{"id":2322,"date":"2016-07-06T06:50:45","date_gmt":"2016-07-05T18:50:45","guid":{"rendered":"http:\/\/www.zoyinc.com\/?p=2322"},"modified":"2016-07-23T07:17:08","modified_gmt":"2016-07-22T19:17:08","slug":"access-contents-on-a-single-disk-from-a-debian-mirror-array","status":"publish","type":"post","link":"http:\/\/www.zoyinc.com\/?p=2322","title":{"rendered":"Access contents on a single disk from a Debian mirror array"},"content":{"rendered":"

I am setting up an Open Media Vault, OMV, NAS box for my home storage requirements, detailed in the post Installing Open Media Vault<\/a>. I don’t have the resources to setup a full RAID 5 array, this would require a box with space for 3 drives plus which I would actually need to purchase 3 drives.<\/p>\n

So I am going with an older box with two 3GB drives in RAID 1 (mirrored). The idea is that if the box fails or I lose a drive the remaining drive can still be read. Not perfect for performance but I am going to use 7200 Barracuda Seagate drives, so hopefully that will help.<\/p>\n

This article is about taking a drive from one from this RAID 1 and reading it on another box – worst case scenario.<\/p>\n

Given that Open Media Vault run Debian the approach taken is to run a live USB version of Debian and mount the drive.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n
1.<\/td>\nCreate a Debian Live USB flash drive as described in article Create a Debian Live USB flash drive<\/a><\/td>\n<\/tr>\n
2.<\/td>\nIf you want to connect to this Debian Live instance using SSH follow the instructions int he post Enabling SSH access to Debian live USB<\/a><\/td>\n<\/tr>\n
3.<\/td>\nShould you get timed out the password for the user \u201cuser\u201d is \u201clive\u201d.<\/td>\n<\/tr>\n
4.<\/td>\nAt this point ensure the terminal window is not too small because the first screen you get will only:<\/p>\n
\"mdadm<\/a>
+ Click to enlarge<\/figcaption><\/figure>\n

If this happens to you just kill your terminal session, make the window bigger and try again. This time you should see:<\/p>\n

\"mdadm<\/a>
+ Click to enlarge<\/figcaption><\/figure><\/td>\n<\/tr>\n
5.<\/td>\nNow install mdadm:<\/p>\n
apt-get install mdadm rsync initramfs-tools<\/pre>\n
You will be asked If “the system’s root file system is located on an MD array (RAID\u2026”<\/p>\n
Ensure you enter \u201cnone<\/strong>\u201d as your answer.<\/td>\n<\/tr>\n
6.<\/td>\nNow we want to see the drives that are available so run:<\/p>\n
lsblk<\/pre>\n
This should produce something like:<\/p>\n
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT\r\nsda 8:0 0 74.5G 0 disk\r\n\u2514\u2500md127 9:127 0 74.5G 0 raid1\r\nsdb 8:16 1 7.5G 0 disk\r\n\u2514\u2500sdb1 8:17 1 1.2G 0 part \/lib\/live\/mount\/medium\r\nloop0 7:0 0 1.1G 1 loop \/lib\/live\/mount\/rootfs\/filesystem.squashfs<\/pre>\n<\/td>\n<\/tr>\n
7<\/td>\nYou can see from above that our remaining Mirror array disk is \u201csda\u201d.<\/p>\n

Create a temp directory to mount it in:<\/p>\n

mkdir \/mirror<\/pre>\n<\/td>\n<\/tr>\n
8.<\/td>\nNow mount it using something like:<\/p>\n
mount \/dev\/md127 \/mirror<\/pre>\n<\/td>\n<\/tr>\n
9.<\/td>\nBecause we enabled ssh login using root you can now sftp using WinSCP as root to move your files back to your laptop or PC.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

 <\/p>\n

A useful command is:<\/p>\n

mdadm --examine \/dev\/sd*<\/pre>\n
Which will give something like:<\/p>\n
\/dev\/sda:\r\nMagic : a92b4efc\r\nVersion : 1.2\r\nFeature Map : 0x0\r\nArray UUID : 99576b9e:6ffe87e8:fc43bf24:9c6b84ab\r\nName : nas2:Mirror1\r\nCreation Time : Sat Jun 4 05:42:20 2016\r\nRaid Level : raid1\r\nRaid Devices : 2\r\n\r\nAvail Dev Size : 156181504 (74.47 GiB 79.96 GB)\r\nArray Size : 78085120 (74.47 GiB 79.96 GB)\r\nUsed Dev Size : 156170240 (74.47 GiB 79.96 GB)\r\nData Offset : 131072 sectors\r\nSuper Offset : 8 sectors\r\nUnused Space : before=130992 sectors, after=11264 sectors\r\nState : clean\r\nDevice UUID : 55c45427:8ba028de:ef53f68a:2cd44a10\r\n\r\nUpdate Time : Wed Jun 22 21:26:19 2016\r\nChecksum : 38926569 - correct\r\nEvents : 122029\r\nDevice Role : Active device 1\r\nArray State : .A ('A' == active, '.' == missing, 'R' == replacing)\r\n\/dev\/sdb:\r\nMBR Magic : aa55\r\nPartition[0] : 2573440 sectors at 64 (type 17)\r\nmdadm: No md superblock detected on \/dev\/sdb1.<\/pre>\n
 <\/p>\n
 <\/p>\n","protected":false},"excerpt":{"rendered":"
I am setting up an Open Media Vault, OMV, NAS box for my home storage requirements, detailed in the post Installing Open Media Vault. I don’t have the resources to setup a full RAID 5 array, this would require a box with space for 3 drives plus which I would actually need to purchase 3 […]<\/p>\n","protected":false},"author":2,"featured_media":2532,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[312,4,313],"tags":[331,319,320,326,332],"class_list":["post-2322","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-debian","category-linux","category-open-media-vault","tag-mirror","tag-omv","tag-open-media-vault","tag-raid","tag-raid1"],"_links":{"self":[{"href":"http:\/\/www.zoyinc.com\/index.php?rest_route=\/wp\/v2\/posts\/2322","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.zoyinc.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.zoyinc.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.zoyinc.com\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/www.zoyinc.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2322"}],"version-history":[{"count":21,"href":"http:\/\/www.zoyinc.com\/index.php?rest_route=\/wp\/v2\/posts\/2322\/revisions"}],"predecessor-version":[{"id":2427,"href":"http:\/\/www.zoyinc.com\/index.php?rest_route=\/wp\/v2\/posts\/2322\/revisions\/2427"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.zoyinc.com\/index.php?rest_route=\/wp\/v2\/media\/2532"}],"wp:attachment":[{"href":"http:\/\/www.zoyinc.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2322"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.zoyinc.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2322"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.zoyinc.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2322"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}