Difference between revisions of "Bidirectional Rsync/Unison based SysVol replication workaround"

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= Introduction =
 
= Introduction =
Samba AD currently doesn't provide support for SysVol replication. To achive this important feature in a Multi-DC environment, until it's implemented, workarounds are necessary to keep it in sync. This HowTo provides a basic workaround solution based on Osync.
+
Samba AD currently doesn't provide support for SysVol replication. To achieve this important feature in a Multi-DC environment, until it's implemented, workarounds are necessary to keep it in sync. This HowTo provides a basic workaround solution based on rsync and unison.
  
= Information on Osync replication =
+
= Information on unison + rsync replication =
  
This HowTo describes a solution for SysVol replication, that is based on Osync, which is two way sync system based on rsync. This howto covers the bidirectional synchronization of two DC servers.
+
This HowTo describes a solution for SysVol replication, that is based on rsync and unison. As Compare to the rsync method, it is bidirectional. This howto only covers a two DC setup.
  
This solution has the following advantages:  
+
It has the following advantages:  
* setup is fast
+
* Quick setup
* configuration is very easy
+
* Configuration is very easy
* Can work with windows (Windows can be used as master using the MinGW environment)
+
* Can work with windows (Please add in)
  
Osnyc uses rsync through a SSH tunnel.
+
We will use rsync through a SSH tunnel.
  
 
= Setup the SysVol replication =
 
= Setup the SysVol replication =
  
== Installation ==
+
Some assumptions:
 +
You are running all commands as root.
 +
rsync location  /usr/bin/rsync
 +
sysvol is located at /var/lib/samba/sysvol on both DC1 and DC2
 +
unison location /usr/bin/unison
 +
The first DC is DC1
 +
The second DC is DC2
 +
sysvolsync log location /var/log/sysvol-sync.log
  
There aren't any deb or rpm packages as osync is a script, but you can get a copy here:
+
Change the paths if your setup is different.
[http://www.netpower.fr/projects/osync/osync.v1.00a.tar.gz]http://www.netpower.fr/projects/osync/osync.v1.00a.tar.gz
 
 
 
You can then install osync with the following commands
 
tar xvf osync.v1.00a.tar.gz
 
cd ./osync
 
sh ./install.sh
 
 
 
This will copy osync to /usr/local/bin and create an example configuration file at /etc/osync/sync.conf
 
  
 
=== Setup on the Domain Controller with the PDC Emulator FSMO role ===
 
=== Setup on the Domain Controller with the PDC Emulator FSMO role ===
Some assumption:
+
* Install rsync by using your package manager or compile from source. Make sure, that you use a version that supports extended ACLs!
* You are running all command as root.
+
* You don't need to setup the rsync server.
* rsync is installed on both servers
+
* Install unison by using your package manager or compile from source. (On Gentoo you need to do <code>eselect unison</code> to create the link)
* sysvol is located /var/lib/samba/sysvol on both DC1 and DC2
 
* osync is located /usr/local/bin/osync
 
* sync.conf is located /etc/osync/sync.conf
 
* DC1 is at DC1
 
* DC2 is at DC2 (And already join DC1)
 
* sysvolsync log is located /var/log/osync_*.log
 
* rsync must support extended ACLs
 
* Install rsync by using your package manager (eg: yum install rsync or apt-get install rsync) or compile from source. Make sure, that you use a version that supports extended ACLs (most versions do)!
 
* sysvol must be on disk which is mounted to support acl and also xattr
 
* We don't need to setup rsync server.
 
 
 
Change the path if that don't fit your setup.
 
  
 
==== Creating SSH Public Key and ssh-copy to DC2====
 
==== Creating SSH Public Key and ssh-copy to DC2====
  ssh-keygen -t dsa
+
  ssh-keygen -t rsa
  ssh-copy-id -i ~/.ssh/id_dsa.pub root@DC2
+
  ssh-copy-id -i ~/.ssh/id_rsa.pub root@DC2
  
 
You can try to access DC2 via ssh  
 
You can try to access DC2 via ssh  
 
  ssh DC2
 
  ssh DC2
  
=== Osync Configuration Setup on DC1 ===
+
==== Setup ssh Control ====
Edit the /etc/osync/sync.conf and make some changes
+
If the remote system enforces rate limits on incoming ssh connections, unison will fail if you try to run it this way.
 +
So we create the first ssh connection as a controlpath file in the location specified, all subsequent connections will reuse on the first connection.
  
  #!/usr/bin/env bash
+
  mkdir ~/.ssh/ctl
  SYNC_ID="sysvol_sync"
+
  cat << EOF > ~/.ssh/ctl/config
MASTER_SYNC_DIR="/var/lib/samba/sysvol"
+
Host *
  SLAVE_SYNC_DIR="ssh://root@DC2:22//var/lib/samba/sysvol"
+
  ControlMaster auto
  SSH_RSA_PRIVATE_KEY="/root/.ssh/id_rsa"
+
  ControlPath ~/.ssh/ctl/%h_%p_%r
PRESERVE_ACL=yes
+
  ControlPersist 1
PRESERVE_XATTR=yes
+
  EOF
  SOFT_DELETE=yes
 
  DESTINATION_MAILS="your@email.com"
 
  
Osync also does backups and soft deletes which will keep a copy of deleted files and folders in a subfolder named .osync_workdir.
+
==== Setup Sysvolsync Log files ====
Unless you have specific reasons to do so, leave these options enabled.
+
Do the following on DC1 so that you can check what happens during the sync.
Osync has one benefit as it will only send email alert if there is problem.
+
Please include this file into logrotate as the log size is not controlled.
  
=== Setup on DC2 ===
+
touch /var/log/sysvol-sync.log
* On DC2 Install rsync by using your package manager or compile from source. Make sure, that you use a version that supports extended ACLs!
+
chmod 640 /var/log/sysvol-sync.log
  
* Shutdown DC2 Samba AD DC
+
==== Setup Unison defaults running parameters ====
mv /var/lib/samba/private/idmap.ldb /var/lib/samba/private/idmap.ldb.backup"
+
Please run the following on DC1
rm /var/cache/samba/gencache.tdb"
 
  
* Copy idmap.ldb from DC1 to sync the idmap.
+
install -o root -g root -m 0750 -d /root/.unison
* Run the following command on '''DC1'''
+
cat << EOF > /root/.unison/default.prf
  scp /var/lib/samba/private/idmap.ldb root@DC2:/var/lib/samba/private/
+
# Unison preferences file
 +
# Roots of the synchronization
 +
#
 +
# copymax & maxthreads params were set to 1 for easier troubleshooting.
 +
# Have to experiment to see if they can be increased again.
 +
  root = /var/lib/samba
 +
# Note that 2 x / behind DC2, it is required
 +
root = ssh://root@DC2//var/lib/samba  
 +
#
 +
# Paths to synchronize
 +
path = sysvol
 +
#
 +
#ignore = Path stats    ## ignores /var/www/stats
 +
auto=true
 +
batch=true
 +
perms=0
 +
rsync=true
 +
maxthreads=1
 +
retry=3
 +
confirmbigdeletes=false
 +
servercmd=/usr/bin/unison
 +
copythreshold=0
 +
copyprog = /usr/bin/rsync -XAavz --rsh='ssh -p 22' --inplace --compress
 +
copyprogrest = /usr/bin/rsync -XAavz --rsh='ssh -p 22' --partial --inplace --compress
 +
copyquoterem = true
 +
copymax = 1
 +
logfile = /var/log/sysvol-sync.log
 +
EOF
  
== 1st Try ==  
+
=== Setup SysVol on DC2 ===
What happen is we use rsync to create the directory structure with extended attributes
+
* On DC2 Install rsync by using your package manager or compile from source. Make sure, that you use a version that supports extended ACLs!
Than unison setup copies only the extened attributes on files.
+
* On DC2 Install unison by using your package manager or compile from source. (On Gentoo you need to do <code>eselect unison</code> to create the link)
 +
* Make sure, that you have [[Joining_a_Samba_DC_to_an_Existing_Active_Directory#Built-in_User_.26_Group_ID_Mappings|identical IDs of built-in groups on all DCs]].
  
<BR>Before starting, make a '''backup''' of your sysvol just in case.
 
  
/usr/local/bin/osync.sh /etc/osync/sync.conf --dry --verbose
+
== 1st Trial ==
 +
You now use rsync to create the directory structure with extended attributes
 +
Then the unison setup will only copy the extended attributes on files.
  
If this runs successfully, you may remove the --dry option and run again.
+
<BR>Please make a '''backup''' of your sysvol, just in case, this is because there is no <code>dry-run</code>
 +
 +
/usr/bin/rsync -XAavz --log-file /var/log/sysvol-sync.log --delete-after -f"+ */" -f"- *"  /var/lib/samba/sysvol root@DC2:/var/lib/samba  &&  /usr/bin/unison
  
/usr/local/bin/osync.sh /etc/osync/sync.conf --verbose
+
:'''Note: The path on DC2 is just /var/lib/samba which is different from DC1, it is by design, there is nothing wrong!'''
  
 
== Add to Crontab on DC1 ==
 
== Add to Crontab on DC1 ==
 
On DC1 run the following:
 
On DC1 run the following:
 
  crontab -e  
 
  crontab -e  
  */5 * * * * root  /usr/local/bin/osync.sh /etc/osync/sync.conf --silent
+
  */5 * * * * /usr/bin/unison -silent
 
 
:'''Warning: Make sure that the destination folder is really your SysVol folder, because the command will replicate to the given directory and sync everything in it that isn't also on the source! You could damage your system! So check the output carefully to see if the replication is doing, what you expect!'''
 
  
 
= When you try to resync the folder =
 
= When you try to resync the folder =
 
:'''Warning: Please follow the steps below OR you can end up with an empty sysvol folder.'''
 
:'''Warning: Please follow the steps below OR you can end up with an empty sysvol folder.'''
# Disable Cron on DC1, like Add a "#" on the line with <tt>crontab -e</tt>
+
# Disable Cron on DC1, like Add a "#" on the line with <code>crontab -e</code>
# Check is any rsync or osync are currently running in <tt>ps -aux | grep sync</tt> if yes, wait for it to finished OR kill it (if it is zombie)
+
# Check if rsync or unison are currently running in <code>ps -aux</code> if yes, wait for it to finish OR kill it (if it is zombie)
# Remove the .osync_workdir hash files on both DC1 and DC2 on <tt>MASTER/SLAVE_SYNC_DIR "/var/lib/samba/sysvol"</tt>
+
# Remove the hash files on both DC1 and DC2 on <code>/root/.unison</code>
 
# Now check your sysvol and resync
 
# Now check your sysvol and resync
# Confirm that everything is working again
+
# Confirm that everything is ok again
# Re-enable the Cron on DC1 again
+
# Re-enable the cron on DC1 again
  
 
= FAQ =
 
= FAQ =
  
 
* How can I do this on windows?
 
* How can I do this on windows?
** Install the MSYS bash environment (read the osync documentation), then you may run osync as master from Windows.
+
** I don't have an answer, please post on the mailing list
  
* What to do if I've more than one DC?
 
** By Theory, We would just make more cron jobs on DC1 and the complete sync will be perform next sync to all server. (Not tested)
 
** Something like:
 
** DC1 <> DC2
 
** DC1 <> DC3
 
** DC1 <> DC2
 
  
 +
* What to do if I've more than two DC's?
 +
** In Theory, We would just make more cron jobs on DC1 and the complete sync will be perform next sync to all server.
  
  
 
* Why can't I simply use a distributed filesystem like GlusterFS, Lustre, etc. for SysVol?
 
* Why can't I simply use a distributed filesystem like GlusterFS, Lustre, etc. for SysVol?
** A cluster file system with Samba requires CTDB to be able to do it safely. And CTDB and AD DC are incompatible. Please check on the [https://lists.samba.org/archive/samba/2014-February/178546.html reply] from Samba Developer on the mailing list .
+
** A cluster file system with Samba requires CTDB to be able to do it safely. And CTDB and AD DC are incompatible.
 +
 
 +
 
 +
 
 +
 
 +
 
 +
----
 +
[[Category:Active Directory]]

Latest revision as of 10:51, 5 May 2020

Introduction

Samba AD currently doesn't provide support for SysVol replication. To achieve this important feature in a Multi-DC environment, until it's implemented, workarounds are necessary to keep it in sync. This HowTo provides a basic workaround solution based on rsync and unison.

Information on unison + rsync replication

This HowTo describes a solution for SysVol replication, that is based on rsync and unison. As Compare to the rsync method, it is bidirectional. This howto only covers a two DC setup.

It has the following advantages:

  • Quick setup
  • Configuration is very easy
  • Can work with windows (Please add in)

We will use rsync through a SSH tunnel.

Setup the SysVol replication

Some assumptions:

You are running all commands as root.
rsync location  /usr/bin/rsync
sysvol is located at /var/lib/samba/sysvol on both DC1 and DC2
unison location /usr/bin/unison
The first DC is DC1
The second DC is DC2
sysvolsync log location /var/log/sysvol-sync.log

Change the paths if your setup is different.

Setup on the Domain Controller with the PDC Emulator FSMO role

  • Install rsync by using your package manager or compile from source. Make sure, that you use a version that supports extended ACLs!
  • You don't need to setup the rsync server.
  • Install unison by using your package manager or compile from source. (On Gentoo you need to do eselect unison to create the link)

Creating SSH Public Key and ssh-copy to DC2

ssh-keygen -t rsa
ssh-copy-id -i ~/.ssh/id_rsa.pub root@DC2

You can try to access DC2 via ssh

ssh DC2

Setup ssh Control

If the remote system enforces rate limits on incoming ssh connections, unison will fail if you try to run it this way. So we create the first ssh connection as a controlpath file in the location specified, all subsequent connections will reuse on the first connection.

mkdir ~/.ssh/ctl
cat << EOF > ~/.ssh/ctl/config
Host *
ControlMaster auto
ControlPath ~/.ssh/ctl/%h_%p_%r
ControlPersist 1
EOF

Setup Sysvolsync Log files

Do the following on DC1 so that you can check what happens during the sync. Please include this file into logrotate as the log size is not controlled.

touch /var/log/sysvol-sync.log
chmod 640 /var/log/sysvol-sync.log

Setup Unison defaults running parameters

Please run the following on DC1

install -o root -g root -m 0750 -d /root/.unison
cat << EOF > /root/.unison/default.prf
# Unison preferences file
# Roots of the synchronization
#
# copymax & maxthreads params were set to 1 for easier troubleshooting.
# Have to experiment to see if they can be increased again.
root = /var/lib/samba
# Note that 2 x / behind DC2, it is required
root = ssh://root@DC2//var/lib/samba 
# 
# Paths to synchronize
path = sysvol
#
#ignore = Path stats    ## ignores /var/www/stats
auto=true
batch=true
perms=0
rsync=true
maxthreads=1
retry=3
confirmbigdeletes=false
servercmd=/usr/bin/unison
copythreshold=0
copyprog = /usr/bin/rsync -XAavz --rsh='ssh -p 22' --inplace --compress
copyprogrest = /usr/bin/rsync -XAavz --rsh='ssh -p 22' --partial --inplace --compress
copyquoterem = true
copymax = 1
logfile = /var/log/sysvol-sync.log
EOF

Setup SysVol on DC2

  • On DC2 Install rsync by using your package manager or compile from source. Make sure, that you use a version that supports extended ACLs!
  • On DC2 Install unison by using your package manager or compile from source. (On Gentoo you need to do eselect unison to create the link)
  • Make sure, that you have identical IDs of built-in groups on all DCs.


1st Trial

You now use rsync to create the directory structure with extended attributes Then the unison setup will only copy the extended attributes on files.


Please make a backup of your sysvol, just in case, this is because there is no dry-run

/usr/bin/rsync -XAavz --log-file /var/log/sysvol-sync.log --delete-after -f"+ */" -f"- *"  /var/lib/samba/sysvol root@DC2:/var/lib/samba  &&  /usr/bin/unison
Note: The path on DC2 is just /var/lib/samba which is different from DC1, it is by design, there is nothing wrong!

Add to Crontab on DC1

On DC1 run the following:

crontab -e 
*/5 * * * * /usr/bin/unison -silent

When you try to resync the folder

Warning: Please follow the steps below OR you can end up with an empty sysvol folder.
  1. Disable Cron on DC1, like Add a "#" on the line with crontab -e
  2. Check if rsync or unison are currently running in ps -aux if yes, wait for it to finish OR kill it (if it is zombie)
  3. Remove the hash files on both DC1 and DC2 on /root/.unison
  4. Now check your sysvol and resync
  5. Confirm that everything is ok again
  6. Re-enable the cron on DC1 again

FAQ

  • How can I do this on windows?
    • I don't have an answer, please post on the mailing list


  • What to do if I've more than two DC's?
    • In Theory, We would just make more cron jobs on DC1 and the complete sync will be perform next sync to all server.


  • Why can't I simply use a distributed filesystem like GlusterFS, Lustre, etc. for SysVol?
    • A cluster file system with Samba requires CTDB to be able to do it safely. And CTDB and AD DC are incompatible.