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| - | Note in the next step, by default <tt>fdisk wants to start the new partition in between partitions 1 and 2 (at block 24415) as there is a small gap. This is not desired and the end of the second partition should be used instead: | + | Note in the next step, by default <tt>fdisk</tt> wants to start the new partition in between partitions 1 and 2 (at block 24415) as there is a small gap. This is not desired and the end of the second partition should be used instead: |
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===Fetching the btrfs software=== | ===Fetching the btrfs software=== | ||
By default, microSD MeeGo images for the N900 contain a root filesystem that is only 1.5GB in size. As btrfs space monitoring is complicated, and the large size of the default package list, such a small root filesystem can cause problems for N900 users. Fortunately btrfs is capable, allowing online resizing and multi-device support: if the user has an SD card larger than 2GB, the root filesystem can be extended and this page documents that process.
Contents |
The only prerequisite is an internet connection as the btrfs-progs package is not installed by default. Any network connection will do, be it Wifi or USB networking.
1. Start a root shell, either by logging in to the N900 via SSH or by starting xterm and su -'ing to root.
2. Using a disk partition tool, examine the microSD card partition table and create a new partition. This example uses a 4GB card and fdisk, but sfdisk or other tools can be used instead:
[root@localhost ~]# fdisk /dev/mmcblk0
The number of cylinders for this disk is set to 60416.
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)
Command (m for help): p
Disk /dev/mmcblk0: 3959 MB, 3959422976 bytes
4 heads, 32 sectors/track, 60416 cylinders
Units = cylinders of 128 * 512 = 65536 bytes
Disk identifier: 0x000b985b
Device Boot Start End Blocks Id System
/dev/mmcblk0p1 1 24415 1562500 83 Linux
/dev/mmcblk0p2 24417 28320 249856 83 Linux
Note in the next step, by default fdisk wants to start the new partition in between partitions 1 and 2 (at block 24415) as there is a small gap. This is not desired and the end of the second partition should be used instead:
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 3
First cylinder (24415-60416, default 24415): 28321
Last cylinder, +cylinders or +size{K,M,G} (28321-60416, default 60416):
Using default value 60416
Command (m for help): p
Disk /dev/mmcblk0: 3959 MB, 3959422976 bytes
4 heads, 32 sectors/track, 60416 cylinders
Units = cylinders of 128 * 512 = 65536 bytes
Disk identifier: 0x000b985b
Device Boot Start End Blocks Id System
/dev/mmcblk0p1 1 24415 1562500 83 Linux
/dev/mmcblk0p2 24417 28320 249856 83 Linux
/dev/mmcblk0p3 28321 60416 2054144 83 Linux
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
3. Once the partition has been created the kernel must be made aware of it. This can be done by rebooting the N900 or by running partx:
[root@localhost ~]# partx /dev/mmcblk0 # 1: 1- 3125000 ( 3125000 sectors, 1600 MB) # 2: 3125248- 3624959 ( 499712 sectors, 255 MB) # 3: 3624960- 7733247 ( 4108288 sectors, 2103 MB) # 4: 0- -1 ( 0 sectors, 0 MB) [root@localhost ~]# partx -a /dev/mmcblk0 BLKPG: Device or resource busy error adding partition 1 BLKPG: Device or resource busy error adding partition 2 BLKPG: Device or resource busy error adding partition 3 BLKPG: Device or resource busy error adding partition 4 [root@localhost ~]# ls /dev/mmcblk0p* mmcblk0p1 mmcblk0p2 mmcblk0p3 mmcblk0p4 [root@localhost ~]#
1. Install the btrfs-progs package using zypper:
[root@localhost ~]# zypper install btrfs-progs Loading repository data... Reading installed packages... Resolving package dependencies... The following NEW package is going to be installed: btrfs-progs 1 new package to install. Overall download size: 551.0 KiB. After the operation, additional 1003.0 KiB will be used. Continue? [y/n/?] (y): y Retrieving package btrfs-progs-0.19-11.4.armv7l (1/1), 551.0 KiB (1003.0 KiB unpacked) Installing: btrfs-progs-0.19-11.4 [done]
The btrfs-progs will undergo a change in the near future and the following method will be deprecated as the commands are replaced with btrfs, it is however still valid as of version btrfs-progs-0.19-11.4.
1. Examine the existing btrfs layout:
[root@localhost ~]# btrfs-show /dev/mmcblk0p1 failed to read /dev/mmcblk0p4 Label: none uuid: 075a887c-4986-4c68-a7f4-2fc013f76db7 Total devices 1 FS bytes used 605.30MB devid 1 size 1.49GB used 1.27GB path /dev/mmcblk0p1
2. Extend onto the third partition:
[root@localhost ~]# btrfs-vol -a /dev/mmcblk0p3 / ioctl returns 0
3. Re-examine the layout:
[root@localhost ~]# btrfs-show /dev/mmcblk0p1 failed to read /dev/mmcblk0p4 Label: none uuid: 075a887c-4986-4c68-a7f4-2fc013f76db7 Total devices 2 FS bytes used 605.30MB devid 1 size 1.49GB used 1.27GB path /dev/mmcblk0p1 devid 2 size 1.96GB used 1.27GB path /dev/mmcblk0p3 Btrfs Btrfs v0.19
4. Finally, rebalance the filesystem. This causes btrfs to reallocate some metadata and data blocks from one device to the other and can reclaim wasted metadata space. It takes several minutes:
[root@localhost ~]# btrfs-vol -b / ioctl returns 0
Needs writing but the commands will be:
btrfs filesystem add /dev/mmcblk0p3
btrfs filesystem balance /