I am trying to mount a source directory from nfs server to a destination directory in embedded board having linux. The following command works perfectly as expected in shell prompt in the board.
mount -t nfs -o nolock 10.126.62.45:/vol/home/avinoba/Sky /mnt
What is the equivalent system call to be used in program for the command above?
I tried the below call but the mount failed with "Invalid Argument"
if(mount("10.126.62.45:/vol/home/avinoba/Sky","/mnt","nfs",MS_MGC_VAL,"nolock") == -1)
{
printf("ERROR: mount failed: %s \n",strerror(errno));
}
Please suggest what is the solution for it.
Thanks
I'm quite surprised here knowing that how this is not covered by any man page regarding NFS mounts. Diving into the kernel code, in the function nfs_validate_text_mount_data, the function nfs_parse_mount_options is responsible for parsing the multiple comma separated options passed as the fifth argument in the mount system call.
struct sockaddr *sap = (struct sockaddr *)&args->nfs_server.address;
if (nfs_parse_mount_options((char *)options, args) == 0)
return -EINVAL;
if (!nfs_verify_server_address(sap))
goto out_no_address;
In the above code block, the last if statement checks whether the nfs server address and socket family is defined to valid values. If they are not updated within nfs_parse_mount_options, mount would end up returning invalid parameter.
If the implementation of nfs_parse_mount_options is walked through, it can be seen that, only for the case Opt_addr, the nfs server address and the socket family is updated by parsing the options argument.
case Opt_addr:
string = match_strdup(args);
if (string == NULL)
goto out_nomem;
mnt->nfs_server.addrlen =
rpc_pton(mnt->net, string, strlen(string),
(struct sockaddr *)
&mnt->nfs_server.address,
sizeof(mnt->nfs_server.address));
kfree(string);
if (mnt->nfs_server.addrlen == 0)
goto out_invalid_address;
break;
The case Opt_addr corresponds to the option "addr=nfs server ip". So for the system call to work, defining this option is a must. As far as I have searched, this is completely missing from all the man pages which describes nfs mounts.
So now considering the problem statement, please try by changing to the below code
if(mount(":/vol/home/avinoba/Sky","/mnt","nfs",0,"nolock,addr=10.126.62.45") == -1)
{
printf("ERROR: mount failed: %s \n",strerror(errno));
}
Also note that when the addr option is put in the argument, the ip address in front of the nfs server path becomes optional. However the ':' is must,as this acts as the delimiter to parse the nfs server path.
MS_MGC_VAL should be in the top 16 bits if needed, not the bottom. If your kernel version is > 2.4, you don't need it at all.
It solved by the following call for me now.
if(system("mount -t nfs -o nolock 10.126.62.45:/vol/home/avinoba/Sky /mnt")==-1);
{
printf("ERROR: mount failed \n");
}
But still searching for the answer with mount() call as it accepts 'filesystemtype' argument as "nfs".
Related
I'm trying to do a report of all the objects in all the projects we have in Cloud Storage of our Org. I'm using this repo from the Google Professionnal Services as it's doing exactly what we want: https://github.com/GoogleCloudPlatform/professional-services/tree/main/tools/gcs2bq
We want to use containers instead of just the go code on a Cloud Function for portability mainly.
Locally everything is good and the program behave as expected but when I try in Cloud Run things get tricky. From what I understand, the go part needs to listen to a port, which I added at the beginning of the main so the container can be deployed, which it is:
// Determine port for HTTP service
port := os.Getenv("PORT")
if port == "" {
port = "8080"
log.Printf("defaulting to port %s", port)
}
Start HTTP server.
log.Printf("listening on port %s", port)
if err := http.ListenAndServe(":"+port, nil); err != nil {
log.Fatal(err)
}
But as you can see in the repo, the first file called is the run.sh one. Which set environment variables and then call the main.go. It sucessfully complete it's task, which is get all the size of the different files. But after that the run.sh doesnt "resume" and go to the part where it uploads the data in a BigQuery table, which locally work.
Here is the part in the run.sh file where I have a problem. Note : I don't have errors from executing the ./gcs2bq Note 2 : Every environment variable has a correct value
./gcs2bq $GCS2BQ_FLAGS || error "Export failed!" 2 <- doesnt get past this line
gsutil mb -p "${GCS2BQ_PROJECT}" -c standard -l "${GCS2BQ_LOCATION}" -b on "gs://${GCS2BQ_BUCKET}" || echo "Info: Storage bucket already exists: ${GCS2BQ_BUCKET}"
gsutil cp "${GCS2BQ_FILE}" "gs://${GCS2BQ_BUCKET}/${GCS2BQ_FILENAME}" || error "Failed copying ${GCS2BQ_FILE} to gs://${GCS2BQ_BUCKET}/${GCS2BQ_FILENAME}!" 3
bq mk --project_id="${GCS2BQ_PROJECT}" --location="${GCS2BQ_LOCATION}" "${GCS2BQ_DATASET}" || echo "Info: BigQuery dataset already exists: ${GCS2BQ_DATASET}"
bq load --project_id="${GCS2BQ_PROJECT}" --location="${GCS2BQ_LOCATION}" --schema bigquery.schema --source_format=AVRO --use_avro_logical_types --replace=true "${GCS2BQ_DATASET}.${GCS2BQ_TABLE}" "gs://${GCS2BQ_BUCKET}/${GCS2BQ_FIL$
error "Failed to load gs://${GCS2BQ_BUCKET}/${GCS2BQ_FILENAME} to BigQuery table ${GCS2BQ_DATASET}.${GCS2BQ_TABLE}!" 4
gsutil rm "gs://${GCS2BQ_BUCKET}/${GCS2BQ_FILENAME}" || error "Failed deleting gs://${GCS2BQ_BUCKET}/${GCS2BQ_FILENAME}!" 5
rm -f "${GCS2BQ_FILE}"
I'm kinda new to containers and Cloud Run and even after reading projects and documentation, I'm not sure what I'm doing wrong, Is it normal that the .sh is "stuck" when calling the main.go? I can provide more details/explaination if needed.
Okay so for anyone who encounter similar situation this is how I made it work for me.
The container isn't supposed to stop so no exit, it will just go back to the main function.
That means that when I called executable it just looped and never exited and completed the task. So the solution here is to "recode" everything past the call in golang directly into the main.go
Here the run.sh is then useless so I used another .go file that listen for http request and then call the code that gather data and send it to Bigquery.
I'm finally able to get the device path ("/dev/rdisk1") - called devname here - after a search but POSIX open() fails with -1. Is this a permission issue? The camera is mounted and can be read normally via /Volumes but I need to access via /dev to control the camera via USB tether.
/* Found PENTAX DIGITAL_CAMERA */
snprintf(pslr.devname, sizeof(pslr.devname), "%s", devpath);
pslr.devname[sizeof(pslr.devname)-1] = '\0';
printf("pslr.devname %s\n", pslr.devname);
pslr.fd = open(pslr.devname, O_RDWR);
if (pslr.fd == -1) {
return NULL;
}
PS: after the discussion below I changed the permissions with sudo chmod command and then tried open but it still fails. I must be missing a step.
I checked with apple support and they say I cannot use posix functions to control a USB device in OS X.
On OS X El Capitan, my log file system.log feels with hundreds of the following lines at times
03/07/2016 11:52:17.000 kernel[0]: hfs_clonefile: cluster_read failed - 34
but there is no indication of the process where this happens. Apart from that, Disk Utility could not find any fault with the file system. But I would still like to know what is going on and it seems to me that dtrace should be perfectly suited to find out that faulty process but I am stuck. I know of the function return probe but it seems to require the PID, e.g.
dtrace -n 'pidXXXX::hfs_clonefile:return { printf("ret: %d", arg1); }'
Is there a way to tell dtrace to probe all processes? And then how would I print the process name?
You can try something like this (I don't have access to an OS X machine to test it)
#!/usr/sbin/dtrace -s
# pragma D option quiet
fbt::hfs_clonefile:return
/ args[ 1 ] != 0 /
{
printf( "\n========\nprocess: %s, pid: %d, ret value: %d\n", execname, pid, args[ 1 ] );
/* get kernel and user-space stacks */
stack( 20 );
ustack( 20 );
}
For the fbt probes, args[ 1 ] is the value returned by the function.
The dTrace script will print out the process name, pid, and return value from hfs_clonefile() whenever the return value is not zero. It also adds the kernel and user space stack traces. That should be more than enough data for you to find the source of the errors.
Assuming it works on OS X, anyway.
You can use the syscall provider rather than the pid provider to do this sort of thing. Something like:
sudo dtrace -n 'syscall::hfs_clonefile*:return /errno != 0/ { printf("ret: %d\n", errno); }'
The above command is a minor variant of what's used within the built-in DTrace-based errinfo utility. You can view /usr/bin/errinfo in any editor to see how it works.
However, there's no hfs_clonefile syscall, as least as far as DTrace is concerned, on my El Capitan (10.11.5) system:
$ sudo dtrace -l -n 'syscall::hfs*:'
ID PROVIDER MODULE FUNCTION NAME
dtrace: failed to match syscall::hfs*:: No probe matches description
Also, unfortunately the syscall provider is prevented from tracing system processes by the System Integrity Protection feature introduced with El Capitan (macOS 10.11). So, you will have to disable SIP which makes your system less secure.
On Mac OS X 10.6.8, some C code that calls readdir_r() sometimes gets an I/O error 5 (EIO) returned. I've seen this just a few times, always on external USB drives. Each time I've seen it, if I immediately cd to the parent direction and do an ls, I appear to see all the files. And, if I re-run the C program that saw the error, it will run fine.
On some platforms, when one gets an error like EIO, there's something else you can call that gives you much more detailed error information (e.g., hperrmsg on MPE/iX, which accesses the per-process error stack). Is there something similar on OS X?
I guess I'm assuming that the error is false
i = readdir_r (dirp, &dire, &dire_ptr);
save_errno = errno;
if (i)
{
if (i == EACCES)
...
else
{
my_perror (save_errno, "readdir_r failed: ");
espout4 ("readdir_r returned %s; errno = %s, dire_ptr = %s; parent = %s\n",
num64 (i), num64 (save_errno), fmt_p (dire_ptr), parent_dir);
espout1 (" (ERROR: readdir_r failed here, errno %s)\n", num64 (save_errno));
}
}
Update, a week later...
I've determined that the combo of the Macally case (model G-S350SU)
and the Western Digital drive was causing sporadic problems. I noticed that the WD SATA connector didn't mate tightly with the Macally socket. Using a Seagate drive with the case was fine, and using the WD drive in a different case was fine.
Of course, I'd still like to be able to get better / more detailed error information in my programs :)
I am trying out ret-to-libc attacks and use the following piece of code to get the address of environment variable /bin/bash
#include <unistd.h>
int main(void)
{
printf("bash address: 0x%lx\n", getenv("SHELL"));
return 0;
}
when i use gdb's x command to check if the address returned by this code is correct it shows up correctly the first time.But when some other program is executed this address changes automatically.What should i do to keep this environment variable's address constant? I am using this address for buffer overflow, but since it keeps changing with every run, the attack is never successful. Any suggestions?
You have to disable the ASLR for the address to not change.
echo 0 | tee /proc/sys/kernel/randomize_va_space