Mounting SMB/CIFS shares from Linux with a credentials file instead of embedding a password

Goal

Mount a Windows/Samba SMB share on Linux with credentials kept out of /etc/fstab and out of the process table, and with file ownership that the local system can actually use.

Prerequisites

cifs-utils installed (provides mount.cifs; also install smbclient for testing). Root for mounting and for creating the credentials file.

Steps

1. Test reachability and list shares first, without mounting anything: smbclient -L //server -U username. A prompt for a password followed by a share list confirms the server, port and authentication are reachable; failures here are cheaper to diagnose than a failed mount.
2. Create a credentials file instead of putting the password on the command line or in fstab:

   # /root/.smb-share-creds
   username=svcaccount
   password=the-actual-password
   domain=EXAMPLE
   

3. Restrict it immediately: chmod 600 /root/.smb-share-creds and keep it owned by root; a world- or group-readable credentials file defeats the entire point of not embedding the password inline.
4. Mount with the credentials file and explicit protocol version and ownership:

   mount -t cifs //server/share /mnt/share \
     -o credentials=/root/.smb-share-creds,vers=3.1.1,uid=1000,gid=1000,file_mode=0640,dir_mode=0750
   

   vers= pins the SMB dialect explicitly (SMB1/vers=1.0 should not be used against modern servers); uid=/gid=/file_mode=/dir_mode= set the Unix ownership and permission bits every file and directory on the mount reports locally, since SMB ACLs on the server do not translate directly into POSIX permissions on the client — chmod/chown on the mounted files return success but have no effect on the server.
5. For a persistent mount, add the same options plus credentials= to /etc/fstab (never the raw username=/password= options there) with _netdev, and re-test with mount -a.

Expected result

mount | grep cifs shows the share mounted with the intended uid/gid, files are readable/writable exactly as file_mode/dir_mode specify, and ps aux or cat /proc/self/mountinfo shows no password anywhere.

Limits and test basis

Options verified against mount.cifs(8) (cifs-utils) and smbclient(1) (Samba project documentation). Undo: umount /mnt/share; remove the fstab line and the credentials file if the share is retired.