Jephe Wu - http://linuxtechres.blogspot.com
Problem: we need to retrieve data from certain directory before we did NFS mount on the same directory,however, we cannot umount it since it's production environment
Problem: we need to retrieve data from certain directory before we did NFS mount on the same directory,however, we cannot umount it since it's production environment
Concept: use mount --bind / to another directory to retrieve data without umounting NFS
Steps:
1. check the existing files under /u05, for testing purpose, I have copied some archive log files from /u03 to /u05.
root@linuxtechres:/u05# ll
total 420
-rw-r----- 1 root root 229888 Oct 15 10:48 1_21996_817700775.arc
-rw-r----- 1 root root 180736 Oct 15 10:48 1_22005_817700775.arc
2. NFS mount /u05 which is using Netapp NFS storage for controlfile
root@linuxtechres:/# mount /u05
root@linuxtechres:/# cd /u05
root@linuxtechres:/u05# ll
total 4
drwxr-xr-x 3 oracle dba 4096 Jun 28 09:51 control
3. Now we need to retrieve the original files under /u05
root@linuxtechres:/u05# mkdir /tmp/recover
root@linuxtechres:/u05# mount --bind / /tmp/recover # use / since original /u05 content is under / partition
4. check mounted directory
root@linuxtechres:/u05# cd /tmp/recover/
root@linuxtechres:/tmp/recover# ls
appdata boot home lost+found mnt proc selinux sys u01 u04 var
backup dev lib media net root srv tftpboot u02 u05
bin etc lib64 misc opt sbin stage tmp u03 usr
root@linuxtechres:/tmp/recover# cd u05
root@linuxtechres:/tmp/recover/u05# ll
total 420
-rw-r----- 1 root root 229888 Oct 15 10:48 1_21996_817700775.arc
-rw-r----- 1 root root 180736 Oct 15 10:48 1_22005_817700775.arc
5. compare file md5sum
root@linuxtechres:/tmp/recover/u05# md5sum 1_21996_817700775.arc
f0af8a88658071aab2babab74c614159 1_21996_817700775.arc
root@linuxtechres:/tmp/recover/u05# md5sum /u03/oraarch/JEPHE/1_21996_817700775.arc
f0af8a88658071aab2babab74c614159 /u03/oraarch/JEPHE/1_21996_817700775.arc
6. umount /tmp/recover after recovery
root@linuxtechres:/tmp/recover/u05# mount | grep recover
/ on /tmp/recover type none (rw,bind)
root@linuxtechres:/tmp/recover/u05# cd /
root@linuxtechres:/# umount /tmp/recover
root@linuxtechres:/# mount | grep recover
Note: you may also use debugfs to retrieve data
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