Phil Hollenback's questions

I've got a CentOS server that's been running for about 10 years. Every few years I wipe it and install the latest CentOS and reconfigure all the services. Obviously much of the hardware has also been changed.

This machine was running CentOS 4 with samba 3.x until recently, and acting as the PDC for a small office network of Windows XP machines. I wiped it and installed the latest CentOS 6 and samba 3.6.9. Then I copied over the old config file and adjusted anything that testparm complained about.

Everything seemed to work fine - existing users could log on to their windows workstations using the existing windows domain.

Here is a testparm dump of the server settings:

[global]
    workgroup = RRMSC_DOM
    server string = RRM Primary Domain Controller Samba Server
    interfaces = 192.168.231.0/24, 10.8.3.0/24
    smb passwd file = /etc/samba/smbpasswd
    passdb backend = smbpasswd
    log file = /var/log/samba/smbd.log
    max log size = 50
    smb ports = 139
    time server = Yes
    socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
    printcap name = /etc/printcap
    add machine script = /usr/sbin/adduser -n -g machines -c Machine -d /dev/null -s /bin/false %m$
    logon script = logon.bat
    logon path = \\%L\Profiles\%U
    domain logons = Yes
    os level = 255
    preferred master = Yes
    domain master = Yes
    dns proxy = No
    wins support = Yes
    message command = /bin/mail -s 'message from #% on %M< %S; rm %S
    idmap config * : backend = tdb
    admin users = root, sdc
    hosts allow = 192.168.231.0/24, 127.0.0.1, 10.8.3.0/24
    cups options = raw

Recently I added a new user jim. Followed the standard procedure of using useradd to add this user and add him to the same unix group as other users. I set his unix password with passwd and his samba password with smbpasswd.

However, I find that jim cannot log on to any of the windows workstations in the office. On the windows workstation you see the message 'Logon failure: unknown user name or bad password.'

I've checked eventvwr on a windows workstation and see nothing related to failed logins.

To troubleshoot this on the linux server side I increased my log level in smb.conf to

log level = 2 auth:10

And I see this in the log:

[2013/05/14 20:28:21.994731,  5] auth/auth_util.c:211(make_user_info_map)
  Mapping user [RRMSC_DOM]\[jim] from workstation [UNCONFINED]
[2013/05/14 20:28:21.994754,  5] auth/auth_util.c:122(make_user_info)
  attempting to make a user_info for jim (jim)
[2013/05/14 20:28:21.994773,  5] auth/auth_util.c:132(make_user_info)
  making strings for jim's user_info struct
[2013/05/14 20:28:21.994792,  5] auth/auth_util.c:164(make_user_info)
  making blobs for jim's user_info struct
[2013/05/14 20:28:21.994811, 10] auth/auth_util.c:182(make_user_info)
  made an encrypted user_info for jim (jim)
[2013/05/14 20:28:21.994829,  3] auth/auth.c:216(check_ntlm_password)
  check_ntlm_password:  Checking password for unmapped user [RRMSC_DOM]\[jim]@[UNCONFINED] with the new password interface
[2013/05/14 20:28:21.994851,  3] auth/auth.c:219(check_ntlm_password)
  check_ntlm_password:  mapped user is: [RRMSC_DOM]\[jim]@[UNCONFINED]
[2013/05/14 20:28:21.994882, 10] auth/auth.c:228(check_ntlm_password)
  check_ntlm_password: auth_context challenge created by random
[2013/05/14 20:28:21.994901, 10] auth/auth.c:230(check_ntlm_password)
  challenge is: 
[2013/05/14 20:28:21.994921, 10] auth/auth.c:256(check_ntlm_password)
  check_ntlm_password: guest had nothing to say
[2013/05/14 20:28:21.995773,  4] auth/auth_sam.c:180(sam_account_ok)
  sam_account_ok: Checking SMB password for user jim
[2013/05/14 20:28:21.995816,  5] auth/auth_sam.c:162(logon_hours_ok)
  logon_hours_ok: user jim allowed to logon at this time (Wed May 15 03:28:21 2013
  )
[2013/05/14 20:28:21.996529,  5] auth/auth_util.c:649(make_server_info_sam)
  make_server_info_sam: made server info for user jim -> jim
[2013/05/14 20:28:21.996573,  3] auth/auth.c:265(check_ntlm_password)
  check_ntlm_password: sam authentication for user [jim] succeeded
[2013/05/14 20:28:21.996611,  5] auth/auth.c:291(check_ntlm_password)
  check_ntlm_password:  PAM Account for user [jim] succeeded
[2013/05/14 20:28:21.996630,  2] auth/auth.c:304(check_ntlm_password)
  check_ntlm_password:  authentication for user [jim] -> [jim] -> [jim] succeeded
[2013/05/14 20:28:21.996652,  5] auth/auth_util.c:2119(free_user_info)
  attempting to free (and zero) a user_info structure
[2013/05/14 20:28:21.996670, 10] auth/auth_util.c:2123(free_user_info)
  structure was created for jim

the thing that particularly confuses me is the message about authentication for use [jim] succeeded. That seems to indicate that the use logs in correctly on the server, but he can't log in on the workstation.

So can anyone tell me what is going wrong here or where else I should look to troubleshoot?

Note that I had previously set selinux to disabled on this machine so it's not a selinux problem.

I know that Yahoo and Google mail support 25MB email attachments. I have an idea from somewhere that 10MB email messages are generally supported by modern email systems.

So if I'm sending an email between two arbitrary users on the internet, what's the safe upper bound on message size? 1MB? 10MB? 25MB?

I know that one answer is 'don't send big emails, use some sort of drop box'. I'm looking for a guideline if you are limited to only using regular smtp email.

I manage a CentOS 4.8 server for a small workgroup. Last year I converted the filesystem to LVM over software RAID (RAID 1, two mirrored drives).

I now have the following filesystems on LVM/RAID:

/dev/mapper/vg-home   619G  231G  358G  40% /home
/dev/mapper/vg-tmp    7.9G   55M  7.5G   1% /tmp
/dev/mapper/vg-usr    7.9G  2.7G  4.9G  36% /usr
/dev/mapper/vg-var    7.9G  3.1G  4.5G  42% /var

To back these filesystems up, I use rsnapshot and a couple of external 2TB USB drives that I rotate weekly. In practice that has worked very well. I have rsnapshot configured to do snapshots every four hours.

Given that configuration, should I also consider doing LVM snapshots? Are LVM snapshots more efficient? Could I be doing them more often than the rsnapshot backups every 4 hours without significantly impacting system performance?

I am aware that LVM snapshots could be used to ensure database consistency for backups, however this server doesn't run a database so that isn't really a concern.

It seems like there might be a way to do both LVM and rsnapshot backups in a complimentary fashion but I am unable to suss it out.