Problems writing to USB drive from _www process - c

I have a macOS C program which is a helper app. It runs as root and has sticky permissions.
One of the jobs of this program is to backup files to an external USB drive.
When I run the program from a terminal window... it works perfectly.
However, when invoked via a web admin page (eg., via the web server), it fails to run with an "operation not permitted".
This is on the latest macOS. I've set the drive to be "ignore ownership on this volume". The drive in /Volumes is also 777.
So... when the process is invoked via the web, the user/group is both _www. It appears that no matter what, the process invoked via _www can't write to the USB stick.
To be more specific... it can't create any new files. It CAN overwrite existing ones. It can't mkdir either.
I've googled my brains out and no solutions seem to work.
Any help would be appreciated!

Ok, I found the solution here.
Open System Preferences and go to Security/Privacy and then click Full Disk Access from the left side and enable the httpd access from the right side.
Thanks!

Related

How can I get access to files transferred from Windows to WSL-2 Ubuntu?

I have a Linux subsystem installed on my Windows machine. I've transferred a tar.gz file I want to access by finding the location of my subsystem and dragging the files over. But when I run the command:
tar -zxvf file_name.tar.gz
I get the error:
tar (child): vmd-1.9.4a51.bin.LINUXAMD64-CUDA102-OptiX650-OSPRay185.opengl.tar.gz: Cannot open: Permission denied
tar (child): Error is not recoverable: exiting now
tar: Child returned status 2
tar: Error is not recoverable: exiting now
I assume permission being denied is to do with having transferred from Windows since I couldn't access directories I created through Windows either. So, is there something I need to change to gain access to these files?
(PS. I know there are other way of getting tar.gz files other than transferring from Windows, but I'll need to do this for other folders too, I only included the filetype in case it was relevant .)
EDIT: You shouldn't attempt to drag files over. See answer below.
For starters, this belongs on Super User since it doesn't deal directly with a programming question. But since you've already provide an answer here that may be slightly dangerous (and even in your question), I didn't want to leave this unanswered for other people to find inadvertently.
If you used the first method in that link, you are using a WSL1 instance, not WSL2. Only WSL1 made the filesystem available in that way. And it's a really, really bad idea:
There is one hard-and-fast rule when it comes to WSL on Windows:
DO NOT, under ANY circumstances, access, create, and/or modify Linux files inside of your %LOCALAPPDATA% folder using Windows apps, tools, scripts, consoles, etc.
Opening files using some Windows tools may read-lock the opened files and/or folders, preventing updates to file contents and/or metadata, essentially resulting in corrupted files/folders.
I'm guessing you probably went through the install process for WSL2, but you installed your distribution before setting wsl --set-default-version 2 or something like that.
As you can see in the Microsoft link above, there's now a safe method for transferring and editing files between Windows and WSL - the \\wsl$\ tmpfs mounts. Note that as a tmpfs mount stored in memory, it's really more for transferring files over. They will disappear when you reboot or shutdown WSL.
But even if you'd used the second method in that article (/mnt/c), you probably would have run into permissions issues. If you do, the solution should be to remount the C: drive with your uid/gid as I describe here.

UWP on Windows 1903 broadFileSystemAccess access denied on Drive D

broadFileSystemAccess works as expected when accessing files on Drive C, however, as soon as I try to access files on another Drive, I get access denied
Without broadFileSystemAccess, load a file from the Desktop. Access Denied as expected.
With broadFileSystemAccess, load a file from the Desktop. Access Granted as expected.
With broadFileSystemAccess, load a file from the Drive D. Access Denied not expected.
Dim file = Await Windows.Storage.StorageFile.GetFileFromPathAsync("D:\TestFile.txt")
I should be able to access any drive. My system has 4 drives and a NAS, only Drive C is accessable using broadFileSystemAccess.
What do I need to do to allow my app to access files on other drives; this is the only thing holding me back from porting my WPF apps.
Thanks in advance
I'm going to close this. I updated to the latest patch today and it's fixed. The prompt to ask a user to allow the app file system permissions is still broken (e.g. it doesn't prompt still), but the access to files on other drives is now working.
Additional info: I also created new C# and vb.net apps to test the theory and they work as expected, I then went back to the failing project and it's now working - hence me assuming the patch fixed it.

Work on a remote project with Eclipse via SSH

I have the following boxes:
a) A Windows box with Eclipse CDT,
b) A Linux box, accessible for me only via SSH.
Both the compiler and the hardware required to build and run my project is only on machine B.
I'd like to work "transparently" from a Windows box on that project using Eclipse CDT and be able to build, run and debug the project remotely from within the IDE.
How do I set up that:
The building will work? Any simpler solutions than writing a local makefile which would rsync the project and then call a remote makefile to initiate the actual build? Does Eclipse managed build have a feature for that?
The debugging will work?
Preferably - the Eclipse CDT code indexing will work? Do I have to copy all required header files from machine B to machine A and add them to include path manually?
Try the Remote System Explorer (RSE). It's a set of plug-ins to do exactly what you want.
RSE may already be included in your current Eclipse installation. To check in Eclipse Indigo go to Window > Open Perspective > Other... and choose Remote System Explorer from the Open Perspective dialog to open the RSE perspective.
To create an SSH remote project from the RSE perspective in Eclipse:
Define a new connection and choose SSH Only from the Select Remote System Type screen in the New Connection dialog.
Enter the connection information then choose Finish.
Connect to the new host. (Assumes SSH keys are already setup.)
Once connected, drill down into the host's Sftp Files, choose a folder and select Create Remote Project from the item's context menu. (Wait as the remote project is created.)
If done correctly, there should now be a new remote project accessible from the Project Explorer and other perspectives within eclipse. With the SSH connection set-up correctly passwords can be made an optional part of the normal SSH authentication process. A remote project with Eclipse via SSH is now created.
The very simplest way would be to run Eclipse CDT on the Linux Box and use either X11-Forwarding or remote desktop software such as VNC.
This, of course, is only possible when you Eclipse is present on the Linux box and your network connection to the box is sufficiently fast.
The advantage is that, due to everything being local, you won't have synchronization issues, and you don't get any awkward cross-platform issues.
If you have no eclipse on the box, you could thinking of sharing your linux working directory via SMB (or SSHFS) and access it from your windows machine, but that would require quite some setup.
Both would be better than having two copies, especially when it's cross-platform.
I'm in the same spot myself (or was), FWIW I ended up checking out to a samba share on the Linux host and editing that share locally on the Windows machine with notepad++, then I compiled on the Linux box via PuTTY. (We weren't allowed to update the ten y/o versions of the editors on the Linux host and it didn't have Java, so I gave up on X11 forwarding)
Now... I run modern Linux in a VM on my Windows host, add all the tools I want (e.g. CDT) to the VM and then I checkout and build in a chroot jail that closely resembles the RTE.
It's a clunky solution but I thought I'd throw it in to the mix.
My solution is similar to the SAMBA one except using sshfs. Mount my remote server with sshfs, open my makefile project on the remote machine. Go from there.
It seems I can run a GUI frontend to mercurial this way as well.
Building my remote code is as simple as: ssh address remote_make_command
I am looking for a decent way to debug though. Possibly via gdbserver?
I tried ssh -X but it was unbearably slow.
I also tried RSE, but it didn't even support building the project with a Makefile (I'm being told that this has changed since I posted my answer, but I haven't tried that out)
I read that NX is faster than X11 forwarding, but I couldn't get it to work.
Finally, I found out that my server supports X2Go (the link has install instructions if yours does not). Now I only had to:
download and unpack Eclipse on the server,
install X2Go on my local machine (sudo apt-get install x2goclient on Ubuntu),
configure the connection (host, auto-login with ssh key, choose to run Eclipse).
Everything is just as if I was working on a local machine, including building, debugging, and code indexing. And there are no noticeable lags.
I had the same problem 2 years ago and I solved it in the following way:
1) I build my projects with makefiles, not managed by eclipse
2) I use a SAMBA connection to edit the files inside Eclipse
3) Building the project:
Eclipse calles a "local" make with a makefile which opens a SSH connection
to the Linux Host. On the SSH command line you can give parameters which
are executed on the Linux host. I use for that parameter a makeit.sh shell script
which call the "real" make on the linux host.
The different targets for building you can give also by parameters from
the local makefile --> makeit.sh --> makefile on linux host.
The way I solved that one was:
For windows:
Export the 'workspace' directory from the Linux machine using samba.
Mount it locally in windows.
Run Eclipse, using the mounted 'workspace' directory as the eclipse workspace.
Import the project you want and work on it.
For Linux:
Mount the 'workspace' directory using sshfs
Run Eclipse.
Run Eclipse, using the mounted 'workspace' directory as the eclipse workspace.
Import the project you want and work on it.
In both cases you can either build and run through Eclipse, or build on the remote machine via ssh.
For this case you can use ptp eclipse https://eclipse.org/ptp/ for source browsing and building.
You can use this pluging to debug your application
http://marketplace.eclipse.org/content/direct-remote-c-debugging
How to edit in Eclipse locally, but use a git-based script I wrote (sync_git_repo_from_pc1_to_pc2.sh) to synchronize and build remotely
The script I wrote to do this is sync_git_repo_from_pc1_to_pc2.sh.
Readme: README_git-sync_repo_from_pc1_to_pc2.md
Update: see also this alternative/competitor: GitSync:
How to use Sublime over SSH
https://github.com/jachin/GitSync
This answer currently only applies to using two Linux computers [or maybe works on Mac too?--untested on Mac] (syncing from one to the other) because I wrote this synchronization script in bash. It is simply a wrapper around git, however, so feel free to take it and convert it into a cross-platform Python solution or something if you wish
This doesn't directly answer the OP's question, but it is so close I guarantee it will answer many other peoples' question who land on this page (mine included, actually, as I came here first before writing my own solution), so I'm posting it here anyway.
I want to:
develop code using a powerful IDE like Eclipse on a light-weight Linux computer, then
build that code via ssh on a different, more powerful Linux computer (from the command-line, NOT from inside Eclipse)
Let's call the first computer where I write the code "PC1" (Personal Computer 1), and the 2nd computer where I build the code "PC2". I need a tool to easily synchronize from PC1 to PC2. I tried rsync, but it was insanely slow for large repos and took tons of bandwidth and data.
So, how do I do it? What workflow should I use? If you have this question too, here's the workflow that I decided upon. I wrote a bash script to automate the process by using git to automatically push changes from PC1 to PC2 via a remote repository, such as github. So far it works very well and I'm very pleased with it. It is far far far faster than rsync, more trustworthy in my opinion because each PC maintains a functional git repo, and uses far less bandwidth to do the whole sync, so it's easily doable over a cell phone hot spot without using tons of your data.
Setup:
Install the script on PC1 (this solution assumes ~/bin is in your $PATH):
git clone https://github.com/ElectricRCAircraftGuy/eRCaGuy_dotfiles.git
cd eRCaGuy_dotfiles/useful_scripts
mkdir -p ~/bin
ln -s "${PWD}/sync_git_repo_from_pc1_to_pc2.sh" ~/bin/sync_git_repo_from_pc1_to_pc2
cd ..
cp -i .sync_git_repo ~/.sync_git_repo
Now edit the "~/.sync_git_repo" file you just copied above, and update its parameters to fit your case. Here are the parameters it contains:
# The git repo root directory on PC2 where you are syncing your files TO; this dir must *already exist*
# and you must have *already `git clone`d* a copy of your git repo into it!
# - Do NOT use variables such as `$HOME`. Be explicit instead. This is because the variable expansion will
# happen on the local machine when what we need is the variable expansion from the remote machine. Being
# explicit instead just avoids this problem.
PC2_GIT_REPO_TARGET_DIR="/home/gabriel/dev/eRCaGuy_dotfiles" # explicitly type this out; don't use variables
PC2_SSH_USERNAME="my_username" # explicitly type this out; don't use variables
PC2_SSH_HOST="my_hostname" # explicitly type this out; don't use variables
Git clone your repo you want to sync on both PC1 and PC2.
Ensure your ssh keys are all set up to be able to push and pull to the remote repo from both PC1 and PC2. Here's some helpful links:
https://help.github.com/en/github/authenticating-to-github/connecting-to-github-with-ssh
https://help.github.com/en/github/authenticating-to-github/generating-a-new-ssh-key-and-adding-it-to-the-ssh-agent
Ensure your ssh keys are all set up to ssh from PC1 to PC2.
Now cd into any directory within the git repo on PC1, and run:
sync_git_repo_from_pc1_to_pc2
That's it! About 30 seconds later everything will be magically synced from PC1 to PC2, and it will be printing output the whole time to tell you what it's doing and where it's doing it on your disk and on which computer. It's safe too, because it doesn't overwrite or delete anything that is uncommitted. It backs it up first instead! Read more below for how that works.
Here's the process this script uses (ie: what it's actually doing)
From PC1: It checks to see if any uncommitted changes are on PC1. If so, it commits them to a temporary commit on the current branch. It then force pushes them to a remote SYNC branch. Then it uncommits its temporary commit it just did on the local branch, then it puts the local git repo back to exactly how it was by staging any files that were previously staged at the time you called the script. Next, it rsyncs a copy of the script over to PC2, and does an ssh call to tell PC2 to run the script with a special option to just do PC2 stuff.
Here's what PC2 does: it cds into the repo, and checks to see if any local uncommitted changes exist. If so, it creates a new backup branch forked off of the current branch (sample name: my_branch_SYNC_BAK_20200220-0028hrs-15sec <-- notice that's YYYYMMDD-HHMMhrs--SSsec), and commits any uncommitted changes to that branch with a commit message such as DO BACKUP OF ALL UNCOMMITTED CHANGES ON PC2 (TARGET PC/BUILD MACHINE). Now, it checks out the SYNC branch, pulling it from the remote repository if it is not already on the local machine. Then, it fetches the latest changes on the remote repository, and does a hard reset to force the local SYNC repository to match the remote SYNC repository. You might call this a "hard pull". It is safe, however, because we already backed up any uncommitted changes we had locally on PC2, so nothing is lost!
That's it! You now have produced a perfect copy from PC1 to PC2 without even having to ensure clean working directories, as the script handled all of the automatic committing and stuff for you! It is fast and works very well on huge repositories. Now you have an easy mechanism to use any IDE of your choice on one machine while building or testing on another machine, easily, over a wifi hot spot from your cell phone if needed, even if the repository is dozens of gigabytes and you are time and resource-constrained.
Resources:
The whole project: https://github.com/ElectricRCAircraftGuy/eRCaGuy_dotfiles
See tons more links and references in the source code itself within this project.
How to do a "hard pull", as I call it: How do I force "git pull" to overwrite local files?
Related:
git repository sync between computers, when moving around?

Live Mesh has screwed up my file permissions

I got the bright idea of using Live Mesh to sync up my development directories between my laptop and desktop machines. It appears that the permission on any new files that are added through Live Mesh do not inherit permissions from the parent directory. Now I cannot overwrite the permissions on those files. I keep getting an "Access is Denied" error when attempting to do so, even if I am running Windows Explorer as administrator. I have two questions:
How can I modify the file permissions to allow them to inherit again?
Has anyone used Live Mesh to do this sort of thing? Or should I be using FolderShare instead?
See the TakeOwn command to regain access to your files. You may also need to use the cacls command depending on the state of your files.
In my experience, Windows Live Mesh does not handle syncing files between multiple user accounts. Windows Live Folder Sync seems to handle this better.

How do I find the database file on an Android virtual device?

My plan is to prepopulate a database on a virtual device and then include database in the distribution of my app.
However, I can't find the database file.
Is it on my hard disk some where?
How do I get it?
I tried connecting using adb, I did an "ls" and then got really scared by this obscure list of directories:
sqlite_stmt_journals
cache
sdcard
etc
system
sys
sbin
proc
init.rc
init.goldfish.rc
init
default.prop
data
root
dev
Even when I cd over to /data/data/your.package.here/databases I still do not have access to the actual database file. I can't use sqlite3 or do a pull on it. Is there a way to change permissions?
This works fine on my emulator, but fails on the actual device
adb pull /data/data//databases/mydb.db .
It should be in /data/data/your.package.here/databases, where your.package.here represents the package associated with your application, as defined in your AndroidManifest.xml file.
If you want to navigate to your database (which is located /data/data/your.package.here/databases), make sure you are a root user while navigating shell. To do so, type "su" once you enter the command prompt. When you are a root user, you can navigate wherever you want.
The blog post below gives a good solution of how to find and access your database. The post talks about using busybox, which provides useful utilities at the command line, to find your database and gives a few useful examples on how to use sqlite3 to access the DB and tables.
http://davanum.wordpress.com/2007/12/11/android-how-to-poke-around-the-sqlite3-databases/

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