Differences

This shows you the differences between two versions of the page.

--- soc:2009:pravin:journal:bkodebianiscsi [2009/07/18 10:31]
less1 created
+++ soc:2009:pravin:journal:bkodebianiscsi [2009/09/25 19:37] (current)
less1
@@ Line 9: / Line 9: @@
 ===== Installing the target =====
 The target for these experiments is installed on my laptop (Ubuntu-9.04) with following procedure.
-Most of these steps are taken from blog [[http://www.howtoforge.com/using-iscsi-on-ubuntu-9.04-initiator-and-target|Using iscsi over ubuntu 9.04]]
+Most of these steps are taken from blog [[http://www.howtoforge.com/using-iscsi-on-ubuntu-9.04-initiator-and-target|Using iscsi over ubuntu 9.04]]\\
+Installing iscsi target
+<code>
+sudo apt-get install iscsitarget
+</code>
+Configure the target by editing ''/etc/default/iscsitarget'', ''/etc/ietd.conf'' and ''/etc/initiators.allow'' files as follows\\
+  - Open ''/etc/default/iscsitarget'' and set ''ISCSITARGET_ENABLE=true''
+  - Open ''/etc/ietd.conf'', and comment out all lines, then add following paragraph
+<code>
+Target iqn.2001-04.com.example:storage.lun1
+        IncomingUser
+        OutgoingUser
+        Lun 0 Path=/var/www/debian-live-501-i386-gnome-desktop.iso,Type=fileio,IOMode=ro
+        Alias LUN1
+</code>
+Now we add following line to "/etc/initiators.allow"
+<code>
+ALL ALL
+</code>
+This should allow any initiator to access any lun device\\
+and then, restart the target
+<code>
+sudo /etc/init.d/iscsitarget restart
+</code>
+===== Testing the target =====
+The iscsi target is tested by installing iscsi initiator on same laptop.  Following is the procedure.\\
+  * Installing
+<code>
+sudo apt-get install open-iscsi
+</code>
+  * configure iscsi initiator to start nodes automatically\\
+Edit the file ''/etc/iscsi/iscsid.conf'' to have line ''node.startup = automatic''
+  * and then restart the initiator
+<code>
+/etc/init.d/open-iscsi restart
+</code>
+  * Now, do the discovery of nodes available
+<code>
+$ sudo iscsiadm -m discovery -t st -p 192.168.0.1
+.168.0.1:3260,1 iqn.2001-04.com.example:storage.lun1
+</code>
+  * I dont know why this command is needed, but it was in the blog, so I am adding it here
+<code>
+$ sudo iscsiadm -m node
+.168.0.1:3260,1 iqn.2001-04.com.example:storage.lun1
+</code>
+  * Logging in
+<code>
+$ sudo iscsiadm -m node --targetname "iqn.2001-04.com.example:storage.lun1" --portal "192.168.0.1:3260" --login
+Logging in to [iface: default, target: iqn.2001-04.com.example:storage.lun1, portal: 192.168.0.1,3260]
+Login to [iface: default, target: iqn.2001-04.com.example:storage.lun1, portal: 192.168.0.1,3260]: successful
+</code>
+  * and it is done, you can see the new device with ''fdisk -l'' command
+<code>
+$ sudo fdisk -l
+[sudo] password for pravin:
+Disk /dev/sda: 250.0 GB, 250059350016 bytes
+heads, 63 sectors/track, 30401 cylinders
+Units = cylinders of 16065 * 512 = 8225280 bytes
+Disk identifier: 0xa9f9aa9b
+   Device Boot      Start         End      Blocks   Id  System
+/dev/sda1               1           5       40131   de  Dell Utility
+[...]
+[...]
+[...]
+Disk /dev/sdc: 724 MB, 724785152 bytes
+heads, 61 sectors/track, 1008 cylinders
+Units = cylinders of 1403 * 512 = 718336 bytes
+Disk identifier: 0x00000000
+Disk /dev/sdc doesn't contain a valid partition table
+$ sudo mount -t iso9660 /dev/sdc mpoint
+mount: block device /dev/sdc is write-protected, mounting read-only
+$ mount
+/dev/sda6 on / type ext3 (rw,relatime,errors=remount-ro)
+[...]
+[...]
+[...]
+/dev/sdc on /home/pravin/Etherboot/git/BKO.git/pxeknife/debian/debian-live-501-i386/mpoint type iso9660 (ro)
+$ ls mpoint
+doc  isolinux  live  md5sum.txt
+</code>
+As Now I know that my target is working correctly, I am free to try out booting from this target 8-)
+===== Configuring initramfs as initiator =====
+I need to add all the tools, configuration files and kernel modules to initramfs so that I can use them from there to connect.
+  * ** Step 1 **, __Kernel Modules__ : on checking the contents of ''/etc/init.d/open-iscsi'' it seems that following kernel modules are to be inserted
+<code>
+modprobe iscsi_tcp
+modprobe ib_iser
+</code>
+  * These modules are already in debian initramfs, so no need to worry about that :)
+  * ** Step 2 ** __Tools needed__ : Again ''/etc/init.d/open-iscsi'' tells us that it uses ''/sbin/iscsid'' and ''/sbin/iscsiadm''\\
+but there are more iscsi related tools in /sbin
+<code>
+$ ls /sbin/iscsi*
+/sbin/iscsiadm  /sbin/iscsid  /sbin/iscsi_discovery  /sbin/iscsi-iname  /sbin/iscsistart
+</code>
+To avoid any missing dependencies, better to add all above tools to initramfs.
+  * ** Step 3 ** __Configuration Files__ : From man page of iscsiadm and iscsid, we can guess that following configuration files will be needed
+<code>
+/etc/iscsi/iscsid.conf
+/etc/iscsi/initiatorname.iscsi
+</code>
+===== Testing new initramfs =====
+The HTTPFS code has been commented out so that initramfs will give me rescue shell, which can be used to start the iscsi initiator.\\
+Following commands were executed once the rescue shell is provided.
+<code>
+modprobe iscsi_tcp
+modprobe ib_iser
+mkdir /var/run
+/sbin/iscsid
+iscsiadm -m discovery -t st -p 192.168.0.1
+</code>
+and no node is shown :(\\
+I tried to run iscsid in debug mode with following command
+<code>
+/sbin/iscsid -d 8 -f
+iscsid : sysfs_init: sysfs_path='/sys'
+[...]
+[...]
+iscsid: reaped pid 994, reap_count now 0
+</code>
+and also ran ''iscsiadm'' in debug mode with following output
+<code>
+(initramfs) iscsiadm -d 8 -m discovery -t st -p 192.168.0.1
+iscsiadm: ip 192.168.0.1, port 3260, tgpt -1
+iscsiadm: Max file limits 1024 1024
+</code>
+This output is definitely very less compare to the output of same command executed on my laptop.\\
+**Note:** __This was executed over qeum.__ I am not sure if qemu has created any problem.
+===== Debugging the problem =====
+To make sure debien in virtual environment can use iscsi with the tools, and configuration files used inside initramfs\\
+  - I booted debian live CD with virtualbox
+  - inserted kernel modules just as above
+  - Copied configuration files into live cd.
+  - Copied tools into live cd
+  - Executed above commands from inside live CD
+  - The ''iscsiadm -m discovery'' command did gave output.
+<code>
+# iscsiadm -m discovery -t st -p 192.168.0.1
+.168.0.1:3260,1 iqn.2001-04.com.example:storage.lun1
+</code>
+So, the tools do work. but may be they are able to use other files, tools and modules which are not present in initrd.\\
+How to find those dependencies?
+===== Debugging v2 =====
+Finally, added the ''strace'' to initramfs, and now trying find what is the problem because of which iscsiadm is dying\\
+<code>
+socket(PF_FILE, SOCK_STREAM, 0)         = 3
+connect(3, {sa_family=AF_FILE, path=@"ISCSIADM_ABSTRACT_NAMESPACE"...}, 110) = 0
+write(3, "\n\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"..., 5244) = -1 EPIPE (Broken pipe)
+</code>
+This is what killing the iscsiadm imatuarly.
+==== Checking the code of open-iscsi ====
+With help of stephana, the likely problem is located at following location
+<code>
+stefanha: http://git.kernel.org/?p=linux/kernel/git/mnc/open-iscsi.git;a=blob;f=usr/mgmt_ipc.c;h=e784bcac019a84522e62beff1b49b1ca62e37f5a;hb=HEAD
+(07/19/2009 04:34:21 PM) stefanha: less1: Perhaps you're hitting this:
+(07/19/2009 04:34:27 PM) stefanha: http://git.kernel.org/?p=linux/kernel/git/mnc/open-iscsi.git;a=blob;f=usr/mgmt_ipc.c;h=e784bcac019a84522e62beff1b49b1ca62e37f5a;hb=HEAD#l549
+(07/19/2009 04:34:31 PM) stefanha: if (!mgmt_peeruser(fd, user) || strncmp(user, "root", PEERUSER_MAX)) {
+(07/19/2009 04:34:43 PM) stefanha: write(2) will return EPIPE if the UNIX domain socket was closed.
+(07/19/2009 04:35:17 PM) stefanha: mgmt_peeruser() is defined here: http://git.kernel.org/?p=linux/kernel/git/mnc/open-iscsi.git;a=blob;f=usr/mgmt_ipc.c;h=e784bcac019a84522e62beff1b49b1ca62e37f5a;hb=HEAD#l342
+(07/19/2009 04:38:15 PM) less1: stefanha: is it checking if I have root privilages? I am not sure if I understand which peeruser credential is it refering.
+(07/19/2009 04:40:08 PM) stefanha: Your user name must be "root".
+(07/19/2009 04:40:25 PM) stefanha: Otherwise iscsid will not accept commands from the UNIX domain socket.
+</code>
+=== Possible solution : hacking open-iscsi ===
+modified the ''iscsiadm'' code so that, it will not fail when username is not ''root''.\\
+With is modification, the discovery part is working, but now there is error at login part. Following is the error.
+<code>
+connection2:0: Could not create connection due to crc32c loading error.  Make sure the crc32c module is build as module into the kernel.
+</code>
+The first attempt will be to download the kernel module from Live CD of debian after booting it from CD.\\
+--- Doing it
+===== Working Solution =====
+There was need for two extra kernel modules
+  - libcrc32c.ko
+  - crc32c.ko
+Fetched these modules from live-CD and added them.\\
+There as also need for small sleep after ''iscsiadm --login'' as ''/dev/sda'' was taking little time to appear.\\
+This was handled by adding ''sleep 2''\\
+Two new parameters were introduced
+  - ''iscsifs=<IP:PORT>''  iscsi server IP and port number
+  - ''target=<targetname>'' the iscsi target name of the disk (entire name is not needed, some part which can uniquely identify apart from other disks exported at same machine)
+===== Remote ISCSI =====
+Following are the errors that I get when connecting to remote iscsi
+<code>
+Connection1:0: ping timeout of 5 secs expired, last rx 307737, last ping 308987, now 310237
+Connection1:0: detected conn error (1011)
+SQUASHFS error : Unable to read page, block 0x1b392
+Bus error
+</code>
+Most of these errors are related to timing, and I believe that
+these errors are there because of delays in accessing required data.
+===== Target behaviour =====
+sometimes, you may get following error when logging in with iscsiadm
+<code>
+iscsiadm -m node --targetname "${targetname}" --portal "${ISCSIFS}" --login
+records not found!.
+</code>
+this is because the ${ISCSIFS} is not IP but dnsname.
+Dnsname may work with ''iscsiadm -m discovery -t st -p "${ISCSIFS}" ''
+but it may verywell fail when same dnsname is given to login.
+[[http://groups.google.com/group/open-iscsi/browse_thread/thread/c556508505ecc461|mailing list discussion]]
+==== Solution ====
+Dont use ''--portal "${ISCSIFS}"'' option, use
+<code>
+iscsiadm -m node --targetname "${targetname}" --login
+</code>

Trace:

Differences

Navigation

Search

Toolbox

QR Code