Centos 7.x - Minimal network setup

This is a continuation of a previous post, but this time dedicated to CentOS 7 (our customer is evolving!!)

Environment:

• Virtualbox 5.1.10
• CentOS 7.4.1708

Before start with the installation, in Virtualbox you have to configure two network adapters:

• Adapter 1: Host only
• Adapter 2: NAT

The first one will be used to communicate host and guest, for example, by using a ssh connection. The second one will be used by the guest in order to gain direct access to the internet.

When CentOS starts for first time, you will already had internet access. But local network will be disabled. Execute the following command to check your network interfaces:

ip add

The result will be something like this:

Here you can see three interfaces:

• lo: Loopback
• enp0s3: Host-Only adapter
• enp0s8: NAT adapter

If you have doubts about which is the host-only, you can check the MAC address and compare it with the Virtualbox adapter.

Once you are sure enp0s3 is your interface, go to /etc/sysconfig/network-scripts/ and edit ifcfg-enp0s3 file, for example with vi. You will have to make two changes:

• Set BOOTPROTO=none
• Set ONBOOT=yes
• Add IPADDR=your IP

Then execute the following command:

systemctl restart network.service

Now you will have your interface up and with the IP address you set before.

Note

As stated in my previous post, remember to configure proxy settings for system and yum configuration:

System config

Edit ~/.bash_profile file and add the following lines:

# The Web proxy server used by this account
http_proxy="http://usuario:password@my.proxy:8080"

export no_proxy=localhost,127.0.0.1
export http_proxy

YUM config

Edit  /etc/yum.conf y add the following lines:

# The proxy server - proxy server:port number
proxy=http://my.proxy:8080
# The account details for yum connections
proxy_username=usuario
proxy_password=password




LibreOffice - Force PDF/A export

I was using LibreOffice to convert documents from disparate formats to PDF. This is done by using the following command:

libreoffice5.3 --headless --convert-to pdf prueba.txt

My problem was that the output file was not int PDF/A format.

LibreOffice, by working with it´s GUI interface, do supports PDF/A conversion, so the problem should be in some kind of default configuration.

There is configuration file called registrymodifications.xcu which contains all settings used by the programa, and during the exportation too. This file is located in  ~/.config/libreoffice/4/user/ directory. For example /root/.config/libreoffice/4/user/registrymodifications.xcu.

This is an xml based file with a lot of (poor/undocumented) preferences. In particular, in order to set PDF/A as default option, you have to insert the following config line:

<?xml version="1.0" encoding="UTF-8"?>
<oor:items xmlns:oor="http://openoffice.org/2001/registry" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 (...)
 <item oor:path="/org.openoffice.Office.Common/Filter/PDF/Export">
  <prop oor:name="SelectPdfVersion" oor:op="fuse">
   <value>1</value>
  </prop>
 </item>
 (...)
</oor:items>

Now, if you launch the conversion again you will get a PDF/A-1A file.

Though registrymodifications.xcu file is quite obscure, you can get mor info by using the GUI version of the program. If you navigate to Tools > Options > LibreOffice > Advanced > Open Expert Configuration, you can check the whole list of settings.

Unix - CIFS / NFS Mount

Mount CIFS

fstab:

//host/server_dir /mnt/unix_dir  cifs gid=jboss,uid=jboss,domain=xxxxx,user=yyyyy,password=zzzzz,_netdev,rw   0 0

Mount NFS

fstab:

host:/server_dir /mnt/unix_dir nfs rsize=8192,timeo=14,intr 0 0

HTTP response '413: Request Entity Too Large' when communicating with 'xxx'

I was able to reproduce this error with Apache 2.2 + mod_ssl.

Just configure a virtual host port 443 and set the SSLVerifyClient to required or optional.

<Location />
    SSLRequireSSL 
    SSLOptions +StdEnvVars +ExportCertData +StrictRequire
    SSLVerifyClient optional
    SSLVerifyDepth 2   
</Location>

When you send a large request, for example a SOAP message which contains a file (bad practice, use MTOM), you could get the following error:

[2017-12-07 16:59:42,313] (LogUtils.java:478) WARN main org.apache.cxf.phase.PhaseInterceptorChain Interceptor for {http:/xxxxxxxxxxxxxxxx}yyyyyyyyy#{http:/xxxxxxxxxxxxxxxx}generarCSV has thrown exception, unwinding now
org.apache.cxf.interceptor.Fault: Could not send Message.
 at org.apache.cxf.interceptor.MessageSenderInterceptor$MessageSenderEndingInterceptor.handleMessage(MessageSenderInterceptor.java:64)
 at org.apache.cxf.phase.PhaseInterceptorChain.doIntercept(PhaseInterceptorChain.java:308)
 at org.apache.cxf.endpoint.ClientImpl.doInvoke(ClientImpl.java:518)
 at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:427)
 at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:328)
 at org.apache.cxf.endpoint.ClientImpl.invoke(ClientImpl.java:281)
 at org.apache.cxf.frontend.ClientProxy.invokeSync(ClientProxy.java:96)
 at org.apache.cxf.jaxws.JaxWsClientProxy.invoke(JaxWsClientProxy.java:139)
 at com.sun.proxy.$Proxy22.generarCSV(Unknown Source)
 at es.sisifo.cxf.client.SinaturaServiceClient.run(SinaturaServiceClient.java:81)
 at es.sisifo.cxf.client.SinaturaServiceClient.main(SinaturaServiceClient.java:93)
Caused by: org.apache.cxf.transport.http.HTTPException: HTTP response '413: Request Entity Too Large' when communicating with https://my-service-endpoint
 at org.apache.cxf.transport.http.HTTPConduit$WrappedOutputStream.doProcessResponseCode(HTTPConduit.java:1609)
 at org.apache.cxf.transport.http.HTTPConduit$WrappedOutputStream.handleResponseInternal(HTTPConduit.java:1616)
 at org.apache.cxf.transport.http.HTTPConduit$WrappedOutputStream.handleResponse(HTTPConduit.java:1560)
 at org.apache.cxf.transport.http.HTTPConduit$WrappedOutputStream.close(HTTPConduit.java:1361)
 at org.apache.cxf.transport.AbstractConduit.close(AbstractConduit.java:56)
 at org.apache.cxf.transport.http.HTTPConduit.close(HTTPConduit.java:658)
 at org.apache.cxf.interceptor.MessageSenderInterceptor$MessageSenderEndingInterceptor.handleMessage(MessageSenderInterceptor.java:62)
 ... 10 more

The solution is to use the SSLRenegBufferSize directive:

If an SSL renegotiation is required in per-location context, for example, any use of SSLVerifyClient in a Directory or Location block, then mod_ssl must buffer any HTTP request body into memory until the new SSL handshake can be performed. This directive can be used to set the amount of memory that will be used for this buffer.

This buffer is referred to the whole size of the request, i.e, if you are sending a 200KB file, then the value should be set to around 250000 (you have to spare some size for the rest of the request).

<Location />
    SSLRequireSSL 
    SSLOptions +StdEnvVars +ExportCertData +StrictRequire
    SSLVerifyClient optional
    SSLVerifyDepth 2
    SSLRenegBufferSize 250000 
</Location>

In other places you can also found that the problem could be solved with other two directives, LimitXMLRequestBody  and LimitRequestBody but I was not able to reproduce my problem by using them.

Java command tools Cheat sheet

JPS - Java Virtual Machine Process Status Tool

Find all java process in a host:

C:\Program Files\Java\jdk1.7.0_79\bin>jps -lv
6192 sun.tools.jps.Jps -Dapplication.home=C:\Program Files\Java\jdk1.7.0_79 -Xms8m
5348 C:\Desarrollo\eclipse-neon-2\\plugins/org.eclipse.equinox.launcher_1.3.201.v20161025-1711.jar -Dosgi.requiredJavaVersion=1.8 -XX:+UseG1GC -XX:+UseStringDeduplication -Dosgi.requiredJavaVersion=1.8 -Xms256m -Xmx2048m
3496 org.jboss.modules.Main -agentlib:jdwp=transport=dt_socket,suspend=y,address=localhost:49626 -Dprogram.name=JBossTools: Red Hat JBoss EAP 6.1+ -Xms512m -Xmx1024m -XX:MaxPermSize=512m -Dorg.jboss.resolver.warning=true -Djava.net.preferIPv4Stack=true -Dsun.rmi.dgc.client.gcInterval=3600000 -Dsun.rmi.dgc.server.gcInterval=3600000 -Djboss.modules.system.pkgs=org.jboss.byteman -Djava.awt.headless=true -Dorg.jboss.boot.log.file=C:/Servers/jboss-eap-6.2/standalone/log/boot.log -Dlogging.configuration=file:/C:/Servers/jboss-eap-6.2/standalone/configuration/logging.properties -Djboss.home.dir=C:/Servers/jboss-eap-6.2 -Dorg.jboss.logmanager.nocolor=true -Djboss.bind.address.management=localhost -Dfile.encoding=Cp1252

JMAP - Memory analysis

Print heap usage sumary:

C:\Program Files\Java\jdk1.7.0_79\bin>jmap -heap 3496
Attaching to process ID 3496, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.79-b02

using thread-local object allocation.
Parallel GC with 4 thread(s)

Heap Configuration:
   MinHeapFreeRatio = 0
   MaxHeapFreeRatio = 100
   MaxHeapSize      = 1073741824 (1024.0MB)
   NewSize          = 1310720 (1.25MB)
   MaxNewSize       = 17592186044415 MB
   OldSize          = 5439488 (5.1875MB)
   NewRatio         = 2
   SurvivorRatio    = 8
   PermSize         = 21757952 (20.75MB)
   MaxPermSize      = 536870912 (512.0MB)
   G1HeapRegionSize = 0 (0.0MB)

Heap Usage:
PS Young Generation
Eden Space:
   capacity = 241172480 (230.0MB)
   used     = 101086072 (96.40319061279297MB)
   free     = 140086408 (133.59680938720703MB)
   41.914430701214336% used
From Space:
   capacity = 56623104 (54.0MB)
   used     = 0 (0.0MB)
   free     = 56623104 (54.0MB)
   0.0% used
To Space:
   capacity = 56623104 (54.0MB)
   used     = 0 (0.0MB)
   free     = 56623104 (54.0MB)
   0.0% used
PS Old Generation
   capacity = 358088704 (341.5MB)
   used     = 194474744 (185.46556854248047MB)
   free     = 163613960 (156.03443145751953MB)
   54.30909766983323% used
PS Perm Generation
   capacity = 296222720 (282.5MB)
   used     = 144879144 (138.16751861572266MB)
   free     = 151343576 (144.33248138427734MB)
   48.90885614715846% used

44021 interned Strings occupying 5210120 bytes.

Print heap histogram:

C:\Program Files\Java\jdk1.7.0_79\bin>jmap -histo 3496
 num     #instances         #bytes  class name
----------------------------------------------
   1:        105723       53508480  [B
   2:        577164       46177512  [C
   3:        245156       35415432  <constMethodKlass>
   4:        245156       31391216  <methodKlass>
   5:         25900       28928112  <constantPoolKlass>
   6:        628395       25135800  java.util.LinkedHashMap$Entry
   [...]
11430:            1             16  org.jboss.as.platform.mbean.ThreadMXBeanFindDeadlockedThreadsHandler
11431:            1             16  org.jboss.msc.service.ServiceContainerImpl$4
11432:            1             16  org.jboss.as.jmx.JMXExtension$JMXSubsystemParser_1_3
Total       8243462      503304768

JCMD

Show JVM Information:

C:\Program Files\Java\jdk1.7.0_79\bin>jcmd 3496 help
3496:
The following commands are available:
VM.native_memory
VM.commercial_features
GC.rotate_log
ManagementAgent.stop
ManagementAgent.start_local
ManagementAgent.start
Thread.print
GC.class_histogram
GC.heap_dump
GC.run_finalization
GC.run
VM.uptime
VM.flags
VM.system_properties
VM.command_line
VM.version
help

For more information about a specific command use 'help <command>'.

Print all JVM Threads:

C:\Program Files\Java\jdk1.7.0_79\bin>jcmd 3496 help Thread.print
3496:
Thread.print
Print all threads with stacktraces.

Impact: Medium: Depends on the number of threads.

Syntax : Thread.print [options]

Options: (options must be specified using the <key> or <key>=<value> syntax)
        -l : [optional] print java.util.concurrent locks (BOOLEAN, false)


C:\Program Files\Java\jdk1.7.0_79\bin>jcmd 3496 Thread.print
[...]

Generate a Heap dump:

C:\Program Files\Java\jdk1.7.0_79\bin>jcmd 3496 help GC.heap_dump
3496:
GC.heap_dump
Generate a HPROF format dump of the Java heap.

Impact: High: Depends on Java heap size and content. Request a full GC unless the '-all' option is specified.

Syntax : GC.heap_dump [options] <filename>

Arguments:
        filename :  Name of the dump file (STRING, no default value)

Options: (options must be specified using the <key> or <key>=<value> syntax)
        -all : [optional] Dump all objects, including unreachable objects (BOOLEAN, false)
 
 
C:\Program Files\Java\jdk1.7.0_79\bin>jcmd 3496 GC.heap_dump D:\tmp\test_jboss.hpprof
3496:
Heap dump file created

Important!! When you execute a heap dump, the JVM performs a garbage collector first. Therefore you will not get the heap´s snapshot, but a cleaner version.

JSTAT

Monitor Garbage Colector:

Program Files\Java\jdk1.7.0_79\bin>jstat -options
-cl
-compiler
-gc
-gccapacity
-gccause
-gcnew
-gcnewcapacity
-gcold
-gcoldcapacity
-gcpermcapacity
-gcutil
-printcompilation


C:\Program Files\Java\jdk1.7.0_79\bin>jstat -gcutil 3496 1000
  S0     S1     E      O      P     YGC     YGCT    FGC    FGCT     GCT
  0,00  24,73  88,78  72,67  99,92     23    0,973     0    0,000    0,973
  0,00  24,73  88,79  72,67  99,92     23    0,973     0    0,000    0,973
  0,00  24,73  89,02  72,67  99,92     23    0,973     0    0,000    0,973