKeepAliveMasterConnectedAndRunning(ConnectionManager.java:2085)
        at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation.getKeepAliveMasterService(ConnectionManager.java:1708)
        at org.apache.hadoop.hbase.client.MasterCallable.prepare(MasterCallable.java:38)
        at org.apache.hadoop.hbase.client.RpcRetryingCaller.callWithRetries(RpcRetryingCaller.java:124)
        at org.apache.hadoop.hbase.client.HBaseAdmin.executeCallable(HBaseAdmin.java:4082)
        at org.apache.hadoop.hbase.client.HBaseAdmin.getTableDescriptor(HBaseAdmin.java:527)
        at org.apache.hadoop.hbase.client.HBaseAdmin.getTableDescriptor(HBaseAdmin.java:549)
        at org.apache.phoenix.query.ConnectionQueryServicesImpl.ensureTableCreated(ConnectionQueryServicesImpl.java:810)

3.  You will see WARNings similar to the following in the hbase-ams-regionserver-<hostname>.log file

2016-09-02 12:52:56,589 INFO  [LruBlockCacheStatsExecutor] hfile.LruBlockCache: totalSize=236.59 KB, freeSize=222.74 MB, max=222.98 MB, blockCount=1, accesses=4, hits=3, hitRatio=75.00%, , cachingAccesses=4, cac
hingHits=3, cachingHitsRatio=75.00%, evictions=119, evicted=0, evictedPerRun=0.0
2016-09-02 12:53:52,091 WARN  [timeline] timeline.HadoopTimelineMetricsSink: Unable to send metrics to collector by address:http://rchapin-wrkstn:6188/ws/v1/timeline/metrics
2016-09-02 12:53:52,092 WARN  [timeline] timeline.HadoopTimelineMetricsSink: Unable to send metrics to collector by address:http://rchapin-wrkstn:6188/ws/v1/timeline/metrics
2016-09-02 12:53:52,094 WARN  [timeline] timeline.HadoopTimelineMetricsSink: Unable to send metrics to collector by address:http://rchapin-wrkstn:6188/ws/v1/timeline/metrics
2016-09-02 12:53:52,096 WARN  [timeline] timeline.HadoopTimelineMetricsSink: Unable to send metrics to collector by address:http://rchapin-wrkstn:6188/ws/v1/timeline/metrics
2016-09-02 12:53:52,097 WARN  [timeline] timeline.HadoopTimelineMetricsSink: Unable to send metrics to collector by address:http://rchapin-wrkstn:6188/ws/v1/timeline/metrics
2016-09-02 12:54:52,091 WARN  [timeline] timeline.HadoopTimelineMetricsSink: Unable to send metrics to collector by address:http://rchapin-wrkstn:6188/ws/v1/timeline/metrics
2016-09-02 12:55:52,092 WARN  [timeline] timeline.HadoopTimelineMetricsSink: Unable to send metrics to collector by address:http://rchapin-wrkstn:6188/ws/v1/timeline/metrics
2016-09-02 12:55:52,093 WARN  [timeline] timeline.HadoopTimelineMetricsSink: Unable to send metrics to collector by address:http://rchapin-wrkstn:6188/ws/v1/timeline/metrics

It turned out that the ambari-metrics hbase instance had gotten into an unstable state and that what I needed to do was delete all of the metrics HBase data and restart all of the services.

Making that happen was not as straight-forward as you might imagine.

1. Shutdown all of the AMS (Ambari Metrics System) components.  Do so in the following order:

1. In the Ambari Dashboard, go to the ‘Ambari Metrics’ section and under the ‘Service Actions’ dropdown click ‘Stop’.  If you want, you can click the checkbox to turn on Maintenance Mode to suppress alerts.

2. After the background operation has completed, on the ambari host where you are having issues confirm that all of the AMS components have stopped:

# ambari-metrics-monitor status
psutil build directory is not empty, continuing...
ambari-metrics-monitor currently not running
Usage: /usr/sbin/ambari-metrics-monitor {start|stop|restart|status}

# ambari-metrics-collector status
AMS is running as process 1062.

If either of the processes still report as running issue a stop command.  In my case, I did as follows

# ambari-metrics-collector stop
WARNING: ambari-metrics-collector did not stop gracefully after 5 seconds: Trying to kill with kill -9
ERROR: Unable to kill 1062
Stopping HBase master
no master to stop because no pid file /var/run/ambari-metrics-collector//hbase-root-master.pid

I then confirmed that pid 1062 was indeed dead

# ps -ef | fgrep 1062

2. Delete the AMS HBase data

In the Ambari Dashboard, under the Ambari Metrics section do a search for the hbase.rootdir configuration value.

In my case, I have AMS configured to write to HDFS so the value of this config was: hdfs://rchapin-wrkstn:8020/user/ams/hbase

Then search for the the hbase.tmp.dir configuration value.

In my case, the setting was: /var/lib/ambari-metrics-collector/hbase-tmp

If your hbase.rootdir points to HDFS delete all of the data as follows (as the hdfs user)

[hdfs@rchapin-wrkstn ~]$ hdfs dfs -rm -r -skipTrash /user/ams/hbase/*

If it is on your local file system, simply rm -rf that data, leaving the parent directory

Delete the data in the hbase.tmp.dir (as the root user)

[root@rchapin-wrkstn ~]# rm -rf /var/lib/ambari-metrics-collector/hbase-tmp/*

3. Now restart the AMS services

First, via the Ambari Dashboard, go to the ‘Ambari Metrics’ section and under the ‘Service Actions’ dropdown click ‘Start’.  If you want, you can click the checkbox to turn off Maintenance Mode if you set it when stopping the services.

Then confirm that both the ambari-metrics-monitor and ambari-metrics-collector services have started

[root@rchapin-wrkstn ~]# ambari-metrics-collector status
AMS is running as process 12229.

[root@rchapin-wrkstn ~]# ambari-metrics-monitor status
psutil build directory is not empty, continuing...
Found ambari-metrics-monitor PID: 12916
ambari-metrics-monitor running.
Monitor PID at: /var/run/ambari-metrics-monitor/ambari-metrics-monitor.pid
Monitor out at: /var/log/ambari-metrics-monitor/ambari-metrics-monitor.out

If you see errors in the ambari-metrics-collector.log similar to the following it means that there was a problem re-creating the HBase tables for the metrics-collector and that the AMS HBase tables are missing:

2016-09-02 13:35:36,200 WARN org.apache.hadoop.yarn.server.applicationhistoryservice.metrics.timeline.query.DefaultPhoenixDataSource: Unable to connect to HBase store using Phoenix.
org.apache.phoenix.exception.PhoenixIOException: SYSTEM.CATALOG
        at org.apache.phoenix.util.ServerUtil.parseServerException(ServerUtil.java:108)
        at org.apache.phoenix.query.ConnectionQueryServicesImpl.metaDataCoprocessorExec(ConnectionQueryServicesImpl.java:1039)
        at org.apache.phoenix.query.ConnectionQueryServicesImpl.metaDataCoprocessorExec(ConnectionQueryServicesImpl.java:1002)
        at org.apache.phoenix.query.ConnectionQueryServicesImpl.createTable(ConnectionQueryServicesImpl.java:1208)
        at org.apache.phoenix.query.DelegateConnectionQueryServices.createTable(DelegateConnectionQueryServices.java:112)
        at org.apache.phoenix.schema.MetaDataClient.createTableInternal(MetaDataClient.java:1974)
....
Caused by: org.apache.hadoop.hbase.TableNotFoundException: SYSTEM.CATALOG
        at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation.locateRegionInMeta(ConnectionManager.java:1264)
        at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation.locateRegion(ConnectionManager.java:1162)
        at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation.locateRegion(ConnectionManager.java:1146)
        at org.apache.hadoop.hbase.client.ConnectionManager$HConnectionImplementation.locateRegion(ConnectionManager.java:1103)

To fix, delete the node in zookeeper, and restart the AMS services

Check the current value of the Ambari Metrics config: zookeeper.znode.parent.  In my case the value was: /ams-hbase-unsecure

Stop all of the AMS services as described above.

Then, using the zookeeper cli connect to your zookeeper cluster and delete the zookeeper node

1. Start up the zookeeper client

# /usr/hdp/current/zookeeper-client/bin/zkCli.sh

2. Connect to the zookeeper cluster, and list the root nodes for the cluster

[zk: localhost:2181(CONNECTED) 1] connect 127.0.0.1:2181
[zk: 127.0.0.1:2181(CONNECTED) 2] ls /
[hiveserver2, zookeeper, hbase-unsecure, ams-hbase-unsecure, rmstore]

3. Delete the ams-hbase-unsecure node

[zk: 127.0.0.1:2181(CONNECTED) 3] rmr /ams-hbase-unsecure

    4. Restart the AMS services as described above and then confirm that the ams-hbase-unsecure node was recreated in zookeeper.

[zk: 127.0.0.1:2181(CONNECTED) 4] ls /
[hiveserver2, zookeeper, hbase-unsecure, ams-hbase-unsecure, rmstore]

    

Dynamically Instantiating Classes in Python

Posted on by rchapin

A common design pattern is to define a class or list of classeses in configuration such that at runtime the classes can be dynamically instantiated.

I’ve done this before in many other languages and had need to do so today in Python (2.7.11)

It seems as though the clean way to do so is by using the Pyton importlib module.  By using it, it enables you to cleanly dynamically import sub modules

Following is an example:

import importlib

klass_1_module = 'some.module.name'
klass_1_classname = 'KlassNameOne'

klass_2_module = 'klass2module'
klass_2_classname = 'KlassNameOne'

Klass1 = getattr(importlib.import_module(klass_1_module), klass_1_classname)
klass1_instance = Klass1()

Klass2 = getattr(importlib.import_module(klass_2_module), klass_2_classname)
klass2_instance = Klass1('some_arg')

Java PowerMock Could not reconfigure JMX java.lang.LinkageError Solution

Posted on by rchapin

If you are using Mockito and PowerMock to build mocks for your Java tests and you run into the following error:

2016-05-05 17:31:20,204 main ERROR Could not reconfigure JMX java.lang.LinkageError: loader constraint violation: loader (instance of org/powermock/core/classloader/MockClassLoader) previously initiated loading for a different type with name "javax/management/MBeanServer"
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:760)
        at org.powermock.core.classloader.MockClassLoader.loadUnmockedClass(MockClassLoader.java:238)
        at org.powermock.core.classloader.MockClassLoader.loadModifiedClass(MockClassLoader.java:182)
        at org.powermock.core.classloader.DeferSupportingClassLoader.loadClass(DeferSupportingClassLoader.java:70)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

Simply add the following as a class level annotation:

@PowerMockIgnore( {"javax.management.*"} )

Blacklisting Kernel Modules

Posted on by rchapin

Following is a walkthrough on how to blacklist a kernel module.  The specific example is blacklisting the nouveau driver so that I can install the OEM Nvidia driver.

1. First, blacklist the nouveau driver: Add a line to the textfile /etc/modprobe.d/nouveau-blacklist.conf that contains they keyword ‘blacklist’ and the name of the driver

blacklist nouveau

2. Rebuild the initramfs image file.  First, backup existing initramfs

mv initramfs-3.10.0-327.18.2.el7.x86_64.img initramfs-3.10.0-327.18.2.el7.x86_64.img_2016-06-09.bak

Build new initramfs

dracut -v /boot/initramfs-$(uname -r).img $(uname -r)

3. Reboot the system and confirm that the driver in question is not loaded.

lsmod | fgrep nouveau

How to Return Hive Query Results Similary to MySQL \G in One Vertical Column

Posted on by rchapin

When trying to look at data in a database with really wide rows even just selecting 1 row to see the data is nearly impossible to understand when the single row wraps 7 or 8 times.

MySQL offers the ‘\G’ option to display the output in a single column.

The corresponding method in Hive is to execute the following set command:

> !set outputformat vertical
> SELECT something FROM some table;

How to Configure a User Account in Active Directory So that the Password Never Expires

Posted on by rchapin

Using ADSI Edit, navigate to the user in question.  Right-click on the user and select Properties.

Then, scroll down to the ‘userAccountControl’ property and click the Edit button.

Enter 66048 into the field and then click ‘OK’ and then ‘Apply’.

After closing the edit window, scroll to the right to confirm that the value indicates the following

'0x10200 = (NORMAL_ACCOUNT|DONT_EXPIRE_PASSWORD)'
© 2005 Ryan Chapin