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alterando o formato do sistema de arquivos do xfs para ext4 sem perder dados
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i am unaware of any way to non-destructively convert a file system. this does not mean it is impossible, but i would put it at very low odds.
you can, for example, convert from ext2 to ext3 without wiping the disk, and from ext3 to ext4.
but to go from something like jfs to ext4 seems highly improbable, without first copying your /home
files to another partition or external hard disk.
even then, you would want to create a new user on your system, with a home directory somewhere like /tmp/tempuser
or copy your configurations for your user, usually the 'dot' files (files beginning with .) in your home directory to a new location off /home and updating /etc/passwd
to use the new home directory, so you can log in as a normal user while you're performing this update.
then, back up your files, unmount /home
and format it using /sbin/mkfs.ext4
or whatever tool you plan to use. mount the fresh partition at /home and copy your files back.
also, i would recommend something 'intelligent' like rsync
to copy your files, to assure you preserve your permissions and all that jazz.