Scripting /etc/fstab changes

[David Tonhofer]

Danda, Richard SFC wrote:
> Greetings all,
>
> I have a NetApp FAS270 filer that I have migrated NFS data directories too.
> I need to make changes to all my RHEL machines to point to the new device
> for mounts. Is there an easy way to script the change?
>
>   

YOU WANT US TO DO YOUR HOMEWORK?!


Try this perl script, it's probably unelegant as hell but I found it in 
my "hacks" directory.
No guarantees!!! Try it first manually, then set reallyWrite to 1 to 
replace your fstab.

Fix the regular expressions for your case.

----------8<-------------------------8<-------------------------8<------------------
#!/usr/bin/perl

# Program that can be used to replace stuff in some file

$file = $ARGV[0];

if (!defined $file) {
  die "You have to pass the name of the file to modify on the 
commandline\n";
}

if (!(-f $file && -r $file && -w $file)) {
  die "The file '$file' is not accessible or not writeable\n";
}

open(FILE,"<$file") or die "Could not open '$file' for reading: $!\n";

@buffer = (); # Takes up the file lines that we will write eventually

while ($line = <FILE>) {
  chomp($line);
  if ($line =~ /^hostA\:(.*)$/) {
    push(@buffer,"hostB:$1");
    next;
  }
  else {
    # just keep the line as is
    push(@buffer,$line);
    next;
  }
  if ($line ne $buffer[@buffer-1]) {
    print STDERR "Line changed\n";
    print STDERR "From: $line\n";
    print STDERR "To:   $buffer[@buffer-1]\n";
  }
}

close(FILE) or die "Could not close '$file': $!\n";

# Now we will write, replacing the existing file (if reallyWrite is set 
to 1)

$reallyWrite = 0;

if ($reallyWrite) {
  open(FILE,">$file") or die "Could not open '$file' for writing: $!\n";
  foreach $line (@buffer) {
    print FILE "$line\n";
  }
close(FILE) or die "Could not close '$file': $!\n";
}
else {
  foreach $line (@buffer) {
    print "$line\n";
  }
}