Cryptic python subprocess error - OSError: [Errno 2] No such file or directory

Tshark has become swiss army knief for me and I was experimenting with tshark to extract DNS traffic. A portion of the code is reproduced here:

command = /usr/bin/tshark -i ens33 -nn -T fields -e frame.time -e ip.src -e ip.dst -e dns.count.queries -e dns.count.answers -e dns.qry.name -e dns.qry.type -e dns.resp.name -e dns.resp.type -e dns.resp.ttl -e dns.a -e dns.ns -e dns.mx.mail_exchange -e dns.cname -e dns.txt -e dns.flags.rcode -Y 'dns.count.answers gt 0' -E separator='|'

Traceback (most recent call last):
  File "collect.py", line 59, in <module>
    main()
  File "collect.py", line 45, in main
    tshark_response = subprocess.Popen(command, stdout=subprocess.PIPE, stdin=subprocess.PIPE)
  File "/usr/lib/python2.7/subprocess.py", line 711, in __init__
    errread, errwrite)
  File "/usr/lib/python2.7/subprocess.py", line 1343, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory


After reading the documentation (http://docs.python.org/2/library/subprocess.html#frequently-used-arguments), I realized that "shell=True" should be added as argument and seems one of the easiest option and Vola! It worked.

Ubuntu Xenial - apt update - E: Some index files failed to download. They have been ignored, or old ones used instead.

Recently, I installed Ubuntu 16.04 on a new PC and updated my repository URLs in "/etc/apt/sources.list" file to point to internal Ubuntu repository servers.


While I was updating my package indexes, I encountered the following errors:

E: Failed to fetch http://repo.xxx.xxx.in/ubuntu/dists/xenial/main/i18n/Translation-en  404  Not Found
E: Failed to fetch http://repo.xxx.xxx.in/ubuntu/dists/xenial-updates/main/i18n/Translation-en  404  Not Found
E: Failed to fetch http://repo.xxx.xxx.in/ubuntu/dists/xenial-backports/main/i18n/Translation-en  404  Not Found
E: Failed to fetch http://repo.xxx.xxx.in/ubuntu/dists/xenial-security/main/i18n/Translation-en  404  Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.

After searching on google and stackoverflow, it seems a language translation issue. To get rid of this issue, please follow the following steps:

1) Create a file named /etc/apt/apt.conf.d/99translations & add the following content to it:

Acquire::Languages "none";

2) You may also need to remove existing translation files in /var/lib/apt/lists/
$ sudo rm -vf /var/lib/apt/lists/*

3) Now, do cleanup and update of package indexes.

$ sudo apt-get clean
$ sudo apt-get update

Some useful references on stackoverflow:
1) https://askubuntu.com/questions/74653/how-can-i-remove-the-translation-entries-in-apt
2) https://askubuntu.com/questions/762273/16-04-upgrade-failed-to-fetch-empty-files-cant-be-valid-archives/764463

pip based python packages installation through proxy on Windows

For installing python packages through pip via proxy on Windows platform:

1) Create a directory: c:\Users\<User name>\pip
2) Then, create a file "pip.conf" in this directory with the following contents:

[global]
trusted-host = pypi.python.org
proxy = http://user:xxx@192.168.1.4:3128

Now, you are ready to install any python packages through pip:
c:\> pip install requests


Useful references:
1) https://stackoverflow.com/questions/28278207/python-cant-find-pip-ini-or-pip-conf-in-windows7
2) https://stackoverflow.com/questions/14149422/using-pip-behind-a-proxy