Discovering new LUNs on Linux without rebooting
When you add new LUNs in VMWare to a Linux server you will not see them right away. A reboot will solve this problem, however, rebooting is not always possible. If this is a production server, you will have to schedule the reboot and coordinate it with the team. This takes time. An easy way to get around this is to do a manual rescan of the iscsi bus.
Viewing what iscsi hosts are available
ls -l /sys/class/scsi_host total 0 lrwxrwxrwx. 1 root root 0 Nov 15 15:04 host0 -> ../../devices/pci0000:00/0000:00:07.1/ata1/host0/scsi_host/host0 lrwxrwxrwx. 1 root root 0 Nov 15 15:04 host1 -> ../../devices/pci0000:00/0000:00:07.1/ata2/host1/scsi_host/host1 lrwxrwxrwx. 1 root root 0 Nov 15 15:04 host2 -> ../../devices/pci0000:00/0000:00:10.0/host2/scsi_host/host2 lrwxrwxrwx. 1 root root 0 Nov 15 15:04 host3 -> ../../devices/pci0000:00/0000:00:11.0/0000:02:01.0/host3/scsi_host/host3
Finding new LUNs
This command will show you all the hosts available on the system. If you wish to see which ones are new, we run the following command:
grep mpt /sys/class/scsi_host/host?/proc_name /sys/class/scsi_host/host2/proc_name:mptspi /sys/class/scsi_host/host3/proc_name:mptspi
Performing the manual scan
The results of the grep command show us host2 and host3. We can then use this information to do a manual scan.
echo "- - -" > /sys/class/scsi_host/host2/scan echo "- - -" > /sys/class/scsi_host/host3/scan
fdisk -l <truncated results> Disk /dev/sde: 1095.2 GB, 1095216660480 bytes, 2139095040 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes
I hope this article helps you out when you need it. For myself, this was helpful as I needed to expand LVM volumes and I did not want to reboot the servers beforehand. If you have any questions or comments, please feel free to write them in the comments section below.
Cheers,
Ivan Windon – RHCSA
