Archive for December 27th, 2016

Record ssh session using screen

Author: daniel

Dec 27

How to record your ssh session using screen.

Per the man page – “Screen is a full-screen window manager that multiplexes a physical terminal between several processes (typically interactive shells)”.
Screen is most commonly used to create multiple sessions to remote hosts within a single terminal window or even run multiple commands locally without leaving your shell terminal. For instance, you could be tailing the log file in one session, then run a long process, then ssh into other machine etc. all within a single window.

Screen is the go to tool when setting up a remote connection, such as ssh, and you want to continue your work at any time or from any other host without worrying of a dropped connection.

In this post, I will show you how you can record your bash session.

Installation –

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yum install screen        (Debian/Ubuntu)
apt-get install screen    (Redhat/CentOS)

My local environment and the remote host I am sshing to –

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daniel@linubuvma:/tmp$ screen -v
Screen version 4.01.00devel (GNU) 2-May-06
daniel@linubuvma:/tmp$ uname -r
3.13.0-106-generic
daniel@linubuvma:/tmp$ cat /etc/issue
Ubuntu 14.04.5 LTS \n \l
 
daniel@linubuvma:/tmp$ ssh ns2 'uname -r ; cat /etc/issue'
2.6.32-642.6.1.el6.x86_64
CentOS release 6.8 (Final)
Kernel \r on an \m

The ‘-L’ option of screen is used to record your session, the session log is automatically saved in a file named ‘screenlog.n’ in your current directory.

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daniel@linubuvma:/tmp$ ls
config-err-hbzs5e  one          ssh-4yheApHRgMBF  ssh-RK7GpeFuzUB8  VMwareDnD    vmware-root-2347660412
gpg-kZux7q         screenlog.0  ssh-BBblvGtb5284  vmware-daniel     vmware-root
daniel@linubuvma:/tmp$ free -m
             total       used       free     shared    buffers     cached
Mem:          3946       2489       1457          6        547       1031
-/+ buffers/cache:        911       3035
Swap:         4092          0       4092
daniel@linubuvma:/tmp$ exit
[screen is terminating]
daniel@linubuvma:/tmp$

The whole bash session will be logged in screenlog.0 in this case –

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daniel@linubuvma:/tmp$ cat screenlog.0
daniel@linubuvma:/tmp$ ls
config-err-hbzs5e  one          ssh-4yheApHRgMBF  ssh-RK7GpeFuzUB8  VMwareDnD    vmware-root-2347660412
gpg-kZux7q         screenlog.0  ssh-BBblvGtb5284  vmware-daniel     vmware-root
daniel@linubuvma:/tmp$ free -m
             total       used       free     shared    buffers     cached
Mem:          3946       2489       1457          6        547       1031
-/+ buffers/cache:        911       3035
Swap:         4092          0       4092
daniel@linubuvma:/tmp$ exit
exit
daniel@linubuvma:/tmp$

Recording your session of an ssh connection to a remote host is also similar, with ‘-L’ option followed by the command to ssh to remote host.
Option -fn (with no flow-control)
Option -t (title bar name) in this case ‘practice’.

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daniel@linubuvma:/tmp$ screen -fn -t practice -L  ssh ns2
Last login: Tue Dec 27 09:46:10 2016 from linubuvma.home.net
 
[daniel@kauai ~]$ hostname -f
kauai.example.net
[daniel@kauai ~]$ uptime
 10:08:18 up 18 days, 10:02, 14 users,  load average: 0.19, 0.49, 0.64
[daniel@kauai ~]$ exit
[screen is terminating]
 
 
daniel@linubuvma:/tmp$ cat screenlog.0
Last login: Tue Dec 27 09:46:10 2016 from linubuvma.home.net
[daniel@kauai ~]$ hostname -f
kauai.example.net
[daniel@kauai ~]$ uptime
 10:08:18 up 18 days, 10:02, 14 users,  load average: 0.19, 0.49, 0.64
[daniel@kauai ~]$ exit
logout
Connection to ns2 closed.
daniel@linubuvma:/tmp$

Additional resources –

https://www.rackaid.com/blog/linux-screen-tutorial-and-how-to/
https://linux.die.net/man/1/screen

  • 11 Comments
  • Filed under: How tos, Linux

    • shuffle files in a directory with python

    Author: daniel

    Dec 27

    Randomly ordering files in a directory with python

    I have a playlist file which contains audio files to play. The audio player unfortunately plays the music files in a sequential order, in whatever order they are listed in the playlist file. So occasionally I have to regenerate the playlist file to randomize the audio files order. Here is a simple script that I had to write for this purpose, the core component is the random.shuffle(list) python function –

    Create script file as shuffle_files.py –

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    #!/usr/bin/env python
     
    import os
    import random
    import sys
     
    music_files=[]
     
    if len(sys.argv) != 2:
      print "Usage:", sys.argv[0], "/path/directory"
    else:
      dir_name=sys.argv[1]
      if os.path.isdir(dir_name):
        for file_name in os.listdir(dir_name):
          music_files.append(file_name)
      else:
        print "Directory", dir_name, "does not exist"
        sys.exit(1)
    # shuffle list
    random.shuffle(music_files)
    for item in music_files:
      print os.path.join(dir_name,item)

    Run the script by providing a path to a directory with files. Each iteration should list the files in the directory in a different order.
    Note – the script does not recurse into the directories, it can be easily modified with os.walk if necessary.

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    root@svm1010:/home/daniel/scripts# python shuffle_files.py /opt/iotop/iotop
    /opt/iotop/iotop/setup.py
    /opt/iotop/iotop/README
    /opt/iotop/iotop/iotop
    /opt/iotop/iotop/iotop.8
    /opt/iotop/iotop/NEWS
    /opt/iotop/iotop/iotop.py
    /opt/iotop/iotop/PKG-INFO
    /opt/iotop/iotop/THANKS
    /opt/iotop/iotop/sbin
    /opt/iotop/iotop/setup.cfg
    /opt/iotop/iotop/ChangeLog
    /opt/iotop/iotop/.gitignore
    /opt/iotop/iotop/COPYING
     
     
    root@svm1010:/home/daniel/scripts# python shuffle_files.py /opt/iotop/iotop
    /opt/iotop/iotop/PKG-INFO
    /opt/iotop/iotop/COPYING
    /opt/iotop/iotop/iotop
    /opt/iotop/iotop/setup.cfg
    /opt/iotop/iotop/NEWS
    /opt/iotop/iotop/README
    /opt/iotop/iotop/.gitignore
    /opt/iotop/iotop/setup.py
    /opt/iotop/iotop/THANKS
    /opt/iotop/iotop/iotop.py
    /opt/iotop/iotop/ChangeLog
    /opt/iotop/iotop/iotop.8
    /opt/iotop/iotop/sbin
     
     
    root@svm1010:/home/daniel/scripts# python shuffle_files.py /opt/iotop/iotop
    /opt/iotop/iotop/THANKS
    /opt/iotop/iotop/setup.py
    /opt/iotop/iotop/NEWS
    /opt/iotop/iotop/README
    /opt/iotop/iotop/iotop.8
    /opt/iotop/iotop/.gitignore
    /opt/iotop/iotop/ChangeLog
    /opt/iotop/iotop/sbin
    /opt/iotop/iotop/PKG-INFO
    /opt/iotop/iotop/iotop
    /opt/iotop/iotop/COPYING
    /opt/iotop/iotop/iotop.py
    /opt/iotop/iotop/setup.cfg

    Reference – https://docs.python.org/2/library/random.html?highlight=shuffle#random.shuffle

  • 0 Comments
  • Filed under: How tos, Linux, Scripting