diff options
Diffstat (limited to 'mount/mount.8')
| -rw-r--r-- | mount/mount.8 | 142 |
1 files changed, 122 insertions, 20 deletions
diff --git a/mount/mount.8 b/mount/mount.8 index cee784bc..0e16bfbe 100644 --- a/mount/mount.8 +++ b/mount/mount.8 @@ -98,7 +98,7 @@ prints a version string .BI "mount [-l] [-t" " type" ] lists all mounted file systems (of type .IR type ). -The option \-l adds the (ext2, ext3 and XFS) labels in this listing. +The option \-l adds the labels in this listing. See below. .RE @@ -409,9 +409,9 @@ exists (with regular non-fake mount, this check is done by kernel). Don't call the /sbin/mount.<filesystem> helper even if it exists. .TP .B \-l -Add the ext2, ext3 and XFS labels in the mount output. Mount must have +Add the labels in the mount output. Mount must have permission to read the disk device (e.g. be suid root) for this to work. -One can set such a label for ext2 or ext3 using the +One can set such a label for ext2, ext3 or ext4 using the .BR e2label (8) utility, or for XFS using .BR xfs_admin (8), @@ -442,10 +442,12 @@ Mount the file system read-only. A synonym is .BR "\-o ro" . Note that, depending on the filesystem type, state and kernel behavior, the -system may still write to the device. For example, Ext3 will replay its journal -if the filesystem is dirty. To prevent this kind of write access, you may want -to set the block device to read-only mode, see command -.BR blockdev (8). +system may still write to the device. For example, Ext3 or ext4 will replay its +journal if the filesystem is dirty. To prevent this kind of write access, you +may want to mount ext3 or ext4 filesystem with "ro,noload" mount options or +set the block device to read-only mode, see command +.BR blockdev (8) +. .TP .B \-w Mount the file system read/write. This is the default. A synonym is @@ -480,6 +482,7 @@ currently supported include: .IR ext , .IR ext2 , .IR ext3 , +.IR ext4 , .IR hfs , .IR hfsplus , .IR hpfs , @@ -1252,7 +1255,105 @@ manual page. Enable POSIX Access Control Lists. See the .BR acl (5) manual page. - + +.SH "Mount options for ext4" +The `ext4' is an an advanced level of the ext3 filesystem which incorporates +scalability and reliability enhancements for supporting large filesystem. + +The options +.B journal_dev, noload, data, commit, orlov, oldalloc, [no]user_xattr +.B [no]acl, bsddf, minixdf, debug, errors, data_err, grpid, bsdgroups, nogrpid +.B sysvgroups, resgid, resuid, sb, quota, noquota, grpquota, usrquota +and +.B [no]bh +are backwardly compatible with ext3 or ext2. +.TP +.BR journal_checksum +Enable checksumming of the journal transactions. This will allow the recovery +code in e2fsck and the kernel to detect corruption in the kernel. It is a +compatible change and will be ignored by older kernels. +.TP +.BR journal_async_commit +Commit block can be written to disk without waiting for descriptor blocks. If +enabled older kernels cannot mount the device. This will enable +'journal_checksum' internally. +.TP +.BR journal=update +Update the ext4 file system's journal to the current format. +.TP +.BR barrier=0 " / " barrier=1 " / " barrier " / " nobarrier +This enables/disables the use of write barriers in the jbd code. barrier=0 +disables, barrier=1 enables. This also requires an IO stack which can support +barriers, and if jbd gets an error on a barrier write, it will disable again +with a warning. Write barriers enforce proper on-disk ordering of journal +commits, making volatile disk write caches safe to use, at some performance +penalty. If your disks are battery-backed in one way or another, disabling +barriers may safely improve performance. The mount options "barrier" and +"nobarrier" can also be used to enable or disable barriers, for consistency +with other ext4 mount options. +.TP +.BI inode_readahead= n +This tuning parameter controls the maximum number of inode table blocks that +ext4's inode table readahead algorithm will pre-read into the buffer cache. +The default value is 32 blocks. +.TP +.BI stripe= n +Number of filesystem blocks that mballoc will try to use for allocation size +and alignment. For RAID5/6 systems this should be the number of data disks * +RAID chunk size in file system blocks. +.TP +.BR delalloc +Deferring block allocation until write-out time. +.TP +.BR nodelalloc +Disable delayed allocation. Blocks are allocation when data is copied from user +to page cache. +.TP +.BI max_batch_time= usec +Maximum amount of time ext4 should wait for additional filesystem operations to +be batch together with a synchronous write operation. Since a synchronous +write operation is going to force a commit and then a wait for the I/O +complete, it doesn't cost much, and can be a huge throughput win, we wait for a +small amount of time to see if any other transactions can piggyback on the +synchronous write. The algorithm used is designed to automatically tune for +the speed of the disk, by measuring the amount of time (on average) that it +takes to finish committing a transaction. Call this time the "commit time". +If the time that the transactoin has been running is less than the commit time, +ext4 will try sleeping for the commit time to see if other operations will join +the transaction. The commit time is capped by the max_batch_time, which +defaults to 15000us (15ms). This optimization can be turned off entirely by +setting max_batch_time to 0. +.TP +.BI min_batch_time= usec +This parameter sets the commit time (as described above) to be at least +min_batch_time. It defaults to zero microseconds. Increasing this parameter +may improve the throughput of multi-threaded, synchronous workloads on very +fast disks, at the cost of increasing latency. +.TP +.BI journal_ioprio= prio +The I/O priority (from 0 to 7, where 0 is the highest priorty) which should be +used for I/O operations submitted by kjournald2 during a commit operation. +This defaults to 3, which is a slightly higher priority than the default I/O +priority. +.TP +.BR auto_da_alloc " / " noauto_da_alloc +Many broken applications don't use fsync() when noauto_da_alloc +replacing existing files via patterns such as + +fd = open("foo.new")/write(fd,..)/close(fd)/ rename("foo.new", "foo") + +or worse yet + +fd = open("foo", O_TRUNC)/write(fd,..)/close(fd). + +If auto_da_alloc is enabled, ext4 will detect the replace-via-rename and +replace-via-truncate patterns and force that any delayed allocation blocks are +allocated such that at the next journal commit, in the default data=ordered +mode, the data blocks of the new file are forced to disk before the rename() +operation is commited. This provides roughly the same level of guarantees as +ext3, and avoids the "zero-length" problem that can happen when a system +crashes before the delayed allocation blocks are forced to disk. + .SH "Mount options for fat" (Note: .I fat @@ -1264,7 +1365,7 @@ and filesystems.) .TP .BR blocksize=512 " / " blocksize=1024 " / " blocksize=2048 -Set blocksize (default 512). +Set blocksize (default 512). This option is obsolete. .TP \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP Set the owner and group of all files. @@ -1362,7 +1463,7 @@ Programs that do computed lseeks won't like in-kernel text conversion. Several people have had their data ruined by this translation. Beware! For file systems mounted in binary mode, a conversion tool -(fromdos/todos) is available. +(fromdos/todos) is available. This option is obsolete. .RE .TP .BI cvf_format= module @@ -1370,9 +1471,10 @@ Forces the driver to use the CVF (Compressed Volume File) module .RI cvf_ module instead of auto-detection. If the kernel supports kmod, the cvf_format=xxx option also controls on-demand CVF module loading. +This option is obsolete. .TP .BI cvf_option= option -Option passed to the CVF module. +Option passed to the CVF module. This option is obsolete. .TP .B debug Turn on the @@ -1691,7 +1793,7 @@ and 1 a byteswapped bigendian encoding. .B posix=[0|1] If enabled (posix=1), the file system distinguishes between upper and lower case. The 8.3 alias names are presented as -hard links instead of being suppressed. +hard links instead of being suppressed. This option is obsolete. .TP \fBuid=\fP\fIvalue\fP, \fBgid=\fP\fIvalue\fP and \fBumask=\fP\fIvalue\fP Set the file permission on the filesystem. @@ -2298,7 +2400,7 @@ One further possible type is a mount via the loop device. For example, the command .nf -.B " mount /tmp/fdimage /mnt -t msdos -o loop=/dev/loop3,blocksize=1024" +.B " mount /tmp/fdimage /mnt -t vfat -o loop=/dev/loop3 .fi will set up the loop device @@ -2323,16 +2425,16 @@ If no explicit loop device is mentioned (but just an option `\fB\-o loop\fP' is given), then .B mount will try to find some unused loop device and use that. -If you are not so unwise as to make -.I /etc/mtab -a symbolic link to -.I /proc/mounts + +Since Linux 2.6.25 is supported auto-destruction of loop devices and then any loop device allocated by .B mount will be freed by -.BR umount . -You can also free a loop device by hand, using `losetup -d', see -.BR losetup (8). +.B umount +independently on +.I /etc/mtab . + +You can also free a loop device by hand, using `losetup -d' or `umount -d`. .SH RETURN CODES .B mount |