How to use sys/mount to mount a NFS system? - c++

Question

So, I am trying to connect two Ubuntu computers using a NFS connection
On the server, I made the following
Install NFS Server on Ubuntu
$ sudo apt-get install nfs-kernel-server portmap
Export shares over NFS
$ sudo mkdir /opt/share
$ sudo chown nobody:nogroup /opt/share
Edit the NFS server exports configuration file
$ sudo gedit /etc/exports
Add the following settings
/home 192.168.0.0/24(rw,sync,no_root_squash,no_subtree_check)
/opt/share 192.168.0.0/24(rw,sync,no_subtree_check)
Apply the new settings by running the following command. This will export all directories listed in /etc/exports file
$ sudo exportfs -a
On the client side, I tried to use the sys/mount library to make the NFS connection
if(mount(":/mnt/share","/opt/share","nfs",0,"nolock,addr=192.168.0.101") == -1)
{
printf("NFS ERROR: mount failed: %s \n",strerror(errno));
}
else
{
printf("NFS connected\n");
}
But it returns
m#m-ThinkPad-L15-Gen-2:~/Desktop/teste$ sudo ./mountnfs
NFS ERROR: mount failed: Permission denied
Does anybody have any clue of what is happening?

Answer 1

According to the documentation:
Linux: the CAP_SYS_ADMIN capability is required to mount file systems.
And according to this page, you can add that capability to your program using something along the lines of the following command (each time after you build it, probably):
sudo setcap CAP_SYS_ADMIN+ep /path/to/your/binary
That's the gist of it anyway, but you might need to a bit more digging to find the optimal solution - in which case you can answer your own question.
Also, what's that leading : doing in your source parameter? Most likely I just don't understand the syntax, but it looks a bit weird to me.