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1 | Documentation for /proc/sys/fs/* kernel version 2.2.10 |
2 | (c) 1998, 1999, Rik van Riel <riel@nl.linux.org> | |
3 | ||
4 | For general info and legal blurb, please look in README. | |
5 | ||
6 | ============================================================== | |
7 | ||
8 | This file contains documentation for the sysctl files in | |
9 | /proc/sys/fs/ and is valid for Linux kernel version 2.2. | |
10 | ||
11 | The files in this directory can be used to tune and monitor | |
12 | miscellaneous and general things in the operation of the Linux | |
13 | kernel. Since some of the files _can_ be used to screw up your | |
14 | system, it is advisable to read both documentation and source | |
15 | before actually making adjustments. | |
16 | ||
17 | Currently, these files are in /proc/sys/fs: | |
18 | - dentry-state | |
19 | - dquot-max | |
20 | - dquot-nr | |
21 | - file-max | |
22 | - file-nr | |
23 | - inode-max | |
24 | - inode-nr | |
25 | - inode-state | |
26 | - overflowuid | |
27 | - overflowgid | |
a2e0b563 | 28 | - suid_dumpable |
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29 | - super-max |
30 | - super-nr | |
31 | ||
32 | Documentation for the files in /proc/sys/fs/binfmt_misc is | |
33 | in Documentation/binfmt_misc.txt. | |
34 | ||
35 | ============================================================== | |
36 | ||
37 | dentry-state: | |
38 | ||
39 | From linux/fs/dentry.c: | |
40 | -------------------------------------------------------------- | |
41 | struct { | |
42 | int nr_dentry; | |
43 | int nr_unused; | |
44 | int age_limit; /* age in seconds */ | |
45 | int want_pages; /* pages requested by system */ | |
46 | int dummy[2]; | |
47 | } dentry_stat = {0, 0, 45, 0,}; | |
48 | -------------------------------------------------------------- | |
49 | ||
50 | Dentries are dynamically allocated and deallocated, and | |
51 | nr_dentry seems to be 0 all the time. Hence it's safe to | |
52 | assume that only nr_unused, age_limit and want_pages are | |
53 | used. Nr_unused seems to be exactly what its name says. | |
54 | Age_limit is the age in seconds after which dcache entries | |
55 | can be reclaimed when memory is short and want_pages is | |
56 | nonzero when shrink_dcache_pages() has been called and the | |
57 | dcache isn't pruned yet. | |
58 | ||
59 | ============================================================== | |
60 | ||
61 | dquot-max & dquot-nr: | |
62 | ||
63 | The file dquot-max shows the maximum number of cached disk | |
64 | quota entries. | |
65 | ||
66 | The file dquot-nr shows the number of allocated disk quota | |
67 | entries and the number of free disk quota entries. | |
68 | ||
69 | If the number of free cached disk quotas is very low and | |
70 | you have some awesome number of simultaneous system users, | |
71 | you might want to raise the limit. | |
72 | ||
73 | ============================================================== | |
74 | ||
75 | file-max & file-nr: | |
76 | ||
77 | The kernel allocates file handles dynamically, but as yet it | |
78 | doesn't free them again. | |
79 | ||
80 | The value in file-max denotes the maximum number of file- | |
81 | handles that the Linux kernel will allocate. When you get lots | |
82 | of error messages about running out of file handles, you might | |
83 | want to increase this limit. | |
84 | ||
85 | The three values in file-nr denote the number of allocated | |
86 | file handles, the number of unused file handles and the maximum | |
87 | number of file handles. When the allocated file handles come | |
88 | close to the maximum, but the number of unused file handles is | |
89 | significantly greater than 0, you've encountered a peak in your | |
90 | usage of file handles and you don't need to increase the maximum. | |
91 | ||
92 | ============================================================== | |
93 | ||
94 | inode-max, inode-nr & inode-state: | |
95 | ||
96 | As with file handles, the kernel allocates the inode structures | |
97 | dynamically, but can't free them yet. | |
98 | ||
99 | The value in inode-max denotes the maximum number of inode | |
100 | handlers. This value should be 3-4 times larger than the value | |
101 | in file-max, since stdin, stdout and network sockets also | |
102 | need an inode struct to handle them. When you regularly run | |
103 | out of inodes, you need to increase this value. | |
104 | ||
105 | The file inode-nr contains the first two items from | |
106 | inode-state, so we'll skip to that file... | |
107 | ||
108 | Inode-state contains three actual numbers and four dummies. | |
109 | The actual numbers are, in order of appearance, nr_inodes, | |
110 | nr_free_inodes and preshrink. | |
111 | ||
112 | Nr_inodes stands for the number of inodes the system has | |
113 | allocated, this can be slightly more than inode-max because | |
114 | Linux allocates them one pageful at a time. | |
115 | ||
116 | Nr_free_inodes represents the number of free inodes (?) and | |
117 | preshrink is nonzero when the nr_inodes > inode-max and the | |
118 | system needs to prune the inode list instead of allocating | |
119 | more. | |
120 | ||
121 | ============================================================== | |
122 | ||
123 | overflowgid & overflowuid: | |
124 | ||
125 | Some filesystems only support 16-bit UIDs and GIDs, although in Linux | |
126 | UIDs and GIDs are 32 bits. When one of these filesystems is mounted | |
127 | with writes enabled, any UID or GID that would exceed 65535 is translated | |
128 | to a fixed value before being written to disk. | |
129 | ||
130 | These sysctls allow you to change the value of the fixed UID and GID. | |
131 | The default is 65534. | |
132 | ||
133 | ============================================================== | |
134 | ||
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135 | suid_dumpable: |
136 | ||
137 | This value can be used to query and set the core dump mode for setuid | |
138 | or otherwise protected/tainted binaries. The modes are | |
139 | ||
140 | 0 - (default) - traditional behaviour. Any process which has changed | |
141 | privilege levels or is execute only will not be dumped | |
142 | 1 - (debug) - all processes dump core when possible. The core dump is | |
143 | owned by the current user and no security is applied. This is | |
144 | intended for system debugging situations only. Ptrace is unchecked. | |
145 | 2 - (suidsafe) - any binary which normally would not be dumped is dumped | |
146 | readable by root only. This allows the end user to remove | |
147 | such a dump but not access it directly. For security reasons | |
148 | core dumps in this mode will not overwrite one another or | |
5d3f083d | 149 | other files. This mode is appropriate when administrators are |
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150 | attempting to debug problems in a normal environment. |
151 | ||
152 | ============================================================== | |
153 | ||
1da177e4 LT |
154 | super-max & super-nr: |
155 | ||
156 | These numbers control the maximum number of superblocks, and | |
157 | thus the maximum number of mounted filesystems the kernel | |
158 | can have. You only need to increase super-max if you need to | |
159 | mount more filesystems than the current value in super-max | |
160 | allows you to. | |
161 | ||
162 | ============================================================== | |
163 | ||
164 | aio-nr & aio-max-nr: | |
165 | ||
166 | aio-nr shows the current system-wide number of asynchronous io | |
167 | requests. aio-max-nr allows you to change the maximum value | |
168 | aio-nr can grow to. | |
169 | ||
170 | ============================================================== |