Random timestamp changes on read-only SAMBA share

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FuLl
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Random timestamp changes on read-only SAMBA share

Post by FuLl » Wed Jun 06, 2018 10:08 am

I run a windows-only backup software called SyncBack Pro in a Windows 7 VM in Virtualbox. It scans & backs up a read-only SAMBA share based on the timestamps. When checking logs I see there are a half-dozen or so random files being copied on a regular basis. Files which aren't expected to be changing on the host.

Any ideas as to why & how to best track down the cause of such a thing?

powerhouse
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Re: Random timestamp changes on read-only SAMBA share

Post by powerhouse » Wed Jun 13, 2018 9:34 am

When you are sharing a Linux file system like ext4 using Samba, it's quite possible that not all file and directory attributes are shared. You may check to see if the Windows ACLs are supported, see https://wiki.samba.org/index.php/Settin ... ndows_ACLs.

Also look at http://pig.made-it.com/samba-file-rights.html.

Note that the information you provided isn't much to go on. What kind of file system you are sharing with Samba? What are the names and file attributes of the "random files" that were copied? The Samba configuration file?

In any case, I hope the above links are helpful.

I wonder why you would use a Windows-based backup software for backing up a Linux file system, or am I completely wrong? If you are indeed sharing a Linux ext2-ext4 file system via Samba, then you might be better off using one of the many Linux options.
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FuLl
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Re: Random timestamp changes on read-only SAMBA share

Post by FuLl » Wed Jun 13, 2018 7:27 pm

powerhouse wrote:
Wed Jun 13, 2018 9:34 am
I wonder why you would use a Windows-based backup software for backing up a Linux file system, or am I completely wrong? If you are indeed sharing a Linux ext2-ext4 file system via Samba, then you might be better off using one of the many Linux options.
The software I use is (An older version of) SyncBack Pro [0], which I find to be a better fit than the linux-based solutions I've tried.
When I tested various linux options (some time ago) I ran into deal-breaking limitations. eg. >24 hours for an rsync pass, or remote files in some non-standard container/archive. SBP provides everything I need in a single UI.
powerhouse wrote:
Wed Jun 13, 2018 9:34 am
When you are sharing a Linux file system like ext4 using Samba, it's quite possible that not all file and directory attributes are shared. You may check to see if the Windows ACLs are supported, see https://wiki.samba.org/index.php/Settin ... ndows_ACLs.
AFAIK my samba configuration is good. See below.
powerhouse wrote:
Wed Jun 13, 2018 9:34 am
Note that the information you provided isn't much to go on. What kind of file system you are sharing with Samba?
ext4
powerhouse wrote:
Wed Jun 13, 2018 9:34 am
What are the names and file attributes of the "random files" that were copied?
Seems random. Some were supposed to be transferred, since they were indeed new. Some were not though. eg. parts of the extracted installers' payload from an Adobe CS4 installer, a php file from an old Wordpress installation, php and svg files from an old CRM installation- both from /var/www/foo of their respective servers' backups.
powerhouse wrote:
Wed Jun 13, 2018 9:34 am
The Samba configuration file?
Note that the Windows app only accesses the read-only share.

Code: Select all

#
# Sample configuration file for the Samba suite for Debian GNU/Linux.
#
#
# This is the main Samba configuration file. You should read the
# smb.conf(5) manual page in order to understand the options listed
# here. Samba has a huge number of configurable options most of which 
# are not shown in this example
#
# Some options that are often worth tuning have been included as
# commented-out examples in this file.
#  - When such options are commented with ";", the proposed setting
#    differs from the default Samba behaviour
#  - When commented with "#", the proposed setting is the default
#    behaviour of Samba but the option is considered important
#    enough to be mentioned here
#
# NOTE: Whenever you modify this file you should run the command
# "testparm" to check that you have not made any basic syntactic 
# errors. 

#======================= Global Settings =======================

[global]

## Browsing/Identification ###

# Change this to the workgroup/NT-domain name your Samba server will part of
   workgroup = foo

# server string is the equivalent of the NT Description field
	server string = %h server (Samba, Ubuntu)

# Windows Internet Name Serving Support Section:
# WINS Support - Tells the NMBD component of Samba to enable its WINS Server
#   wins support = no

# WINS Server - Tells the NMBD components of Samba to be a WINS Client
# Note: Samba can be either a WINS Server, or a WINS Client, but NOT both
;   wins server = w.x.y.z

# This will prevent nmbd to search for NetBIOS names through DNS.
   dns proxy = no

#### Networking ####

# The specific set of interfaces / networks to bind to
# This can be either the interface name or an IP address/netmask;
# interface names are normally preferred
;   interfaces = 127.0.0.0/8 eth0

# Only bind to the named interfaces and/or networks; you must use the
# 'interfaces' option above to use this.
# It is recommended that you enable this feature if your Samba machine is
# not protected by a firewall or is a firewall itself.  However, this
# option cannot handle dynamic or non-broadcast interfaces correctly.
;   bind interfaces only = yes



#### Debugging/Accounting ####

# This tells Samba to use a separate log file for each machine
# that connects
   log file = /var/log/samba/log.%m

# Cap the size of the individual log files (in KiB).
   max log size = 1000

# If you want Samba to only log through syslog then set the following
# parameter to 'yes'.
#   syslog only = no

# We want Samba to log a minimum amount of information to syslog. Everything
# should go to /var/log/samba/log.{smbd,nmbd} instead. If you want to log
# through syslog you should set the following parameter to something higher.
   syslog = 0

# Do something sensible when Samba crashes: mail the admin a backtrace
   panic action = /usr/share/samba/panic-action %d


####### Authentication #######

# Server role. Defines in which mode Samba will operate. Possible
# values are "standalone server", "member server", "classic primary
# domain controller", "classic backup domain controller", "active
# directory domain controller". 
#
# Most people will want "standalone sever" or "member server".
# Running as "active directory domain controller" will require first
# running "samba-tool domain provision" to wipe databases and create a
# new domain.
   server role = standalone server

	security = USER


# If you are using encrypted passwords, Samba will need to know what
# password database type you are using.  
   passdb backend = tdbsam

   obey pam restrictions = yes

# This boolean parameter controls whether Samba attempts to sync the Unix
# password with the SMB password when the encrypted SMB password in the
# passdb is changed.
#   unix password sync = yes

# For Unix password sync to work on a Debian GNU/Linux system, the following
# parameters must be set (thanks to Ian Kahan <<kahan@informatik.tu-muenchen.de> for
# sending the correct chat script for the passwd program in Debian Sarge).
   passwd program = /usr/bin/passwd %u
   passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .

# This boolean controls whether PAM will be used for password changes
# when requested by an SMB client instead of the program listed in
# 'passwd program'. The default is 'no'.
   pam password change = yes

# This option controls how unsuccessful authentication attempts are mapped
# to anonymous connections
   map to guest = bad user

########## Domains ###########

#
# The following settings only takes effect if 'server role = primary
# classic domain controller', 'server role = backup domain controller'
# or 'domain logons' is set 
#

# It specifies the location of the user's
# profile directory from the client point of view) The following
# required a [profiles] share to be setup on the samba server (see
# below)
;   logon path = \\%N\profiles\%U
# Another common choice is storing the profile in the user's home directory
# (this is Samba's default)
#   logon path = \\%N\%U\profile

# The following setting only takes effect if 'domain logons' is set
# It specifies the location of a user's home directory (from the client
# point of view)
;   logon drive = H:
#   logon home = \\%N\%U

# The following setting only takes effect if 'domain logons' is set
# It specifies the script to run during logon. The script must be stored
# in the [netlogon] share
# NOTE: Must be store in 'DOS' file format convention
;   logon script = logon.cmd

# This allows Unix users to be created on the domain controller via the SAMR
# RPC pipe.  The example command creates a user account with a disabled Unix
# password; please adapt to your needs
; add user script = /usr/sbin/adduser --quiet --disabled-password --gecos "" %u

# This allows machine accounts to be created on the domain controller via the 
# SAMR RPC pipe.  
# The following assumes a "machines" group exists on the system
; add machine script  = /usr/sbin/useradd -g machines -c "%u machine account" -d /var/lib/samba -s /bin/false %u

# This allows Unix groups to be created on the domain controller via the SAMR
# RPC pipe.  
; add group script = /usr/sbin/addgroup --force-badname %g

############ Misc ############

# Using the following line enables you to customise your configuration
# on a per machine basis. The %m gets replaced with the netbios name
# of the machine that is connecting
;   include = /home/samba/etc/smb.conf.%m

# Some defaults for winbind (make sure you're not using the ranges
# for something else.)
;   idmap uid = 10000-20000
;   idmap gid = 10000-20000
;   template shell = /bin/bash

# Setup usershare options to enable non-root users to share folders
# with the net usershare command.

# Maximum number of usershare. 0 (default) means that usershare is disabled.
;   usershare max shares = 100

# Allow users who've been granted usershare privileges to create
# public shares, not just authenticated ones
   usershare allow guests = yes

#======================= Share Definitions =======================

# Un-comment the following (and tweak the other settings below to suit)
# to enable the default home directory shares. This will share each
# user's home directory as \\server\username
;[homes]
;   comment = Home Directories
;   browseable = no

# By default, the home directories are exported read-only. Change the
# next parameter to 'no' if you want to be able to write to them.
   read only = no

# File creation mask is set to 0700 for security reasons. If you want to
# create files with group=rw permissions, set next parameter to 0775.
   create mask = 0775

# Directory creation mask is set to 0700 for security reasons. If you want to
# create dirs. with group=rw permissions, set next parameter to 0775.
   directory mask = 0775
   directory mode = 0775

# By default, \\server\username shares can be connected to by anyone
# with access to the samba server.
# Un-comment the following parameter to make sure that only "username"
# can connect to \\server\username
# This might need tweaking when using external authentication schemes
;   valid users = %S

# Un-comment the following and create the netlogon directory for Domain Logons
# (you need to configure Samba to act as a domain controller too.)
;[netlogon]
;   comment = Network Logon Service
;   path = /home/samba/netlogon
;   guest ok = yes
;   read only = yes

# Un-comment the following and create the profiles directory to store
# users profiles (see the "logon path" option above)
# (you need to configure Samba to act as a domain controller too.)
# The path below should be writable by all users so that their
# profile directory may be created the first time they log on
;[profiles]
;   comment = Users profiles
;   path = /home/samba/profiles
;   guest ok = no
;   browseable = no
;   create mask = 0600
;   directory mask = 0700

[printers]
   comment = All Printers
   browseable = no
   path = /var/spool/samba
   printable = yes
   guest ok = no
   read only = yes
   create mask = 0700

# Windows clients look for this share name as a source of downloadable
# printer drivers
[print$]
   comment = Printer Drivers
   path = /var/lib/samba/printers
   browseable = yes
   read only = yes
   guest ok = no
# Uncomment to allow remote administration of Windows print drivers.
# You may need to replace 'lpadmin' with the name of the group your
# admin users are members of.
# Please note that you also need to set appropriate Unix permissions
# to the drivers directory for these users to have write rights in it
;   write list = root, @lpadmin

[XX]
path = /home/user/dirxx
available = yes
valid users = user
read only = no
browseable = yes
public = yes
writable = yes

[YY]
path = /mnt/YY
available = yes
valid users = user
read only = yes
browseable = yes
public = yes
writable = no

#[ZZ]
#path = /mnt/ZZ/user/this
#available = yes
#valid users = user
#read only = no
#browseable = yes
#public = yes
#writable = yes

acl allow execute always = True
Another thing maybe worth mentioning is that I only recently changed from Ubuntu 16.04.3 LTS to Mint 18.3- was soon after the LTS switched up. Previously on Ubuntu I ran everything the same & never noticed the behavior I happened to come across here. I wouldn't have known in this case had I not checked the log out of the blue. IIRC it should be all the same with Mint being Ubuntu, but obviously something's different.

[0]
https://www.2brightsparks.com/syncback/sbpro.html

powerhouse
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Re: Random timestamp changes on read-only SAMBA share

Post by powerhouse » Fri Jun 15, 2018 1:44 pm

Linux Mint is based on Ubuntu, but there are some differences. I don't know whether or not they have a bearing on your problem, though.

My guess is that your Windows backup utility reads the Samba file attributes somewhat differently, or that they aren't exactly identical with the way Windows handles them. Have a look at this post: https://stackoverflow.com/questions/308 ... ng-3-hours.

Look at these smb.conf options: https://www.oreilly.com/openbook/samba/ ... 08_01.html.

It's kind of poking in the dark for me, but perhaps the following config options may be relevant:

Code: Select all

time service = yes
dos filetimes = yes
fake directory create times = yes
dos filetime resolution = yes
Hope you find a way to solve it.

EDIT: It seems your Windows software needs the SyncbackTouch application so sync with Linux, see here: https://www.2brightsparks.com/syncback/sbt.html
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altair4
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Re: Random timestamp changes on read-only SAMBA share

Post by altair4 » Fri Jun 15, 2018 3:24 pm

This is more an FYI as I have no great insight into this particular problem but your two share definitions differ by more than just its "read only" setting.

Samba will interpret your [YY] share this way:
[YY]
path = /mnt/YY
available = yes
valid users = user
read only = yes
browseable = yes
public = yes
writable = no
acl allow execute always = True
Samba reads from [section] to [section] so even though you commented out the [ZZ] share the last line in smb.conf is not commented out so it will be included in the definition for [YY].

You can run testparm -s to verify.
Please add a [SOLVED] at the end of your original subject header if your question has been answered and solved.

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