Hack The Sec-Leading Resource Of Linux Tutorial: LVM

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Extend a root LVM partition online</div>
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There is also a quick remedy for the emergency situation when your root partition runs out of disk space. There is a feature specific to ext3 and ext4 that can help the goal of resolving the full disk situation. Unless explicitly changed during filesystem creation, both by default reserve five percent (5%) of a volume capacity to the superuser (root). 
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<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"># df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg_main-lv_root
 ext4 8.4G 8.0G 952K 100% /
tmpfs tmpfs 499M 0 499M 0% /dev/shm
/dev/vda1 ext4 485M 33M 428M 8% /boot

# dumpe2fs /dev/vg_main/lv_root | grep 'Reserved block count'
dumpe2fs 1.41.12 (17-May-2010)
Reserved block count: 111513</pre>
It turned out 111513 of 4KB blocks were reserved for the superuser, which was exactly five percent of the volume capacity. 
 
How to enable it? 
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"># tune2fs -m 0 /dev/vg_main/lv_root 
tune2fs 1.41.12 (17-May-2010)
Setting reserved blocks percentage to 0% (0 blocks)
# df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg_main-lv_root
 ext4 8.4G 8.0G 437M 95% /
tmpfs tmpfs 499M 0 499M 0% /dev/shm
/dev/vda1 ext4 485M 33M 428M 8% /boot</pre>
 
Now that we have some free space on the root partition to work on we can extend the LVM partition: 
 
 
Create a new partition of appropriate size using fdisk 
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;">fdisk /dev/sdb1</pre>
 
This is a key sequence on the keyboard to create a new LVM type (8e) partition: 
 
n, p, 1, enter (accept default first sector), enter (accept default last sector), t, 8e, w 
 
 
Create a new Physical Volume 
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"># pvcreate /dev/sdb1
 Writing physical volume data to disk "/dev/sdb1"
 Physical volume "/dev/sdb1" successfully created</pre>
Extend a Volume Group 
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"># vgextend vg_main /dev/sdb1
 Volume group "vg_main" successfully extended</pre>
Extend your LVM 
 
 
- extend the size of your LVM by the amount of free space on PV 
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"># lvextend /dev/vg_main/lv_root /dev/sdb1
 Extending logical volume lv_root to 18.50 GiB
 Logical volume lv_root successfully resized</pre>
- or with a given size 
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;">lvextend -L +10G /dev/vg_main/lv_root</pre>
 
Finally resize the file system online 
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;"># resize2fs /dev/vg_main/lv_root
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/vg_main/lv_root is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 2
Performing an on-line resize of /dev/vg_main/lv_root to 4850688 (4k) blocks.
The filesystem on /dev/vg_main/lv_root is now 4850688 blocks long.</pre>
Now we can set the reserved blocks back to the default percentage - 5% 
<pre style="background: rgb(68, 67, 65); border-radius: 6px; border: 1px solid rgb(227, 227, 227); box-sizing: border-box; clear: none !important; margin-bottom: 10px !important; margin-top: 10px !important; overflow: auto; padding: 10px !important; width: auto !important; word-break: break-all;">tune2fs -m 5 /dev/mapper/vg_main-lv_root
Results:

# df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg_main-lv_root
 ext4 19G 8.0G 9.4G 46% /
tmpfs tmpfs 499M 0 499M 0% /dev/shm
/dev/vda1 ext4 485M 33M 428M 8% /boot</pre>
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How-to extend a root LVM partition online

Extend a root LVM partition online There is also a quick remedy for the emergency situation when your root partition runs out of disk s...