Is it possible to install and run applications using the regular filesystem but make created files and changes written to a specific directory?
I want to make an application believe it is installed to the system root and remove it by just deleting one folder from my home directory. A lightweight solution would be great!
It should be possible by combining unionfs and namespace. Create a mount namespace (using unshare(1)), mount a unionfs over everything and run the application there (I haven't done it myself, so no example commands, sorry).
Take a look at mbox http://pdos.csail.mit.edu/mbox/
It intercepts system calls to a temporary directory which you can specify
Related
my application is required update its program files when it detects a new version on the server. The update mechanism is performed by the application itself, and it replaces old code with new code in the same directory. Which directory in linux is best suited for this? If there is a standard directory which has write access by default(analogous to %AppData%\Local for windows), I would like to know which one it is.
I have tried using /var/<my-app-name-here> and /opt/<my-app-name-here>, but none of these directories have write access by default. The only way I can use them update files in them is if the user uses sudo, so i would just like to avoid making those problems by just installing to a directory with write access to begin with.
I am using a tool called jpackage to make the .deb file which install the application.
I require a VM for developing and my host is where my IDE is. I have discovered that inotifywait does not work with shared folders, as I am sharing a local folder with my Linux guest using Virtual Box.
Basically, I have a simple bash script which needs to watch a directory and wait for any file changes. Inotifywait would be the best option but I cannot get it to work with my shared folder.
I was wondering if there is another option for my problem?
Depending on the sizes of the files and the nature of the changes you could:
Create a checksum (md5, CRC, SHA256) of the files and watch for changes
check the size of the files and watch for changes
I have a standalone server running Cygwin -- I did not setup this server, it was inherited. Anyway, I'd like to know what options the installing admin selected in the setup program.
I've read that I could look in /etc/setup, /etc/postinstall, or /etc/preremove but there are a lot of packages in those directories... same goes for the output of cygcheck -c.
I don't want to know every single library on the system... just how to duplicate the install. Is there a way to determine which packages were select in the GUI setup program?
Thanks!
Cygwin is pretty standalone. You should be able to archive up the entire Cygwin directory (and subdirectories) and move it to the same location on another system.
If you archive it up I recommend 7-zip. You can get it free here. The built in Windows archiver can create permission problems when an archive is extracted on a destination system. I recommend 7-zip for both archiving and unarchiving. If you use the built in Windows archiver and then move it to the new system and extract it - it will extract without errors. However you may find things don't actually work right while using some Cygwin applications
If you don't copy everything you won't move any of the original admin's custom changes.
On arangodb's documentation it is suggested to use a different folder to databases during development phase (/tmp/fancy_db). I try to use this but I get errors saying that no database exists... How can I create databases on this temporary folder?
Thank you
arangod will not create any folder for you, you have to give it an existing folder on your system.
/tmp/fancy_db
is just a suggestion you can use any folder at any location on your machine.
However to create a folder in /tmp on a unix system open a terminal and enter:
bash> mkdir /tmp/fancy_db
On a windows system (as far as i know) \tmp is not available, you can use
C:\tmp\fancy_db
instead (create it with Explorer)
I have Qt application which should work on multiple platforms. One of those platforms is Linux. I am completely new in Linux world.
My application need to create and manage set of data files. After reading some links about linux directory structure I decided to store data files in /var/myapp directory and in its subdirectories.
Here is the problem: if my application runs without superuser privileges then it has no rights to create /var/myapp directory. Even if i will create directory manually (with sudo) my application will not have rights to write files there.
Is it possible to temporary elevate application's permissions from Qt code to create /var/myapp directory and write files there?
Or possibly there is another place in Linux directory structure which is by default available for storing application's data files?
Only root can create directories in /var. If your application needs a subdirectory under /var, you need to create it during installation (which typically runs with root permissions), and chmod it appropriately: either create a group for users that may run your application, put /var/myapp in that group, and chmod it to 770; or just chmod the directory to 777 to allow everyone to access it. If you want to prevent writing by regular users, use 755 or 750 instead. (For data files, don't set the execute bit though: the appropriate permissions here are 666/660/644/640). Instead of octal triplets, you may prefer the more elaborate mnemoic syntax to chmod, e.g. chmod ug+x filename adds (+) the execute bit (x) to filename for the owning user (u) and group (g).
However, /var is not necessarily the best choice: /var is typically used for volatile data (temporary files etc.), as well as things that are expected to change frequently (mail, log files, etc.). Other data should go into either:
/usr/share/{appname} for system-wide data files and resources
/etc/{appname} for system-wide configuration files
~/.{appname} (old convention) or ~/.config/{appname} for per-user configuration files
/var/tmp/{appname} for temporary files
Also, you want to make the /usr prefix configurable; most distributions reserve /usr for package-managed files, except /usr/local, which mirrors /usr for out-of-distro installs (so in that case, your system-wide resources go into /usr/local/share instead of /usr/share).
You could distribute it without installation scripts, but you'd have to tell them to run it once as root... or have the app run itself as root using gksudo/kdesudo if its system wide data files do not exist.
The custom though is to make a package (.deb, .rpm, or even a .tar.gz that the user will extract himself) including all necessary files.
But linux (and OS X for that matter) are multi user systems. Are you sure your files belong in /var or /usr? If they're created at runtime as you say, don't they depend on user input? In which case you need to put them in some directory inside the user's home directory (getenv("HOME")).