cannot create directory : Permission denied

I had created a directory mkdir xyz with user centos

The following is the output of ll command:
drw——-. 2 centos centos 6 Oct 6 06:11 xyz

When I executed cd xyz I received the following error:
bash: cd: xyz/: Permission denied

I could not access the directory in any case
mkdir xyz/abc
touch xyz/test.txt
All returned the same error.

The solution for this is to add +x permission on the directory.
chmod 700 xyz/
Then I could cd into the directory and create files and folders.

The logic behind this is as belows:

Read bit = If set, you can read this list. So, for example, if you have a directory named poems:

  • You can ls poems and you’ll get a list of items living within (-l won’t reveal any details!).
  • You can use command-line completion i.e. touch poems/so <TAB> poems/somefile.
  • You cannot make poems your working directory (i.e. cd into it).

Write bit = If set, you can modify this list i.e. you can {add,rename,delete} names on it. But! You can actually do it only if the execute bit is set too.

Execute bit = Make this directory your working directory i.e. cd into it. You need this permission if you want to:

  • access (read, write, execute) items living within.
  • modify the list itself i.e. add, rename, delete names on it (of course the write bit must be set on the directory).

Interesting case 1: If you have write + execute permissions on a directory, you can {delete,rename} items living within even if you don’t have write perimission on those items. (use sticky bit to prevent this)

Interesting case 2: If you have execute (but not write) permission on a directory AND you have write permission on a file living within, you cannot delete the file (because it involves removing it from the list). However, you can erase its contents e.g. if it’s a text file you can use vi to open it and delete everything. The file will still be there, but it will be empty.

So the solution is to add +x to the directory.
You will be able to cd into the directory even if you don’t have +x if you are the root user.

Advertisements

Setting your username in Git

Git uses a username to associate commits with an identity. The Git username is not the same as your GitHub username.

You can change the name that is associated with your Git commits using the git config command. The new name you set will be visible in any future commits you push to GitHub from the command line. If you’d like to keep your real name private, you can use any text as your Git username.

Changing the name associated with your Git commits using git config will only affect future commits and will not change the name used for past commits.

Setting your Git username for every repository on your computer

  1. Open Git Bash.
  2. Set a Git username:
    $ git config --global user.name "Mona Lisa"
    
  3. Confirm that you have set the Git username correctly:
    $ git config --global user.name
    > Mona Lisa
    

Setting your Git username for a single repository

  1. Open Git Bash.
  2. Change the current working directory to the local repository where you want to configure the name that is associated with your Git commits.
  3. Set a Git username:
    $ git config user.name "Mona Lisa"
    
  4. Confirm that you have set the Git username correctly:
    $ git config user.name
    > Mona Lisa

Jenkins – Publish Over SSH Plugin: How to copy directory

Problem:

I’m trying to use Jenkins’ Publish Over SSH plugin to copy all files AND sub-directories of some given directory, but so far, I’ve only able to copy files and NOT directory.

I have a directory named foo in my workspace, and during the build, I want to copy everything in this directory to a remote server. I’ve tried this pattern foo/**, but it doesn’t copy all sub-directories.

Solution:

For recursive copy of directory you should give

foo/**/*

Jenkins: publish over ssh does not put files to remote server

Problem:

I have strange issue on the latest Jenkins 1.634.
Publish over ssh writes to log that it puts correctly file but nothing appears on remote server.
e.g. I have logs
SSH: cd [var/www/data-fb-localtest]
SSH: OK
SSH: put [asm.js]
SSH: OK
SSH: put [asm.js.gz]
SSH: OK
SSH: put [hero.data]
SSH: OK
SSH: put [hero_main.js]
SSH: OK
SSH: cd [/home/dev]
SSH: OK
SSH: cd [var/www/data-fb-localtest/]
SSH: OK
SSH: put [achievements.exm]
SSH: OK
SSH: put [ai.exm]
SSH: OK
SSH: put [atlas0.atlas]
SSH: OK
SSH: put [atlas0.rgbz]
SSH: OK
but nothing appears in var/www/data-fb-localtest

 

Solution:

I found the issue. I do not set root remote directory and in publish task use absolute path. But plugin does use not absolute path but path relative to my user’s home directory

fswatch – Monitors Files and Directory Changes or Modifications in Linux

fswatch is a cross-platform, file change monitor that gets notification alerts when the contents of the specified files or directories are altered or modified.

It executes four types of monitors on different operating systems such as:

  1. A monitor build on the File System Events API of Apple OS X.
  2. A monitor based on kqueue, a notification interface present in FreeBSD 4.1 also supported on many *BSD systems, OS X inclusive.
  3. A monitor based on File Events Notification API of the Solaris kernel plus its spin-offs.
  4. A monitor based on inotify, a kernel subsystem that shows file system modifications to apps.
  5. A monitor based on ReadDirectoryChangesW, a Windows API that records alters to a directory.
  6. A monitor that regularly check that status of file system, keeps file modification times in memory, and manually determine file system changes (which works anywhere, where stat can be used).

Features of fswatch

  1. Supports several OS-specific APIs
  2. Allows recursive directory monitoring
  3. Performs path filtering using including and excluding regular expressions
  4. Supports customizable record format
  5. Additionally, it supports periodic idle events

How To Install fswatch in Linux Systems

Unfortunately, fswatch package is not available to install from the default system repositories in any Linux distributions. The only way to install the latest version of fswatch is to build from source tarball as show in the following installation instructions.

First grab the latest fswatch tarball using following wget command and install it as shown:

$ wget https://github.com/emcrisostomo/fswatch/releases/download/1.9.3/fswatch-1.9.3.tar.gz
$ tar -xvzf fswatch-1.9.3.tar.gz
$ cd fswatch-1.9.3
$ ./configure
$ make
$ sudo make install 

Important: Make sure you’ve GNU GCC (C and C++ Compiler) and Development Tools (build-essential on Debian/Ubuntu) installed on the system, before you compile fswatch from source. If not, install it using following command on your respective Linux distributions..

# yum group install 'Development Tools'		[On CentOS/RHEL]
# dnf group install 'Development Tools'		[On Fedora 22+ Versions]
$ sudo apt-get install build-essential          [On Debian/Ubuntu Versions]

On Debian/Ubuntu distributions, you might get following error while executing fswatch command..

fswatch: error while loading shared libraries: libfswatch.so.6: cannot open shared object file: No such file or directory

To fix it, you need to execute the command below, this will help refresh the links and cache to the dynamic libraries before you can start using fswatch.

$ sudo ldconfig

How do I use fswatch on Linux?

The general syntax for running fswatch is:

$ fswatch [option] [path]

On Linux, it is recommended that you use the default inotify monitor, you can list available monitors by employing the -M or - list-monitors option:

$ fswatch -M
$ fswatch --list-monitors

fswatch - List Monitors

The command below enables you to watch the changes in the current directory (/home/tecmint), with events being delivered to standard output every 4 seconds.

The -l or –-latency option allows you to set the latency in seconds, the default being 1 second.

$ fswatch -l 4 .

fswatch - Monitor Home Directory Changes

The next command monitors changes to the /var/log/auth.log file every 5 seconds:

$ fswatch -l 5 /var/log/auth.log

Using -t or --timestamp option prints the time stamp for every event, to print the time in UTC format, employ -u or --utf-time option. You can as well format time using -f or --format-time format option:

$ fswatch --timestamp /var/log/auth.log

Next, -x or --event-flags tells fswatch to print the event flags along side the event path. You can use –event-field-seperator option to print events using the particular separator.

$ fswatch --events-flags ~ /var/log/auth.log

To print the numeric value of an event indicating changes in your home directory and /var/log/auth.log file, use -n or --numeric option as below:

$ fswatch --numeric ~ /var/log/auth.log 

Perhaps you can look through the fswatch man page for detailed usage options and information:

$ man fswatch

Pyinotify – Monitor Filesystem Changes in Real-Time in Linux

Pyinotify is a simple yet useful Python module for monitoring filesystems changes in real-time in Linux.

As a System administrator, you can use it to monitor changes happening to a directory of interest such as web directory or application data storage directory and beyond.

It depends on inotify (a Linux kernel feature incorporated in kernel 2.6.13), which is an event-driven notifier, its notifications are exported from kernel space to user space via three system calls.

The purpose of pyinotify is to bind the three system calls, and support an implementation on top of them providing a common and abstract means to manipulate those functionalities.

In this article, we will show you how to install and use pyinotify in Linux to monitor filesystem changes or modifications in real-time.

Dependencies

In order to use pyinotify, your system must be running:

  1. Linux kernel 2.6.13 or higher
  2. Python 2.4 or higher

How to Install Pyinotify in Linux

First start by checking the kernel and Python versions installed on your system as follows:

# uname -r 
# python -V

Once dependencies are met, we will use pip to install pynotify. In most Linux distributions, Pip is already installed if you’re using Python 2 >=2.7.9 or Python 3 >=3.4 binaries downloaded from python.org, otherwise, install it as follows:

# yum install python-pip      [On CentOS based Distros]
# apt-get install python-pip  [On Debian based Distros]
# dnf install python-pip      [On Fedora 22+]

Now, install pyinotify like so:

# pip install pyinotify

It will install available version from the default repository, if you are looking to have a latest stable version of pyinotify, consider cloning it’s git repository as shown.

# git clone https://github.com/seb-m/pyinotify.git
# cd pyinotify/
# ls
# python setup.py install

How to Use pyinotify in Linux

In the example below, I am monitoring any changes to the user tecmint’s home (/home/tecmint) directory as root user (logged in via ssh) as shown in the screenshot:

# python -m pyinotify -v /home/tecmint

Monitor Directory Changes

Next, we will keep a watch for any changes to the web directory (/var/www/html/tecmint.com):

# python -m pyinotify -v /var/www/html/tecmint.com

To exit the program, simply hit [Ctrl+C].

Note: When you run pyinotify without specifying any directory to monitor, the /tmp directory is considered by default.