[Samba] MacOS clients - best options

[Thomas Hukkelberg]

Hi Tobias,

We have exact same problem but never really found the underlying issue and whether it's a cephfs bug, a samba bug or only related to vfs_fruit. We did a lot of digging and found that the issue occurs when macOS Finder is copying files to a samba file share backed by CephFS. When copying starts, Finder writes the hex sequence 'brokMACS' into a part of the xattr named 'user.DosStream.AFP_AfpInfo' to indicate that the file is being copied and displayed as grayed out by Finder. When copying is done, it's rather random whether Finder are able to overwrite the bytes back to original state, hence some files remain grayed out.

If anyone are able to shed some more light upon why this happens or how to prevent this it would be most welcome!

Our "solution" to this problem is to remove the offending xattr bytes at regular intervals. It's possible to workaround the problem with streams_depot but for us it's not optimal as it generates a lot of i/o and extraneous files.

We have written the following bash script that takes a file as argument and overwrites the xattr bytes in question so the files are not grayed out. Furthermore we have coupled this with a cronjob that scans for new files every minute.


--thomas



----

#!/bin/bash
# remove_brokMACS_xattr.sh
AFP_XATTR_HEX=$( getfattr -e hex -n 'user.DosStream.AFP_AfpInfo:$DATA' "$1" 2>/dev/null )
if [ $? -eq "0" ]
then
    echo "$AFP_XATTR_HEX" | grep -q "62726f6b4d414353" -
    if [ $? -eq "0" ]
    then
        TIMESTAMP=$(date -R)
        NEW_XATTR_HEX=$( echo "$AFP_XATTR_HEX" | sed -n 's/.*AFP_AfpInfo:\$DATA=\(.*\)$/\1/p' | sed 's/62726f6b4d414353/0000000000000000/g' )
        setfattr -n 'user.DosStream.AFP_AfpInfo:$DATA' -v $NEW_XATTR_HEX "$1"
        if [ $? -eq "0" ]
        then
            echo -e "$TIMESTAMP INFO: Removed FinderInfo parameter brokMACS xattr from $1"
            exit 0
        else
            echo -e "$TIMESTAMP ERROR: Removing FinderInfo parameter brokMACS xattr from $1"
            exit 1
        fi
    fi
fi
exit 0

----

#crontab *
* * * * * find /mnt/cephfs/storage -type f -exec /root/remove_brokMACS_xattr.sh '{}' \; exit 0 >> /var/log/brokmacs.log

----

* It should be noted that scanning all files every minute do not scale very well if there's a lot of files. In production we use a custom python script that look at the special cephfs xattr ceph.dir.rctime to find recently changed directories and only scan for new files in those dirs. However I'm not able to share that python script publicly...




9. mai 2023 kl. 12:13 skrev Tobias Hachmer via samba <samba at lists.samba.org>:

Hi list,

we have migrated a single node Samba server from Ubuntu Trusty to a 3-node CTDB Cluster on Debian Bullseye with Sernet packages. Storage is CephFS. We are running Samba in Standalone Mode with LDAP Backend.

Samba Version: sernet-samba 99:4.18.2-2debian11

I don't know if it is relevant here's how we have mounted CephFS on the samba nodes:

(fstab):/samba  /srv/samba ceph    name=samba,_netdev   0   0

Client caps:
client.samba
key: ...
caps: [mds] allow rw fsname=cephfs path=/samba
caps: [mon] allow r fsname=cephfs
caps: [osd] allow rw tag cephfs data=cephfs

After the migration everything seems fine but we experience problems with MacOS Clients. We have ~97% MacOS Clients here.

Problem description:
Many files are greyed out in the Finder and appear to be read only. Documents can't be opened or copied. In case of pictures the preview works but the pics can't be opened by any application.
Which files are greyed out seems random.

We have tested with several fruit options. If we set "fruit:metadata" to default (netatalk) the greyed out files are accessible again.

We're unsure which fruit options are the best for a 97% MacOS environment. We have first use the config described in [1].

Our Samba Configuration: https://pastebin.com/4zbzezZk

Would be great if someone can explain what fruit options are best or why the files are greyed out with "fruit:metadata = stream".

Thanks and kind regards
Tobias

[1] https://knowledgebase.45drives.com/kb/macos-samba-optimization/
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