General :: Possible To Bypass NFS File Permissions By Using A User-space NFS Client?

Jul 4, 2011

There are some user-space based NFS clients (e.g. NFS Client library). Can I bypass file permissions by using such client? code...

Client1 uses usual NFS client (kernel-mode based) and user1@client1 can read only file1, but not file2.
As I understand, client1 sends uid in nfs request, server1 do a permissions check based on the request data. So, I suggest this is possible to have a client2:

Client2 uses user-space client, and hacker@client2 knows uids of user1 and user2; If he wants to read file1 he can send uid of user1; if he wants to read file2, he sends uid of user2.

Is the scheme possible?

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General :: Install Torrent Client In User Space

Jul 14, 2011

I've been looking to get some torrent downloads running on school servers, but I obviously can't install a torrent client because I don't have root (and by extent, can't run anything requiring root privileges). Servers are running various versions of Red Hat (at least the x86_64 ones are, I don't want to recompile if I don't have to). Google has failed me thus far.

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General :: Division Of Logical Memory Space In To User Space And Kernel Space

Jan 4, 2010

Logical Memory Space of 4GB is divided in to 3GB User Space and 1GB Kernel Space. Always. Correct?

1. How can we change it? (just changing value of PAGE_OFFSET is okay?)

2. If system have only 256MB of memory (embedded system) and suppose Kernel Modules eat away all the memory during boot. User space will be left will no memory. Is this case possible?

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General :: Permissions - Manually Mount A File System Read/write As A Normal User?

Oct 6, 2010

I want to simply mount an ext4 file-system onto a normal mount point in Ubuntu (/media/whereever), as read-writable for the current logged-in user, i.e. me.

I don't want to add anything into /etc/fstab, I just want to do it now, manually. I need super-user privileges to mount a device, but then only root can read-write that mount. I've tried various of the mount options, added it into fstab, but with no luck.

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General :: Calling User Space Callback Function From Kernel Space?

Sep 22, 2009

I am writing device driver in which i have to call callback function from kernel space, which are saving my data. But the callback functions are in userspace. While accessing them i am getting segmentation fault.

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General :: Virtual Space Seen By Each New Process In User Space?

Jun 21, 2010

In a 32-bit system, max memory addressable is 4GB. Now Linux kernel does memory mapping division of 1GB for kernel address space and 3GB for user address space. That means 4GB of virtual address space is divided between kernel (1GB) and user (3GB).

Q1. All virtual mapping utilizes the available physical RAM without any division? I mean to say that if RAM is 512MB then a page in kernel space can lie any where RAM (leave aside old PCI dma accesses)? (How this fits to fact that kernel memory is non-pageble)

Q2. If a process is created in user space, it has visibility 4GB address space or 3GB address space?

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Ubuntu :: Chmod File Permissions Between User And Root ?

Jan 26, 2011

I want to have two kind of users in a work machine having ubuntu 10.04,

1) He is the admin, have sudo privilages and install, do all types of work, his username is abhilash

2) A user who is normally a IT administrator, who can just install or remove softwares, but cannot access files of abhilash.

I'm trying to do this and my head is going blank, The problem where i'm stuck is, if IT admin can install softwares, then he can become sudo as sudo su, then he can view my files

So here is a small test i did, first with abhilash.

Code:

Now others and group don't have any permissions! But when IT Administrator becomes root, he can see this file

Code:

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Security :: User Names And File Permissions On Two Different Computers?

Jul 23, 2009

Picture the following:On computer A, local user John (and John alone) has rwx access to file1.txtComputer B also has a local user account named John. If file1.txt was to be copied from computer A to computer B, would the user account John on computer B be able to access it?I guess this wouldn't work using two windows computers due to the User name / GUID relationship. Maybe linux has something similar?

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Software :: Squid Dansguardian Allow User To Bypass With Password?

Apr 14, 2010

I have Squid and Dans set up on a passthrough box with 2 nics, port 80 requestsEverything is working great. I need to know if there is a way to set up Dansguardian so that a user can enter a password on a blocked page to access it.

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Security :: Folder Permissions To Avoid File Upload By Http User?

Feb 24, 2011

However, configured a website on a dedicated server using WHM/cPanel. The site was uploaded using the master account for the website.

The security issue is public users are able to upload files on to my server via the website. They could even access the root and execute whatever they want on the server.

I have consulted with 2-3 Linux experts. According to them, the PHP user has rights to execute anything on the server or upload & store files in whichever folder they want.

Can I protect my folders to avoid file uploads via the website. The application has security vulnerabilites. However, I want to prevent hackers to enter my site until the vulnerabilities are fixed.

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General :: Measure Kernel Space Time And User Space Time?

Nov 28, 2010

measure kernel space time and user space time?

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General :: Add New User With Same Permissions?

Oct 26, 2010

I have just installed Ubuntu on a machine at work and wondered how i can add a new user with the same permissions as the "main user"? I added a user via the "users&groups" gui but sorting permissions looks tricky.

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General :: Make NIS User Information Override Local User Information On Client Systems?

Jul 30, 2011

How would you make NIS user information override local user information on client systems? This is what I think is right? Add nis on the passwd registration file on the second line Is this correct?

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General :: Ubuntu Working On Thin Client Cannot Provide Accurate Disk Space Reports?

Jul 26, 2011

We are using thin client systems in our work environment. There is a central ubuntu server and by using thin clients, we are connecting to our homes. The problem is when I try to install an application, it reported me that I had 200 mb of disk space. But when i try to look from console, I see that /home folder has over 250 gb s of disk space. Even when I try to look from baobab, Disk Usage Analyzer in Ubuntu, i see that my home file system is full.

So what's the reason that I am receiving different kinds of disk space report from different sources? Our system admin here told me that some applications foolishly try to see the physical devices on the thin client and got confused as a result. Is this true?

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Programming :: Passing Data Between Kernel Space To User Space In Asynchronous Way

Dec 13, 2010

I am developing a I2C CDROM client driver. The CDROM firmware supports TOC information read through a I2C command. It sends the TOC information in burst ( Interrupts a GPIO pin when it is ready ) and my CPU does a I2C read to read the TOC. When the CDROM firmware finishes sending the last data burst , it informs my CPU that it is done with the TOC, by a flag in the last data burst. I would like to know, which is the most efficinet way I can send these TOC information to userspace?

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Programming :: Function In Kernel Space Called Form User Space

Jul 7, 2009

I wanna write a file in kernel space but from my searching I can to know that instead of writeing file in kernel space ,I can write data to user space by copy_to_user space.

But link is missing ...I dont know how will my user space will access kernel space means my function in kernel space which will do copy_to_user /....How my user space function will call my kernel level function ..

Can any one of you provide me with some example file which are doing this .I know every char driver is using it ...but i could not trace back how user level function is accessing it ...i m confused between user space and kernel space.

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Programming :: Call Socket Prog Code Written In User Space From Kernel Space?

Jul 14, 2009

How to use execv from kernel space to call a user space program writtenfor socket prog.

I tried to write code for socket in kernel but its not working.

Socket code in kernel is also needed.

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General :: Ssh Permissions For Single User?

Jun 10, 2011

I have a user that can ssh to every computer on our network expect for one. I verified that it has to be the account by having the user ssh from a different computer. the results were the same.

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General :: User And Group Permissions

Jul 10, 2010

I am doing rhce course but i am very confused to answer these user and group permissions.the questions are like this...the owner of the /data must be user tom.primary group of /data must be the group sysadmins.the members of the group test must be able to write and create files in the /data.the members of the group web have no access to these directory.the user jack not belong to any of these gropus must have to edit files created in /data.the user tim can only list the contents.

the questions are always like these..i am okay with sgid and sticky bit.but i dnt know where to set default acl and other permissions.

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General :: Check Whether A User Has Login Permissions?

Jul 12, 2010

I want to make sure that the user www-data cannot be used to login on my system (Ubuntu Lucid). How can I find out? - is there a command I can run against this user? (traditionally run by Apache daemon)

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General :: Give An User 777 Permissions Without Affecting Others?

Aug 16, 2011

I have a user on my CentOS server who is not part of any group, just by themselves.

How can I give that user 777 permissions without affecting any other user on the server? I have chroot off, so I can see everything, but the user cannot write.

Do I use chown?

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Programming :: Signal From Kernel Space To User Space?

Jul 21, 2011

I have the following requirement in my module. The driver gets some data from the external device. After getting 1MB of data it has to send it to the user space application. What is the best thing to implement for this in driver.? Is it ok to implement like, after getting data, the driver will send a signal to the user space application. Then the user space application sends an ioctl to read the data. Is there any alternate, that the driver directly sends the data without the user space application asks for it.?

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General :: Understanding Ubuntu User / Group Permissions

May 20, 2010

I'm beginning to deal with more than one user on my system (it's a VPS serving some sites) and I need to make sure I understand how group permissions work. I have an account named "admin" .. it's basically the primary account that is used for serving most of the sites that I control myself. Now, I added a second account named "Ville" as one of my users wants to be able to administer that site. So, I can do this the easy way and just chown their domains folder under the ville user, they have permission to do whatever they need be and so forth. However, let's say I want to also give the admin user access to the files (modifying and all) .. how can I put both users into the same group and give them both permission?

I've tried doing:
sudo usermod -a -G admin ville
To add the ville into the admin group, but ville still cannot edit files by admin. Permissions for the primary directory for the ville user are read/write for both owner and group, and the current group for the files is admin:admin ..
But ville still can't write into the directory. So, what should I be doing here to get this right and secure at the same time?

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General :: Setting Permissions For Specific User And Groups?

May 25, 2010

i wonder, why nobody has written about it ...

How can i grant permission for files to specific user or specific group ??

Updated:

We have 3 groups: "g12" ("u1" and "u2), "g34" and "g56".

"g12" should only read the file.

"g34" should write and read it.

"g56" should have all permissions (rwx).

And others should not access the file at all.

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General :: Shared FTP Directory - Separate User Permissions

Mar 30, 2011

I am trying to setup 2 individual FTP users. They should both have access to the same directory. They both need to be able to read/write into the directory. But, I want them not to be able to write to each other's files (e.g. delete, remove, rename, etc.).

So let's say the shared directory is: /home/ftp/shared/

UserA needs read/write access to /home/ftp/shared/. UserA should only have write access to his own files. UserB also needs read/write access to /home/ftp/shared/. UserB should only have write access to his own files.

It would be a unix box of sorts, but that is the only restriction. I could use whatever software. I am currently thinking pure-ftpd or vsftp but I am open to all ideas.

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General :: Unable To Change The User And Root Permissions?

Mar 23, 2011

I was unable to change the permissions for root node and for other users also. WE have tried all the possibilities like chmod and chmod -R 777 filenem. But we are unable to change that.

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General :: User Permissions Vs Rights In System / Difference Between Them?

Aug 9, 2010

What's the difference between user permissions & users rights in linux.

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CentOS 5 :: Bypass File System Check?

Dec 1, 2009

On my laptop I have a dual boot system, CentOS 5.4 on one partition and Windows Vista on the other. In Windows, I have a program installed that allows me to access my linux partition so I have access to the files. Every time I boot into linux after accessing the linux partition through windows, I get a forced file system check. I was wondering if there is a way to disable or perhaps bypass this check?

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General :: Kernel Module Run In It / User Space?

Oct 25, 2010

I'm pretty new to this whole (micro)kernel architecture story.

Im wondering if a kernel module is running in kernel or in user space?

Is a driver running as kernel module slower than a driver build into kernel?
If so, are there some current articles, benchmarks?

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General :: Getting Notified In User-space On Interrupts?

Jun 27, 2010

I hope this is the right place to post to because I haven't found any other related forums.I'm working on an AMD opteron running Linux 2.6.28.6 I want to preload a hardware performance counter (register) with a value to have it overflow after a number of a specific event counts. As I understand, when the counter in the register overflows, an interrupt will be generated and handled by the appropriate interrupt handler. How can my user-level application get notified whenever the interrupt occurs? I want to obtain information on the instruction that caused the overflow. Is this possible? I think this is different than responding to signals with sigaction().

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