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diff --git a/man2/mount.2 b/man2/mount.2 deleted file mode 100644 index f2511c4..0000000 --- a/man2/mount.2 +++ /dev/null @@ -1,971 +0,0 @@ -.\" Copyright (C) 1993 Rickard E. Faith <faith@cs.unc.edu> -.\" and Copyright (C) 1994 Andries E. Brouwer <aeb@cwi.nl> -.\" and Copyright (C) 2002, 2005, 2016 Michael Kerrisk <mtk.manpages@gmail.com> -.\" -.\" SPDX-License-Identifier: Linux-man-pages-copyleft -.\" -.\" Modified 1996-11-04 by Eric S. Raymond <esr@thyrsus.com> -.\" Modified 2001-10-13 by Michael Kerrisk <mtk.manpages@gmail.com> -.\" Added note on historical behavior of MS_NOSUID -.\" Modified 2002-05-16 by Michael Kerrisk <mtk.manpages@gmail.com> -.\" Extensive changes and additions -.\" Modified 2002-05-27 by aeb -.\" Modified 2002-06-11 by Michael Kerrisk <mtk.manpages@gmail.com> -.\" Enhanced descriptions of MS_MOVE, MS_BIND, and MS_REMOUNT -.\" Modified 2004-06-17 by Michael Kerrisk <mtk.manpages@gmail.com> -.\" 2005-05-18, mtk, Added MNT_EXPIRE, plus a few other tidy-ups. -.\" 2008-10-06, mtk: move umount*() material into separate umount.2 page. -.\" 2008-10-06, mtk: Add discussion of namespaces. -.\" -.TH mount 2 2023-10-31 "Linux man-pages 6.7" -.SH NAME -mount \- mount filesystem -.SH LIBRARY -Standard C library -.RI ( libc ", " \-lc ) -.SH SYNOPSIS -.nf -.B "#include <sys/mount.h>" -.P -.BI "int mount(const char *" source ", const char *" target , -.BI " const char *" filesystemtype ", unsigned long " mountflags , -.BI " const void *_Nullable " data ); -.fi -.SH DESCRIPTION -.BR mount () -attaches the filesystem specified by -.I source -(which is often a pathname referring to a device, -but can also be the pathname of a directory or file, -or a dummy string) to the location (a directory or file) -specified by the pathname in -.IR target . -.P -Appropriate privilege (Linux: the -.B CAP_SYS_ADMIN -capability) is required to mount filesystems. -.P -Values for the -.I filesystemtype -argument supported by the kernel are listed in -.I /proc/filesystems -(e.g., "btrfs", "ext4", "jfs", "xfs", "vfat", "fuse", -"tmpfs", "cgroup", "proc", "mqueue", "nfs", "cifs", "iso9660"). -Further types may become available when the appropriate modules -are loaded. -.P -The -.I data -argument is interpreted by the different filesystems. -Typically it is a string of comma-separated options -understood by this filesystem. -See -.BR mount (8) -for details of the options available for each filesystem type. -This argument may be specified as NULL, if there are no options. -.P -A call to -.BR mount () -performs one of a number of general types of operation, -depending on the bits specified in -.IR mountflags . -The choice of which operation to perform is determined by -testing the bits set in -.IR mountflags , -with the tests being conducted in the order listed here: -.IP \[bu] 3 -Remount an existing mount: -.I mountflags -includes -.BR MS_REMOUNT . -.IP \[bu] -Create a bind mount: -.I mountflags -includes -.BR MS_BIND . -.IP \[bu] -Change the propagation type of an existing mount: -.I mountflags -includes one of -.BR MS_SHARED , -.BR MS_PRIVATE , -.BR MS_SLAVE , -or -.BR MS_UNBINDABLE . -.IP \[bu] -Move an existing mount to a new location: -.I mountflags -includes -.BR MS_MOVE . -.IP \[bu] -Create a new mount: -.I mountflags -includes none of the above flags. -.P -Each of these operations is detailed later in this page. -Further flags may be specified in -.I mountflags -to modify the behavior of -.BR mount (), -as described below. -.\" -.SS Additional mount flags -The list below describes the additional flags that can be specified in -.IR mountflags . -Note that some operation types ignore some or all of these flags, -as described later in this page. -.\" -.\" FIXME 2.6.25 Added MS_I_VERSION, which needs to be documented. -.\" commit 7a224228ed79d587ece2304869000aad1b8e97dd -.\" (This is a per-superblock flag) -.\" -.TP -.BR MS_DIRSYNC " (since Linux 2.5.19)" -Make directory changes on this filesystem synchronous. -(This property can be obtained for individual directories -or subtrees using -.BR chattr (1).) -.TP -.BR MS_LAZYTIME " (since Linux 4.0)" -.\" commit 0ae45f63d4ef8d8eeec49c7d8b44a1775fff13e8 -.\" commit fe032c422c5ba562ba9c2d316f55e258e03259c6 -.\" commit a26f49926da938f47561f386be56a83dd37a496d -Reduce on-disk updates of inode timestamps (atime, mtime, ctime) -by maintaining these changes only in memory. -The on-disk timestamps are updated only when: -.RS -.IP \[bu] 3 -the inode needs to be updated for some change unrelated to file timestamps; -.IP \[bu] -the application employs -.BR fsync (2), -.BR syncfs (2), -or -.BR sync (2); -.IP \[bu] -an undeleted inode is evicted from memory; or -.IP \[bu] -more than 24 hours have passed since the inode was written to disk. -.RE -.IP -This mount option significantly reduces writes -needed to update the inode's timestamps, especially mtime and atime. -However, in the event of a system crash, the atime and mtime fields -on disk might be out of date by up to 24 hours. -.IP -Examples of workloads where this option could be of significant benefit -include frequent random writes to preallocated files, -as well as cases where the -.B MS_STRICTATIME -mount option is also enabled. -(The advantage of combining -.B MS_STRICTATIME -and -.B MS_LAZYTIME -is that -.BR stat (2) -will return the correctly updated atime, but the atime updates -will be flushed to disk only in the cases listed above.) -.TP -.B MS_MANDLOCK -Permit mandatory locking on files in this filesystem. -(Mandatory locking must still be enabled on a per-file basis, -as described in -.BR fcntl (2).) -Since Linux 4.5, -.\" commit 95ace75414f312f9a7b93d873f386987b92a5301 -this mount option requires the -.B CAP_SYS_ADMIN -capability and a kernel configured with the -.B CONFIG_MANDATORY_FILE_LOCKING -option. -Mandatory locking has been fully deprecated in Linux 5.15, so -this flag should be considered deprecated. -.TP -.B MS_NOATIME -Do not update access times for (all types of) files on this filesystem. -.TP -.B MS_NODEV -Do not allow access to devices (special files) on this filesystem. -.TP -.B MS_NODIRATIME -Do not update access times for directories on this filesystem. -This flag provides a subset of the functionality provided by -.BR MS_NOATIME ; -that is, -.B MS_NOATIME -implies -.BR MS_NODIRATIME . -.TP -.B MS_NOEXEC -Do not allow programs to be executed from this filesystem. -.\" (Possibly useful for a filesystem that contains non-Linux executables. -.\" Often used as a security feature, e.g., to make sure that restricted -.\" users cannot execute files uploaded using ftp or so.) -.TP -.B MS_NOSUID -Do not honor set-user-ID and set-group-ID bits or file capabilities -when executing programs from this filesystem. -In addition, SELinux domain -transitions require the permission -.IR nosuid_transition , -which in turn needs -also the policy capability -.IR nnp_nosuid_transition . -.\" (This is a security feature to prevent users executing set-user-ID and -.\" set-group-ID programs from removable disk devices.) -.TP -.B MS_RDONLY -Mount filesystem read-only. -.TP -.BR MS_REC " (since Linux 2.4.11)" -Used in conjunction with -.B MS_BIND -to create a recursive bind mount, -and in conjunction with the propagation type flags to recursively change -the propagation type of all of the mounts in a subtree. -See below for further details. -.TP -.BR MS_RELATIME " (since Linux 2.6.20)" -When a file on this filesystem is accessed, -update the file's last access time (atime) only if the current value -of atime is less than or equal to the file's last modification time (mtime) -or last status change time (ctime). -This option is useful for programs, such as -.BR mutt (1), -that need to know when a file has been read since it was last modified. -Since Linux 2.6.30, the kernel defaults to the behavior provided -by this flag (unless -.B MS_NOATIME -was specified), and the -.B MS_STRICTATIME -flag 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. -.\" Matthew Garrett notes in the patch that added this behavior -.\" that this lets utilities such as tmpreaper (which deletes -.\" files based on last access time) work correctly. -.TP -.BR MS_SILENT " (since Linux 2.6.17)" -Suppress the display of certain -.RI ( printk ()) -warning messages in the kernel log. -This flag supersedes the misnamed and obsolete -.B MS_VERBOSE -flag (available since Linux 2.4.12), which has the same meaning. -.TP -.BR MS_STRICTATIME " (since Linux 2.6.30)" -Always update the last access time (atime) when files on this -filesystem are accessed. -(This was the default behavior before Linux 2.6.30.) -Specifying this flag overrides the effect of setting the -.B MS_NOATIME -and -.B MS_RELATIME -flags. -.TP -.B MS_SYNCHRONOUS -Make writes on this filesystem synchronous (as though -the -.B O_SYNC -flag to -.BR open (2) -was specified for all file opens to this filesystem). -.TP -.BR MS_NOSYMFOLLOW " (since Linux 5.10)" -.\" dab741e0e02bd3c4f5e2e97be74b39df2523fc6e -Do not follow symbolic links when resolving paths. -Symbolic links can still be created, -and -.BR readlink (1), -.BR readlink (2), -.BR realpath (1), -and -.BR realpath (3) -all still work properly. -.P -From Linux 2.4 onward, some of the above flags are -settable on a per-mount basis, -while others apply to the superblock of the mounted filesystem, -meaning that all mounts of the same filesystem share those flags. -(Previously, all of the flags were per-superblock.) -.P -The per-mount-point flags are as follows: -.IP \[bu] 3 -Since Linux 2.4: -.BR MS_NODEV ", " MS_NOEXEC ", and " MS_NOSUID -flags are settable on a per-mount-point basis. -.IP \[bu] -Additionally, since Linux 2.6.16: -.B MS_NOATIME -and -.BR MS_NODIRATIME . -.IP \[bu] -Additionally, since Linux 2.6.20: -.BR MS_RELATIME . -.P -The following flags are per-superblock: -.BR MS_DIRSYNC , -.BR MS_LAZYTIME , -.BR MS_MANDLOCK , -.BR MS_SILENT , -and -.BR MS_SYNCHRONOUS . -.\" And MS_I_VERSION? -The initial settings of these flags are determined on the first -mount of the filesystem, and will be shared by all subsequent mounts -of the same filesystem. -Subsequently, the settings of the flags can be changed -via a remount operation (see below). -Such changes will be visible via all mounts associated -with the filesystem. -.P -Since Linux 2.6.16, -.B MS_RDONLY -can be set or cleared on a per-mount-point basis as well as on -the underlying filesystem superblock. -The mounted filesystem will be writable only if neither the filesystem -nor the mountpoint are flagged as read-only. -.\" -.SS Remounting an existing mount -An existing mount may be remounted by specifying -.B MS_REMOUNT -in -.IR mountflags . -This allows you to change the -.I mountflags -and -.I data -of an existing mount without having to unmount and remount the filesystem. -.I target -should be the same value specified in the initial -.BR mount () -call. -.P -The -.I source -and -.I filesystemtype -arguments are ignored. -.P -The -.I mountflags -and -.I data -arguments should match the values used in the original -.BR mount () -call, except for those parameters that are being deliberately changed. -.P -The following -.I mountflags -can be changed: -.BR MS_LAZYTIME , -.\" FIXME -.\" MS_LAZYTIME seems to be available only on a few filesystems, -.\" and on ext4, it seems (from experiment that this flag -.\" can only be enabled (but not disabled) on a remount. -.\" The following code in ext4_remount() (kernel 4.17) seems to -.\" confirm this: -.\" -.\" if (*flags & SB_LAZYTIME) -.\" sb->s_flags |= SB_LAZYTIME; -.BR MS_MANDLOCK , -.BR MS_NOATIME , -.BR MS_NODEV , -.BR MS_NODIRATIME , -.BR MS_NOEXEC , -.BR MS_NOSUID , -.BR MS_RELATIME , -.BR MS_RDONLY , -.B MS_STRICTATIME -(whose effect is to clear the -.B MS_NOATIME -and -.B MS_RELATIME -flags), -and -.BR MS_SYNCHRONOUS . -Attempts to change the setting of the -.\" See the definition of MS_RMT_MASK in include/uapi/linux/fs.h, -.\" which excludes MS_DIRSYNC and MS_SILENT, although SB_DIRSYNC -.\" and SB_SILENT are split out as per-superblock flags in do_mount() -.\" (Linux 4.17 source code) -.B MS_DIRSYNC -and -.B MS_SILENT -flags during a remount are silently ignored. -Note that changes to per-superblock flags are visible via -all mounts of the associated filesystem -(because the per-superblock flags are shared by all mounts). -.P -Since Linux 3.17, -.\" commit ffbc6f0ead47fa5a1dc9642b0331cb75c20a640e -if none of -.BR MS_NOATIME , -.BR MS_NODIRATIME , -.BR MS_RELATIME , -or -.B MS_STRICTATIME -is specified in -.IR mountflags , -then the remount operation preserves the existing values of these flags -(rather than defaulting to -.BR MS_RELATIME ). -.P -Since Linux 2.6.26, the -.B MS_REMOUNT -flag can be used with -.B MS_BIND -to modify only the per-mount-point flags. -.\" See https://lwn.net/Articles/281157/ -This is particularly useful for setting or clearing the "read-only" -flag on a mount without changing the underlying filesystem. -Specifying -.I mountflags -as: -.P -.in +4n -.EX -MS_REMOUNT | MS_BIND | MS_RDONLY -.EE -.in -.P -will make access through this mountpoint read-only, without affecting -other mounts. -.\" -.SS Creating a bind mount -If -.I mountflags -includes -.B MS_BIND -(available since Linux 2.4), -.\" since Linux 2.4.0-test9 -then perform a bind mount. -A bind mount makes a file or a directory subtree visible at -another point within the single directory hierarchy. -Bind mounts may cross filesystem boundaries and span -.BR chroot (2) -jails. -.P -The -.I filesystemtype -and -.I data -arguments are ignored. -.P -The remaining bits (other than -.BR MS_REC , -described below) in the -.I mountflags -argument are also ignored. -(The bind mount has the same mount options as -the underlying mount.) -However, see the discussion of remounting above, -for a method of making an existing bind mount read-only. -.P -By default, when a directory is bind mounted, -only that directory is mounted; -if there are any submounts under the directory tree, -they are not bind mounted. -If the -.B MS_REC -flag is also specified, then a recursive bind mount operation is performed: -all submounts under the -.I source -subtree (other than unbindable mounts) -are also bind mounted at the corresponding location in the -.I target -subtree. -.\" -.SS Changing the propagation type of an existing mount -If -.I mountflags -includes one of -.BR MS_SHARED , -.BR MS_PRIVATE , -.BR MS_SLAVE , -or -.B MS_UNBINDABLE -(all available since Linux 2.6.15), -then the propagation type of an existing mount is changed. -If more than one of these flags is specified, an error results. -.P -The only other flags that can be specified while changing -the propagation type are -.B MS_REC -(described below) and -.B MS_SILENT -(which is ignored). -.P -The -.IR source , -.IR filesystemtype , -and -.I data -arguments are ignored. -.P -The meanings of the propagation type flags are as follows: -.TP -.B MS_SHARED -Make this mount shared. -Mount and unmount events immediately under this mount will propagate -to the other mounts that are members of this mount's peer group. -Propagation here means that the same mount or unmount will automatically -occur under all of the other mounts in the peer group. -Conversely, mount and unmount events that take place under -peer mounts will propagate to this mount. -.TP -.B MS_PRIVATE -Make this mount private. -Mount and unmount events do not propagate into or out of this mount. -.TP -.B MS_SLAVE -If this is a shared mount that is a member of a peer group -that contains other members, convert it to a slave mount. -If this is a shared mount that is a member of a peer group -that contains no other members, convert it to a private mount. -Otherwise, the propagation type of the mount is left unchanged. -.IP -When a mount is a slave, -mount and unmount events propagate into this mount from -the (master) shared peer group of which it was formerly a member. -Mount and unmount events under this mount do not propagate to any peer. -.IP -A mount can be the slave of another peer group -while at the same time sharing mount and unmount events -with a peer group of which it is a member. -.TP -.B MS_UNBINDABLE -Make this mount unbindable. -This is like a private mount, -and in addition this mount can't be bind mounted. -When a recursive bind mount -.RB ( mount () -with the -.B MS_BIND -and -.B MS_REC -flags) is performed on a directory subtree, -any unbindable mounts within the subtree are automatically pruned -(i.e., not replicated) -when replicating that subtree to produce the target subtree. -.P -By default, changing the propagation type affects only the -.I target -mount. -If the -.B MS_REC -flag is also specified in -.IR mountflags , -then the propagation type of all mounts under -.I target -is also changed. -.P -For further details regarding mount propagation types -(including the default propagation type assigned to new mounts), see -.BR mount_namespaces (7). -.\" -.SS Moving a mount -If -.I mountflags -contains the flag -.B MS_MOVE -(available since Linux 2.4.18), -then move a subtree: -.I source -specifies an existing mount and -.I target -specifies the new location to which that mount is to be relocated. -The move is atomic: at no point is the subtree unmounted. -.P -The remaining bits in the -.I mountflags -argument are ignored, as are the -.I filesystemtype -and -.I data -arguments. -.\" -.SS Creating a new mount -If none of -.BR MS_REMOUNT , -.BR MS_BIND , -.BR MS_MOVE , -.BR MS_SHARED , -.BR MS_PRIVATE , -.BR MS_SLAVE , -or -.B MS_UNBINDABLE -is specified in -.IR mountflags , -then -.BR mount () -performs its default action: creating a new mount. -.I source -specifies the source for the new mount, and -.I target -specifies the directory at which to create the mount point. -.P -The -.I filesystemtype -and -.I data -arguments are employed, and further bits may be specified in -.I mountflags -to modify the behavior of the call. -.\" -.SH RETURN VALUE -On success, zero is returned. -On error, \-1 is returned, and -.I errno -is set to indicate the error. -.SH ERRORS -The error values given below result from filesystem type independent -errors. -Each filesystem type may have its own special errors and its -own special behavior. -See the Linux kernel source code for details. -.TP -.B EACCES -A component of a path was not searchable. -(See also -.BR path_resolution (7).) -.TP -.B EACCES -Mounting a read-only filesystem was attempted without giving the -.B MS_RDONLY -flag. -.IP -The filesystem may be read-only for various reasons, including: -it resides on a read-only optical disk; -it is resides on a device with a physical switch that has been set to -mark the device read-only; -the filesystem implementation was compiled with read-only support; -or errors were detected when initially mounting the filesystem, -so that it was marked read-only -and can't be remounted as read-write (until the errors are fixed). -.IP -Some filesystems instead return the error -.B EROFS -on an attempt to mount a read-only filesystem. -.TP -.B EACCES -The block device -.I source -is located on a filesystem mounted with the -.B MS_NODEV -option. -.\" mtk: Probably: write permission is required for MS_BIND, with -.\" the error EPERM if not present; CAP_DAC_OVERRIDE is required. -.TP -.B EBUSY -An attempt was made to stack a new mount directly on -top of an existing mount point that was created in this -mount namespace with the same -.I source -and -.IR target . -.TP -.B EBUSY -.I source -cannot be remounted read-only, -because it still holds files open for writing. -.TP -.B EFAULT -One of the pointer arguments points outside the user address space. -.TP -.B EINVAL -.I source -had an invalid superblock. -.TP -.B EINVAL -A remount operation -.RB ( MS_REMOUNT ) -was attempted, but -.I source -was not already mounted on -.IR target . -.TP -.B EINVAL -A move operation -.RB ( MS_MOVE ) -was attempted, but the mount tree under -.I source -includes unbindable mounts and -.I target -is a mount that has propagation type -.BR MS_SHARED . -.TP -.B EINVAL -A move operation -.RB ( MS_MOVE ) -was attempted, but the parent mount of -.I source -mount has propagation type -.BR MS_SHARED . -.TP -.B EINVAL -A move operation -.RB ( MS_MOVE ) -was attempted, but -.I source -was not a mount, or was \[aq]/\[aq]. -.TP -.B EINVAL -A bind operation -.RB ( MS_BIND ) -was requested where -.I source -referred a mount namespace magic link (i.e., a -.IR /proc/ pid /ns/mnt -magic link or a bind mount to such a link) -and the propagation type of the parent mount of -.I target -was -.BR MS_SHARED , -.\" See commit 8823c079ba7136dc1948d6f6dcb5f8022bde438e -but propagation of the requested bind mount could lead to a circular -dependency that might prevent the mount namespace from ever being freed. -.TP -.B EINVAL -.I mountflags -includes more than one of -.BR MS_SHARED , -.BR MS_PRIVATE , -.BR MS_SLAVE , -or -.BR MS_UNBINDABLE . -.TP -.B EINVAL -.I mountflags -includes -.BR MS_SHARED , -.BR MS_PRIVATE , -.BR MS_SLAVE , -or -.B MS_UNBINDABLE -and also includes a flag other than -.B MS_REC -or -.BR MS_SILENT . -.TP -.B EINVAL -An attempt was made to bind mount an unbindable mount. -.TP -.B EINVAL -In an unprivileged mount namespace -(i.e., a mount namespace owned by a user namespace -that was created by an unprivileged user), -a bind mount operation -.RB ( MS_BIND ) -was attempted without specifying -.RB ( MS_REC ), -which would have revealed the filesystem tree underneath one of -the submounts of the directory being bound. -.TP -.B ELOOP -Too many links encountered during pathname resolution. -.TP -.B ELOOP -A move operation was attempted, and -.I target -is a descendant of -.IR source . -.TP -.B EMFILE -(In case no block device is required:) -Table of dummy devices is full. -.TP -.B ENAMETOOLONG -A pathname was longer than -.BR MAXPATHLEN . -.TP -.B ENODEV -.I filesystemtype -not configured in the kernel. -.TP -.B ENOENT -A pathname was empty or had a nonexistent component. -.TP -.B ENOMEM -The kernel could not allocate a free page to copy filenames or data into. -.TP -.B ENOTBLK -.I source -is not a block device (and a device was required). -.TP -.B ENOTDIR -.IR target , -or a prefix of -.IR source , -is not a directory. -.TP -.B ENXIO -The major number of the block device -.I source -is out of range. -.TP -.B EPERM -The caller does not have the required privileges. -.TP -.B EPERM -An attempt was made to modify -.RB ( MS_REMOUNT ) -the -.BR MS_RDONLY , -.BR MS_NOSUID , -or -.B MS_NOEXEC -flag, or one of the "atime" flags -.RB ( MS_NOATIME , -.BR MS_NODIRATIME , -.BR MS_RELATIME ) -of an existing mount, but the mount is locked; see -.BR mount_namespaces (7). -.TP -.B EROFS -Mounting a read-only filesystem was attempted without giving the -.B MS_RDONLY -flag. -See -.BR EACCES , -above. -.\" -.SH STANDARDS -Linux. -.SH HISTORY -The definitions of -.BR MS_DIRSYNC , -.BR MS_MOVE , -.BR MS_PRIVATE , -.BR MS_REC , -.BR MS_RELATIME , -.BR MS_SHARED , -.BR MS_SLAVE , -.BR MS_STRICTATIME , -and -.B MS_UNBINDABLE -were added to glibc headers in glibc 2.12. -.P -Since Linux 2.4 a single filesystem can be mounted at -multiple mount points, and multiple mounts can be stacked -on the same mount point. -.\" Multiple mounts on same mount point: since Linux 2.3.99pre7. -.P -The -.I mountflags -argument may have the magic number 0xC0ED (\fBMS_MGC_VAL\fP) -in the top 16 bits. -(All of the other flags discussed in DESCRIPTION -occupy the low order 16 bits of -.IR mountflags .) -Specifying -.B MS_MGC_VAL -was required before Linux 2.4, -but since Linux 2.4 is no longer required and is ignored if specified. -.P -The original -.B MS_SYNC -flag was renamed -.B MS_SYNCHRONOUS -in 1.1.69 -when a different -.B MS_SYNC -was added to \fI<mman.h>\fP. -.P -Before Linux 2.4 an attempt to execute a set-user-ID or set-group-ID program -on a filesystem mounted with -.B MS_NOSUID -would fail with -.BR EPERM . -Since Linux 2.4 the set-user-ID and set-group-ID bits are -just silently ignored in this case. -.\" The change is in patch-2.4.0-prerelease. -.\" -.SH NOTES -.SS Mount namespaces -Starting with Linux 2.4.19, Linux provides mount namespaces. -A mount namespace is the set of filesystem mounts that -are visible to a process. -Mount namespaces can be (and usually are) -shared between multiple processes, -and changes to the namespace (i.e., mounts and unmounts) by one process -are visible to all other processes sharing the same namespace. -(The pre-2.4.19 Linux situation can be considered as one in which -a single namespace was shared by every process on the system.) -.P -A child process created by -.BR fork (2) -shares its parent's mount namespace; -the mount namespace is preserved across an -.BR execve (2). -.P -A process can obtain a private mount namespace if: -it was created using the -.BR clone (2) -.B CLONE_NEWNS -flag, -in which case its new namespace is initialized to be a -.I copy -of the namespace of the process that called -.BR clone (2); -or it calls -.BR unshare (2) -with the -.B CLONE_NEWNS -flag, -which causes the caller's mount namespace to obtain a private copy -of the namespace that it was previously sharing with other processes, -so that future mounts and unmounts by the caller are invisible -to other processes (except child processes that the caller -subsequently creates) and vice versa. -.P -For further details on mount namespaces, see -.BR mount_namespaces (7). -.\" -.SS Parental relationship between mounts -Each mount has a parent mount. -The overall parental relationship of all mounts defines -the single directory hierarchy seen by the processes within a mount namespace. -.P -The parent of a new mount is defined when the mount is created. -In the usual case, -the parent of a new mount is the mount of the filesystem -containing the directory or file at which the new mount is attached. -In the case where a new mount is stacked on top of an existing mount, -the parent of the new mount is the previous mount that was stacked -at that location. -.P -The parental relationship between mounts can be discovered via the -.IR /proc/ pid /mountinfo -file (see below). -.\" -.SS \fI/proc/\fPpid\fI/mounts\fP and \fI/proc/\fPpid\fI/mountinfo\fP -The Linux-specific -.IR /proc/ pid /mounts -file exposes the list of mounts in the mount -namespace of the process with the specified ID. -The -.IR /proc/ pid /mountinfo -file exposes even more information about mounts, -including the propagation type and mount ID information that makes it -possible to discover the parental relationship between mounts. -See -.BR proc (5) -and -.BR mount_namespaces (7) -for details of this file. -.SH SEE ALSO -.BR mountpoint (1), -.BR chroot (2), -.BR ioctl_iflags (2), -.BR mount_setattr (2), -.BR pivot_root (2), -.BR umount (2), -.BR mount_namespaces (7), -.BR path_resolution (7), -.BR findmnt (8), -.BR lsblk (8), -.BR mount (8), -.BR umount (8) |