Tag Archives: CentOS

Samba, Windows, *nix, SELinux and you

Let’s face it: SMB/CIFS comes in handy plenty of times. Works great under Linux, works great with Windows, and if it’s configured properly it’s fun times for everyone. There are multiple potential behavioural problems though, mostly involving charsets.

Samba charset (and filesystem) setup

While I’ve been successfully using iso-8859-1 by default for a long time in my Samba servers, until recently I also used the same charset in the *nix filesystem, which brought all kind of oddities. 20/20 hindsight, as per usual. In smb.conf, you can configurn though you can specify different charsets to make everyone happy:

[global]
dos charset = iso-8859-1
unix charset = utf-8
preserve case = yes
short preserve case = yes
default case = lower
case sensitive = no

This has multiple advantages:

  • Windows gets its iso-8859-1 charset, and is happy;
  • Linux gets its utf-8 charset, and is happy;
  • preserve cases make sure that filenames aren’t changed while moving files across machines;
  • disabling case sensitive avoid weird behaviour under Windows.

This is the configuration I’ve been running for years, sharing files across Windows/Linux/OS X machines since Windows XP, and has been working perfectly.

Changing filesystem charset

If you’re switching the unix charset though, you might need to convert existing files/directories to the new charset. Cue in convmv:

convmv -f <from_charset> -t <to_charset> -r --preserve-mtimes <dir>

In my case:

convmv -f iso-8859-1 -t utf-8 -r --preserve-mtimes .

With this simple command I was able to mass rename thousands of files in one go. Note that you also need the --notest parameter to actually apply the changes, and not just list the files in a dry run.

SELinux

While playing around Centos I stumbled into SELinux problems I wasn’t prepared for. Consider the following:

[Share]
comment = Personal share
path = /home/<username>/share/
guest ok = no
browseable = yes
writable = no
create mask = 0660
directory mask = 0775
write list = <username>

Supposing the path actually exists, that the username is added to the samba user database and that the password is correct, everything should work fine. Except that it mostly likely won’t, because we need to configure SELinux on top of everything else:

restorecon -R -v /home/<username>/share/
chcon -R -t samba_share_t /home/<username>/share/

That’s all there is to properly setup and have the content accessible. Contrary to what other people, claims you don’t have to increase permissions in the samba path tree. A 0700 on the /home/<user> works perfectly fine.

CentOS 7 & DHCPv6

Sometimes instead of the usual SLAAC you might need or want to use DHCPv6. The dhcp package and a very short manual configuration will take care of everything for you on the server, but what about the client? What if you configured the DHCPv6 client but it is not working?

I setup both the server and the firewall, then I proceeded to configure the client, but it would always fail. No v6 traffic would hit the server machine, even though I added the DHCPV6C=yes on the client machine. After hours spent without a solution, I found a video with the answer: the problem is Network Manager! On top of adding the DHCPV6C parameter you also need to add NM_CONTROLLED=no. I ended up with the following /etc/sysconfig/network-scripts/ifcfg-ethX:

TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=none
DEFROUTE=no
IPV4_FAILURE_FATAL=no
IPV4INIT=no
IPV6INIT=yes
NM_CONTROLLED=no
DHCPV6C=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=no
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=ethX
DEVICE=ethX
ONBOOT=yes
IPV6_PRIVACY=yes
ZONE=public

Perfectly disabled IPv4, IPv6 configured automatically, all fine and dandy. Happy fun times!