zpool scrub operations can help to catch data corruption or drive issues before they cause data loss, and checksumming of all data blocks will ensure that all corruption during a rebuild is caught.
Web application is in the directory: /var/www/html - Raid Array device is: /dev/md0
mount /dev/md0 /mnt
cp -r /var/www/html/* /mnt
umount /mnt
service httpd stop
mount /dev/md0 /var/www/html
service httpd start
/dev/md0 /var/www/html .... REFERENCEShttp://serverfault.com/questions/316891/move-web-directory-to-raid-array
[root@localhost mnt]# fdisk /dev/sdb The number of cylinders for this disk is set to 30401. 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/sdb: 250.0 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 1 30401 244196001 85 Linux extended Command (m for help): d Selected partition 1 Command (m for help): p Disk /dev/sdb: 250.0 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System Command (m for help): n Command action e extended p primary partition (1-4) e Partition number (1-4): 1 First cylinder (1-30401, default 1): Using default value 1 Last cylinder or +size or +sizeM or +sizeK (1-30401, default 30401): Using default value 30401 Command (m for help): p Disk /dev/sdb: 250.0 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 1 30401 244196001 5 Extended Command (m for help): t Selected partition 1 Hex code (type L to list codes): 85 Changed system type of partition 1 to 85 (Linux extended) Command (m for help): p Disk /dev/sdb: 250.0 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 1 30401 244196001 85 Linux extended Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks. [root@localhost mnt]# fdisk /dev/sdb The number of cylinders for this disk is set to 30401. 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/sdb: 250.0 GB, 250059350016 bytes 255 heads, 63 sectors/track, 30401 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 1 30401 244196001 85 Linux extended Command (m for help): q [root@localhost mnt]# mkfs -t ext3 /dev/sdb1 mke2fs 1.39 (29-May-2006) /dev/sdb1: Invalid argument passed to ext2 library while setting up superblock [root@localhost mnt]#
cfdisk /dev/sdb
fdisk -l
mkfs -t ext3 /dev/sdb1
[root@localhost boot]# fdisk /dev/sdb<br /><br />The number of cylinders for this disk is set to 30401.<br />There is nothing wrong with that, but this is larger than 1024,<br />and could in certain setups cause problems with:<br />1) software that runs at boot time (e.g., old versions of LILO)<br />2) booting and partitioning software from other OSs<br /> (e.g., DOS FDISK, OS/2 FDISK)<br /><br />Command (m for help): m<br />Command action<br /> a toggle a bootable flag<br /> b edit bsd disklabel<br /> c toggle the dos compatibility flag<br /> d delete a partition<br /> l list known partition types<br /> m print this menu<br /> n add a new partition<br /> o create a new empty DOS partition table<br /> p print the partition table<br /> q quit without saving changes<br /> s create a new empty Sun disklabel<br /> t change a partition's system id<br /> u change display/entry units<br /> v verify the partition table<br /> w write table to disk and exit<br /> x extra functionality (experts only)<br /><br />Command (m for help): p<br /><br />Disk /dev/sdb: 250.0 GB, 250059350016 bytes<br />255 heads, 63 sectors/track, 30401 cylinders<br />Units = cylinders of 16065 * 512 = 8225280 bytes<br /><br /> Device Boot Start End Blocks Id System<br />/dev/sdb1 1 30401 244196001 85 Linux extended<br /><br />Command (m for help): d<br />Selected partition 1<br /><br />Command (m for help): p<br /><br />Disk /dev/sdb: 250.0 GB, 250059350016 bytes<br />255 heads, 63 sectors/track, 30401 cylinders<br />Units = cylinders of 16065 * 512 = 8225280 bytes<br /><br /> Device Boot Start End Blocks Id System<br /><br />Command (m for help): w<br />The partition table has been altered!<br /><br />Calling ioctl() to re-read partition table.<br />Syncing disks.<br />[root@localhost boot]#<br />[root@localhost boot]# fdisk /dev/sdb<br /><br />The number of cylinders for this disk is set to 30401.<br />There is nothing wrong with that, but this is larger than 1024,<br />and could in certain setups cause problems with:<br />1) software that runs at boot time (e.g., old versions of LILO)<br />2) booting and partitioning software from other OSs<br /> (e.g., DOS FDISK, OS/2 FDISK)<br /><br />Command (m for help): m<br />Command action<br /> a toggle a bootable flag<br /> b edit bsd disklabel<br /> c toggle the dos compatibility flag<br /> d delete a partition<br /> l list known partition types<br /> m print this menu<br /> n add a new partition<br /> o create a new empty DOS partition table<br /> p print the partition table<br /> q quit without saving changes<br /> s create a new empty Sun disklabel<br /> t change a partition's system id<br /> u change display/entry units<br /> v verify the partition table<br /> w write table to disk and exit<br /> x extra functionality (experts only)<br /><br />Command (m for help): p<br /><br />Disk /dev/sdb: 250.0 GB, 250059350016 bytes<br />255 heads, 63 sectors/track, 30401 cylinders<br />Units = cylinders of 16065 * 512 = 8225280 bytes<br /><br /> Device Boot Start End Blocks Id System<br /><br />Command (m for help): n<br />Command action<br /> e extended<br /> p primary partition (1-4)<br />p<br />Partition number (1-4): 1<br />First cylinder (1-30401, default 1):<br />Using default value 1<br />Last cylinder or +size or +sizeM or +sizeK (1-30401, default 30401):<br />Using default value 30401<br /><br />Command (m for help): p<br /><br />Disk /dev/sdb: 250.0 GB, 250059350016 bytes<br />255 heads, 63 sectors/track, 30401 cylinders<br />Units = cylinders of 16065 * 512 = 8225280 bytes<br /><br /> Device Boot Start End Blocks Id System<br />/dev/sdb1 1 30401 244196001 83 Linux<br /><br />Command (m for help): w<br />The partition table has been altered!<br /><br />Calling ioctl() to re-read partition table.<br />Syncing disks.<br />[root@localhost boot]# mkfs -t ext3 /dev/sdb1<br />mke2fs 1.39 (29-May-2006)<br />Filesystem label=<br />OS type: Linux<br />Block size=4096 (log=2)<br />Fragment size=4096 (log=2)<br />30539776 inodes, 61049000 blocks<br />3052450 blocks (5.00%) reserved for the super user<br />First data block=0<br />Maximum filesystem blocks=0<br />1864 block groups<br />32768 blocks per group, 32768 fragments per group<br />16384 inodes per group<br />Superblock backups stored on blocks:<br /> 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,<br /> 4096000, 7962624, 11239424, 20480000, 23887872<br /><br />Writing inode tables: done<br />Creating journal (32768 blocks): done<br />Writing superblocks and filesystem accounting information: done<br /><br />This filesystem will be automatically checked every 29 mounts or<br />180 days, whichever comes first. Use tune2fs -c or -i to override.<br />[root@localhost boot]#<br />[root@localhost boot]# cd /mnt<br />[root@localhost mnt]# ls<br />common sdb1 video_ext<br />[root@localhost mnt]# mount -t ext3 /dev/sdb1 /mnt/video_ext<br />[root@localhost mnt]# ls<br />common sdb1 video_ext<br />[root@localhost mnt]# cd video_ext<br />[root@localhost video_ext]# ls<br />lost+found
/dev/sdb1 /mnt/video_ext auto defaults 0 0
/dev/sdb1 /mnt/video_ext auto defaults,noexec 0 0
QUESTION:
I currently have LVM on software RAID, but I'd like to ask you what you think it is better solution, maybe some pros and cons?
Edit: It is about software raid on lvm or lvm on software raid. I know than hardware raid is better if we are thinking about performance.
ANSWER:
1.You're current setup is like this:
<code>| / | /var | /usr | /home |
--------------------------
| LVM Volume |
--------------------------
| RAID Volume |
--------------------------
| Disk 1 | Disk 2 | Disk 3 |
</code>
It's a much simpler setup with more flexibility. You can use all of the disks in the RAID volume and slice and dice them whatever way you like with LVM. The other way isn't even worth thinking about - it's ridiculously complicated and you lose the benefits of LVM at the filesystem level.
If you tried to RAID LVM volumes, you're left with a normal device without any of the LVM volume benefits (e.g. growing filesystems etc.)
2.have hardware raid and you can have lvm on top - best combination.
3.Your current setup is fine. This is the recommended way to do it.
Raid deals with keeping the bits secure/redundant/fast/whatever and LVM helps you present them in a esasy to use way.
REFERENCES
http://serverfault.com/questions/217666/what-is-better-lvm-on-raid-or-raid-on-lvm
WARNING! These examples may crash your computer or may result into data loss if not executed properly. These examples involves disk partition manipulation using the fdisk command and building (formatting) file systems using the mkfs.ext3 command. So make sure you backup all data before typing any one of the following command.
+------------+
| |
| /dev/sda3 | ===============+
| | |
+------------+ |
37GB | =======> RAID-1 /dev/md0
|
+------------+ |
| | |
| /dev/sdb1 | ===============+
| |
+------------+
37GB# fdisk -l
# fdisk -l /dev/sdaDisk /dev/sda: 73.2 GB, 73295462400 bytes
255 heads, 63 sectors/track, 8910 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 13 104391 83 Linux
/dev/sda2 14 3929 31455270 83 Linux
/dev/sda3 3930 8779 38957625 83 Linux
/dev/sda4 8780 8910 1052257+ 5 Extended
/dev/sda5 8780 8910 1052226 82 Linux swap / SolarisFor example, purpose you will use /dev/sda3 (size 37G). Now, list second disk partitions, enter:# fdisk -l /dev/sdbDisk /dev/sdb: 73.2 GB, 73295462400 bytes 255 heads, 63 sectors/track, 8910 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System
# fdisk /dev/sdbThe number of cylinders for this disk is set to 8910. 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):To add a new partition, type n command followed by p command as follows:
Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 1 First cylinder (1-8910, default 1): Using default value 1 Last cylinder or +size or +sizeM or +sizeK (1-8910, default 8910): +37GTo print the partition table type p command, enter:
Command (m for help): p
Disk /dev/sdb: 73.2 GB, 73295462400 bytes
255 heads, 63 sectors/track, 8910 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 1 37 297171 83 LinuxFinally, set partition type to "Software Raid" i.e. type 0xfd *(type t command followed by fd code to change partition type to Software RAID):Command (m for help): t Selected partition 1 Hex code (type L to list codes): fd Command (m for help): p Disk /dev/sdb: 73.2 GB, 73295462400 bytes 255 heads, 63 sectors/track, 8910 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 1 37 297171 fd Linux raid autodetectSave the changes and exit to shell prompt by typing w command:
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.# fdisk /dev/sdaThe number of cylinders for this disk is set to 8910. 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/sda: 73.2 GB, 73295462400 bytes 255 heads, 63 sectors/track, 8910 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sda1 * 1 13 104391 83 Linux /dev/sda2 14 3929 31455270 83 Linux /dev/sda3 3930 8779 38957625 83 Linux /dev/sda4 8780 8910 1052257+ 5 Extended /dev/sda5 8780 8910 1052226 82 Linux swap / Solaris Command (m for help): t Partition number (1-5): 3 Hex code (type L to list codes): fd Changed system type of partition 3 to fd (Linux raid autodetect) Command (m for help): p Disk /dev/sda: 73.2 GB, 73295462400 bytes 255 heads, 63 sectors/track, 8910 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sda1 * 1 13 104391 83 Linux /dev/sda2 14 3929 31455270 83 Linux /dev/sda3 3930 8779 38957625 fd Linux raid autodetect /dev/sda4 8780 8910 1052257+ 5 Extended /dev/sda5 8780 8910 1052226 82 Linux swap / Solaris 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. Syncing disks.
# partprobe /dev/sda# echo 1 > /sys/block/sdb/device/rescan # mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda3 /dev/sdb1# watch cat /proc/mdstat
# mkfs.ext3 /dev/md0 mke2fs 1.39 (29-May-2006) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) 4872896 inodes, 9737360 blocks 486868 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=4294967296 298 block groups 32768 blocks per group, 32768 fragments per group 16352 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000, 7962624 Writing inode tables: done Creating journal (32768 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 39 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override.
# mkdir /raid1
# mount /dev/md0 /raid1/
# df -H /raid1/Filesystem Size Used Avail Use% Mounted on /dev/md0 40G 185M 38G 1% /raid1
# cd /raid1/
# dd if=/dev/zero of=output bs=8k count=256k
# rm output262144+0 records in 262144+0 records out 2147483648 bytes (2.1 GB) copied, 6.01068 seconds, 357 MB/s
# echo '/dev/md0 /raid1 ext3 noatime,rw 0 0' >> /etc/fstab# mdadm --query --detail /dev/md0/dev/md0:
Version : 0.90
Creation Time : Wed May 26 01:58:53 2010
Raid Level : raid1
Array Size : 38949440 (37.15 GiB 39.88 GB)
Used Dev Size : 38949440 (37.15 GiB 39.88 GB)
Raid Devices : 2
Total Devices : 2
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Wed May 26 02:18:22 2010
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
UUID : b6f207e4:7f73484f:53f64bfd:e70b77d8
Events : 0.2
Number Major Minor RaidDevice State
0 8 3 0 active sync /dev/sda3
1 8 17 1 active sync /dev/sdb1REFERENCES
http://www.cyberciti.biz/faq/centos-redhat-rhel-linux-setup-create-raid1/
The following warning/error was logged by the smartd daemon: Device: /dev/sdb, 1 Currently unreadable (pending) sectorsTo determine the extent of the problem, execute a long selftest:
# smartctl -t long /dev/sdbSome of the symptoms during the pre-failure period are:
A Fail event had been detected on md device /dev/md1.
It could be related to component device /dev/sdb2.
Faithfully yours, etc.
P.S. The /proc/mdstat file currently contains the following:
Personalities : [raid6] [raid5] [raid4] [raid1]
md0 : active raid1 sda1[0] sdb1[1] sdc1[2] sdd1[3]
128384 blocks [4/4] [UUUU]
md1 : active raid5 sdd2[3] sdc2[2] sdb2[4](F) sda2[0]
1464765696 blocks level 5, 256k chunk, algorithm 2 [4/3] [U_UU]
unused devices:
You can verify this information using mdadm: [root@hal ~]# mdadm --detail /dev/md1
/dev/md1:
Version : 0.90
Creation Time : Sun Sep 2 18:56:50 2007
Raid Level : raid5
Array Size : 1464765696 (1396.91 GiB 1499.92 GB)
Used Dev Size : 488255232 (465.64 GiB 499.97 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 1
Persistence : Superblock is persistent
Update Time : Tue Feb 2 12:16:34 2010
State : clean, degraded
Active Devices : 3
Working Devices : 3
Failed Devices : 1
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 256K
UUID : f8a183b6:6748af53:6c1c8c11:87458cf7
Events : 0.964132
Number Major Minor RaidDevice State
0 8 2 0 active sync /dev/sda2
1 0 0 1 removed
2 8 34 2 active sync /dev/sdc2
3 8 50 3 active sync /dev/sdd2
4 8 18 - faulty spare /dev/sdb2The RAID array is running in degraded mode - the failed disk needs to be replaced as soon as possible. Again, check your backups! [root@hal ~]# mdadm --fail /dev/md0 /dev/sdb1 mdadm: set /dev/sdb1 faulty in /dev/md0The faulty disk is no longer part of any RAID array; erase all data before sending it in for replacement:
[root@hal ~]# dd if=/dev/zero of=/dev/sdb1 [root@hal ~]# dd if=/dev/zero of=/dev/sdb2
[root@hal ~]# fdisk -l /dev/sdb
Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 * 1 16 128488+ fd Linux raid autodetect
/dev/sdb2 17 121601 976631512+ fd Linux raid autodetectNote that the replacement disk is 1TB, while the original disk was 500GB. You can safely create a partition that is larger than the original one - in fact, this may be useful when doing a "rolling upgrade" to a set of larger disks. [root@hal ~]# mdadm --add /dev/md0 /dev/sdb1 mdadm: added /dev/sdb1 [root@hal ~]# mdadm --add /dev/md1 /dev/sdb2 mdadm: added /dev/sdb2Array reconstruction should now begin automatically:
[root@hal ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [raid1]
md0 : active raid1 sdb1[1] sda1[0] sdc1[2] sdd1[3]
128384 blocks [4/4] [UUUU]
md1 : active raid5 sdb2[4] sdd2[3] sdc2[2] sda2[0]
1464765696 blocks level 5, 256k chunk, algorithm 2 [4/3] [U_UU]
[>....................] recovery = 0.0% (84068/488255232) finish=193.4min speed=42034K/sec
unused devices:
[root@hal ~]# file -s /dev/sda
/dev/sda: x86 boot sector; partition 1: ID=0xfd, active, starthead 1, startsector 63, 256977 sectors;
partition 2: ID=0xfd, starthead 0, startsector 257040, 976511025 sectors, code offset 0x48
[root@hal ~]# file -s /dev/sdb
/dev/sdb: x86 boot sector; partition 1: ID=0xfd, active, starthead 1, startsector 63, 256977 sectors;
partition 2: ID=0xfd, starthead 0, startsector 257040, 1953263025 sectorsInstall GRUB on the new disk, /dev/sdb (GRUB uses different names for your disks, /dev/sda => hd0, /dev/sdb => hd1 etc.): [root@hal ~]# grub
<...snip...>
grub> root (hd1,0)
root (hd1,0)
Filesystem type is ext2fs, partition type 0xfd
grub> setup (hd1)
setup (hd1)
Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 (hd1)"... 15 sectors are embedded.
succeeded
Running "install /grub/stage1 (hd1) (hd1)1+15 p (hd1,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.
grub> quit
quitVerify the result: [root@hal ~]# file -s /dev/sdb
/dev/sdb: x86 boot sector; partition 1: ID=0xfd, active, starthead 1, startsector 63, 256977 sectors;
partition 2: ID=0xfd, starthead 0, startsector 257040, 1953263025 sectors, code offset 0x48[root@hal ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [raid1]
md0 : active raid1 sdb1[1] sda1[0] sdc1[2] sdd1[3]
128384 blocks [4/4] [UUUU]
md1 : active raid5 sdb2[4] sdd2[3] sdc2[2] sda2[0]
1464765696 blocks level 5, 256k chunk, algorithm 2 [4/3] [U_UU]
[===>.................] recovery = 18.5% (90480896/488255232) finish=147.6min speed=44912K/sec
unused devices:
fsck, which, like mkfs, is really a front end to filesystem-checking routines for the various filesystem types. Some of the underlying check routines are shown in Listing 1. [ian@echidna ~]$ ls /sbin/*fsck* /sbin/btrfsck /sbin/fsck /sbin/fsck.ext3 /sbin/fsck.msdos /sbin/dosfsck /sbin/fsck.cramfs /sbin/fsck.ext4 /sbin/fsck.vfat /sbin/e2fsck /sbin/fsck.ext2 /sbin/fsck.ext4dev /sbin/fsck.xfs |
[ian@echidna ~]$ find /sbin -samefile /sbin/e2fsck /sbin/fsck.ext4dev /sbin/e2fsck /sbin/fsck.ext3 /sbin/fsck.ext4 /sbin/fsck.ext2 |
fsck with the -A option to check the root filesystem and any other filesystems that are specified for checking in the /etc/fstab control file. If the filesystem was not cleanly unmounted, a consistency check is performed and repairs are made, if they can be done safely. This is controlled by the pass (or passno) field (the sixth field) of the /etc/fstab entry. Filesystems with pass set to zero are not checked at boot time. The root filesystem has a pass value of 1 and is checked first. Other filesystems will usually have a pass value of 2 (or higher), indicating the order in which they should be checked.fsck operations can run in parallel if the system determines it is advantageous, so different filesystems are allowed to have the same pass value, as is the case for the /grubfile and //mnt/ext3test filesystems shown in Listing 3. Note that fsck will avoid running multiple filesystem checks on the same physical disk. To learn more about the layout of /etc/fstab, check the man pages for fstab.filesystem mount point type options dump pass UUID=a18492c0-7ee2-4339-9010-3a15ec0079bb / ext3 defaults 1 1 UUID=488edd62-6614-4127-812d-cbf58eca85e9 /grubfile ext3 defaults 1 2 UUID=2d4f10a6-be57-4e1d-92ef-424355bd4b39 swap swap defaults 0 0 UUID=ba38c08d-a9e7-46b2-8890-0acda004c510 swap swap defaults 0 0 LABEL=EXT3TEST /mnt/ext3test ext3 defaults 0 2 /dev/sda8 /mnt/xfstest xfs defaults 0 0 LABEL=DOS /dos vfat defaults 0 0 tmpfs /dev/shm tmpfs defaults 0 0 devpts /dev/pts devpts gid=5,mode=620 0 0 sysfs /sys sysfs defaults 0 0 proc /proc proc defaults 0 0 |
fsck, does the filesystem consistency check and repair. On the other hand, some filesystems, such as /proc, are built at initialization time and therefore do need to be checked.blkid command to find the device given a label or UUID, and the label and UUID, given the device.[root@echidna ~]# # find the device for LABEL=EXT3TEST [root@echidna ~]# blkid -L EXT3TEST /dev/sda7 [root@echidna ~]# # Find label and UUID for /dev/sda7 [root@echidna ~]# blkid /dev/sda7 /dev/sda7: LABEL="EXT3TEST" UUID="7803f979-ffde-4e7f-891c-b633eff981f0" SEC_TYPE="ext2" TYPE="ext3" [root@echidna ~]# # Check /dev/sda7 [root@echidna ~]# fsck /dev/sda7 fsck from util-linux-ng 2.16.2 e2fsck 1.41.9 (22-Aug-2009) EXT3TEST: clean, 11/7159808 files, 497418/28637862 blocks [root@echidna ~]# # Check it by label using fsck.ext3 [root@echidna ~]# fsck.ext3 LABEL=EXT3TEST e2fsck 1.41.9 (22-Aug-2009) EXT3TEST: clean, 11/7159808 files, 497418/28637862 blocks [root@echidna ~]# # Check it by UUID using e2fsck [root@echidna ~]# e2fsck UUID=7803f979-ffde-4e7f-891c-b633eff981f0 e2fsck 1.41.9 (22-Aug-2009) EXT3TEST: clean, 11/7159808 files, 497418/28637862 blocks [root@echidna ~]# # Finally check the vfat partition [root@echidna ~]# fsck LABEL=DOS fsck from util-linux-ng 2.16.2 dosfsck 3.0.9, 31 Jan 2010, FAT32, LFN /dev/sda9: 1 files, 1/513064 clusters |
[root@echidna ~]# fsck UUID=a18492c0-7ee2-4339-9010-3a15ec0079bb fsck from util-linux-ng 2.16.2 e2fsck 1.41.9 (22-Aug-2009) /dev/sdb9 is mounted. WARNING!!! Running e2fsck on a mounted filesystem may cause SEVERE filesystem damage. Do you really want to continue (y/n)? no check aborted. |
fsck figure out which check to run on a filesystem; running the wrong check can corrupt the filesystem. If you want to see what fsck would do for a given filesystem or set of filesystems, use the -N option as shown in Listing 6.[root@echidna ~]# fsck -N /dev/sda7 /dev/sda[89] fsck from util-linux-ng 2.16.2 [/sbin/fsck.ext3 (1) -- /mnt/ext3test] fsck.ext3 /dev/sda7 [/sbin/fsck.xfs (2) -- /mnt/xfstest] fsck.xfs /dev/sda8 [/sbin/fsck.vfat (3) -- /dos] fsck.vfat /dev/sda9 |
fsck command simply tells us that we should use the xfs_check command. If there are no errors, then xfs_check does not display any output. There is a -v option for verbose output, but it is much too verbose for a simple check.[root@echidna ~]# fsck /dev/sda8 fsck from util-linux-ng 2.16.2 If you wish to check the consistency of an XFS filesystem or repair a damaged filesystem, see xfs_check(8) and xfs_repair(8). [root@echidna ~]# xfs_check /dev/sda8 |
df command displays information about mounted filesystems. If you add the -T option, the filesystem type is included in the display; otherwise, it is not. The output from df for the Fedora 12 system that we used above is shown in Listing 8.[ian@echidna ~]$ df -T Filesystem Type 1K-blocks Used Available Use% Mounted on /dev/sdb9 ext3 45358500 24670140 18384240 58% / tmpfs tmpfs 1927044 808 1926236 1% /dev/shm /dev/sda2 ext3 772976 17760 716260 3% /grubfile /dev/sda8 xfs 41933232 4272 41928960 1% /mnt/xfstest /dev/sda7 ext3 112754024 192248 106834204 1% /mnt/ext3test /dev/sda9 vfat 2052256 4 2052252 1% /dos |
tmpfs entry is for a virtual memory filesystem. These exist only in RAM or swap space and are created when mounted without need for a mkfs command. You can read more about tmpfs in "Common threads: Advanced filesystem implementor's guide, Part 3". -i option on the df command. You can exclude certain filesystem types using the -x option, or restrict information to just certain filesystem types using the -t option. Use these multiple times if necessary. See the examples in Listing 9. [ian@echidna ~]$ df -i -x tmpfs Filesystem Inodes IUsed IFree IUse% Mounted on /dev/sdb9 2883584 308920 2574664 11% / /dev/sda2 48768 41 48727 1% /grubfile /dev/sda8 20976832 3 20976829 1% /mnt/xfstest /dev/sda7 7159808 11 7159797 1% /mnt/ext3test /dev/sda9 0 0 0 - /dos [ian@echidna ~]$ df -iT -t vfat -t ext3 Filesystem Type Inodes IUsed IFree IUse% Mounted on /dev/sdb9 ext3 2883584 308920 2574664 11% / /dev/sda2 ext3 48768 41 48727 1% /grubfile /dev/sda7 ext3 7159808 11 7159797 1% /mnt/ext3test /dev/sda9 vfat 0 0 0 - /dos |
df to limit the display to local filesystems or control the format of output. For example, use the -H option to display human readable sizes, such as 1K for 1024, or use the -h (or --si) option to get sizes in powers of 10 (1K=1000).df command a parameter of a directory name or even a filename as shown in Listing 10. [ian@echidna ~]$ df --si ~ian/index.html Filesystem Size Used Avail Use% Mounted on /dev/sdb9 47G 26G 19G 58% / |
tune2fs, which can be used to inspect information about the block count as well as information about whether the filesystem is journaled (ext3 or ext4) or not (ext2). The command can also be used to set many parameters or convert an ext2 filesystem to ext3 by adding a journal. Listing 11 shows the output for a near-empty ext3 filesystem using the -l option to simply display the existing information.[root@echidna ~]# tune2fs -l /dev/sda7 tune2fs 1.41.9 (22-Aug-2009) Filesystem volume name: EXT3TEST Last mounted on: |
mkfs.xfs displayed when the filesystem was created using the xfs_info as shown in Listing 12. You need to use xfs_info on a mounted filesystem.[root@echidna ~]# xfs_info /dev/sda8
meta-data=/dev/sda8 isize=256 agcount=4, agsize=2622108 blks
= sectsz=512 attr=2
data = bsize=4096 blocks=10488429, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0
log =internal bsize=4096 blocks=5121, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0 |
df command gives information about a whole filesystem. Sometimes you might want to know how much space is used by your home directory, or how big a partition to use if you wanted to move /usr to its own filesystem. To answer this kind of question, use the du command.du command displays information about the filename (or filenames) given as parameters. If a directory name is given, then du recurses and calculates sizes for every file and subdirectory of the given directory. The result can be a lot of output. Fortunately, you can use the -s option to request just a summary for a directory. If you use du to get information for multiple directories, then add the -c option to get a grand total. You can also control output format with the same set of size options (-h, -H, --si, and so on) that are used for df. Listing 13 shows two views of the home directory of a newly created user who has logged in once and created an index.html file.[testuser1@echidna ~]$ du -hc * 4.0K Desktop 4.0K Documents 4.0K Downloads 16K index.html 4.0K Music 4.0K Pictures 4.0K Public 4.0K Templates 4.0K Videos 48K total [testuser1@echidna ~]$ du -hs . 1.1M . |
du -c * and the 1.1M summary from du -s is that the latter includes the entries starting with a dot, such as .bashrc, while the former does not.du is that you must be able to read the directories that you are running it against.du to display the total space used by the /usr tree and each of its first-level subdirectories. The result is shown in Listing 14. Use root authority to make sure you have appropriate access permissions.[root@echidna ~]# du -shc /usr/* 394M /usr/bin 4.0K /usr/etc 4.0K /usr/games 156M /usr/include 628K /usr/kerberos 310M /usr/lib 1.7G /usr/lib64 110M /usr/libexec 136K /usr/local 30M /usr/sbin 2.9G /usr/share 135M /usr/src 0 /usr/tmp 5.7G total |
fsck command that you saw above can repair filesystems as well as check them. Usually the automatic boot-time check will fix the problems and you can proceed. fsck manually. For an ext2 filesystem, which is not journaled, you may be presented with a series of requests asking you to confirm proposed actions to fix particular blocks on the filesystem. You should generally allow fsck to attempt to fix problems, by responding y (for yes). When the system reboots, check for any missing data or files. telinit 1) and then remount the root filesystem read-only, at which time you should be able to perform a consistency check. A better way to check a filesystem is to boot a recovery system, such as a live CD or a USB memory key, and perform the check of your unmounted filesystems from that.fsck cannot fix the problem, you do have some other tools available, although you will generally need advanced knowledge of the filesystem layout to successfully fix it. fsck scan of an ext2 disk can take quite a while to complete, because the internal data structure (or metadata) of the filesystem must be scanned completely. As filesystems get larger and larger, this takes longer and longer, even though disks also keep getting faster, so a full check may take one or more hours. fsck check is generally not required. In fact, for the xfs filesystem, fsck does nothing!fsck command (fsck.ext3, e2fsck , reiserfsck, and so on) to determine the appropriate parameters. The -p option, when used with ext2, ext3, or ext4 filesystems will cause fsck to automatically fix all problems that can be safely fixed. This is, in fact, what happens at boot time.e2fsck and xfs_check by first running e2fsck on an empty XFS filesystem and then using xfs_check to fix it. Remember we suggested that you use the fsck front end to be sure you are using the right checker, and we warned you that failure to do so may result in filesystem corruption. e2fsck against /dev/sda8, which contains an XFS filesystem. After a few interactions we use ctrl-Break to break out, but it is too late. Warning: Do NOT do this unless you are willing to destroy your filesystem.[root@echidna ~]# e2fsck /dev/sda8 e2fsck 1.41.9 (22-Aug-2009) /dev/sda8 was not cleanly unmounted, check forced. Resize inode not valid. Recreate |
xfs_check to repair the XFS filesystem. The xfs_check command is quite verbose, but it has a -s option which reports only serious errors. The output is shown in Listing 16.[root@echidna ~]# xfs_check -s /dev/sda8 cache_node_purge: refcount was 1, not zero (node=0x1cf3ee0) xfs_check: cannot read root inode (117) cache_node_purge: refcount was 1, not zero (node=0x1cf7400) xfs_check: cannot read realtime bitmap inode (117) bad magic # 0x1040000 in btbno block 0/1 bad magic # 0x4000 in btcnt block 0/2 bad magic # 0x58465342 in inobt block 0/0 |
xfs_repair to repair an XFS filesystem. Like xfs_check, it is quite verbose, and it does not have an -s option. If you'd like just to see what needs repair without actually repairing it, use xfs_repair -n.-n option of mke2fs to display the superblock locations for an existing filesystem. If you specified parameters such as the bytes per inode ratio, you should invoke mke2fs with the same parameters when you use the -n option. Listing 17 shows the location of the superblocks on /dev/sda7.[root@echidna ~]# mke2fs -n /dev/sda7 mke2fs 1.41.9 (22-Aug-2009) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) 7159808 inodes, 28637862 blocks 1431893 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=4294967296 874 block groups 32768 blocks per group, 32768 fragments per group 8192 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 4096000, 7962624, 11239424, 20480000, 23887872 |
debugfs command, which allows you to explore the inner workings of an ext family filesystem. By default, it opens the filesystem in read-only mode. It does have many commands that allow you to attempt undeletion of files or directories, as well as other operations that require write access, so you will specifically have to enable write access with the -w option. Use it with extreme care. Listing 18 shows how to open the root filesystem on my system; navigate to my home directory; display information, including the inode number, about a file called index.html; and finally, map that inode number back to the pathname of the file. [root@echidna ~]# debugfs /dev/sdb9 debugfs 1.41.9 (22-Aug-2009) debugfs: cd home/ian debugfs: pwd [pwd] INODE: 165127 PATH: /home/ian [root] INODE: 2 PATH: / debugfs: stat index.html Inode: 164815 Type: regular Mode: 0644 Flags: 0x0 Generation: 2621469650 Version: 0x00000000 User: 1000 Group: 1000 Size: 14713 File ACL: 0 Directory ACL: 0 Links: 1 Blockcount: 32 Fragment: Address: 0 Number: 0 Size: 0 ctime: 0x4bf1a3e9 -- Mon May 17 16:15:37 2010 atime: 0x4c619cf0 -- Tue Aug 10 14:39:44 2010 mtime: 0x4bf1a3e9 -- Mon May 17 16:15:37 2010 Size of extra inode fields: 4 Extended attributes stored in inode body: selinux = "unconfined_u:object_r:user_home_t:s0\000" (37) BLOCKS: (0-2):675945-675947, (3):1314836 TOTAL: 4 debugfs: ncheck 164815 Inode Pathname 164815 /home/ian/index.html debugfs: q |
