Introduction

SMB (stands for Server Message Block), sometimes known as CIFS (Common Internet File System), is a network file share protocol which is commonly used for publishing folders or entire drives across a network.

It's most commonly used on Microsoft Windows, with Windows Server running the actual SMB server(s) for standard Windows clients to be able to access. However, it's also possible to connect or serve SMB from other operating systems, such as Linux, BSD's, and macOS - albeit most non-Windows implementations can experience performance issues or general compatibility bugs, due to the fact the official SMB server and client are closed source (both a part of Windows and Windows Server).

Connecting to SMB server from client

Install SMB Client

First, install the SMB client programs if it's not already installed, via apt / dnf / yum / whatever.

Debian / Ubuntu / Linux Mint / other Debian-based distros

apt update
apt install cifs-utils smbclient

Redhat (RHEL) / CentOS / Fedora / Oracle Linux / SuSE

dnf install cifs-utils

On older Redhat-based distros, such as CentOS 7, older versions of Fedora/RHEL/Oracle, etc. - you may need to use yum instead of dnf

yum install cifs-utils

Become Root

If you aren't already logged in as root - you should probably become root now.

sudo su -

Mount the share(s) you want

Create the directory where you want to mount the share onto, e.g. /mnt/myshare

mkdir -p /mnt/myshare

Connecting to authenticated shares/SMB servers

If you're connecting to a share or SMB server that requires a username and password to connect, then follow this segment, otherwise skip to the segment below which covers "guest shares"

Adjust the command below to match the details of the share you're mounting.

• Replace example.com with the domain/hostname/IP of the host which serves the share
• Replace MyShare with the name of the share (the folder name seen in GUI clients) you want to mount
• Replace johndoe with the username of your account that you'll be connecting to the share with

• Replace /mnt/myshare with the mountpoint where you'd like to mount your share

  mount -v -t cifs //example.com/MyShare -o username=johndoe /mnt/myshare

You'll be asked to enter your password (if required), and if the server accepts your credentials, then the SMB share will now be accessible at the mountpoint you chose.

root@host ~ # ls /mnt/myshare
important.txt photos/ docs/ README.md

Connecting to guest/public shares (no username or password generally required)

Some SMB servers may make certain shares public to guests, meaning that anyone can access them - without needing login details.

To access a "guest" share, you must use the guest option in the mount options, otherwise you'll be prompted for a username/password.

For example, to mount the public share publicstuff from the server example.com onto the mountpoint /mnt/public - you'd run the following command:

mkdir -p /mnt/public
mount -v -t cifs //example.com/publicstuff -o guest /mnt/public

Unattended SMB mounting (fstab)

First, add the mountpoint to fstab, as follows.

The credentials= option - points to a file that will contain the username and password needed to connect to the share.

If you are adding a guest/public share which doesn't require any login, simply use the option guest instead of credentials=/etc/samba/myshare.cred

#   SRC/DEVICE                     MOUNTPOINT       FS TYPE    OPTIONS                           
# Below is a share which requires authentication. It reads the login details from /etc/samba/myshare.cred
//example.com/MyShare     /mnt/tmpstore    cifs       credentials=/etc/samba/myshare.cred   0   0 
# Below is a public/guest share. It doesn't require any login details, so we specify 'guest' instead of credentials=/somefile
//example.com/publicstuff    /mnt/public       cifs       guest           0    0

Open up the credentials file in whatever text editor.

nano /etc/samba/myshare.cred

Fill out the credentials file as follows, replacing USER with the actual SMB username for logging in, and PASSWORD with the actual password for the user account.

username=USER
password=PASSWORD

Close and save the file.

Your SMB shares will now be automatically mounted when your system boots, and can also be manually mounted with just the mountpoint, e.g. mount -v /mnt/public

Setting up an SMB server

As mentioned at the start of this article, it's possible to run an SMB server on most OS's, despite being primarily a Windows protocol.

On Linux, the most popular/common SMB server is called Samba - an open source SMB/CIFS server for Linux, which is very easy to configure, and supports most features of the SMB protocol, including file sharing, restricting shares and individual share permissions (read/write/browse) to specific users, printer sharing, and more!

Install Samba Server

Debian / Ubuntu / Linux Mint / other Debian-based distros

apt update
apt install samba

Redhat (RHEL) / CentOS / Fedora / Oracle Linux / SuSE

dnf install samba

On older Redhat-based distros, such as CentOS 7, older versions of Fedora/RHEL/Oracle, etc. - you may need to use yum instead of dnf

yum install samba

Add shares to the config / adjust any config options you want

Once Samba is installed, you'll likely want to add some shares to the config. While adding shares, you're free to tweak some of the settings in the file if you're comfortable doing so - however with most distros' default Samba config, there's no need to edit the config (other than for adding shares) unless you have a usecase where you need to do so.

Open up /etc/samba/smb.conf and add public / private SMB shares as required, along with any other config adjustments you might want.

nano etc/samba/smb.conf

Below are two example share config blocks

• web is a public/guest share, which is read only by guests and users, but authorizes the SMB users chris and kale to be able to write to the share.

• documents is a private share, which cannot be read, written, nor browsed by guests, but ANY logged in SMB user can read/write/browse the share.

  ####
  # Example of a public share named 'web'. Guests can browse and read
  # files on the share, but they cannot create new files, or write to 
  # existing files on the share.
  # The users 'chris' and 'kale' however, are whitelisted for write access,
  # so those two SMB users may create files and write to existing files.
  ###
  [web]
  comment = Privex Public Fileserver
  path = /filesrv/web
  read only = yes
  guest ok = yes
  browseable = yes
  write list = chris kale
  
  ###
  #
  # Example of a private share named 'documents'.
  # Guests may be able to see this share's name in the available share list, 
  # but they cannot browse the share itself, nor read/write any files inside
  # of the share.
  #
  # Since there are no whitelisted/blacklisted users (other than guests),
  # all authenticated SMB users can browse/read/write to this share,
  # ONLY guests (unauthenticated users) are restricted from the share.
  #
  ### 
  [documents]
  comment = PRIVATE Temporary Network Storage
  path = /filesrv/tmpstore
  read only = no
  browseable = yes
  guest ok = no
  

Create and/or set passwords for SMB users

Samba expects each SMB username to actually exist as a system account. Despite this, the users will have a separate SMB password rather than using their Linux/UNIX login.

You'll need to create an actual Linux system user for each SMB user using adduser (or useradd on some systems), and then set the users' password using smbpasswd

###
# Create the system user 'chris' - and set an SMB password for them
###

# Create the Linux/UNIX system account 'chris', with their system login password disabled for security.
adduser --disabled-password --gecos "" chris
# Set the SMB (Samba) password for the user 'chris'
smbpasswd -a chris

###
# Create the system user 'kale' - and set an SMB password for them
###
adduser --disabled-password --gecos "" chris
smbpasswd -a kale

Enable and (re)start the SMB service

The smbd service isn't enabled by default (at least not on Ubuntu server), so you may need to enable it first.

Make sure to at least restart smbd after making the config / user changes.

systemctl enable smbd
systemctl restart smbd

Thanks for reading!