iSCSI的用法

Using iSCSI On Ubuntu 9.04 (Initiator And Target)

Version 1.0
Author: Falko Timme
Last edited 05/11/2009

This guide explains how you can set up an iSCSI target and an iSCSI initiator (client), both running Ubuntu 9.04. The iSCSI protocol is a storage area network (SAN) protocol which allows iSCSI initiators to use storage devices on the (remote) iSCSI target using normal ethernet cabling. To the iSCSI initiator, the remote storage looks like a normal, locally-attached hard drive.

I do not issue any guarantee that this will work for you!

1 Preliminary Note

I'm using two Ubuntu 9.04 servers here:

• server1.example.com (Initiator): IP address 192.168.0.100
• server2.example.com (Target): IP address 192.168.0.101

Because we will run all the steps from this tutorial with root privileges, we can either prepend all commands in this tutorial with the string sudo, or we become root right now by typing

sudo su

2 Setting Up The Target (server2)

server2:

First we set up the target (server2):

aptitude install iscsitarget

Open /etc/default/iscsitarget...

vi /etc/default/iscsitarget

... and set ISCSITARGET_ENABLE to true:

ISCSITARGET_ENABLE=true

We can use unused logical volumes, image files, hard drives (e.g. /dev/sdb), hard drive partitions (e.g. /dev/sdb1) or RAID devices (e.g. /dev/md0) for the storage. In this example I will create a logical volume of 20GB named storage_lun1 in the volume group vg0:

lvcreate -L20G -n storage_lun1 vg0

(If you want to use an image file, you can create it as follows:

mkdir /storage
dd if=/dev/zero of=/storage/lun1.img bs=1024k count=20000

This creates the image file /storage/lun1.img with a size of 20GB.

)

Next we edit /etc/ietd.conf...

vi /etc/ietd.conf

... and comment out everything in that file. At the end we add the following stanza:

[...]            Target iqn.2001-04.com.example:storage.lun1            IncomingUser someuser secret            OutgoingUser            Lun 0 Path=/dev/vg0/storage_lun1,Type=fileio            Alias LUN1            #MaxConnections  6

The target name must be a globally unique name, the iSCSI standard defines the "iSCSI Qualified Name" as follows: iqn.yyyy-mm.[:identifier]; yyyy-mm is the date at which the domain is valid; the identifier is freely selectable. The IncomingUser line contains a username and a password so that only the initiators (clients) that provide this username and password can log in and use the storage device; if you don't need authentication, don't specify a username and password in the IncomingUser line. In the Lun line, we must specify the full path to the storage device (e.g. /dev/vg0/storage_lun1, /storage/lun1.img, /dev/sdb, etc.).

Now we tell the target that we want to allow connections to the device iqn.2001-04.com.example:storage.lun1 from the IP address 192.168.0.100 (server1.example.com)...

vi /etc/initiators.allow

[...]            iqn.2001-04.com.example:storage.lun1 192.168.0.100

... and start the target:

/etc/init.d/iscsitarget start

3 Setting Up The Initiator (server1)

server1:

On server1, we install the initiator:

aptitude install open-iscsi

Next we open /etc/iscsi/iscsid.conf...

vi /etc/iscsi/iscsid.conf

... and set node.startup to automatic:

[...]            node.startup = automatic            [...]

Then we restart the initiator:

/etc/init.d/open-iscsi restart

Now we connect to the target (server2) and check what storage devices it has to offer:

iscsiadm -m discovery -t st -p 192.168.0.101

server1:~# iscsiadm -m discovery -t st -p 192.168.0.101
192.168.0.101:3260,1 iqn.2001-04.com.example:storage.lun1
server1:~#

iscsiadm -m node

server1:~# iscsiadm -m node
192.168.0.101:3260,1 iqn.2001-04.com.example:storage.lun1
server1:~#

The settings for the storage device iqn.2001-04.com.example:storage.lun1 on 192.168.0.101:3260,1 are stored in the file /etc/iscsi/nodes/iqn.2001-04.com.example:storage.lun1/192.168.0.101,3260,1/default. We need to set the username and password for the target in that file; instead of editing that file manually, we can use the iscsiadm command to do this for us:

iscsiadm -m node --targetname "iqn.2001-04.com.example:storage.lun1" --portal "192.168.0.101:3260" --op=update --name node.session.auth.authmethod --value=CHAP
iscsiadm -m node --targetname "iqn.2001-04.com.example:storage.lun1" --portal "192.168.0.101:3260" --op=update --name node.session.auth.username --value=someuser
iscsiadm -m node --targetname "iqn.2001-04.com.example:storage.lun1" --portal "192.168.0.101:3260" --op=update --name node.session.auth.password --value=secret

Now we can log in, either by running...

iscsiadm -m node --targetname "iqn.2001-04.com.example:storage.lun1" --portal "192.168.0.101:3260" --login

server1:~# iscsiadm -m node --targetname "iqn.2001-04.com.example:storage.lun1" --portal "192.168.0.101:3260" --login
Logging in to [iface: default, target: iqn.2001-04.com.example:storage.lun1, portal: 192.168.0.101,3260]
Login to [iface: default, target: iqn.2001-04.com.example:storage.lun1, portal: 192.168.0.101,3260]: successful
server1:~#

... or by restarting the initiator:

/etc/init.d/open-iscsi restart

(If you want to log out, you can run

iscsiadm -m node --targetname "iqn.2001-04.com.example:storage.lun1" --portal "192.168.0.101:3260" --logout

)

In the output of

fdisk -l

you should now find a new hard drive (/dev/sdb in this example); that's our iSCSI storage device:

server1:~# fdisk -l

Disk /dev/sda: 32.2 GB, 32212254720 bytes
255 heads, 63 sectors/track, 3916 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00031334

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        3749    30113811   83  Linux
/dev/sda2            3750        3916     1341427+   5  Extended
/dev/sda5            3750        3916     1341396   82  Linux swap / Solaris

Disk /dev/sdb: 21.4 GB, 21474836480 bytes
64 heads, 32 sectors/track, 20480 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes
Disk identifier: 0x00000000

Disk /dev/sdb doesn't contain a valid partition table
server1:~#

To use that device, we must format it:

fdisk /dev/sdb

server1:~# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x882944df.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.


The number of cylinders for this disk is set to 20480.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
   (e.g., DOS FDISK, OS/2 FDISK)
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m for help): <-- m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help): <-- n
Command action
   e   extended
   p   primary partition (1-4)
<-- p
Partition number (1-4): <-- 1
First cylinder (1-20480, default 1): <-- ENTER
Using default value 1
Last cylinder or +size or +sizeM or +sizeK (1-20480, default 20480): <-- ENTER
Using default value 20480

Command (m for help): <-- t
Selected partition 1
Hex code (type L to list codes): <-- L

 0  Empty           1e  Hidden W95 FAT1 80  Old Minix       be  Solaris boot
 1  FAT12           24  NEC DOS         81  Minix / old Lin bf  Solaris
 2  XENIX root      39  Plan 9          82  Linux swap / So c1  DRDOS/sec (FAT-
 3  XENIX usr       3c  PartitionMagic  83  Linux           c4  DRDOS/sec (FAT-
 4  FAT16 <32M      40  Venix 80286     84  OS/2 hidden C:  c6  DRDOS/sec (FAT-
 5  Extended        41  PPC PReP Boot   85  Linux extended  c7  Syrinx
 6  FAT16           42  SFS             86  NTFS volume set da  Non-FS data
 7  HPFS/NTFS       4d  QNX4.x          87  NTFS volume set db  CP/M / CTOS / .
 8  AIX             4e  QNX4.x 2nd part 88  Linux plaintext de  Dell Utility
 9  AIX bootable    4f  QNX4.x 3rd part 8e  Linux LVM       df  BootIt
 a  OS/2 Boot Manag 50  OnTrack DM      93  Amoeba          e1  DOS access
 b  W95 FAT32       51  OnTrack DM6 Aux 94  Amoeba BBT      e3  DOS R/O
 c  W95 FAT32 (LBA) 52  CP/M            9f  BSD/OS          e4  SpeedStor
 e  W95 FAT16 (LBA) 53  OnTrack DM6 Aux a0  IBM Thinkpad hi eb  BeOS fs
 f  W95 Ext'd (LBA) 54  OnTrackDM6      a5  FreeBSD         ee  EFI GPT
10  OPUS            55  EZ-Drive        a6  OpenBSD         ef  EFI (FAT-12/16/
11  Hidden FAT12    56  Golden Bow      a7  NeXTSTEP        f0  Linux/PA-RISC b
12  Compaq diagnost 5c  Priam Edisk     a8  Darwin UFS      f1  SpeedStor
14  Hidden FAT16 <3 61  SpeedStor       a9  NetBSD          f4  SpeedStor
16  Hidden FAT16    63  GNU HURD or Sys ab  Darwin boot     f2  DOS secondary
17  Hidden HPFS/NTF 64  Novell Netware  b7  BSDI fs         fd  Linux raid auto
18  AST SmartSleep  65  Novell Netware  b8  BSDI swap       fe  LANstep
1b  Hidden W95 FAT3 70  DiskSecure Mult bb  Boot Wizard hid ff  BBT
1c  Hidden W95 FAT3 75  PC/IX
Hex code (type L to list codes): <-- 83

Command (m for help): <-- w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
server1:~#

Afterwards, the output of

fdisk -l

should look as follows:

server1:~# fdisk -l

Disk /dev/sda: 32.2 GB, 32212254720 bytes
255 heads, 63 sectors/track, 3916 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00031334

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        3749    30113811   83  Linux
/dev/sda2            3750        3916     1341427+   5  Extended
/dev/sda5            3750        3916     1341396   82  Linux swap / Solaris

Disk /dev/sdb: 21.4 GB, 21474836480 bytes
64 heads, 32 sectors/track, 20480 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes
Disk identifier: 0x882944df

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       20480    20971504   83  Linux
server1:~#

Now we create a filesystem on /dev/sdb1...

mkfs.ext3 /dev/sdb1

... and mount it for test purposes:

mount /dev/sdb1 /mnt

You should now see the new device in the outputs of...

mount

server1:~# mount
/dev/sda1 on / type ext3 (rw,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
/dev/sdb1 on /mnt type ext3 (rw)
server1:~#

... and

df -h

server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              29G  685M   27G   3% /
tmpfs                 253M     0  253M   0% /lib/init/rw
udev                   10M   88K   10M   1% /dev
tmpfs                 253M     0  253M   0% /dev/shm
/dev/sdb1              20G  173M   19G   1% /mnt
server1:~#

You can unmount it like this:

umount /mnt

To have the device mounted automatically at boot time, e.g. in the directory /storage, we create that directory...

mkdir /storage

... and add the following line to /etc/fstab:

vi /etc/fstab

[...]            /dev/sdb1       /storage        ext3    defaults,auto,_netdev 0 0

For test purposes, you can now reboot the system:

reboot

After the reboot, the device should be mounted:

mount

server1:~# mount
/dev/sda1 on / type ext3 (rw,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
/dev/sdb1 on /storage type ext3 (rw,_netdev)
server1:~#

df -h

server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              29G  685M   27G   3% /
tmpfs                 253M     0  253M   0% /lib/init/rw
udev                   10M   88K   10M   1% /dev
tmpfs                 253M     0  253M   0% /dev/shm
/dev/sdb1              20G  173M   19G   1% /storage
server1:~#

4 Links

• Open-iSCSI: http://www.open-iscsi.org/
• iSCSI Enterprise Target: http://iscsitarget.sourceforge.net/
• Ubuntu: http://www.ubuntu.com/