GURU4HP: October 2012

Tuesday, October 2, 2012

How to mount remote windows partition (windows share) under Linux

Procedure to mount remote windows partition (NAS share)

1) Make sure you have following information:
==> Windows username and password to access share name
==> Sharename (such as //server/share) or IP address
==> root level access on Linux
2) Login to Linux as a root user (or use su command)
3) Create the required mount point:
# mkdir -p /mnt/ntserver
4) Use the mount command as follows:
# mount -t cifs //ntserver/download -o username=vivek,password=myPassword /mnt/ntserver
Use following command if you are using Old version such as RHEL <=4 or Debian <= 3:
# mount -t smbfs -o username=vivek,password=D1W4x9sw //ntserver/download /mnt/ntserver
5) Access Windows 2003/2000/NT share using cd and ls command:
# cd /mnt/ntserver; ls -l
Where,

-t smbfs : File system type to be mount (outdated, use cifs)
-t cifs : File system type to be mount
-o : are options passed to mount command, in this example I had passed two options. First argument is password (vivek) and second argument is password to connect remote windows box
//ntserver/download : Windows 2000/NT share name
/mnt/ntserver Linux mount point (to access share after mounting)

Monday, October 1, 2012

HOW-TO enable multipathing on RedHat Linux 5.x

In Red Hat Enterprise Linux 5, device-mapper-multipath is installed by default. This is a change from Red Hat Enterprise Linux 4. If a third party multipathing solution is in use, device-mapper-multipath should be disabled to avoid any conflict between the multiple multipathing technologies. But RedHat multipathing is NOT ACTIVATED by default and you must enable it.

To enable it, modify the setting in /etc/sysconfig/mkinitrd/multipath file by changing MULTIPATH from NO to YES
        MULTIPATH=YES
By default, /etc/multipath.conf has all devices blacklisted. If this default configuration has been changed, the change should be reverted. Comment out following three lines:
        # Blacklist all devices by default. Remove this to enable multipathing
        # on the default devices.
        blacklist {
               devnode "\*"
        }
Then reboot. Enable the multipathd on boot and start it by
        chkconfig mutipathd on
      service multipathd start
At this time, you should be able to see multiple connections to the LUNs on the storage array if everything set correctly and you can verify it using   "fdisk -l". You should see some newly enabled "dm-??" devices. Also run "/sbin/multipath -ll" command and should see the path to each device. i.e. the path mpath2 for device dm-7 pointing to two devices sdj and sdx.
     mpath2 (3600a0b80004879f0000004064a5b5d9f) dm-7 SUN,CSM200_R
   [size=50G][features=1 queue_if_no_path][hwhandler=1 rdac][rw]
    \\\\\\_ round-robin 0 [prio=200][active]
     \\\\\\_ 0:0:1:2 sdj 8:144 [active][ready]
     \\\\\\_ 1:0:1:2 sdx 65:112 [active][ready]
     \\\\\\_ round-robin 0 [prio=0][enabled]
     \\\\\\_ 0:0:0:2 sdc 8:32   [active][ghost]
     \\\\\\_ 1:0:0:2 sdq 65:0   [active][ghost]
You should see I/O activities on both sdj and sdx when running dd test on dm-7.

Rescan the SCSI bus w/out rebooting

To add or remove a SCSI device explicitly, or to re-scan an entire SCSI bus without rebooting a running system:

Red Hat Enterprise Linux 4 or 5:

To rescan an entire SCSI bus and re-register all devices found:
When dealing with fibre attached storage, it is necessary to issue a LIP (loop initialization primitive) on the fabric:

shell> echo "1" > /sys/class/fc_host/host#/issue_lip

Replace the “#” with the number of the SCSI bus to be rescanned.

Note: Issueing a LIP (above) on Red Hat Enterprise Linux 5 is all that is needed to rescan fibre
attached storage. Once the LIP is issued, the bus scan may take a few seconds to complete.

To rescan all other SCSI attached storage, a rescan should be issued:

shell> echo "- - -" > /sys/class/scsi_host/host#/scan

Replace the “#” with the number of the SCSI bus to be rescanned.

In addition to re-scanning the entire bus, a specific device can be added or deleted for some versions or Red Hat Enterprise Linux as specified below.

Red Hat Enterprise Linux 4 or 5:

To remove a single existing device explicitly

shell> echo 1 > /sys/block//device/delete

Red Hat Enterprise Linux 3 or 4:

To add a single device explicitly:

shell> echo "scsi add-single-device    " > /proc/scsi/scsi

To remove a device explicitly:

shell> echo "scsi remove-single-device    " > /proc/scsi/scsi

Where are the host, bus, target, and LUN numbers for the device,as reported in /sys (2.6 kernels only) or /proc/scsi/scsi or dmesg. These numbers are sometimes refered to as “Host”, “Channel”, “Id”, and “Lun” in Linux tool output and documentation.

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