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Specify the inode of a file?

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Operating Systems Solaris Specify the inode of a file?
# 15  
Old 03-27-2014
I believe that this might be possible (for ufs filesystems) via a combination of fsdb and fsck. I don't have a test system available so I am not going to try it. The general flow would be:
  1. create a filesystem with enough inodes but do not mount it
  2. use fsdb to increment the link count of the desired inode
  3. use fsck to find what now looks like an orphaned file and reattach it to lost+found

I have never tried this because I have always been content with the inode number I get. My feeling is that I could make it work... but I would not be real surprised if I trash the file system a few times during the attempt. I definately would not try this on a filesystem that I cared about.

If you try this and get it to work, please post the fsdb commands used to increment the link count on your chosen inode number.
This User Gave Thanks to Perderabo For This Post:
rbatte1
# 16  
Old 03-27-2014
There are only a few ways to get an inode number. Offhand, I know of getdents(), stat(), and fstat(). Oh, and getdents64(), stat64(), and fstat64().

You can truss the failing process and see what it uses:

Code:
truss -f -a -vall -o /truss/output/file command args...

FWIW, I'd bet quite a sum that your program is compiled as a 32-bit process and is using standard calls such as stat(), open(), etc. Read the man page for types.h. Note that an ino_t is an unsigned long, which in an ILP32 environment such as a 32-bit Solaris application is a 32-bit value. But in the LP64 environment of a 64-bit Solaris application an ino_t is 64 bit value. If you need the 64-bit value in a 32-bit application you need to use the open64(), stat64(), etc functions throughout your code.

Read and heed the man pages for lfcompile, lfcompile64, and lf64.

Another thing to watch out for: NFSv2. NFSv2 does not handle 64-bit values. And most NFS mounts are set to autonegotiate. And guess what? The negotiation is done via UDP. Sometimes that fails and you don't get your desired NFSv4 or NFSv3 mount and you get a fallback to an NFSv2 mount. If you have large files, or files with large inode values, you will see some really strange results. Run nfsstat, and if your v2 stats aren't all zero, you're in trouble. So always, always, always specify "vers=3" or "vers=4" in your mounts, or set the minimum version your server will serve to 3. (It's in a config file somewhere, that I'm too lazy to look up right now.)
# 17  
Old 03-28-2014
I've modified the DTrace script to handle "fstat64" as well:
Code:
BEGIN
{
  filename = "passwd";
}

syscall::stat64:entry, syscall::lstat64:entry
/strstr(copyinstr(arg0), filename) != NULL/
{
  self->statptr = arg1;
}

syscall::fstat64:entry
/strstr(fds[arg0].fi_name, filename) != NULL/
{
  self->statptr = arg1;
}

syscall::stat64:return, syscall::lstat64:return
/self->statptr != NULL && curpsinfo->pr_dmodel == PR_MODEL_ILP32/
{
  self->st64_32 = (struct stat64_32 *)copyin(self->statptr, sizeof(struct stat64_32));
  self->st64_32->st_ino = 100000000000;
  copyout(self->st64_32, self->statptr, sizeof(struct stat64_32));
}

syscall::stat64:return, syscall::lstat64:return
/self->statptr != NULL && curpsinfo->pr_dmodel == PR_MODEL_LP64/
{
  self->st64 = (struct stat64 *)copyin(self->statptr, sizeof(struct stat64));
  self->st64->st_ino = 100000000000;
  copyout(self->st64, self->statptr, sizeof(struct stat64));
}

syscall::fstat64:return
/self->statptr != NULL && curpsinfo->pr_dmodel == PR_MODEL_ILP32/
{
  self->st64_32 = (struct stat64_32 *)copyin(self->statptr, sizeof(struct stat64_32));
  self->st64_32->st_ino = 100000000000;
  copyout(self->st64_32, self->statptr, sizeof(struct stat64_32));
}

syscall::fstat64:return
/self->statptr != NULL && curpsinfo->pr_dmodel == PR_MODEL_LP64/
{
  self->st64 = (struct stat64 *)copyin(self->statptr, sizeof(struct stat64));
  self->st64->st_ino = 100000000000;
  copyout(self->st64, self->statptr, sizeof(struct stat64));
}

Simple test to see if it is really working:
Code:
# perl -le 'open $fh, "<", "/etc/passwd";print ((stat $fh)[1])' 
100000000000

BTW, when faking the inode for "/etc/passwd", I noticed that I can not login to the server by SSH, so it is probably better to use some other file name for your tests Smilie
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