Backing up ext3 root partition with dd

[tweeks]

For the same reason you can't xerox a piece of paper that your wiggling. ;)

More precisely... the act of mounting it in a state other than read only makes 
it "uncopy-able" (from an image perspective).  It sounds like you want a type 
of snapshot feature like what XFS offers.

Tweeks

On Tuesday 20 February 2007 14:45, Yassin Hania-CHY002 wrote:
> Is there a reason why an ext3 root partition cannot be copied to an
> alternate partition using the "dd" command?
> The dd is copying the mounted root partition into an alternate partition
> that is not mounted.  The dd returns success, but the fsck on that
> partition fails with errors as follows:
> -----------------
> fsck 1.37 (21-Mar-2005)
> /dev/Active_Update/root2: recovering journal
> /dev/Active_Update/root2: Clearing orphaned inode 57554 (uid=0, gid=0,
> mode=010600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57552 (uid=1010,
> gid=3002, mode=010600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57548 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57547 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57546 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57545 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57544 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57543 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57542 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57541 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57540 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57539 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57538 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57537 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Clearing orphaned inode 57536 (uid=0, gid=0,
> mode=020600, size=0)
> /dev/Active_Update/root2: Deleted inode 90369 has zero dtime.  FIXED.
> /dev/Active_Update/root2: Inode 90370 is in use, but has dtime set.
> FIXED.
> /dev/Active_Update/root2: Inode 90371 is in use, but has dtime set.
> FIXED.
> /dev/Active_Update/root2: Inode 90372 is in use, but has dtime set.
> FIXED.
> /dev/Active_Update/root2: Inode 90373 is in use, but has dtime set.
> FIXED.
> /dev/Active_Update/root2: Inode 90373 has imagic flag set.  retfrom fsck
> is 1024
> -------------------------------
>
> When mounting that partition, an error is logged to /var/log/messages as
> follows:
> EXT3-fs warning: mounting fs with errors, running e2fsck is recommended
>
> We are seeing this on boxes running RHEL4 and even boxes running a PPC
> version of Linux.
> This failure is not seen on every run of the scripts, and is mostly seen
> when mirroring the root partition.
>
> Here is the script which reproduces this ext3 corruption after running
> it 5-6 times:
> ------------------------------------------
> #!/usr/bin/perl -w
> my $ret;
>
> ##
> ## Determine the backup partitions
> ##
> my @temp =  `cat /etc/fstab | grep alt_root`;
> my (@temp2, @alt_parts, @parts, @part);
> my $cnt = 0;
> foreach (@temp)
> {
>    @temp2 = split / /;
>    push @alt_parts, $temp2[0];
> }
>
> ##
> ## Determine the active partitions
> ##
> @temp = `cat /etc/fstab | grep Active_Update | grep -v alt_root | grep
> -v log | grep -v swap`;
> foreach (@temp)
> {
>    @temp2 = split / /;
>    push @parts, $temp2[0];
> }
>
>
> while (`cat /var/log/messages | grep -ci "running e2fsck is
> recommended"` <= 0)
> {
>    foreach my $alt_part (@alt_parts)
>    {
>       $alt_part =~ /(\D+)\d/;
>       @part = grep /$1/, @parts;
>       `dd if=$part[0] of=$alt_part > /dev/null 2>&1`;
>       $ret = $?;
>
>       ##
>       ## Abort if the partition copy fails as there is likely something
>       ## seriously wrong
>       ##
>       if ($ret != 0)
>       {
>          `logger "ERROR: Problems copying data to $alt_part."`;
>          `logger "       Contact Motorola for assistance."`;
>          `logger "Partition Copy exit code: $ret"`;
>          exit 1;
>       }
>
>       ##
>       ## Check the filesystem on the copied partition
>       ##
>       `/sbin/fsck -fp $alt_part > /dev/null 2>&1`;
>       $ret = $?;
>       `logger "fsck exit code for $alt_part was: $ret"`;
>    }
>
>    ##
>    ## Modify the copied partition
>    ##
>    `mount /mnt/alt_root; rm -f /mnt/alt_root/bob; touch
> /mnt/alt_root/bob; umount /mnt/alt_root`;
> }
>
> -------------------------


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