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README.txt
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命令列程式的使用經驗 | CLI-Program-Using-Experiences
=====智慧財產授權條款開始=====
授權條款版本：1.01(1)201101020309
智慧財產權歸屬：
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以及所有此專案的協作人士
本作品使用的智慧財產授權：
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您擁有的權利及義務簡單描述如下：
1.您必須於本作品之衍伸作品中標明本作品的名稱及官方網站位址以及採用的授權條款。
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=====智慧財產授權條款結束=====
專案說明
常常遇到什麼終端機底下的程式不知道怎麼用嗎？
常常想要掛載某個磁碟分割區卻卡死在man mount幾萬行※的使用說明嗎？
歡迎加入「文字介面程式使用經驗 | CLI Program Using Experience」專案的開發行列！
本專案企圖營造一個良好的「快速查詢並快速使用(fast search and fast use)」的文字介面程式／命令的使用／學習環境，藉由應用導向的撰寫方式增加使用者了解文字介面程式／命令的時間，減少不必要內容的閱讀時間與成本
歡迎使用並參與本專案的開發／維護／提供建議等！
「文字介面程式使用經驗」專案網站
https://github.com/Vdragon/CLI_Program_Using_Experiences
歡迎使用GitHub帳號協作開發！
Fork me on GitHub! 歡迎建立屬於自己的分支版本！
「文字介面程式使用經驗」專案問題回報網址
https://github.com/Vdragon/CLI_Program_Using_Experiences/issues
常見問題與解答 | Frequently Asked Questions And Answers
全形字元解讀方法
全形字元（包括但不限於「「」」、「（）」等全形字元）包含的文字為需要視情況替換的項目。
「（）」包含的文字代表於某些情形下可省略
子目錄檔案名稱說明
Usage.txt
程式的使用方式
Format.txt
命令的格式
Commandline_auguments_&_options.txt
命令列的參數與選項
Use_history.txt
執行命令的使用紀錄（可能包含不正確使用的紀錄）（如果時間緊急直接看這個就夠了：））
Attention.txt
注意事項
※mount的使用手冊完整內容如下（ubuntu 12.04LTS中的版本）（事實上mount的使用手冊只有2000多行，不過字數絕對會讓您覺得有幾萬行那麼多（笑））
MOUNT(8) System Administration MOUNT(8)
NAME
mount - mount a filesystem
SYNOPSIS
mount [-lhV]
mount -a [-fFnrsvw] [-t vfstype] [-O optlist]
mount [-fnrsvw] [-o option[,option]...] device|dir
mount [-fnrsvw] [-t vfstype] [-o options] device dir
DESCRIPTION
All files accessible in a Unix system are arranged in one big tree, the
file hierarchy, rooted at /. These files can be spread out over several
devices. The mount command serves to attach the filesystem found on some
device to the big file tree. Conversely, the umount(8) command will detach
it again.
The standard form of the mount command, is
mount -t type device dir
This tells the kernel to attach the filesystem found on device (which is
of type type) at the directory dir. The previous contents (if any) and
owner and mode of dir become invisible, and as long as this filesystem
remains mounted, the pathname dir refers to the root of the filesystem on
device.
If only directory or device is given, for example:
mount /dir
then mount looks for a mountpoint and if not found then for a device in
the /etc/fstab file.
The listing and help.
Three forms of invocation do not actually mount anything:
mount -h
prints a help message
mount -V
prints a version string
mount [-l] [-t type]
lists all mounted filesystems (of type type). The option -l
adds the labels in this listing. See below.
The device indication.
Most devices are indicated by a file name (of a block special
device), like /dev/sda1, but there are other possibilities. For
example, in the case of an NFS mount, device may look like
knuth.cwi.nl:/dir. It is possible to indicate a block special
device using its volume LABEL or UUID (see the -L and -U options
below).
The recommended setup is to use LABEL=<label> or UUID=<uuid> tags
rather than /dev/disk/by-{label,uuid} udev symlinks in the
/etc/fstab file. The tags are more readable, robust and portable.
The mount(8) command internally uses udev symlinks, so use the sym‐
links in /etc/fstab has no advantage over LABEL=/UUID=. For more
details see libblkid(3).
Note that mount(8) uses UUIDs as strings. The UUIDs from command
line or fstab(5) are not converted to internal binary representa‐
tion. The string representation of the UUID should be based on
lower case characters.
The proc filesystem is not associated with a special device, and
when mounting it, an arbitrary keyword, such as proc can be used
instead of a device specification. (The customary choice none is
less fortunate: the error message `none busy' from umount can be
confusing.)
The /etc/fstab, /etc/mtab and /proc/mounts files.
The file /etc/fstab (see fstab(5)), may contain lines describing
what devices are usually mounted where, using which options.
The command
mount -a [-t type] [-O optlist]
(usually given in a bootscript) causes all filesystems mentioned in
fstab (of the proper type and/or having or not having the proper
options) to be mounted as indicated, except for those whose line
contains the noauto keyword. Adding the -F option will make mount
fork, so that the filesystems are mounted simultaneously.
When mounting a filesystem mentioned in fstab or mtab, it suffices
to give only the device, or only the mount point.
The programs mount and umount maintain a list of currently mounted
filesystems in the file /etc/mtab. If no arguments are given to
mount, this list is printed.
The mount program does not read the /etc/fstab file if device (or
LABEL/UUID) and dir are specified. For example:
mount /dev/foo /dir
If you want to override mount options from /etc/fstab you have to
use:
mount device|dir -o <options>
and then the mount options from command line will be appended to
the list of options from /etc/fstab. The usual behaviour is that
the last option wins if there is more duplicated options.
When the proc filesystem is mounted (say at /proc), the files
/etc/mtab and /proc/mounts have very similar contents. The former
has somewhat more information, such as the mount options used, but
is not necessarily up-to-date (cf. the -n option below). It is pos‐
sible to replace /etc/mtab by a symbolic link to /proc/mounts, and
especially when you have very large numbers of mounts things will
be much faster with that symlink, but some information is lost that
way, and in particular using the "user" option will fail.
The non-superuser mounts.
Normally, only the superuser can mount filesystems. However, when
fstab contains the user option on a line, anybody can mount the
corresponding system.
Thus, given a line
/dev/cdrom /cd iso9660 ro,user,noauto,unhide
any user can mount the iso9660 filesystem found on his CDROM using
the command
mount /dev/cdrom
or
mount /cd
For more details, see fstab(5). Only the user that mounted a
filesystem can unmount it again. If any user should be able to
unmount, then use users instead of user in the fstab line. The
owner option is similar to the user option, with the restriction
that the user must be the owner of the special file. This may be
useful e.g. for /dev/fd if a login script makes the console user
owner of this device. The group option is similar, with the
restriction that the user must be member of the group of the spe‐
cial file.
The bind mounts.
Since Linux 2.4.0 it is possible to remount part of the file hier‐
archy somewhere else. The call is
mount --bind olddir newdir
or shortoption
mount -B olddir newdir
or fstab entry is:
/olddir /newdir none bind
After this call the same contents is accessible in two places. One
can also remount a single file (on a single file). It's also possi‐
ble to use the bind mount to create a mountpoint from a regular
directory, for example:
mount --bind foo foo
The bind mount call attaches only (part of) a single filesystem,
not possible submounts. The entire file hierarchy including sub‐
mounts is attached a second place using
mount --rbind olddir newdir
or shortoption
mount -R olddir newdir
Note that the filesystem mount options will remain the same as
those on the original mount point, and cannot be changed by passing
the -o option along with --bind/--rbind. The mount options can be
changed by a separate remount command, for example:
mount --bind olddir newdir
mount -o remount,ro newdir
Note that behavior of the remount operation depends on the
/etc/mtab file. The first command stores the 'bind' flag to the
/etc/mtab file and the second command reads the flag from the file.
If you have a system without the /etc/mtab file or if you explic‐
itly define source and target for the remount command (then
mount(8) does not read /etc/mtab), then you have to use bind flag
(or option) for the remount command too. For example:
mount --bind olddir newdir
mount -o remount,ro,bind olddir newdir
The move operation.
Since Linux 2.5.1 it is possible to atomically move a mounted tree
to another place. The call is
mount --move olddir newdir
or shortoption
mount -M olddir newdir
This will cause the contents which previously appeared under olddir
to be accessed under newdir. The physical location of the files is
not changed. Note that the olddir has to be a mountpoint.
The shared subtrees operations.
Since Linux 2.6.15 it is possible to mark a mount and its submounts
as shared, private, slave or unbindable. A shared mount provides
ability to create mirrors of that mount such that mounts and
umounts within any of the mirrors propagate to the other mirror. A
slave mount receives propagation from its master, but any not vice-
versa. A private mount carries no propagation abilities. A
unbindable mount is a private mount which cannot be cloned through
a bind operation. Detailed semantics is documented in Documenta‐
tion/filesystems/sharedsubtree.txt file in the kernel source tree.
mount --make-shared mountpoint
mount --make-slave mountpoint
mount --make-private mountpoint
mount --make-unbindable mountpoint
The following commands allows one to recursively change the type of
all the mounts under a given mountpoint.
mount --make-rshared mountpoint
mount --make-rslave mountpoint
mount --make-rprivate mountpoint
mount --make-runbindable mountpoint
COMMAND LINE OPTIONS
The full set of mount options used by an invocation of mount is determined
by first extracting the mount options for the filesystem from the fstab
table, then applying any options specified by the -o argument, and finally
applying a -r or -w option, when present.
Command line options available for the mount command:
-V, --version
Output version.
-h, --help
Print a help message.
-v, --verbose
Verbose mode.
-a, --all
Mount all filesystems (of the given types) mentioned in fstab.
-F, --fork
(Used in conjunction with -a.) Fork off a new incarnation of mount
for each device. This will do the mounts on different devices or
different NFS servers in parallel. This has the advantage that it
is faster; also NFS timeouts go in parallel. A disadvantage is that
the mounts are done in undefined order. Thus, you cannot use this
option if you want to mount both /usr and /usr/spool.
-f, --fake
Causes everything to be done except for the actual system call; if
it's not obvious, this ``fakes'' mounting the filesystem. This
option is useful in conjunction with the -v flag to determine what
the mount command is trying to do. It can also be used to add
entries for devices that were mounted earlier with the -n option.
The -f option checks for existing record in /etc/mtab and fails
when the record already exists (with regular non-fake mount, this
check is done by kernel).
-i, --internal-only
Don't call the /sbin/mount.<filesystem> helper even if it exists.
-l 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, ext3 or ext4 using the e2label(8) util‐
ity, or for XFS using xfs_admin(8), or for reiserfs using reiserfs‐
tune(8).
-n, --no-mtab
Mount without writing in /etc/mtab. This is necessary for example
when /etc is on a read-only filesystem.
--no-canonicalize
Don't canonicalize paths. The mount command canonicalizes all paths
(from command line or fstab) and stores canonicalized paths to the
/etc/mtab file. This option can be used together with the -f flag
for already canonicalized absolut paths.
-p, --pass-fd num
In case of a loop mount with encryption, read the passphrase from
file descriptor num instead of from the terminal.
-s Tolerate sloppy mount options rather than failing. This will ignore
mount options not supported by a filesystem type. Not all filesys‐
tems support this option. This option exists for support of the
Linux autofs-based automounter.
-r, --read-only
Mount the filesystem read-only. A synonym is -o ro.
Note that, depending on the filesystem type, state and kernel
behavior, the 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 blockdev(8).
-w, --rw
Mount the filesystem read/write. This is the default. A synonym is
-o rw.
-L label
Mount the partition that has the specified label.
-U uuid
Mount the partition that has the specified uuid. These two options
require the file /proc/partitions (present since Linux 2.1.116) to
exist.
-t, --types vfstype
The argument following the -t is used to indicate the filesystem
type. The filesystem types which are currently supported include:
adfs, affs, autofs, cifs, coda, coherent, cramfs, debugfs, devpts,
efs, ext, ext2, ext3, ext4, hfs, hfsplus, hpfs, iso9660, jfs,
minix, msdos, ncpfs, nfs, nfs4, ntfs, proc, qnx4, ramfs, reiserfs,
romfs, squashfs, smbfs, sysv, tmpfs, ubifs, udf, ufs, umsdos,
usbfs, vfat, xenix, xfs, xiafs. Note that coherent, sysv and xenix
are equivalent and that xenix and coherent will be removed at some
point in the future — use sysv instead. Since kernel version 2.1.21
the types ext and xiafs do not exist anymore. Earlier, usbfs was
known as usbdevfs. Note, the real list of all supported filesys‐
tems depends on your kernel.
The programs mount and umount support filesystem subtypes. The
subtype is defined by '.subtype' suffix. For example
'fuse.sshfs'. It's recommended to use subtype notation rather than
add any prefix to the mount source (for example 'sshfs#example.com'
is depreacated).
For most types all the mount program has to do is issue a simple
mount(2) system call, and no detailed knowledge of the filesystem
type is required. For a few types however (like nfs, nfs4, cifs,
smbfs, ncpfs) ad hoc code is necessary. The nfs, nfs4, cifs, smbfs,
and ncpfs filesystems have a separate mount program. In order to
make it possible to treat all types in a uniform way, mount will
execute the program /sbin/mount.TYPE (if that exists) when called
with type TYPE. Since various versions of the smbmount program
have different calling conventions, /sbin/mount.smbfs may have to
be a shell script that sets up the desired call.
If no -t option is given, or if the auto type is specified, mount
will try to guess the desired type. Mount uses the blkid library
for guessing the filesystem type; if that does not turn up anything
that looks familiar, mount will try to read the file /etc/filesys‐
tems, or, if that does not exist, /proc/filesystems. All of the
filesystem types listed there will be tried, except for those that
are labeled "nodev" (e.g., devpts, proc and nfs). If /etc/filesys‐
tems ends in a line with a single * only, mount will read
/proc/filesystems afterwards.
The auto type may be useful for user-mounted floppies. Creating a
file /etc/filesystems can be useful to change the probe order
(e.g., to try vfat before msdos or ext3 before ext2) or if you use
a kernel module autoloader.
More than one type may be specified in a comma separated list. The
list of filesystem types can be prefixed with no to specify the
filesystem types on which no action should be taken. (This can be
meaningful with the -a option.) For example, the command:
mount -a -t nomsdos,ext
mounts all filesystems except those of type msdos and ext.
-O, --test-opts opts
Used in conjunction with -a, to limit the set of filesystems to
which the -a is applied. Like -t in this regard except that it is
useless except in the context of -a. For example, the command:
mount -a -O no_netdev
mounts all filesystems except those which have the option _netdev
specified in the options field in the /etc/fstab file.
It is different from -t in that each option is matched exactly; a
leading no at the beginning of one option does not negate the rest.
The -t and -O options are cumulative in effect; that is, the com‐
mand
mount -a -t ext2 -O _netdev
mounts all ext2 filesystems with the _netdev option, not all
filesystems that are either ext2 or have the _netdev option speci‐
fied.
-o, --options opts
Options are specified with a -o flag followed by a comma separated
string of options. For example:
mount LABEL=mydisk -o noatime,nouser
For more details, see FILESYSTEM INDEPENDENT MOUNT OPTIONS and
FILESYSTEM SPECIFIC MOUNT OPTIONS sections.
-B, --bind
Remount a subtree somewhere else (so that its contents are avail‐
able in both places). See above.
-R, --rbind
Remount a subtree and all possible submounts somewhere else (so
that its contents are available in both places). See above.
-M, --move
Move a subtree to some other place. See above.
FILESYSTEM INDEPENDENT MOUNT OPTIONS
Some of these options are only useful when they appear in the /etc/fstab
file.
Some of these options could be enabled or disabled by default in the sys‐
tem kernel. To check the current setting see the options in /proc/mounts.
The following options apply to any filesystem that is being mounted (but
not every filesystem actually honors them - e.g., the sync option today
has effect only for ext2, ext3, fat, vfat and ufs):
async All I/O to the filesystem should be done asynchronously. (See also
the sync option.)
atime Do not use noatime feature, then the inode access time is con‐
trolled by kernel defaults. See also the description for stricta‐
time and reatime mount options.
noatime
Do not update inode access times on this filesystem (e.g., for
faster access on the news spool to speed up news servers).
auto Can be mounted with the -a option.
noauto Can only be mounted explicitly (i.e., the -a option will not cause
the filesystem to be mounted).
context=context, fscontext=context, defcontext=context and rootcon‐
text=context
The context= option is useful when mounting filesystems that do not
support extended attributes, such as a floppy or hard disk format‐
ted with VFAT, or systems that are not normally running under
SELinux, such as an ext3 formatted disk from a non-SELinux worksta‐
tion. You can also use context= on filesystems you do not trust,
such as a floppy. It also helps in compatibility with xattr-sup‐
porting filesystems on earlier 2.4.<x> kernel versions. Even where
xattrs are supported, you can save time not having to label every
file by assigning the entire disk one security context.
A commonly used option for removable media is context=sys‐
tem_u:object_r:removable_t.
Two other options are fscontext= and defcontext=, both of which are
mutually exclusive of the context option. This means you can use
fscontext and defcontext with each other, but neither can be used
with context.
The fscontext= option works for all filesystems, regardless of
their xattr support. The fscontext option sets the overarching
filesystem label to a specific security context. This filesystem
label is separate from the individual labels on the files. It rep‐
resents the entire filesystem for certain kinds of permission
checks, such as during mount or file creation. Individual file
labels are still obtained from the xattrs on the files themselves.
The context option actually sets the aggregate context that fscon‐
text provides, in addition to supplying the same label for individ‐
ual files.
You can set the default security context for unlabeled files using
defcontext= option. This overrides the value set for unlabeled
files in the policy and requires a filesystem that supports xattr
labeling.
The rootcontext= option allows you to explicitly label the root
inode of a FS being mounted before that FS or inode because visable
to userspace. This was found to be useful for things like stateless
linux.
Note that kernel rejects any remount request that includes the con‐
text option even if unchanged from the current context.
For more details, see selinux(8)
defaults
Use default options: rw, suid, dev, exec, auto, nouser, and async.
dev Interpret character or block special devices on the filesystem.
nodev Do not interpret character or block special devices on the file
system.
diratime
Update directory inode access times on this filesystem. This is the
default.
nodiratime
Do not update directory inode access times on this filesystem.
dirsync
All directory updates within the filesystem should be done syn‐
chronously. This affects the following system calls: creat, link,
unlink, symlink, mkdir, rmdir, mknod and rename.
exec Permit execution of binaries.
noexec Do not allow direct execution of any binaries on the mounted
filesystem. (Until recently it was possible to run binaries anyway
using a command like /lib/ld*.so /mnt/binary. This trick fails
since Linux 2.4.25 / 2.6.0.)
group Allow an ordinary (i.e., non-root) user to mount the filesystem if
one of his groups matches the group of the device. This option
implies the options nosuid and nodev (unless overridden by subse‐
quent options, as in the option line group,dev,suid).
encryption
Specifies an encryption algorithm to use. Used in conjunction with
the loop option.
keybits
Specifies the key size to use for an encryption algorithm. Used in
conjunction with the loop and encryption options. nofail Do not
report errors for this device if it does not exist. iversion Every
time the inode is modified, the i_version field will be incre‐
mented.
noiversion
Do not increment the i_version inode field.
mand Allow mandatory locks on this filesystem. See fcntl(2).
nomand Do not allow mandatory locks on this filesystem.
_netdev
The filesystem resides on a device that requires network access
(used to prevent the system from attempting to mount these filesys‐
tems until the network has been enabled on the system).
nofail Do not report errors for this device if it does not exist.
relatime
Update inode access times relative to modify or change time.
Access time is only updated if the previous access time was earlier
than the current modify or change time. (Similar to noatime, but
doesn't break mutt or other applications that need to know if a
file has been read since the last time it was modified.)
Since Linux 2.6.30, the kernel defaults to the behavior provided by
this option (unless noatime was specified), and the strictatime
option is required to obtain traditional semantics. In addition,
since Linux 2.6.30, the file's last access time is always updated
if it is more than 1 day old.
norelatime
Do not use relatime feature. See also the strictatime mount option.
strictatime
Allows to explicitly requesting full atime updates. This makes it
possible for kernel to defaults to relatime or noatime but still
allow userspace to override it. For more details about the default
system mount options see /proc/mounts.
nostrictatime
Use the kernel's default behaviour for inode access time updates.
suid Allow set-user-identifier or set-group-identifier bits to take
effect.
nosuid Do not allow set-user-identifier or set-group-identifier bits to
take effect. (This seems safe, but is in fact rather unsafe if you
have suidperl(1) installed.)
silent Turn on the silent flag.
loud Turn off the silent flag.
owner Allow an ordinary (i.e., non-root) user to mount the filesystem if
he is the owner of the device. This option implies the options
nosuid and nodev (unless overridden by subsequent options, as in
the option line owner,dev,suid).
remount
Attempt to remount an already-mounted filesystem. This is commonly
used to change the mount flags for a filesystem, especially to make
a readonly filesystem writable. It does not change device or mount
point.
The remount functionality follows the standard way how the mount
command works with options from fstab. It means the mount command
doesn't read fstab (or mtab) only when a device and dir are fully
specified.
mount -o remount,rw /dev/foo /dir
After this call all old mount options are replaced and arbitrary
stuff from fstab is ignored, except the loop= option which is
internally generated and maintained by the mount command.
mount -o remount,rw /dir
After this call mount reads fstab (or mtab) and merges these
options with options from command line ( -o ).
ro Mount the filesystem read-only.
rw Mount the filesystem read-write.
sync All I/O to the filesystem should be done synchronously. In case of
media with limited number of write cycles (e.g. some flash drives)
"sync" may cause life-cycle shortening.
user Allow an ordinary user to mount the filesystem. The name of the
mounting user is written to mtab so that he can unmount the
filesystem again. This option implies the options noexec, nosuid,
and nodev (unless overridden by subsequent options, as in the
option line user,exec,dev,suid).
nouser Forbid an ordinary (i.e., non-root) user to mount the filesystem.
This is the default.
users Allow every user to mount and unmount the filesystem. This option
implies the options noexec, nosuid, and nodev (unless overridden by
subsequent options, as in the option line users,exec,dev,suid).
FILESYSTEM SPECIFIC MOUNT OPTIONS
The following options apply only to certain filesystems. We sort them by
filesystem. They all follow the -o flag.
What options are supported depends a bit on the running kernel. More info
may be found in the kernel source subdirectory Documentation/filesystems.
Mount options for adfs
uid=value and gid=value
Set the owner and group of the files in the filesystem (default:
uid=gid=0).
ownmask=value and othmask=value
Set the permission mask for ADFS 'owner' permissions and 'other'
permissions, respectively (default: 0700 and 0077, respectively).
See also /usr/src/linux/Documentation/filesystems/adfs.txt.
Mount options for affs
uid=value and gid=value
Set the owner and group of the root of the filesystem (default:
uid=gid=0, but with option uid or gid without specified value, the
uid and gid of the current process are taken).
setuid=value and setgid=value
Set the owner and group of all files.
mode=value
Set the mode of all files to value & 0777 disregarding the original
permissions. Add search permission to directories that have read
permission. The value is given in octal.
protect
Do not allow any changes to the protection bits on the filesystem.
usemp Set uid and gid of the root of the filesystem to the uid and gid of
the mount point upon the first sync or umount, and then clear this
option. Strange...
verbose
Print an informational message for each successful mount.
prefix=string
Prefix used before volume name, when following a link.
volume=string
Prefix (of length at most 30) used before '/' when following a sym‐
bolic link.
reserved=value
(Default: 2.) Number of unused blocks at the start of the device.
root=value
Give explicitly the location of the root block.
bs=value
Give blocksize. Allowed values are 512, 1024, 2048, 4096.
grpquota|noquota|quota|usrquota
These options are accepted but ignored. (However, quota utilities
may react to such strings in /etc/fstab.)
Mount options for cifs
See the options section of the mount.cifs(8) man page (cifs-utils package
must be installed).
Mount options for coherent
None.
Mount options for debugfs
The debugfs filesystem is a pseudo filesystem, traditionally mounted on
/sys/kernel/debug. There are no mount options.
Mount options for devpts
The devpts filesystem is a pseudo filesystem, traditionally mounted on
/dev/pts. In order to acquire a pseudo terminal, a process opens
/dev/ptmx; the number of the pseudo terminal is then made available to the
process and the pseudo terminal slave can be accessed as /dev/pts/<num‐
ber>.
uid=value and gid=value
This sets the owner or the group of newly created PTYs to the spec‐
ified values. When nothing is specified, they will be set to the
UID and GID of the creating process. For example, if there is a
tty group with GID 5, then gid=5 will cause newly created PTYs to
belong to the tty group.
mode=value
Set the mode of newly created PTYs to the specified value. The
default is 0600. A value of mode=620 and gid=5 makes "mesg y" the
default on newly created PTYs.
newinstance
Create a private instance of devpts filesystem, such that indices
of ptys allocated in this new instance are independent of indices
created in other instances of devpts.
All mounts of devpts without this newinstance option share the same
set of pty indices (i.e legacy mode). Each mount of devpts with
the newinstance option has a private set of pty indices.
This option is mainly used to support containers in the linux ker‐
nel. It is implemented in linux kernel versions starting with
2.6.29. Further, this mount option is valid only if CON‐
FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configura‐
tion.
To use this option effectively, /dev/ptmx must be a symbolic link
to pts/ptmx. See Documentation/filesystems/devpts.txt in the linux
kernel source tree for details.
ptmxmode=value
Set the mode for the new ptmx device node in the devpts filesystem.
With the support for multiple instances of devpts (see newinstance
option above), each instance has a private ptmx node in the root of
the devpts filesystem (typically /dev/pts/ptmx).
For compatibility with older versions of the kernel, the default
mode of the new ptmx node is 0000. ptmxmode=value specifies a more
useful mode for the ptmx node and is highly recommended when the
newinstance option is specified.
This option is only implemented in linux kernel versions starting
with 2.6.29. Further this option is valid only if CON‐
FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configura‐
tion.
Mount options for ext
None. Note that the `ext' filesystem is obsolete. Don't use it. Since
Linux version 2.1.21 extfs is no longer part of the kernel source.
Mount options for ext2
The `ext2' filesystem is the standard Linux filesystem. Since Linux
2.5.46, for most mount options the default is determined by the filesystem
superblock. Set them with tune2fs(8).
acl|noacl
Support POSIX Access Control Lists (or not).
bsddf|minixdf
Set the behaviour for the statfs system call. The minixdf behaviour
is to return in the f_blocks field the total number of blocks of
the filesystem, while the bsddf behaviour (which is the default) is
to subtract the overhead blocks used by the ext2 filesystem and not
available for file storage. Thus
% mount /k -o minixdf; df /k; umount /k
Filesystem 1024-blocks Used Available Capacity Mounted on
/dev/sda6 2630655 86954 2412169 3% /k
% mount /k -o bsddf; df /k; umount /k
Filesystem 1024-blocks Used Available Capacity Mounted on
/dev/sda6 2543714 13 2412169 0% /k
(Note that this example shows that one can add command line options
to the options given in /etc/fstab.)
check={none|nocheck}
No checking is done at mount time. This is the default. This is
fast. It is wise to invoke e2fsck(8) every now and then, e.g. at
boot time.
debug Print debugging info upon each (re)mount.
errors={continue|remount-ro|panic}
Define the behaviour when an error is encountered. (Either ignore
errors and just mark the filesystem erroneous and continue, or
remount the filesystem read-only, or panic and halt the system.)
The default is set in the filesystem superblock, and can be changed
using tune2fs(8).
grpid|bsdgroups and nogrpid|sysvgroups
These options define what group id a newly created file gets. When
grpid is set, it takes the group id of the directory in which it is
created; otherwise (the default) it takes the fsgid of the current
process, unless the directory has the setgid bit set, in which case
it takes the gid from the parent directory, and also gets the set‐
gid bit set if it is a directory itself.
grpquota|noquota|quota|usrquota
These options are accepted but ignored.
nouid32
Disables 32-bit UIDs and GIDs. This is for interoperability with
older kernels which only store and expect 16-bit values.
oldalloc or orlov
Use old allocator or Orlov allocator for new inodes. Orlov is
default.
resgid=n and resuid=n
The ext2 filesystem reserves a certain percentage of the available
space (by default 5%, see mke2fs(8) and tune2fs(8)). These options
determine who can use the reserved blocks. (Roughly: whoever has
the specified uid, or belongs to the specified group.)
sb=n Instead of block 1, use block n as superblock. This could be useful
when the filesystem has been damaged. (Earlier, copies of the
superblock would be made every 8192 blocks: in block 1, 8193,
16385, ... (and one got thousands of copies on a big filesystem).
Since version 1.08, mke2fs has a -s (sparse superblock) option to
reduce the number of backup superblocks, and since version 1.15
this is the default. Note that this may mean that ext2 filesystems
created by a recent mke2fs cannot be mounted r/w under Linux
2.0.*.) The block number here uses 1k units. Thus, if you want to
use logical block 32768 on a filesystem with 4k blocks, use
"sb=131072".
user_xattr|nouser_xattr
Support "user." extended attributes (or not).
Mount options for ext3
The ext3 filesystem is a version of the ext2 filesystem which has been
enhanced with journalling. It supports the same options as ext2 as well
as the following additions:
journal=update
Update the ext3 filesystem's journal to the current format.
journal=inum
When a journal already exists, this option is ignored. Otherwise,
it specifies the number of the inode which will represent the ext3
filesystem's journal file; ext3 will create a new journal, over‐
writing the old contents of the file whose inode number is inum.
journal_dev=devnum
When the external journal device's major/minor numbers have
changed, this option allows the user to specify the new journal
location. The journal device is identified through its new
major/minor numbers encoded in devnum.
norecovery/noload
Don't load the journal on mounting. Note that if the filesystem
was not unmounted cleanly, skipping the journal replay will lead to
the filesystem containing inconsistencies that can lead to any num‐
ber of problems.
data={journal|ordered|writeback}
Specifies the journalling mode for file data. Metadata is always
journaled. To use modes other than ordered on the root filesystem,
pass the mode to the kernel as boot parameter, e.g. root‐
flags=data=journal.
journal
All data is committed into the journal prior to being writ‐
ten into the main filesystem.
ordered
This is the default mode. All data is forced directly out
to the main file system prior to its metadata being commit‐
ted to the journal.
writeback
Data ordering is not preserved - data may be written into
the main filesystem after its metadata has been committed to
the journal. This is rumoured to be the highest-throughput
option. It guarantees internal filesystem integrity, how‐
ever it can allow old data to appear in files after a crash
and journal recovery.
barrier=0 / barrier=1
This enables/disables barriers. barrier=0 disables it, barrier=1
enables it. Write barriers enforce proper on-disk ordering of
journal commits, making volatile disk write caches safe to use, at
some performance penalty. The ext3 filesystem does not enable
write barriers by default. Be sure to enable barriers unless your
disks are battery-backed one way or another. Otherwise you risk
filesystem corruption in case of power failure.
commit=nrsec
Sync all data and metadata every nrsec seconds. The default value
is 5 seconds. Zero means default.
user_xattr
Enable Extended User Attributes. See the attr(5) manual page.
acl Enable POSIX Access Control Lists. See the acl(5) manual page.
Mount options for ext4
The ext4 filesystem is an advanced level of the ext3 filesystem which
incorporates scalability and reliability enhancements for supporting large
filesystem.
The options journal_dev, noload, data, commit, orlov, oldalloc,
[no]user_xattr [no]acl, bsddf, minixdf, debug, errors, data_err, grpid,
bsdgroups, nogrpid sysvgroups, resgid, resuid, sb, quota, noquota,
grpquota and usrquota are backwardly compatible with ext3 or ext2.
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.
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.
journal=update