admin-guide/sysctl/fs.rst

11 ------------------------------------------------------------------------------
31 aio-nr & aio-max-nr
32 -------------------
34 ``aio-nr`` shows the current system-wide number of asynchronous io
35 requests.  ``aio-max-nr`` allows you to change the maximum value
36 ``aio-nr`` can grow to.  If ``aio-nr`` reaches ``aio-nr-max`` then
38 ``aio-max-nr`` does not result in the
39 pre-allocation or re-sizing of any kernel data structures.
42 dentry-state
43 ------------
70 they help speeding up rejection of non-existing files provided
74 file-max & file-nr
75 ------------------
77 The value in ``file-max`` denotes the maximum number of file-
83 dynamically, but not to free them again. The three values in
84 ``file-nr`` denote the number of allocated file handles, the number
86 file handles. Linux 2.6 and later always reports 0 as the number of free
87 file handles -- this is not an error, it just means that the
91 Attempts to allocate more file descriptors than ``file-max`` are
94   VFS: file-max limit <number> reached
99 inode-nr & inode-state
100 ----------------------
103 dynamically, but can't free them yet.
105 The file ``inode-nr`` contains the first two items from
106 ``inode-state``, so we'll skip to that file...
108 ``inode-state`` contains three actual numbers and four dummies.
115 ``nr_free_inodes`` represents the number of free inodes (?) and
121 mount-max
122 ---------
129 -------
131 This denotes the maximum number of file-handles a process can
138 -------------------------
140 Some filesystems only support 16-bit UIDs and GIDs, although in Linux
149 pipe-user-pages-hard
150 --------------------
152 Maximum total number of pages a non-privileged user may allocate for pipes.
158 pipe-user-pages-soft
159 --------------------
161 Maximum total number of pages a non-privileged user may allocate for pipes
171 ---------------
174 an attacker-controlled FIFO, where a program expected to create a regular
189 --------------------
191 A long-standing class of security issues is the hardlink-based
192 time-of-check-time-of-use race, most commonly seen in world-writable
209 -----------------
212 avoids writes to an attacker-controlled regular file, where a program
225 ------------------
227 A long-standing class of security issues is the symlink-based
228 time-of-check-time-of-use race, most commonly seen in world-writable
233 https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=/tmp
238 a sticky world-writable directory, or when the uid of the symlink and
245 -------------
261 		:ref:`Documentation/admin-guide/sysctl/kernel.rst <core_pattern>`)
264 		details on this limitation, see CVE-2006-2451.) This mode is
280 in Documentation/admin-guide/binfmt-misc.rst.
283 3. /proc/sys/fs/mqueue - POSIX message queues filesystem
289 API (as noted by the  MSG tag in the  POSIX 1003.1-2001 version  of the System
319 4. /proc/sys/fs/epoll - Configuration options for the epoll interface
325 ----------------
331 Each "watch" costs roughly 90 bytes on a 32-bit kernel, and roughly 160 bytes
332 on a 64-bit one.