Develop Reference

Denied persmission to .py file on ev3dev, PuTTY

I have EV3 Lego Mindstorms and I instaled on it ev3dev operating system. I set the connection with the PC via SSH and using PuTTY I started to "programming". I used the cat > test2.py and wrote this code:
#!/usr/bin/env python3
import ev3dev.ev3 as ev3
motor = ev3.LargeMotor('outA')
motor.run_timed(time_sp = 1000, speed_sp = 500)
I saved the file and initialized it using ./test2.py. I got this output:
-bash: ./test2.py: Persmission denied
What caused it and what should I change?

try this:
sudo python3 test2.py
that will allows you to open almost anything in linux

Use ls -la ./test2.py in order to see the file permissions.
Look at the beginning of the output, you'll see something like this:
-rw-rw-r--
The first - means if is a directory or a file. In this case means that is a file.
Now If you observe the remaining chars there are 3 sets of 3 chars with means the permissions for the owner of the file, the owner group and the last set is for the rest of the users.
We have permissions to read, write and execute and in the example I showed there are read and write permissions for the owner user and the owner group but non permissions for the other users.
As Is said above you can just use sudo every time you execute the script but to run it with root privileges. However I would recommend you change your file permissions and using chmod
sudo chmod +x ./test2.py
This will let you execute the script. Take a look at chmod documentation to learn more: https://help.ubuntu.com/community/FilePermissions

Can't connect MongoDb on AWS EC2 using python

I have installed Mongodb 3.0 using this tutorial -
https://docs.mongodb.com/v3.0/tutorial/install-mongodb-on-amazon/
It has installed fine. I have also given permissions to 'ec2-user' to all the data and log folders ie var/lib/mongo and var/log/mongodb but and have set conf file as well.
Now thing is that mongodb server always fails to start with command
sudo service mongod start
it just say failed, nothing else.
While if I run command -
mongod --dbpath var/lib/mongo
it starts the mongodb server correctly (though I have mentioned same dbpath in .conf file as well)
What is it I am doing wrong here?

When you run sudo mongod it does not load a config file at all, it literally starts with the compiled in defaults - port 27017, database path of /data/db etc. - that is why you got the error about not being able to find that folder. The "Ubuntu default" is only used when you point it at the config file (if you start using the service command, this is done for you behind the scenes).
Next you ran it like this:
sudo mongod -f /etc/mongodb.conf
If there weren't problems before, then there will be now - you have run the process, with your normal config (pointing at your usual dbpath and log) as the root user. That means that there are going to now be a number of files in that normal MongoDB folder with the user:group of root:root.
This will cause errors when you try to start it as a normal service again, because the mongodb user (which the service will attempt to run as) will not have permission to access those root:root files, and most notably, it will probably not be able to write to the log file to give you any information.
Therefore, to run it as a normal service, we need to fix those permissions. First, make sure MongoDB is not currently running as root, then:
cd /var/log/mongodb
sudo chown -R mongodb:mongodb .
cd /var/lib/mongodb
sudo chown -R mongodb:mongodb .
That should fix it up (assuming the user:group is mongodb:mongodb), though it's probably best to verify with an ls -al or similar to be sure. Once this is done you should be able to get the service to start successfully again.
If you’re starting mongod as a service using:
sudo service mongod start
Make sure the directories defined for logpath, dbpath, and pidfilepath in your mongod.conf exist and are owned by mongod:mongod.

shutil.copy2 on a cifs share only works as root

-when writing the file to the cifs share from linux as root using python 2.7 shutil, no issue
-when writing the file manually using cp as a normal user, no issues
-when using python shutil.copy or copy2 as a normal user:
File "/usr/lib64/python2.7/shutil.py", line 120, in copy
copymode(src, dst)
File "/usr/lib64/python2.7/shutil.py", line 91, in copymode
os.chmod(dst, mode)
OSError: [Errno 1] Operation not permitted: '/mnt/RW_H-drive/file.csv

I was wrong about Debian vs CentOS in the comment above, the Debian system drive died and I'm running my jobs on an enterprise box where the only possibilities are CentOS or SUSE so I can't compare /etc/fstab files. I was trying to mount the share using dir_mode=0777,file_mode=0777 without the uid=xxxx. I don't understand why but when you specify dir_mode and file_mode you get the permissions you expect and can write files to the share manually but using shutil fails with the error above. If you remove dir_mode and file_mode and use user uid=xxxx where xxxx is the user ID of any locally recognozised user (Local,LDAP or NIS) then permissions work as expected manually (cp or touch command etc) and also via python with shutil. I may have had the same issue with Debian when I first setup the fstab file that's why I had this little bell telling me to try uid, nothing else. Bizare thing is that the UID of the user in fstab and the cifs user are unrelated as far as I recall, they don't even have to have the same name. Also both mount lines work when you change files on the share as root user.
Example:
//nasx/sharex/ /mnt/RW_H-drive/ cifs credentials=/root/smbcredentials,_netdev,uid=4321 0 0
Rather than:
//nasx/sharex/ /mnt/RW_H-drive/ cifs credentials=/root/smbcredentials,_netdev,file_mode=0777,dir_mode=0777 0 0

Ansible with Github: Permission denied (Publickey)

I'm trying to understand the GitHub ssh configuration with Ansible (I'm working on the Ansible: Up & Running book). I'm running into two issues.
Permission denied (publickey) -
When I first ran the ansible-playbook mezzanine.yml playbook, I got a permission denied:
failed: [web] => {"cmd": "/usr/bin/git ls-remote '' -h refs/heads/HEAD", "failed": true, "rc": 128}
stderr: Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
msg: Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
FATAL: all hosts have already failed -- aborting
Ok, fair enough, I see several people have had this problem. So I jumped to appendix A on running Git with SSH and it said to run the ssh-agent and add the id_rsa public key:
eval `ssh-agent -s`
ssh-add ~/.ssh/id_rsa
Output: Identity AddedI ran ssh-agent -l to check and got the long string: 2048 e3:fb:... But I got the same output. So I checked the Github docs on ssh key generations and troubleshooting which recommended updating the ssh config file on my host machine:
Host github.com
User git
Port 22
Hostname github.com
IdentityFile ~/.ssh/id_rsa
TCPKeepAlive yes
IdentitiesOnly yes
But this still provides the same error. So at this point, I start thinking it's my rsa file, which leads me to my second problem.
Key Generation Issues - I tried to generate an additional cert to use, because the Github test threw another "Permission denied (publickey)" error.
Warning: Permanently added the RSA host key for IP address '192.30.252.131' to the list of known hosts.
Permission denied (publickey).
I followed the Github instructions from scratch and generated a new key with a different name.
ssh-keygen -t rsa -b 4096 -C "me#example.com"
I didn't enter a passphrase and saved it to the .ssh folder with the name git_rsa.pub. I ran the same test and got the following:
$ ssh -i ~/.ssh/git_rsa.pub -T git#github.com
###########################################################
# WARNING: UNPROTECTED PRIVATE KEY FILE! #
###########################################################
Permissions 0644 for '/Users/antonioalaniz1/.ssh/git_rsa.pub' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
bad permissions: ignore key: ~/.ssh/github_rsa.pub
Permission denied (publickey).
I checked on the permissions and did a chmod 700 on the file and I still get Permission denied (publickey). I even attempted to enter the key into my Github account, but first got a message that the key file needs to start with ssh-rsa. So I started researching and hacking. Started with just entering the long string in the file (it started with --BEGIN PRIVATE KEY--, but I omitted that part after it failed); however, Github's not accepting it, saying it's invalid.
This is my Ansible command in the YAML file:
- name: check out the repository on the host
git: repo={{ repo_url }} dest={{ proj_path }} accept_hostkey=yes
vars:
repo_url: git#github.com:lorin/mezzanine-example.git
This is my ansible.cfg file with ForwardAgent configured:
[defaults]
hostfile = hosts
remote_user = vagrant
private_key_file = .vagrant/machines/default/virtualbox/private_key
host_key_checking = False
[ssh_connection]
ssh_args = -o ControlMaster=auto -o ControlPersist=60s -o ForwardAgent=yes
The box is an Ubuntu Trusty64 using Mac OS. If anyone could clue me into the file permissions and/or Github key generation, I would appreciate it.

I suspect the key permissions issue is because you are passing the public key instead of the private key as the arugment to "ssh -i". Try this instead:
ssh -i ~/.ssh/git_rsa -T git#github.com
(Note that it's git_rsa and not git_rsa.pub).
If that works, then make sure it's in your ssh-agent. To add:
ssh-add ~/.ssh/git_rsa
To verify:
ssh-add -l
Then check that Ansible respects agent forwarding by doing:
ansible web -a "ssh-add -l"
Finally, check that you can reach GitHub via ssh by doing:
ansible web -a "ssh -T git#github.com"
You should see something like:
web | FAILED | rc=1 >>
Hi lorin! You've successfully authenticated, but GitHub does not provide shell access.

I had the same problem, it took me some time, but I have found the solution.
The problem is the URL is incorrect.
Just try to change it to:
repo_url: git://github.com/lorin/mezzanine-example.git

I ran into this issue and discovered it by turning verbosity up on the ansible commands (very very useful for debugging).
Unfortunately, ssh often throws error messages that don't quite lead you in the right direction (aka permission denied is very generic...though to be fair that is often thrown when there is a file permission issue so perhaps not quite so generic). Anyways, running the ansible test command with verbose on helps recreate the issue as well as verify when it is solved.
ansible -vvv all -a "ssh -T git#github.com"
Again, the setup I use (and a typical one) is to load your ssh key into the agent on the control machine and enable forwarding.
steps are found here Github's helpful ssh docs
it also stuck out to me that when I ssh'd to the box itself via the vagrant command and ran the test, it succeeded. So I had narrowed it down to how ansible was forwarding the connection. For me what eventually worked was setting
[paramiko_connection]
record_host_keys = False
In addition to the other config that controls host keys verification
host_key_checking = False
which essentially adds
-o StrictHostKeyChecking=no
to the ssh args for you, and
-o UserKnownHostsFile=/dev/null
was added to the ssh args as well
found here:
Ansible issue 9442
Again, this was on vagrant VMs, more careful consideration around host key verification should be taken on actual servers.
Hope this helps

psexec run python script passed from host

I am trying to run a python script on a remote computer via psexec. I am able to connect and run python.exe with the following:
C:\test>psexec \\192.168.X.X -u domain\administrator -p password -i C:\Anaconda\python.exe
The path to python.exe is the path on the remote machine. This opens a python window on the remote machine - all good.
I want to now pass a python script from the host machine to run on the remote. This script is on the host machine in C:\test\test.py. I tried
psexec \\192.168.X.X -u domain\administrator -p password -i "C:\Anaconda\python.exe" -c C:\test\test.py
and get:
C:\Anaconda\python.exe exited on 192.168.X.X with error code 1.
I also tried-c test.py without the full path, and got a similar error. My thought is the remote application cannot find C:\test\test.py. I want to be able to pass the script from the host machine.
Any help is much appreciated. Thanks.

If the .py extension has been associated with the Python installation on the remote machine, you may be able to run your Python script by simply removing the Python executable from the command line:
psexec \\192.168.X.X -u domain\administrator -p password -i -c C:\test\test.py
Please note that I have not tried this as I don't presently have access to a remote machine, so I can't guarantee that it will work.
The line
psexec \\192.168.X.X -u domain\administrator -p password -i "C:\Anaconda\python.exe" -c C:\test\test.py
may be trying to run the command "C:\Anaconda\python.exe" -c C:\test\test.py on the remote machine. In other words, Python may be interpreting the -c switch, rather than PsExec. The Python switch -c specifies some Python code to run, and of course a filename is not valid Python code:
C:\Users\Luke>python -c "print 2 + 2"
4
C:\Users\Luke>python -c C:\test\test.py
File "<string>", line 1
C:\test\test.py
^
SyntaxError: invalid syntax
C:\Users\Luke>echo %ERRORLEVEL%
1

Was able to access a python script on a shared drive from the remote computer and host, and so by copying to the share from the host and reading from the share on the remote machine i had a suitable workaround (the -i switch is not required).
psexec \\remote_machine_name -u domain\user -p pswrd -i C:/Anaconda/python.exe \\server\share\test\test.py
Related: if you are running on windows and writing to a UNC path from a python script i.e test.py above, helpful path formatting help:
python copy files to a network location on Windows without mapping a drive