{"id":2725,"date":"2013-02-06T17:19:50","date_gmt":"2013-02-06T17:19:50","guid":{"rendered":"http:\/\/really.zonky.org\/?p=2725"},"modified":"2013-02-06T17:19:50","modified_gmt":"2013-02-06T17:19:50","slug":"linux-volume-manager-growing-filesystems","status":"publish","type":"post","link":"https:\/\/really.zonky.org\/?p=2725","title":{"rendered":"Linux Volume Manager: Growing Filesystems"},"content":{"rendered":"

If you have previously used Linux’s volume manager (LVM<\/a>) to set up disk storage, you may want to know about how to grow a filesystem safely.<\/p>\n

Which is probably the big feature of\u00a0any<\/em> decent volume manager because accurately predicting the size of filesystems is a black art, and the only alternative – to make the root filesystem contain all of the storage is a dumb idea.<\/p>\n

It’s actually\u00a0really<\/em> easy and can be done non-disruptively. It is done in two parts – effectively growing the “disk” device and then growing the filesystem itself.<\/p>\n

Extending The Volume<\/h2>\n

First identify the volume you need to extend. You can of course simply run\u00a0lvscan<\/em> which will show a list of the volumes, and if you have named them sensibly will allow you to pick out the volume to extend. But the simplest way is simply to run\u00a0df<\/em> to look at the filesystem you want to extend :-<\/p>\n

\/dev\/mapper\/ssd-opt \u00a0 \u00a0 \u00a0 \u00a0 7.9G \u00a05.5G \u00a02.1G \u00a073% \/opt<\/pre>\n
The device (in the first column) is what we extend. Now to decide how much to grow the volume by; just for the case of this example, we’ll assume that 2Gbytes is a sensible amount to grow the volume by. The command needed is :-<\/p>\n
lvextend --size +2G \/dev\/mapper\/ssd-opt<\/pre>\n
And that’s it. No need to shut down the server, dismount the filesystem, etc. Of course we haven’t quite finished yet.<\/p>\n
Growing The Filesystem<\/h2>\n
What we have done at this point is the equivalent of making the disk bigger. We also need to tell the filesystem it is sitting on a bigger disk, and to do so we need to know the type of the filesystem. The canonical place for checking that is the file\u00a0\/etc\/fstab<\/em> (actually it’s the filesystem itself but that is going too far) :-<\/p>\n
\r\n# grep opt \/etc\/fstab\r\n\/dev\/mapper\/ssd-opt\t\/opt\t\text4\tnoatime\t\t0 3\r\n<\/pre>\n
\nIt is probable<\/em> that you are looking at growing an ext3, ext4, or xfs filesystem. If not you will have to look up the details yourself.<\/p>\n
Growing ext3, or ext4 Filesystems<\/h3>\n
\nThis is done with the resize2fs<\/em> command :-<\/p>\n
\r\nresize2fs \/dev\/mapper\/ssd-opt\r\n<\/pre>\n
\nSeveral points :-<\/p>\n
    \n
  1. Yes it can<\/em> be done “online” whilst the filesystem is mounted (and applications are busy using it).\n
  2. You need to specify the device containing the filesystem to grow and not the mount point.\n
  3. There is no need to specify the size … the size will be determined from the size of the device underneath the filesystem.\n<\/ol>\n
    Growing xfs Filesystems<\/h3>\n
    \nThis is done with the xfs_growfs<\/em> command :-<\/p>\n
    \r\n# xfs_growfs \/opt\r\n<\/pre>\n
    \nSeveral points :-<\/p>\n
      \n
    1. Yes, it can be done “online”. In fact you have<\/em> to do it with the filesystem mounted.\n
    2. You need to specify the mountpoint of the filesystem and not the device. Irritatingly different from the above!\n
    3. There is no need to specify the size.\n<\/ol>\n
      How Reliable Is This?<\/h2>\n
      \nVery.<\/p>\n
      \nThere is always the chance that something could go wrong especially if you are operating “at the edge” (say you have a filesystem that is unusually large – several petabytes). But I’ve done online filesystem resizing for years in countless circumstances without an issue.<\/p>\n
      \nI’ll quite happily do it on the most important systems during working hours without losing a moment’s thought. However I do work in a place that takes backups seriously!<\/p>\n","protected":false},"excerpt":{"rendered":"
      If you have previously used Linux’s volume manager (LVM) to set up disk storage, you may want to know about how to grow a filesystem safely. Which is probably the big feature of\u00a0any decent volume manager because accurately predicting the size of filesystems is a black art, and the only alternative – to make the […]<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2},"_share_on_mastodon":"0"},"categories":[4,209,226],"tags":[1061,1062,539,485,1063],"class_list":["post-2725","post","type-post","status-publish","format-standard","hentry","category-it","category-linux-it","category-working-notes","tag-ext3","tag-ext4","tag-filesystems","tag-lvm","tag-xfs","category-4-id","category-209-id","category-226-id","post-seq-1","post-parity-odd","meta-position-corners","fix"],"share_on_mastodon":{"url":"","error":""},"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p1f2KI-HX","_links":{"self":[{"href":"https:\/\/really.zonky.org\/index.php?rest_route=\/wp\/v2\/posts\/2725","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/really.zonky.org\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/really.zonky.org\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/really.zonky.org\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/really.zonky.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2725"}],"version-history":[{"count":4,"href":"https:\/\/really.zonky.org\/index.php?rest_route=\/wp\/v2\/posts\/2725\/revisions"}],"predecessor-version":[{"id":2729,"href":"https:\/\/really.zonky.org\/index.php?rest_route=\/wp\/v2\/posts\/2725\/revisions\/2729"}],"wp:attachment":[{"href":"https:\/\/really.zonky.org\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2725"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/really.zonky.org\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2725"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/really.zonky.org\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2725"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}