Change the partition type. By default, new partitions are created as _Linux_ partitions.
*u*::
-Dump the current in-memory partition table to an sfdisk-compatible script file.
+Dump the current in-memory partition table to an **sfdisk**(8)-compatible script file.
+
The script files are compatible between *cfdisk*, *fdisk*(8) *sfdisk*(8) and other libfdisk applications. For more details see *sfdisk*(8).
+
When listing partition tables, show sizes in 'sectors' or in 'cylinders'. The default is to show sizes in sectors. For backward compatibility, it is possible to use the option without the _unit_ argument -- then the default is used. Note that the optional _unit_ argument cannot be separated from the *-u* option by a space, the correct form is for example '**-u=**__cylinders__'.
*-C*, *--cylinders* _number_::
-Specify the number of cylinders of the disk. I have no idea why anybody would want to do so.
+Specify the _number_ of cylinders of the disk. I have no idea why anybody would want to do so.
*-H*, *--heads* _number_::
Specify the number of heads of the disk. (Not the physical number, of course, but the number used for partition tables.) Reasonable values are 255 and 16.
//TRANSLATORS: Keep {plus} untranslated.
The relative sizes are always aligned according to device I/O limits. The {plus}/-<size>{K,B,M,G,...} notation is recommended.
-For backward compatibility fdisk also accepts the suffixes KB=1000, MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB. These 10^N suffixes are deprecated.
+For backward compatibility *fdisk* also accepts the suffixes KB=1000, MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB. These 10^N suffixes are deprecated.
== SCRIPT FILES
*IRIX/SGI-type*::
An IRIX/SGI disklabel can describe 16 partitions, the eleventh of which should be an entire `volume' partition, while the ninth should be labeled `volume header'. The volume header will also cover the partition table, i.e., it starts at block zero and extends by default over five cylinders. The remaining space in the volume header may be used by header directory entries. No partitions may overlap with the volume header. Also do not change its type or make some filesystem on it, since you will lose the partition table. Use this type of label only when working with Linux on IRIX/SGI machines or IRIX/SGI disks under Linux.
+
-A sync() and an ioctl(BLKRRPART) (rereading the partition table from disk) are performed before exiting when the partition table has been updated.
+A *sync*(2) and an ioctl(BLKRRPART) (rereading the partition table from disk) are performed before exiting when the partition table has been updated.
== DOS mode and DOS 6.x WARNING
The DOS 6.x FORMAT command looks for some information in the first sector of the data area of the partition, and treats this information as more reliable than the information in the partition table. DOS FORMAT expects DOS FDISK to clear the first 512 bytes of the data area of a partition whenever a size change occurs. DOS FORMAT will look at this extra information even if the /U flag is given -- we consider this a bug in DOS FORMAT and DOS FDISK.
-The bottom line is that if you use *fdisk* or *cfdisk* to change the size of a DOS partition table entry, then you must also use *dd*(1) to *zero the first 512 bytes* of that partition before using DOS FORMAT to format the partition. For example, if you were using *fdisk* to make a DOS partition table entry for _/dev/sda1_, then (after exiting *fdisk* and rebooting Linux so that the partition table information is valid) you would use the command *dd if=/dev/zero of=/dev/sda1 bs=512 count=1* to zero the first 512 bytes of the partition.
+The bottom line is that if you use *fdisk* or *cfdisk*(8) to change the size of a DOS partition table entry, then you must also use *dd*(1) to *zero the first 512 bytes* of that partition before using DOS FORMAT to format the partition. For example, if you were using *fdisk* to make a DOS partition table entry for _/dev/sda1_, then (after exiting *fdisk* and rebooting Linux so that the partition table information is valid) you would use the command *dd if=/dev/zero of=/dev/sda1 bs=512 count=1* to zero the first 512 bytes of the partition.
*fdisk* usually obtains the disk geometry automatically. This is not necessarily the physical disk geometry (indeed, modern disks do not really have anything like a physical geometry, certainly not something that can be described in the simplistic Cylinders/Heads/Sectors form), but it is the disk geometry that MS-DOS uses for the partition table.
The _size_ parameter is superfluous but retained for backwards compatibility. (It specifies the desired size of the swap area in 1024-byte blocks. *mkswap* will use the entire partition or file if it is omitted. Specifying it is unwise - a typo may destroy your disk.)
-After creating the swap area, you need the *swapon* command to start using it. Usually swap areas are listed in _/etc/fstab_ so that they can be taken into use at boot time by a *swapon -a* command in some boot script.
+After creating the swap area, you need the *swapon*(8) command to start using it. Usually swap areas are listed in _/etc/fstab_ so that they can be taken into use at boot time by a *swapon -a* command in some boot script.
== WARNING
Also, without this option, *mkswap* will refuse to erase the first block on a device with a partition table.
*-L*, *--label* _label_::
-Specify a _label_ for the device, to allow *swapon* by label.
+Specify a _label_ for the device, to allow *swapon*(8) by label.
*--lock*[=_mode_]::
Use exclusive BSD lock for device or file it operates. The optional argument _mode_ can be *yes*, *no* (or 1 and 0) or *nonblock*. If the _mode_ argument is omitted, it defaults to *"yes"*. This option overwrites environment variable *$LOCK_BLOCK_DEVICE*. The default is not to use any lock at all, but it's recommended to avoid collisions with udevd or other tools.
partx --show /dev/sdb3::
partx --show --nr 3 /dev/sdb::
partx --show /dev/sdb3 /dev/sdb::
-All three commands list partition 3 of /dev/sdb.
+All three commands list partition 3 of _/dev/sdb_.
partx --show - /dev/sdb3::
Lists all subpartitions on _/dev/sdb3_ (the device is used as whole-disk).
== NOTES
-Rather than using raw devices applications should prefer open2 devices, such as _/dev/sda1_, with the *O_DIRECT* flag.
+Rather than using raw devices applications should prefer *open*(2) devices, such as _/dev/sda1_, with the *O_DIRECT* flag.
== BUGS
*--move-data*[**=**__path__]::
Move data after partition relocation, for example when moving the beginning of a partition to another place on the disk. The size of the partition has to remain the same, the new and old location may overlap. This option requires option *-N* in order to be processed on one specific partition only.
+
-The optional _path_ specifies log file name. The log file contains information about all read/write operations on the partition data. The word "@default" as a _path_ forces sfdisk to use _~/sfdisk-<devname>.move_ for the log. The log is optional since v2.35.
+The optional _path_ specifies log file name. The log file contains information about all read/write operations on the partition data. The word "@default" as a _path_ forces *sfdisk* to use _~/sfdisk-<devname>.move_ for the log. The log is optional since v2.35.
+
Note that this operation is risky and not atomic. *Don't forget to backup your data!*
+
*grain*::
Specify minimal size in bytes used to calculate partitions alignment. The default is 1MiB and it's strongly recommended to use the default. Do not modify this variable if you're not sure.
*sector-size*::
-Specify sector size. This header is informative only and it is not used when sfdisk creates a new partition table, in this case the real device specific value is always used and sector size from the dump is ignored.
+Specify sector size. This header is informative only and it is not used when *sfdisk* creates a new partition table, in this case the real device specific value is always used and sector size from the dump is ignored.
Note that it is only possible to use header lines before the first partition is specified in the input.
== ENVIRONMENT
-SFDISK_DEBUG=all::
+*SFDISK_DEBUG*=all::
enables *sfdisk* debug output.
-LIBFDISK_DEBUG=all::
+*LIBFDISK_DEBUG*=all::
enables libfdisk debug output.
-LIBBLKID_DEBUG=all::
+*LIBBLKID_DEBUG*=all::
enables libblkid debug output.
-LIBSMARTCOLS_DEBUG=all::
+*LIBSMARTCOLS_DEBUG*=all::
enables libsmartcols debug output.
-LOCK_BLOCK_DEVICE=<mode>::
+*LOCK_BLOCK_DEVICE*=<mode>::
use exclusive BSD lock. The mode is "1" or "0". See *--lock* for more details.
== NOTES
The _name_ is a utility name. The name is optional and when none is specified then the file is used for all unspecified utilities.
-The _term_ is a terminal identifier (the TERM environment variable). The terminal identifier is optional and when none is specified then the file is used for all unspecified terminals.
+The _term_ is a terminal identifier (the *TERM* environment variable). The terminal identifier is optional and when none is specified then the file is used for all unspecified terminals.
The _type_ is a file type. Supported file types are:
== ENVIRONMENT
-TERMINAL_COLORS_DEBUG=all::
+*TERMINAL_COLORS_DEBUG*=all::
enables debug output.
== FILES
== COMPATIBILITY
-The terminal-colors.d functionality is currently supported by all util-linux utilities which provides colorized output. For more details always see the COLORS section in the man page for the utility.
+The *terminal-colors.d* functionality is currently supported by all util-linux utilities which provides colorized output. For more details always see the COLORS section in the man page for the utility.
include::man-common/bugreports.adoc[]
The *uuid_generate_random*() function forces the use of the all-random UUID format, even if a high-quality random number generator is not available, in which case a pseudo-random generator will be substituted. Note that the use of a pseudo-random generator may compromise the uniqueness of UUIDs generated in this fashion.
-The *uuid_generate_time*() function forces the use of the alternative algorithm which uses the current time and the local ethernet MAC address (if available). This algorithm used to be the default one used to generate UUIDs, but because of the use of the ethernet MAC address, it can leak information about when and where the UUID was generated. This can cause privacy problems in some applications, so the *uuid_generate*() function only uses this algorithm if a high-quality source of randomness is not available. To guarantee uniqueness of UUIDs generated by concurrently running processes, the uuid library uses a global clock state counter (if the process has permissions to gain exclusive access to this file) and/or the *uuidd* daemon, if it is running already or can be spawned by the process (if installed and the process has enough permissions to run it). If neither of these two synchronization mechanisms can be used, it is theoretically possible that two concurrently running processes obtain the same UUID(s). To tell whether the UUID has been generated in a safe manner, use *uuid_generate_time_safe*.
+The *uuid_generate_time*() function forces the use of the alternative algorithm which uses the current time and the local ethernet MAC address (if available). This algorithm used to be the default one used to generate UUIDs, but because of the use of the ethernet MAC address, it can leak information about when and where the UUID was generated. This can cause privacy problems in some applications, so the *uuid_generate*() function only uses this algorithm if a high-quality source of randomness is not available. To guarantee uniqueness of UUIDs generated by concurrently running processes, the uuid library uses a global clock state counter (if the process has permissions to gain exclusive access to this file) and/or the *uuidd*(8) daemon, if it is running already or can be spawned by the process (if installed and the process has enough permissions to run it). If neither of these two synchronization mechanisms can be used, it is theoretically possible that two concurrently running processes obtain the same UUID(s). To tell whether the UUID has been generated in a safe manner, use *uuid_generate_time_safe*.
The *uuid_generate_time_safe*() function is similar to *uuid_generate_time*(), except that it returns a value which denotes whether any of the synchronization mechanisms (see above) has been used.
*last* searches back through the _/var/log/wtmp_ file (or the file designated by the *-f* option) and displays a list of all users logged in (and out) since that file was created. One or more _usernames_ and/or _ttys_ can be given, in which case *last* will show only the entries matching those arguments. Names of _ttys_ can be abbreviated, thus *last 0* is the same as *last tty0*.
-When catching a *SIGINT* signal (generated by the interrupt key, usually control-C) or a SIGQUIT signal, *last* will show how far it has searched through the file; in the case of the *SIGINT* signal *last* will then terminate.
+When catching a *SIGINT* signal (generated by the interrupt key, usually control-C) or a *SIGQUIT* signal, *last* will show how far it has searched through the file; in the case of the *SIGINT* signal *last* will then terminate.
The pseudo user *reboot* logs in each time the system is rebooted. Thus *last reboot* will show a log of all the reboots since the log file was created.
Defines the *PATH* environment variable for root. *ENV_SUPATH* takes precedence. The default value is _/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin_.
*ALWAYS_SET_PATH* (boolean)::
-If set to _yes_ and --login and --preserve-environment were not specified *runuser* initializes *PATH*.
+If set to _yes_ and *--login* and *--preserve-environment* were not specified *runuser* initializes *PATH*.
The environment variable *PATH* may be different on systems where _/bin_ and _/sbin_ are merged into _/usr_; this variable is also affected by the *--login* command-line option and the PAM system setting (e.g., *pam_env*(8)).
:man source: util-linux {release-version}
:page-layout: base
:command: su
+:colon: :
== NAME
*-P*, *--pty*::
Create a pseudo-terminal for the session. The independent terminal provides better security as the user does not share a terminal with the original session. This can be used to avoid TIOCSTI ioctl terminal injection and other security attacks against terminal file descriptors. The entire session can also be moved to the background (e.g., "su --pty - username -c application &"). If the pseudo-terminal is enabled, then *su* works as a proxy between the sessions (copy stdin and stdout).
+
-This feature is mostly designed for interactive sessions. If the standard input is not a terminal, but for example a pipe (e.g., echo "date" | su --pty), then the ECHO flag for the pseudo-terminal is disabled to avoid messy output.
+This feature is mostly designed for interactive sessions. If the standard input is not a terminal, but for example a pipe (e.g., echo "date" | su --pty), then the *ECHO* flag for the pseudo-terminal is disabled to avoid messy output.
*-s*, **--shell**=__shell__::
Run the specified _shell_ instead of the default. The shell to run is selected according to the following rules, in order:
* the shell listed in the passwd entry of the target user
* /bin/sh
-If the target user has a restricted shell (i.e., not listed in /etc/shells), the *--shell* option and the *SHELL* environment variables are ignored unless the calling user is root.
+If the target user has a restricted shell (i.e., not listed in _/etc/shells_), the *--shell* option and the *SHELL* environment variables are ignored unless the calling user is root.
**--session-command=**__command__::
Same as *-c*, but do not create a new session. (Discouraged.)
== CONFIG FILES
-*su* reads the _/etc/default/su_ and _/etc/login.defs_ configuration files. The following configuration items are relevant for *su:*
+//TRANSLATORS: Keep {colon} untranslated
+*su* reads the _/etc/default/su_ and _/etc/login.defs_ configuration files. The following configuration items are relevant for *su*{colon}
*FAIL_DELAY* (number)::
Delay in seconds in case of an authentication failure. The number must be a non-negative integer.
== CONFIGURATION FILE
-The standard location of the _/etc/blkid.conf_ config file can be overridden by the environment variable BLKID_CONF. The following options control the libblkid library:
+The standard location of the _/etc/blkid.conf_ config file can be overridden by the environment variable *BLKID_CONF*. The following options control the libblkid library:
_SEND_UEVENT=<yes|not>_::
Sends uevent when _/dev/disk/by-{label,uuid,partuuid,partlabel}/_ symlink does not match with LABEL, UUID, PARTUUID or PARTLABEL on the device. Default is "yes".
Use JSON output format.
*-k*, *--kernel*::
-Search in _/proc/self/mountinfo_. The output is in the tree-like format. This is the default. The output contains only mount options maintained by kernel (see also *--mtab)*.
+Search in _/proc/self/mountinfo_. The output is in the tree-like format. This is the default. The output contains only mount options maintained by kernel (see also *--mtab*).
*-l*, *--list*::
Use the list output format. This output format is automatically enabled if the output is restricted by the *-t*, *-O*, *-S* or *-T* option and the option *--submounts* is not used or if more that one source file (the option *-F*) is specified.
Specify an upper limit on the time for which *--poll* will block, in milliseconds.
*-x*, *--verify*::
-Check mount table content. The default is to verify _/etc/fstab_ parsability and usability. It's possible to use this option also with *--tab-file*. It's possible to specify source (device) or target (mountpoint) to filter mount table. The option *--verbose* forces findmnt to print more details.
+Check mount table content. The default is to verify _/etc/fstab_ parsability and usability. It's possible to use this option also with *--tab-file*. It's possible to specify source (device) or target (mountpoint) to filter mount table. The option *--verbose* forces *findmnt* to print more details.
*--verbose*::
-Force findmnt to print more information (*--verify* only for now).
+Force *findmnt* to print more information (*--verify* only for now).
*--vfs-all*::
When used with *VFS-OPTIONS* column, print all VFS (fs-independent) flags. This option is designed for auditing purposes to list also default VFS kernel mount options which are normally not listed.
== ENVIRONMENT
+
*LIBMOUNT_FSTAB*=<path>::
overrides the default location of the fstab file
+
*LIBMOUNT_MTAB*=<path>::
overrides the default location of the mtab file
-LIBMOUNT_DEBUG=all::
+*LIBMOUNT_DEBUG*=all::
enables libmount debug output
-LIBSMARTCOLS_DEBUG=all::
+*LIBSMARTCOLS_DEBUG*=all::
enables libsmartcols debug output
-LIBSMARTCOLS_DEBUG_PADDING=on::
+*LIBSMARTCOLS_DEBUG_PADDING*=on::
use visible padding characters.
== EXAMPLES
The original *hardlink* implementation uses the option *-f* to force hardlinks creation between filesystem. This very rarely usable feature is no more supported by the current hardlink.
-*hardlink* assumes that the trees it operates on do not change during operation. If a tree does change, the result is undefined and potentially dangerous. For example, if a regular file is replaced by a device, hardlink may start reading from the device. If a component of a path is replaced by a symbolic link or file permissions change, security may be compromised. Do not run hardlink on a changing tree or on a tree controlled by another user.
+*hardlink* assumes that the trees it operates on do not change during operation. If a tree does change, the result is undefined and potentially dangerous. For example, if a regular file is replaced by a device, *hardlink* may start reading from the device. If a component of a path is replaced by a symbolic link or file permissions change, security may be compromised. Do not run *hardlink* on a changing tree or on a tree controlled by another user.
== AUTHOR
The command *kill* sends the specified _signal_ to the specified processes or process groups.
-If no signal is specified, the TERM signal is sent. The default action for this signal is to terminate the process. This signal should be used in preference to the KILL signal (number 9), since a process may install a handler for the TERM signal in order to perform clean-up steps before terminating in an orderly fashion. If a process does not terminate after a TERM signal has been sent, then the KILL signal may be used; be aware that the latter signal cannot be caught, and so does not give the target process the opportunity to perform any clean-up before terminating.
+If no signal is specified, the *TERM* signal is sent. The default action for this signal is to terminate the process. This signal should be used in preference to the *KILL* signal (number 9), since a process may install a handler for the TERM signal in order to perform clean-up steps before terminating in an orderly fashion. If a process does not terminate after a *TERM* signal has been sent, then the *KILL* signal may be used; be aware that the latter signal cannot be caught, and so does not give the target process the opportunity to perform any clean-up before terminating.
Most modern shells have a builtin *kill* command, with a usage rather similar to that of the command described here. The *--all*, *--pid*, and *--queue* options, and the possibility to specify processes by command name, are local extensions.
+
The *--timeout* option can be specified multiple times: the signals are sent sequentially with the specified timeouts. The *--timeout* option can be combined with the *--queue* option.
+
-As an example, the following command sends the signals QUIT, TERM and KILL in sequence and waits for 1000 milliseconds between sending the signals:
+As an example, the following command sends the signals *QUIT*, *TERM* and *KILL* in sequence and waits for 1000 milliseconds between sending the signals:
+
....
kill --verbose --timeout 1000 TERM --timeout 1000 KILL \
== ENVIRONMENT
-LSBLK_DEBUG=all::
+*LSBLK_DEBUG*=all::
enables *lsblk* debug output.
-LIBBLKID_DEBUG=all::
+*LIBBLKID_DEBUG*=all::
enables *libblkid* debug output.
-LIBMOUNT_DEBUG=all::
+*LIBMOUNT_DEBUG*=all::
enables *libmount* debug output.
-LIBSMARTCOLS_DEBUG=all::
+*LIBSMARTCOLS_DEBUG*=all::
enables *libsmartcols* debug output.
-LIBSMARTCOLS_DEBUG_PADDING=on::
+*LIBSMARTCOLS_DEBUG_PADDING*=on::
use visible padding characters.
== NOTES
For partitions, some information (e.g., queue attributes) is inherited from the parent device.
-The *lsblk* command needs to be able to look up each block device by major:minor numbers, which is done by using _/sys/dev/block_. This sysfs block directory appeared in kernel 2.6.27 (October 2008). In case of problems with a new enough kernel, check that CONFIG_SYSFS was enabled at the time of the kernel build.
+The *lsblk* command needs to be able to look up each block device by major:minor numbers, which is done by using _/sys/dev/block_. This sysfs block directory appeared in kernel 2.6.27 (October 2008). In case of problems with a new enough kernel, check that *CONFIG_SYSFS* was enabled at the time of the kernel build.
== AUTHORS
== OPTIONS
*-d*, *--debug*::
-Run uuidd in debugging mode. This prevents uuidd from running as a daemon.
+Run *uuidd* in debugging mode. This prevents *uuidd* from running as a daemon.
*-F*, *--no-fork*::
Do not daemonize using a double-fork.
== ENVIRONMENT
-WHEREIS_DEBUG=all::
+*WHEREIS_DEBUG*=all::
enables debug output.
== EXAMPLES
When used without any options, *wipefs* lists all visible filesystems and the offsets of their basic signatures. The default output is subject to change. So whenever possible, you should avoid using default outputs in your scripts. Always explicitly define expected columns by using *--output* _columns-list_ in environments where a stable output is required.
-*wipefs* calls the BLKRRPART ioctl when it has erased a partition-table signature to inform the kernel about the change. The ioctl is called as the last step and when all specified signatures from all specified devices are already erased. This feature can be used to wipe content on partitions devices as well as partition table on a disk device, for example by *wipefs -a /dev/sdc1 /dev/sdc2 /dev/sdc*.
+*wipefs* calls the *BLKRRPART* ioctl when it has erased a partition-table signature to inform the kernel about the change. The ioctl is called as the last step and when all specified signatures from all specified devices are already erased. This feature can be used to wipe content on partitions devices as well as partition table on a disk device, for example by *wipefs -a /dev/sdc1 /dev/sdc2 /dev/sdc*.
Note that some filesystems and some partition tables store more magic strings on the device (e.g., FAT, ZFS, GPT). The *wipefs* command (since v2.31) lists all the offset where a magic strings have been detected.
The _offset_ and _length_ arguments may be followed by the multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has the same meaning as "KiB") or the suffixes KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.
*-f*, *--force*::
-Disable all checking. Since v2.36 the block device is open in exclusive mode (O_EXCL) by default to avoid collision with mounted filesystem or another kernel subsystem. The *--force* option disables the exclusive access mode.
+Disable all checking. Since v2.36 the block device is open in exclusive mode (*O_EXCL*) by default to avoid collision with mounted filesystem or another kernel subsystem. The *--force* option disables the exclusive access mode.
*-o*, *--offset* _offset_::
Byte offset into the device from which to start discarding. The provided value must be aligned to the device sector size. The default value is zero.
This option controls locking of the hardware eject button. When enabled, the drive will not be ejected when the button is pressed. This is useful when you are carrying a laptop in a bag or case and don't want it to eject if the button is inadvertently pressed.
*-M*, *--no-partitions-unmount*::
-The option tells eject to not try to unmount other partitions on partitioned devices. If another partition is still mounted, the program will not attempt to eject the media. It will attempt to unmount only the device or mountpoint given on the command line.
+The option tells *eject* to not try to unmount other partitions on partitioned devices. If another partition is still mounted, the program will not attempt to eject the media. It will attempt to unmount only the device or mountpoint given on the command line.
*-m*, *--no-unmount*::
The option tells eject to not try to unmount at all. If this option is not specified then *eject* opens the device with *O_EXCL* flag to be sure that the device is not used (since v2.35).
== DESCRIPTION
-*fallocate* is used to manipulate the allocated disk space for a file, either to deallocate or preallocate it. For filesystems which support the fallocate system call, preallocation is done quickly by allocating blocks and marking them as uninitialized, requiring no IO to the data blocks. This is much faster than creating a file by filling it with zeroes.
+*fallocate* is used to manipulate the allocated disk space for a file, either to deallocate or preallocate it. For filesystems which support the *fallocate*(2) system call, preallocation is done quickly by allocating blocks and marking them as uninitialized, requiring no IO to the data blocks. This is much faster than creating a file by filling it with zeroes.
The exit status returned by *fallocate* is 0 on success and 1 on failure.
+
Available since Linux 3.15 for ext4 (only for extent-based files) and XFS.
+
-A filesystem may place limitations on the granularity of the operation, in order to ensure efficient implementation. Typically, offset and len must be a multiple of the filesystem logical block size, which varies according to the filesystem type and configuration. If a filesystem has such a requirement, the operation will fail with the error EINVAL if this requirement is violated.
+A filesystem may place limitations on the granularity of the operation, in order to ensure efficient implementation. Typically, _offset_ and _length_ must be a multiple of the filesystem logical block size, which varies according to the filesystem type and configuration. If a filesystem has such a requirement, the operation will fail with the error *EINVAL* if this requirement is violated.
*-d*, *--dig-holes*::
Detect and dig holes. This makes the file sparse in-place, without using extra disk space. The minimum size of the hole depends on filesystem I/O block size (usually 4096 bytes). Also, when using this option, *--keep-size* is implied. If no range is specified by *--offset* and *--length*, then the entire file is analyzed for holes.
Note that "shell> " in examples is a command line prompt.
shell1> flock /tmp -c cat; shell2> flock -w .007 /tmp -c echo; /bin/echo $?::
-Set exclusive lock to directory /tmp and the second command will fail.
+Set exclusive lock to directory _/tmp_ and the second command will fail.
shell1> flock -s /tmp -c cat; shell2> flock -s -w .007 /tmp -c echo; /bin/echo $?::
-Set shared lock to directory /tmp and the second command will not fail. Notice that attempting to get exclusive lock with second command would fail.
+Set shared lock to directory _/tmp_ and the second command will not fail. Notice that attempting to get exclusive lock with second command would fail.
shell> flock -x local-lock-file echo 'a b c'::
Grab the exclusive lock "local-lock-file" before running echo with 'a b c'.
== OPTIONS
*-f*, *--freeze*::
-This option requests the specified a filesystem to be frozen from new modifications. When this is selected, all ongoing transactions in the filesystem are allowed to complete, new write system calls are halted, other calls which modify the filesystem are halted, and all dirty data, metadata, and log information are written to disk. Any process attempting to write to the frozen filesystem will block waiting for the filesystem to be unfrozen.
+This option requests the specified a filesystem to be frozen from new modifications. When this is selected, all ongoing transactions in the filesystem are allowed to complete, new *write*(2) system calls are halted, other calls which modify the filesystem are halted, and all dirty data, metadata, and log information are written to disk. Any process attempting to write to the frozen filesystem will block waiting for the filesystem to be unfrozen.
+
Note that even after freezing, the on-disk filesystem can contain information on files that are still in the process of unlinking. These files will not be unlinked until the filesystem is unfrozen or a clean mount of the snapshot is complete.
*--listed-in /etc/fstab:/proc/self/mountinfo*.
*-m, --minimum* _minimum-size_::
-Minimum contiguous free range to discard, in bytes. (This value is internally rounded up to a multiple of the filesystem block size.) Free ranges smaller than this will be ignored and fstrim will adjust the minimum if it's smaller than the device's minimum, and report that (fstrim_range.minlen) back to userspace. By increasing this value, the fstrim operation will complete more quickly for filesystems with badly fragmented freespace, although not all blocks will be discarded. The default value is zero, discarding every free block.
+Minimum contiguous free range to discard, in bytes. (This value is internally rounded up to a multiple of the filesystem block size.) Free ranges smaller than this will be ignored and *fstrim* will adjust the minimum if it's smaller than the device's minimum, and report that (fstrim_range.minlen) back to userspace. By increasing this value, the *fstrim* operation will complete more quickly for filesystems with badly fragmented freespace, although not all blocks will be discarded. The default value is zero, discarding every free block.
*-v, --verbose*::
Verbose execution. With this option *fstrim* will output the number of bytes passed from the filesystem down the block stack to the device for potential discard. This number is a maximum discard amount from the storage device's perspective, because _FITRIM_ ioctl called repeated will keep sending the same sectors for discard repeatedly.
+
The System Clock must be kept in the UTC timescale for date-time applications to work correctly in conjunction with the timezone configured for the system. If the Hardware Clock is kept in local time then the time read from it must be shifted to the UTC timescale before using it to set the System Clock. The *--hctosys* function does this based upon the information in the _{ADJTIME_PATH}_ file or the command line arguments *--localtime* and *--utc*. Note: no daylight saving adjustment is made. See the discussion below, under *LOCAL vs UTC*.
+
-The kernel also keeps a timezone value, the *--hctosys* function sets it to the timezone configured for the system. The system timezone is configured by the TZ environment variable or the _/etc/localtime_ file, as *tzset*(3) would interpret them. The obsolete _tz_dsttime_ field of the kernel's timezone value is set to zero. (For details on what this field used to mean, see *settimeofday*(2).)
+The kernel also keeps a timezone value, the *--hctosys* function sets it to the timezone configured for the system. The system timezone is configured by the *TZ* environment variable or the _/etc/localtime_ file, as *tzset*(3) would interpret them. The obsolete _tz_dsttime_ field of the kernel's timezone value is set to zero. (For details on what this field used to mean, see *settimeofday*(2).)
+
When used in a startup script, making the *--hctosys* function the first caller of *settimeofday*(2) from boot, it will set the NTP '11 minute mode' timescale via the _persistent_clock_is_local_ kernel variable. If the Hardware Clock's timescale configuration is changed then a reboot is required to inform the kernel. See the discussion below, under *Automatic Hardware Clock Synchronization by the Kernel*.
+
It's possible to create more independent loop devices for the same backing file. *This setup may be dangerous, can cause data loss, corruption and overwrites.* Use *--nooverlap* with *--find* during setup to avoid this problem.
-The loop device setup is not an atomic operation when used with *--find*, and *losetup* does not protect this operation by any lock. The number of attempts is internally restricted to a maximum of 16. It is recommended to use for example flock1 to avoid a collision in heavily parallel use cases.
+The loop device setup is not an atomic operation when used with *--find*, and *losetup* does not protect this operation by any lock. The number of attempts is internally restricted to a maximum of 16. It is recommended to use for example *flock*(1) to avoid a collision in heavily parallel use cases.
== OPTIONS
The _size_ and _offset_ arguments may be followed by the multiplicative suffixes KiB (=1024), MiB (=1024*1024), and so on for GiB, TiB, PiB, EiB, ZiB and YiB (the "iB" is optional, e.g., "K" has the same meaning as "KiB") or the suffixes KB (=1000), MB (=1000*1000), and so on for GB, TB, PB, EB, ZB and YB.
*-a*, *--all*::
-Show the status of all loop devices. Note that not all information is accessible for non-root users. See also *--list*. The old output format (as printed without *--list)* is deprecated.
+Show the status of all loop devices. Note that not all information is accessible for non-root users. See also *--list*. The old output format (as printed without *--list*) is deprecated.
*-d*, *--detach* _loopdev_...::
Detach the file or device associated with the specified loop device(s). Note that since Linux v3.7 kernel uses "lazy device destruction". The detach operation does not return *EBUSY* error anymore if device is actively used by system, but it is marked by autoclear flag and destroyed later.
== ENVIRONMENT
-LOOPDEV_DEBUG=all::
+*LOOPDEV_DEBUG*=all::
enables debug output.
== FILES
+
*mount -o remount,rw /dir*
+
-After this call, mount reads _fstab_ and merges these options with the options from the command line (*-o*). If no mountpoint is found in _fstab_, then a remount with unspecified source is allowed.
+After this call, *mount* reads _fstab_ and merges these options with the options from the command line (*-o*). If no mountpoint is found in _fstab_, then a remount with unspecified source is allowed.
+
*mount* allows the use of *--all* to remount all already mounted filesystems which match a specified filter (*-O* and *-t*). For example:
+
== ENVIRONMENT
+
*LIBMOUNT_FSTAB*=<path>::
overrides the default location of the _fstab_ file (ignored for suid)
+
*LIBMOUNT_MTAB*=<path>::
overrides the default location of the _mtab_ file (ignored for suid)
-LIBMOUNT_DEBUG=all::
+*LIBMOUNT_DEBUG*=all::
enables libmount debug output
-LIBBLKID_DEBUG=all::
+*LIBBLKID_DEBUG*=all::
enables libblkid debug output
-LOOPDEV_DEBUG=all::
+*LOOPDEV_DEBUG*=all::
enables loop device setup debug output
== FILES
== ENVIRONMENT
-LIBMOUNT_DEBUG=all::
+*LIBMOUNT_DEBUG*=all::
enables libmount debug output.
== NOTES
== NOTES
-The *prlimit* system call is supported since Linux 2.6.36, older kernels will break this program.
+The *prlimit*(2) system call is supported since Linux 2.6.36, older kernels will break this program.
== EXAMPLES
Set for the current process both the soft and ceiling values for the number of processes to unlimited.
*prlimit --cpu=10 sort -u hugefile*::
-Set both the soft and hard CPU time limit to ten seconds and run 'sort'.
+Set both the soft and hard CPU time limit to ten seconds and run *sort*(1).
== AUTHORS
Use the partition that has the specified _label_. (For this, access to _/proc/partitions_ is needed.)
*-o*, *--options* _opts_::
-Specify swap options by an fstab-compatible comma-separated string. For example:
+Specify swap options by an __fstab__-compatible comma-separated string. For example:
+
*swapon -o pri=1,discard=pages,nofail /dev/sda2*
+
system has insufficient memory to stop swapping (OOM)
*4*::
-swapoff syscall failed for another reason
+*swapoff*(2) syscall failed for another reason
*8*::
non-swapoff syscall system error (out of memory, ...)
== ENVIRONMENT
-LIBMOUNT_DEBUG=all::
+*LIBMOUNT_DEBUG*=all::
enables *libmount* debug output.
-LIBBLKID_DEBUG=all::
+*LIBBLKID_DEBUG*=all::
enables *libblkid* debug output.
== FILES
=== Suspend
-*swapon* automatically detects and rewrites a swap space signature with old software suspend data (e.g., S1SUSPEND, S2SUSPEND, ...). The problem is that if we don't do it, then we get data corruption the next time an attempt at unsuspending is made.
+*swapon* automatically detects and rewrites a swap space signature with old software suspend data (e.g., *S1SUSPEND*, *S2SUSPEND*, ...). The problem is that if we don't do it, then we get data corruption the next time an attempt at unsuspending is made.
== HISTORY
*-f*, *--force*::
Force an unmount (in case of an unreachable NFS system).
+
-Note that this option does not guarantee that umount command does not hang. It's strongly recommended to use absolute paths without symlinks to avoid unwanted readlink and stat system calls on unreachable NFS in *umount*.
+Note that this option does not guarantee that umount command does not hang. It's strongly recommended to use absolute paths without symlinks to avoid unwanted *readlink*(2) and *stat*(2) system calls on unreachable NFS in *umount*.
*-i*, *--internal-only*::
Do not call the **/sbin/umount.**__filesystem__ helper even if it exists. By default such a helper program is called if it exists.
*-l*, *--lazy*::
Lazy unmount. Detach the filesystem from the file hierarchy now, and clean up all references to this filesystem as soon as it is not busy anymore.
+
-A system reboot would be expected in near future if you're going to use this option for network filesystem or local filesystem with submounts. The recommended use-case for *umount -l* is to prevent hangs on shutdown due to an unreachable network share where a normal umount will hang due to a downed server or a network partition. Remounts of the share will not be possible.
+A system reboot would be expected in near future if you're going to use this option for network filesystem or local filesystem with submounts. The recommended use-case for *umount -l* is to prevent hangs on shutdown due to an unreachable network share where a normal *umount* will hang due to a downed server or a network partition. Remounts of the share will not be possible.
*-N*, *--namespace* _ns_::
-Perform umount in the mount namespace specified by _ns_. _ns_ is either PID of process running in that namespace or special file representing that namespace.
+Perform *umount* in the mount namespace specified by _ns_. _ns_ is either PID of process running in that namespace or special file representing that namespace.
+
*umount* switches to the namespace when it reads _/etc/fstab_, writes _/etc/mtab_ (or writes to _/run/mount_) and calls *umount*(2) system call, otherwise it runs in the original namespace. It means that the target mount namespace does not have to contain any libraries or other requirements necessary to execute *umount*(2) command.
+
Normally, only the superuser can umount filesystems. However, when _fstab_ contains the *user* option on a line, anybody can umount the corresponding filesystem. For more details see *mount*(8) man page.
-Since version 2.34 the *umount* command can be used to perform umount operation also for fuse filesystems if kernel mount table contains user's ID. In this case fstab *user=* mount option is not required.
+Since version 2.34 the *umount* command can be used to perform umount operation also for fuse filesystems if kernel mount table contains user's ID. In this case _fstab_ *user=* mount option is not required.
Since version 2.35 *umount* command does not exit when user permissions are inadequate by internal libmount security rules. It drops suid permissions and continue as regular non-root user. This can be used to support use-cases where root permissions are not necessary (e.g., fuse filesystems, user namespaces, etc).
== ENVIRONMENT
-overrides the default location of the fstab file (ignored for suid)
+
*LIBMOUNT_FSTAB*=<path>::
+overrides the default location of the _fstab_ file (ignored for *suid*)
-overrides the default location of the mtab file (ignored for suid)
+
*LIBMOUNT_MTAB*=<path>::
+overrides the default location of the _mtab_ file (ignored for *suid*)
-LIBMOUNT_DEBUG=all::
+*LIBMOUNT_DEBUG*=all::
enables *libmount* debug output
== FILES
*Be careful!* Do not forget that the typescript may contains arbitrary commands. It is recommended to use *"scriptreplay --stream in --log-in typescript"* (or with *--log-io* instead of *--log-in*) to verify the typescript before it is executed by *scriptlive*.
-The timing information is what script1 outputs to file specified by *--log-timing*. The typescript has to contain stdin information and it is what script1 outputs to file specified by *--log-in* or *--log-io*.
+The timing information is what *script*(1) outputs to file specified by *--log-timing*. The typescript has to contain stdin information and it is what script1 outputs to file specified by *--log-in* or *--log-io*.
== OPTIONS
== HISTORY
-The column command appeared in 4.3BSD-Reno.
+The *column* command appeared in 4.3BSD-Reno.
== BUGS
An asterisk (*) may not be used as a field width or precision.
2.::
-A byte count or field precision _is_ required for each *s* conversion character (unlike the fprintf3 default which prints the entire string if the precision is unspecified).
+A byte count or field precision _is_ required for each *s* conversion character (unlike the *fprintf*(3) default which prints the entire string if the precision is unspecified).
3.::
The conversion characters *h*, *l*, *n*, *p*, and *q* are not supported.
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