Matthew Richardson
2025-Jul-29 14:21 UTC
[Samba] SMB3 Unix Extensions - creating special files
Hi,
I'm currently investigating using the smb3 unix extensions. I can
list/stat special files in the samba mount, and can create and delete
'ordinary' files, but when I try to create special files I get an error:
$ ln -s b.txt sym_b
ln: failed to create symbolic link 'a.sym': Operation not supported
or
$ mkfifo b.fifo
mkfifo: cannot create fifo 'b.fifo': Operation not supported
My test setup is as follows:
Samba - Docker samba.org/samba-server:devbuilds-centos-amd64 (publishing
to host port 445)
Host Ubuntu Noble with kernel 6.15.7 (cifs.ko v2.54)
cifs-utils v7.0
Samba config:
[global]
workgroup = WORKGROUP
security = user
map to guest = never
log level = 3
guest ok = no
smb3 unix extensions = yes
[myshare]
path = /opt/smb
browsable = yes
writable = yes
read only = no
valid users = sambauser #uid/gid 1000
create mask = 0777
directory mask = 0777
I'm mounting the share as follows:
mount -t cifs //localhost/myshare /mnt -o
user=sambauser,pass=samba,unix,uid=1000,gid=1000
Resulting in mount:
//localhost/myshare on /mnt type cifs
(rw,relatime,vers=3.1.1,cache=strict,upcall_target=app,username=sambauser,uid=1000,forceuid,gid=1000,forcegid,addr=127.0.0.1,file_mode=0755,dir_mode=0755,soft,posix,posixpaths,serverino,mapposix,reparse=nfs,nativesocket,symlink=unix,rsize=4194304,wsize=4194304,bsize=1048576,retrans=1,echo_interval=60,actimeo=1,closetimeo=1)
There's nothing immediately obvious in the server logs which might add
more information.
I'm not sure if I'm missing something in my config that is limiting the
creation of special files, or if this is a limitation in the current
development of the smb3 unix extensions code, and I just need to be patient.
Any advice appreciated!
Thanks,
Matthew
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Hi Matthew, as a starting point: can you send us a network trace of this? Iirc the mailing list server is not particularily fond of attachements, so either put it somewhere to grab it or file a Samba bug and attach it there. Cheers! -slow -- SerNet Samba Team Lead https://sernet.de/ Samba Team Member https://samba.org/ Samba Support and Dev https://samba.plus/services/ SAMBA+ packages https://samba.plus/products/samba On 7/29/25 4:21 PM, Matthew Richardson via samba wrote:> Hi, > > I'm currently investigating using the smb3 unix extensions. I can list/ > stat special files in the samba mount, and can create and delete > 'ordinary' files, but when I try to create special files I get an error: > > $ ln -s b.txt sym_b > ln: failed to create symbolic link 'a.sym': Operation not supported > > or > > $ mkfifo b.fifo > mkfifo: cannot create fifo 'b.fifo': Operation not supported > > > My test setup is as follows: > > Samba - Docker samba.org/samba-server:devbuilds-centos-amd64 (publishing > to host port 445) > Host Ubuntu Noble with kernel 6.15.7 (cifs.ko v2.54) > cifs-utils v7.0 > > > Samba config: > > [global] > ?? workgroup = WORKGROUP > ?? security = user > ?? map to guest = never > ?? log level = 3 > ?? guest ok = no > ?? smb3 unix extensions = yes > > [myshare] > ?? path = /opt/smb > ?? browsable = yes > ?? writable = yes > ?? read only = no > ?? valid users = sambauser #uid/gid 1000 > ?? create mask = 0777 > ?? directory mask = 0777 > > > I'm mounting the share as follows: > > mount -t cifs //localhost/myshare /mnt -o > user=sambauser,pass=samba,unix,uid=1000,gid=1000 > > Resulting in mount: > //localhost/myshare on /mnt type cifs > (rw,relatime,vers=3.1.1,cache=strict,upcall_target=app,username=sambauser,uid=1000,forceuid,gid=1000,forcegid,addr=127.0.0.1,file_mode=0755,dir_mode=0755,soft,posix,posixpaths,serverino,mapposix,reparse=nfs,nativesocket,symlink=unix,rsize=4194304,wsize=4194304,bsize=1048576,retrans=1,echo_interval=60,actimeo=1,closetimeo=1) > > There's nothing immediately obvious in the server logs which might add > more information. > > I'm not sure if I'm missing something in my config that is limiting the > creation of special files, or if this is a limitation in the current > development of the smb3 unix extensions code, and I just need to be > patient. > > Any advice appreciated! > > Thanks, > > Matthew >-------------- next part -------------- A non-text attachment was scrubbed... Name: OpenPGP_signature.asc Type: application/pgp-signature Size: 840 bytes Desc: OpenPGP digital signature URL: <http://lists.samba.org/pipermail/samba/attachments/20250729/48dded6d/OpenPGP_signature.sig>
Hi, Do you know the share type on Domain and this specific case? In https://wiki.samba.org/ See: Setting up a Share Using POSIX ACLs - SambaWiki <https://wiki.samba.org/index.php/Setting_up_a_Share_Using_POSIX_ACLs> and Setting up a Share Using Windows ACLs - SambaWiki <https://wiki.samba.org/index.php/Setting_up_a_Share_Using_Windows_ACLs> SH On 29/07/2025 17.21, Matthew Richardson via samba wrote:> Hi, > > I'm currently investigating using the smb3 unix extensions. I can > list/stat special files in the samba mount, and can create and delete > 'ordinary' files, but when I try to create special files I get an error: > > $ ln -s b.txt sym_b > ln: failed to create symbolic link 'a.sym': Operation not supported > > or > > $ mkfifo b.fifo > mkfifo: cannot create fifo 'b.fifo': Operation not supported > > > My test setup is as follows: > > Samba - Docker samba.org/samba-server:devbuilds-centos-amd64 > (publishing to host port 445) > Host Ubuntu Noble with kernel 6.15.7 (cifs.ko v2.54) > cifs-utils v7.0 > > > Samba config: > > [global] > ?? workgroup = WORKGROUP > ?? security = user > ?? map to guest = never > ?? log level = 3 > ?? guest ok = no > ?? smb3 unix extensions = yes > > [myshare] > ?? path = /opt/smb > ?? browsable = yes > ?? writable = yes > ?? read only = no > ?? valid users = sambauser #uid/gid 1000 > ?? create mask = 0777 > ?? directory mask = 0777 > > > I'm mounting the share as follows: > > mount -t cifs //localhost/myshare /mnt -o > user=sambauser,pass=samba,unix,uid=1000,gid=1000 > > Resulting in mount: > //localhost/myshare on /mnt type cifs > (rw,relatime,vers=3.1.1,cache=strict,upcall_target=app,username=sambauser,uid=1000,forceuid,gid=1000,forcegid,addr=127.0.0.1,file_mode=0755,dir_mode=0755,soft,posix,posixpaths,serverino,mapposix,reparse=nfs,nativesocket,symlink=unix,rsize=4194304,wsize=4194304,bsize=1048576,retrans=1,echo_interval=60,actimeo=1,closetimeo=1) > > There's nothing immediately obvious in the server logs which might add > more information. > > I'm not sure if I'm missing something in my config that is limiting > the creation of special files, or if this is a limitation in the > current development of the smb3 unix extensions code, and I just need > to be patient. > > Any advice appreciated! > > Thanks, > > Matthew >-- Sami Hulkko +358 45 8569 319 sahulkko at gmail.com sahulkko at icloud.com