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Example 3: mount multiple instances of one filesystem
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The device # mkfs /dev/sda2 # mount /dev/sda2 /mnt/myfs # cp .... lotsofdata .... /mnt/myfs # umount /dev/sda2This filesystem can now be mounted several times via the cowloop driver to obtain multiple writable instances of the same filesystem: # modprobe cowloop # cowdev -a /dev/sda2 /fsdir/inst0.cow /dev/cow/0 # the command returns this name now # cowdev -a /dev/sda2 /fsdir/inst1.cow /dev/cow/1 # the command returns this name now # cowdev -a /dev/sda2 /fsdir/inst2.cow /dev/cow/2 # the command returns this name now # cowdev -l cowdevice read-only file copy-on-write file --------------------------------------------------- /dev/cow/0 /dev/sda2 /fsdir/inst0.cow /dev/cow/1 /dev/sda2 /fsdir/inst1.cow /dev/cow/2 /dev/sda2 /fsdir/inst2.cow # mount /dev/cow/0 /mnt/fs0 # mount /dev/cow/1 /mnt/fs1 # mount /dev/cow/2 /mnt/fs2 # df Filesystem 1K-blocks Used Available Use% Mounted on .... /dev/cow/0 2016044 1057832 855800 56% /mnt/fs0 /dev/cow/1 2016044 1057832 855800 56% /mnt/fs1 /dev/cow/2 2016044 1057832 855800 56% /mnt/fs2Every instance can be modified independent of the other instances, while the underlying filesystem on device /dev/sda2
will not be modified at all.
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