List of virtual adapters your Virtual Linux can access

Hello ,

Its me again Raja and this time I came up with one more new post.

I have been through interesting problem.

As many of you know Virtual Box , sometimes even though we enable new adapter and configured IP in conf file it wont comes up. Everything seems fine , we have enabled adapter and configured name and IP for it but still it wont come up.

Simple solution : How many adapters your VM able to access can be easily know by using command

                             ls /sys/class/net

  In my case I have 3 adapters so it will display them

root@fresh:~# ls /sys/class/net
enp0s3  enp0s8  lo
root@fresh:~#

If you come across errors like device not found errors , try to found out how your VM identified the adapters that you have enabled.

Hope it helps.

Thank you.

Linux : full path of a file

Hello ,

Sometimes we need to have full or absolute path of file. And most of the times we used to pwd + filename manually.

But with google search I came across a command named as readlink.


readlink -f filename.txt

that will print complete path of filename along with filename append to it.

linuxmen@linuxmen-fresh:~/test/test1$ readlink -f ex4.js
/home/linuxmen/test/test1/ex4.js
linuxmen@linuxmen-fresh:~/test/test1$  

Note : make sure you are same directory where file resides else give relative path to file.

Hope it helps

Install R Programming Language in Ubuntu

This post describe about installation steps for R- Programming Language.

For Windows we have direct exe file but for Linux its in a single click way but you can still do it below commands easily.

Open your terminal and type below commands as root user.

echo "
deb https://cloud.r-project.org/bin/linux/ubuntu xenial/
deb https://cloud.r-project.org/ trusty-backports main restricted universe" >> /etc/apt/sources.list
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 51716619E084DAB9
sudo apt-get update
sudo apt-get install -y r-base r-base-dev
sudo apt-get install r-cran-boot r-cran-class r-cran-cluster r-cran-codetools r-cran-foreign r-cran-kernsmooth r-cran-lattice r-cran-mass r-cran-matrix r-cran-mgcv r-cran-nlme r-cran-nnet r-cran-rpart r-cran-spatial r-cran-survival r-cran-rodbc

If any questions please dont hesitate to ask.

Thank you.

JVMMON help commands

Hello ,

jvmmon is an excellent tool for JBOSS administrators and please find below list of commands for jvmmon

 Print commands: __________________________

  print arenastat                             - Prints brief arena statistics
  print arenastat full                        - Prints detailed arena statistics
  print class statistic                       - Prints class statistics of a VM
  print cluster memory information            - Prints information about the memory consumption of the cluster
  print codeblobs                             - Prints information about code blobs with specified name
  print debugging information                 - Prints information about the debugging state of a VM
  print detailed class statistic              - Prints detailed class statistics of a VM
  print dll info                              - Prints information about the loaded shared libraries of a VM
  print flight recorder                       - Prints part of the flight recorder of a VM
  print gc history                            - Prints the GC history of a VM
  print hs_err_info                           - Prints the hs-err-info of a VM
  print jit info                              - Prints information about JIT compiler and code cache
  print mallocstat                            - Prints malloc statistics
  print mallocstat internals                  - Prints internals for malloc statistics
  print memhist                               - Prints memory history
  print performance information               - Prints information about the performance of a VM
  print signal handlers                       - Prints currently active signal handlers
  print stacktrace                            - Prints the stacks of all threads in a VM
  print symbol info                           - Prints information about symbols and interned strings of a VM
  print system information                    - Prints system information
  print system properties                     - Prints VM system properties
  print trace flags                           - Prints the active trace flags of a VM
  print virtualization info                   - Prints the platform virtualization info
  print vm compressed class space information - Prints information about the compressed class space of a VM
  print vm information                        - Prints information about a VM
  print vm memory information                 - Prints information about the memory consumption of a VM

__ Dump commands: ___________________________

  dump class statistic                        - Dumps class statistics of a VM
  dump codeblobs                              - Dumps information about code blobs with specified name
  dump detailed class statistic               - Dumps detailed class statistics of a VM
  dump dll info                               - Dumps information about the loaded shared libraries of a VM
  dump gc history                             - Dumps the GC history of a VM
  dump heap                                   - Dumps the heap of a VM
  dump heap with info                         - Dumps the heap and additional information describing the heap of a VM
  dump hs_err_info                            - Dumps the hs-err-info of a VM
  dump jit info                               - Dumps information about JIT compiler and code cache
  dump safepoint state                        - Dumps information about the safepoint state of the specified VM
  dump stacktrace                             - Dumps the stacks of all threads in a VM
  dump stacktrace with info                   - Dumps the stacks of all threads with additional information
  dump symbol info                            - Dumps information about symbols and interned strings of a VM

__ GC commands: _____________________________

  force gc                                    - Forces a full garbage collection
  force max gc                                - Forces a maximum compaction garbage collection
  retrieve complete gc history                - Retrieves the complete GC history of a VM into a local file

__ JIT commands: ____________________________

  compile                                     - Forces compilation of the specified method(s)
  deoptimize                                  - Deoptimizes all activations of the specified method(s)
  deoptimizeall                               - Deoptimizes all methods
  osrcompile                                  - Forces osr compilation of the specified method

__ VM commands: _____________________________

  change command line flag                    - Changes command line flags of a VM
  crash vm                                    - Crashes a VM
  exit vm                                     - Exits a VM
  mallocstat reset                            - Resets malloc statistics value
  mallocstat startcap                         - Starts malloc statistics capture
  mallocstat stopcap                          - Stops malloc statistics capture
  set core size to max                        - Set current soft limit of core size to hard limit
  set debugging port range                    - Sets debugging port range of a VM
  set trace flags                             - Sets trace flags of a VM
  start debugging                             - Starts on-the-fly debugging
  stop command line profiling                 - Stops command line profiling of a VM
  stop debugging                              - Stops on-the-fly debugging

__ VM selection commands: ___________________

  display vms                                 - Displays the VMs in the cluster
  select vm                                   - Selects a VM (in the cluster)
  select vm all                               - Selects all VMs in the cluster

__ Jvmmon commands: _________________________

  exit                                        - Exits Jvmmon
  help                                        - Shows the help text
  history                                     - Shows a list of the commands executed
  print to console                            - Redirect print commands to console output
  print to file                               - Redirect print commands to local file
  quit                                        - Quits Jvmmon
  help ""                            - Displays detailed help about the specified command
  !                                           - Repeats the last command
  !!                                          - Repeats the last command
  !N                                          - Repeats command with number N in history
  !TEXT                                       - Repeats command that started with TEXT

Hope it will helps. 

Python Object reference well explained with list

Assume you have a list and you want to make exact copy of the list.

What command you will use in python to copy a list from another list.

I used List1=List2 and List1 got copied as exactly as List2 but what happen internally is they have shared command object reference location.

Dont believe ? then lets try and try to see both lists location with id function id()

I mean do as  id(List1) and id(List2) , you will find command location for these two which means they are sharing common location and what ever operations you do they will reflect on both lists.And this is completely harmful and dangerous.

So to avoid this list copying can be done in other methods where two list will have two different object locations.

They are

list2=copy.copy(list1)
(or)
list2=list1[:]
(or)
list2=list(list1)

and for more information about object reference understanding in python I recommend you to read these

http://stackoverflow.com/questions/36244451/how-to-program-python-variable-to-point-different-reference-location-but-same-va/36244490#36244490

http://www.python-course.eu/python3_variables.php

How to get full application propery reports by using jvmmon ?

Hello ,

Let come straight to the point.

If you want to see right now with what properties your Jboss application servers are running ,

Please type jvmmon and choose current PID of your JBOSS process.

Then type print system properties

It will flood your stdout , copy and paste it in a file and you can use to analyse.

else

you can save it to a file in your system.

$ print to file
file = /tmp/fromjvmmon
$ print system properties
-- printed to local file /tmp/fromjvmmon
$ exit

and to take thread dump use 

jvmmon

$ print to file

file =/tmp/threaddump

$print stacktrace

it will autosave threaddump in the above location

and similarly to take heap dump. 

type

jvmmon

$dump heap

it will dump heap automatically into location as mentioned in run.conf

Thank you.

Regards
Raja

Suspended Jobs vs Running jobs in Linux

Background Job : A job which is running background in the same shell. You can use bg command to see any background jobs.

Foreground job : A Job which is running in the same shell right before your eyes.

Suspended Job : Its a stopped/pause job but you can resume their running.

Let me explain with example very clealy

virt00# sleep 180
^Z
zsh: suspended  sleep 180
virt00# jobs
[1]  + suspended  sleep 180
virt00# bg
[1]  + continued  sleep 180
virt00# fg
[1]  + running    sleep 180
^Z
zsh: suspended  sleep 180
virt00# jobs
[1]  + suspended  sleep 180
virt00#

I have started a Job named sleep 180 then I stopped with CTRL+Z . right now my job is in suspended mode.

I see it by typing jobs command. Now I want to resume its running in background so I typed bgcommand then it will move from suspended state to running state but in background it will run.

now I typed command fg to bring it foreground , now job wont get stepped but it will pull from background jobs queue and push into foreground jobs queue.

So yes background jobs and foreground jobs always are in running state.

Deny SSH access to particular users

We all know SSH is very famous and the best service for remote access.

Today I am going to tell you how to block or allow only particular users or group from SSH access.

open sshd_config file as per your environment

in Debian

vim /etc/ssh/sshd_config

Then add below line to enable access for only below users

AllowUsers username1 username2

to deny access for only below users add a line as

DenyUsers username1 username2

as in the same way

AllowGroups group1 group2

and to deny groups

DenyGroups group1 group2

 But there is something very important you have to follow here. It is the order of mentioning.

From manpage of SSH 

The allow/deny directives are processed in the following
      order: DenyUsers, AllowUsers, DenyGroups, and finally
      AllowGroups.

So first mention DenyUsers and then AllowUsers then only it will works and same for DenyGroups and AllowGroups

Hope it helps.

How to see IOWAIT in Linux

Hello ,

You can use sar command.

in Ubuntu you can install it with

sudo apt-get install systat

and enable data collecting

sed -i 's/ENABLED="false"/ENABLED="true"/' /etc/default/sysstat

start service with

 

/etc/init.d/sysstat start

To see I/O latency type command as

sar 1 1

that means it will give two responses with 1 sec as interval.

Example :

root@virt01:~# sar 1 3
Linux 3.19.0-42-generic (virt01.ubuntu.com)     13/02/16        _x86_64_        (1 CPU)


12:26:23        CPU     %user     %nice   %system   %iowait    %steal     %idle
12:26:24        all      0.00      0.00      0.00      0.00      0.00    100.00
12:26:25        all      0.00      0.00      0.99      0.00      0.00     99.01
12:26:26        all      2.02      0.00      0.00      0.00      0.00     97.98
Average:        all      0.67      0.00      0.33      0.00      0.00     99.00
root@virt01:~#

Hope that helps.

grep: unknown device method

Today while using grep command via rundeck I was through grep: unknown device method error.

And the reason is due to I am having ' - ' in my search pattern I was through this error.

I mean search includes

grep "-search.this" /path/to/file

Then you may get error with grep. So remove ' - ' in pattern and repeat your search.

grep "search.this" /path/to/file

Hope that helps.

Uploading files to FTP/SFTP using CURL

Hello,

Today I am writing below article which can help you to upload files to SFTP/FTP by using CURL.

Ok why we need that ? Let me tell explain!!

How we login into SFTP/FTP ?

[root@virt03 test]# sftp 192.168.56.110
Connecting to 192.168.56.110...
root@192.168.56.110's password:
sftp> ls
anaconda-ks.cfg       nodes                 post-install          post-install.log

sftp> exit

and uploading files with put command. Its a lengthy way. So recently I have gone through few articles and with some R&D I have modified it as script and command-line argument support.So you can call the script with filename as argument. 

So Lets do this!!!

1. Command 1 : This is for uploading a single to SFTP/FTP by using CURL. 

SFTP

curl -k  -u virt03:virt03 -T file4  sftp://192.168.56.110/home/virt03/

Syntax : 

curl -k  -u username:password -T filename sftp://IP_Addreess OR Hostname:/path/to/upload 

FTP

curl -k  -u virt03:virt03 -T file6  ftp://192.168.56.110

Example

[root@virt03 test]# curl -k  -u virt03:virt03 -T file4  sftp://192.168.56.110/home/virt03/

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current

                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0

[root@virt03 test]# touch file6

[root@virt03 test]# curl -k  -u virt03:virt03 -T file6  ftp://192.168.56.110

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current

                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0

[root@virt03 test]# ls /home/virt03/ | grep file

file1

file2

file3

file4

file5

file6

[root@virt03 test]#

So hope you understand whats happening now. Lets make some script!!! 

[root@virt03 test]# ls

file1  file3  file5  file7  file9  lab2.sh     upload1.sh

file2  file4  file6  file8  lab1   rackspace3  upload2.sh

[root@virt03 test]# ls /home/virt03/ | grep file

file1

file2

file3

file4

file5

file6

[root@virt03 test]# ./upload1.sh file7

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current

                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0

[root@virt03 test]# ls /home/virt03/ | grep file

file1

file2

file3

file4

file5

file6

file7

[root@virt03 test]# ./upload2.sh file8 file9

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current

                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0

[root@virt03 test]# ls /home/virt03/ | grep file

file1

file2

file3

file4

file5

file6

file7

file8

file9

[root@virt03 test]# 

And the scripts are 

[root@virt03 test]# tail upload*

==> upload1.sh <==

#!/bin/bash




curl -k  -u virt03:virt03 -T "{$1}" sftp://192.168.56.110/home/virt03/




==> upload2.sh <==

#!/bin/bash

curl -k  -u virt03:virt03 -T "{$1,$2}" sftp://192.168.56.110/home/virt03/

[root@virt03 test]#

I hope you can understand what the scripts are doing. To upload more than 2 files you can use for loop like below.

for i in file1 file2 file3 file4 file5

do

./upload1.sh $i

done

Example: 

[root@virt03 test]# for i in file10 file11 file12

> do

> ./upload1.sh $i

> done

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current

                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:--  0:00:01 --:--:--     0

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current

                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current

                                 Dload  Upload   Total   Spent    Left  Speed

  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0




[root@virt03 test]# ls /home/virt03/ | grep file1

file1

file10

file11

file12

[root@virt03 test]#

Hope you understand!! , If any doubts please dont hesitate to ask.

List the installed RPMs by date of installation in CentOS/RHEL 6.x

How to list  the installed packages on date wise

Command is : 

#rpm -qa --qf '%{INSTALLTIME} (%{INSTALLTIME:date}): %{NAME}-%{VERSION}-%{RELEASE}.%{ARCH}\n' | sort -n

How To Configure VSFTPD With TLS/SSL On RHEL/CentOS 6.x and How To Connect Secure VSFTPD(TLS/SSL) in Heterogeneous Environments Using Client Programs. (Part..A)

Traditional FTP is rather insecure. When you login, your username and password are transmitted in clear text, raising the possibility of your credentials being 'sniffed' by a malicious person. Fortunately there's an easy answer to this. You can quite easily configure your vsftpd server to use OpenSSL encryption, so that usernames & password, and even data files, are encrypted during transfer. It takes just a few simple steps: 

Vsftpd is already available under CentOS/RHEL  default repositories. We assume that CentOS/RHEL users have enabled default repositories in his system. Now execute following command. 

Note:- This post works with Security-Enhanced Linux (SELinux) is enabled  

Installing and Configuring the Vsftpd in RHEL/CentOS 6.x 

Step1:-  Install VsFTPd 

# yum install vsftpd 

Step2:-  Configure Basic VsFTPd Settings 

Now Edit Vsftpd configuration file /etc/vsftpd/vsftpd.conf in CentOS/RHEL and do the some basic settings like below. If you are configuring FTP for private users then we strictly advice to disable anonymous login. 

Before editing any configuration file please maintain a backup. Its good practice 

# cp -a /etc/vsftpd/vsftpd.conf_bkp /etc/vsftpd/vsftpd.conf 

1. Allow anonymous FTP? Set this value to NO to disable anonymous login. default value is YES 

• anonymous_enable=NO  

2. Uncomment below line to allow local system users to log in via ftp 

• local_enable=YES 

3. Uncomment below line to enable any form of FTP write command like, creating or uploading files and directory. 

• write_enable=YES 

3. Uncomment below line to enable local system users to permit  their home directory only. 

• chroot_local_user=YES 

Note : - While using chroot_local_user=YES  you must set user default shell as /sbin/nologin Otherwise ftp users can gain the access to ssh login 

Now start the vsftpd service  

# service vsftpd start 

To check the vsftpd service running or not 

# service vsftpd status 

To check the vsftpd service running port 

# netstat -nptelu | grep vsftpd 

Step3:-  First load the following module to make sure passive ftp connections are not rejected and also allow the port 

Open the following file /etc/sysconfig/iptables-config and change IPTABLES_MODULES=" " to IPTABLES_MODULES="ip_conntrack_ftp"  

Make sure ftp port is allowed in iptables. 

# iptables -L --line-number -n  

Now restart the iptables and vsftpd service  

# service iptables restart && service vsftpd restart  

Step4:- Create user and check the login 

# useradd -s /sbin/nologin test 

# passwd test 

Now use FileZilla client software to check. Because it will give exact issue if any problem 

I think SELinux will prevent while switching to the home directory. the error like below 

 

Now you have to allow the polices in selinux. 

# setsebool -P ftp_home_dir 1 

# setsebool -P allow_ftpd_full_access 1 

Till now we are done with basic vsftpd installation and configuration. Now we are going to configure TLS/SSL. 

Configuring the TLS/SSL  

Step5:-  Make sure openssl package is installed on machine. Here we are securing vsftpd by using self signed certificates 

Please follow the below steps for generating self signed certificates 

#openssl req -x509 -nodes -days 3650 -newkey rsa:2048 -keyout /etc/vsftpd/vsftpdkey.pem -out /etc/vsftpd/vsftpd.pem 

In "Common Name (eg, your name or your server's hostname)" part give proper domain name otherwise use wildcards Ex: *.google.com, *.xyz.com 

Then change the permissions to these certificate files 

# chmod 400 /etc/vsftpd/vsftpd.pem 

# chmod 400 /etc/vsftpd/vsftpdkey.pem 

Step6:- Securing the ftp can be done by two ways. 

1) Implicit SSL of vsftp (Port 990) 

2) Explicit TLS of vsftp (Port 21) 

1) Implicit SSL of vsftp (Port 990) 

In this method client must use SSL to connect using the port number 990. 

Follow the below configuration details. 

Open vsftpd file /etc/vsftpd/vsftpd.conf  add below lines in end of this file 

#ssl/tsl enable 

rsa_cert_file=/etc/vsftpd/vsftpd.pem 

rsa_private_key_file=/etc/vsftpd/vsftpdkey.pem 

ssl_enable=YES 

allow_anon_ssl=NO 

force_local_data_ssl=YES 

force_local_logins_ssl=YES 

ssl_tlsv1=YES 

ssl_sslv2=NO 

ssl_sslv3=NO 

require_ssl_reuse=NO 

ssl_ciphers=HIGH 

 #Implicit SSL Configuration 

implicit_ssl=YES 

listen_port=990 

# Pasive ftp enable (These ports are up to you ) 

pasv_min_port=2100 

pasv_max_port=2200 

# Ftp Loging 

xferlog_file=/var/log/vsftpd.log 

xferlog_enable=YES 

dirmessage_enable=YES 

xferlog_std_format=NO 

data_connection_timeout=600 

dual_log_enable=YES 

log_ftp_protocol=YES 

debug_ssl=YES 

Save and Exit the file 

#service vsftpd restart 

To check the vsftpd service running port 

# netstat -nptelu | grep vsftpd 

Note:- Allow the ports 2100 to 2200 in iptables (These ports are up to you ) 

2) Explicit TLS of vsftp (Port 21) 

In this method client can send the connection using default port only( Port 21). 

Follow the below configuration details. 

Open vsftpd file /etc/vsftpd/vsftpd.conf  add below lines in end of this file 

#ssl/tsl enable 

rsa_cert_file=/etc/vsftpd/vsftpd.pem 

rsa_private_key_file=/etc/vsftpd/vsftpdkey.pem 

ssl_enable=YES 

allow_anon_ssl=NO 

force_local_data_ssl=YES 

force_local_logins_ssl=YES 

ssl_tlsv1=YES 

ssl_sslv2=NO 

ssl_sslv3=NO 

require_ssl_reuse=NO 

ssl_ciphers=HIGH 

#Explicit TLS Configuration 

#implicit_ssl=YES 

#listen_port=990 

# Pasive ftp enable(These ports are up to you ) 

pasv_min_port=2100 

pasv_max_port=2200 

# Ftp Loging 

xferlog_file=/var/log/vsftpd.log 

xferlog_enable=YES 

dirmessage_enable=YES 

xferlog_std_format=NO 

data_connection_timeout=600 

dual_log_enable=YES 

log_ftp_protocol=YES 

debug_ssl=YES 

Save and Exit the file 

#service vsftpd restart 

To check the vsftpd service running port 

# netstat -nptelu | grep vsftpd 

Note:- Allow the ports 2100 to 2200 in iptables ( These ports are up to you )