cp: failed to preserve ownership error when mounted manually [closed]

StackOverflow https://stackoverflow.com/questions/23520744

  •  17-07-2023
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Question

I copied files from a partition of bootable pendrive using

sudo cp -Rrf --preserve=all /media/Necktwi/BOOT/* BOOT/

I could able copy back as it is using sudo cp -Rrf --preserve=all BOOT* /media/Necktwi/BOOT/ when ubuntu mounts the partition.

But when I mount using

sudo mount -w /dev/sdc1 /mnt/boot

and try to copy back all its contents I get cp: failed to preserve ownership for each file being copied.

the /etc/mtab entry for the partition when ubuntu mounts it is

/dev/sdc1 /media/Necktwi/boot vfat rw,nosuid,nodev,uid=1000,gid=1000,shortname=mixed,dmask=0077,utf8=1,showexec,flush,uhelper=udisks2 0 0

the /etc/mtab entry for the partion when I mount with mount command above is

/dev/sdc1 /mnt/boot vfat rw 0 0

so I think I should specify some extra options in my mount command. My partition is fat16. How to avoid the cp: failed to preserve ownership error?

Était-ce utile?

La solution

The FAT file system has no support for ownership. So what Linux does is it simulated the owner and group fields of the file by passing uid=1000,gid=1000 to mount which says: "Every file and directory is owned by 1000 and group 1000."

To find out what these IDs mean, use getent:

getent passwd 1000

gives you the owner (user) and

getent group 1000

gives you the group.

To fix the error, use

sudo mount -o uid=1000,gid=1000 /dev/sdc1 /mnt/boot

but the other options work around other, important issues with FAT and Linux so a better solution is to take all of them and mount via a script.

#!/bin/bash
options="rw,nosuid,nodev,uid=1000,gid=1000,shortname=mixed,dmask=0077,utf8=1,showexec,flush,uhelper=udisks2"
mount -o "$options" /dev/sdc1 /mnt/boot

and invoke the script with sudo.

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