Unable to run compiled files - bash: ./a.out: Permission denied. (I've tried chmod)

Question

I've compiled my C source using cc test.c, and it did generate a.out file.

However when I run it I get this error -

bash: ./a.out: Permission denied

My source is not in the home directory, it is on different FAT-32 partition, so I've mounted the drive in which the code is using the following command -

$ udisks --mount /dev/sda7 --mount-options umask=022
Mounted /org/freedesktop/UDisks/devices/sda7 at /media/48E9-FD53
$ cd /media/48E9-FD53/C

Then I compile my code using cc

I've also tried gcc. But still I get the same error.

Then I did - chmod +x a.out, still the same problem. Also with(chmod 755 a.out) and chmod u+x a.out.

I've also tried compiling and executing the program using sudo.

I've also tried - sudo chown sannidhya:sannidhya a.out.

I've tried every thing that I found after googling, still couldn't get it to work.

How can I run .out file (without moving it to home directory)?

Note - I am using Ubuntu 12.04 LTS.

But a weird thing here is, even after running chmod +x a.out, on running - ls -l a.out, I get-

-rw-r--r-- 1

also when I check the properties of a.out, under Permissions tab, when I check Allow executing file as program,the tick appears and quickly disappears.

Solution 1

Seems that you've mounted the partition with with no-exec flag set. You'll have to remount the partition:

sudo mount -o remount -o exec /dev/sda7

Solution 2

I'd guess you are doing all of this on an NTFS/FAT partition that you probably share with windows. chmod permissions do not work on them.

You should move it to an ext4 (or equivalent linux) partition, and then perform permission changes.

---

Else, for an NTFS/FAT partition, you set permissions for the entire partition, at the time of mounting. For example,

sudo umount /mnt/my_partition
sudo mount -t vfat -o rw,auto,user,fmask=0000,dmask=0000 /dev/sda7 /mnt/my_partition

This would give you 777 on all directories and files (eeeek!), but once set, you can't modify them till you remount.

Comments

[hek2mgl]

can you add the output of mount | grep sda7 ?

[Anirudh Ramanathan]

@Sann Same logic. You can only apply permissions to the entire partition when you mount, if it isn't a linux native partition. Move it to a linux partition for chmod to work.

[ShuklaSannidhya]

What do I pass in for mount point parameter? I am getting this error - mount: mount point /media/48E9-FD53 does not exist

[ShuklaSannidhya]

/dev/sda7 on /media/48E9-FD53 type vfat (rw,nosuid,nodev,uid=1000,gid=1000,shortname=mixed,dmask=007‌​7,utf8=1,showexec,fl‌​‌​ush,uhelper=udisks‌​)

[hek2mgl]

I'm having the same mount options, and the same filesystem (vfat). And it works... Hmm

[ShuklaSannidhya]

Do I need chmod even after that?

[Anirudh Ramanathan]

Did you manage to mount it successfully? mount | grep sda7 should now reflect the new dmask and fmask set. Can you check?

[hek2mgl]

I would for testing do anything as root. And then check if ls if the executable bit is set. Then try to run ./a.out

[hek2mgl]

Hehe! :) fine!.. Although in this case it seems to be an usb stick, you should have this in mind any time you mount a cdrom.

[ShuklaSannidhya]

All right, so this command will unmount if the drive was already mounted and the mount it again, right? How do mount it if it wasn't mounted before? Is this alright - sudo mount -o exec /dev/sda7. BTW: what is the purpose of the -o parameter?

[hek2mgl]

yes, then just drop the -o remount and use your regular mount command and add -o exec . Btw, for usb sticks this should work out of the box with ubuntu 12.04 as I'm using it too. It looks like that you have enabled this no-exec monting to prevent form malware etc on usb sticks..

[ShuklaSannidhya]

When I mount it freshly using sudo mount -o exec /dev/sda7, I get this error - mount: can't find /dev/sda7 in /etc/fstab or /etc/mtab.

[hek2mgl]

you missed the path where it should be mounted. Call it like: mount OPTIONS DEVICE TARGET_PATH

[ShuklaSannidhya]

When I compile, I get this - /usr/bin/ld: cannot open output file a.out: Permission denied collect2: ld returned 1 exit status. However, there is no problem while running the file. Strange...