Differences between version 9 and predecessor to the previous major change of PartitioningSuggestions.
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| Newer page: | version 9 | Last edited on Tuesday, July 19, 2005 4:25:51 pm | by DanielLawson | Revert |
| Older page: | version 8 | Last edited on Monday, July 11, 2005 11:15:17 am | by DanielLawson | Revert |
@@ -93,7 +93,26 @@
! /usr (whatever your feel is adaquate/sufficient for your situation)
To add additional protection to your applications from system crackers you can mount your <tt>/usr</tt> partition readonly.
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+----
+!! Mounting partitions
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+There are a number of ways you can address partitions within linux. You can either use the raw device name, eg /dev/sda1, or you have the option of setting a label on the partition, or using the partition's [UUID].
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+In most cases the raw device name will do, but there are some situations in which this is less than optimal. The SCSI/SATA layer, for example, creates devices in the order they are detected, with an incrementing device name /dev/sda, /dev/sdb etc. If devices are reordered they will get a different device name. Devices might be reordered due to controller changes or scan order changes - IDE will suffer the same problem here - or they might change due to a device disappearing (for example, if you remove a faulty disk from a RAID set).
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+Another situation in which this can occur is if you use external storage devices, such as flash disks, external harddrives or digital cameras. If you don't plug them in in the right order, they'll end up with different device names. This is ok if you do all your mounts manually, but if you want to use fstab to remember things then this just won't work.
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+Disk labels provide one way of abstracting the partitions away, however they cannot be guaranteed to be unique for a system. Consider what might happen if you have a system installed using labels, with labels like ROOT, VAR, USR etc, and then you put another disk into your machine with the same labels. Which ones get mounted? This isn't such a contrived example - some linux distributions will label partitions for you, eg RedHat.
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+The partition [UUID] is guaranteed to be universally unique, and will always point to the same partition. [UUID]s are supported on all (AddToMe: check this) filesystems linux supports, including swap.
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+To find out the [UUID] of an existing partition, use the blkid program that comes with e2fsprogs.
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+To specify a [UUID] or a label in your /etc/fstab, replace the device name (eg, /dev/sda1) with UUID=..... or LABEL=....
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+Another option for persistent mount points is to use udev to match on some other criteria, eg a USB serial ID for a particular external enclosure. This makes sense if you change the physical drive in the enclosure but still want it to mount to the same place
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CategoryDiskNotes
