1 /* vi: set sw=4 ts=4: */
3 * Mini umount implementation for busybox
5 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
6 * Copyright (C) 2005 by Rob Landley <rob@landley.net>
8 * Licensed under GPLv2, see file LICENSE in this source tree.
10 //config:config UMOUNT
11 //config: bool "umount (4.5 kb)"
13 //config: select PLATFORM_LINUX
15 //config: When you want to remove a mounted filesystem from its current mount
16 //config: point, for example when you are shutting down the system, the
17 //config: 'umount' utility is the tool to use. If you enabled the 'mount'
18 //config: utility, you almost certainly also want to enable 'umount'.
20 //config:config FEATURE_UMOUNT_ALL
21 //config: bool "Support -a (unmount all)"
23 //config: depends on UMOUNT
25 //config: Support -a option to unmount all currently mounted filesystems.
27 //applet:IF_UMOUNT(APPLET_NOEXEC(umount, umount, BB_DIR_BIN, BB_SUID_DROP, umount))
29 * On one hand, in some weird situations you'd want umount
30 * to not do anything surprising, to behave as a usual fork+execed executable.
32 * OTOH, there can be situations where execing would not succeed, or even hang
33 * (say, if executable is on a filesystem which is in trouble and accesses to it
35 * In this case, you might be actually happy if your standalone bbox shell
36 * does not fork+exec, but only forks and calls umount_main() which it already has!
37 * Let's go with NOEXEC.
39 * bb_common_bufsiz1 usage here is safe wrt NOEXEC: not expecting it to be zeroed.
42 //kbuild:lib-$(CONFIG_UMOUNT) += umount.o
44 //usage:#define umount_trivial_usage
45 //usage: "[OPTIONS] FILESYSTEM|DIRECTORY"
46 //usage:#define umount_full_usage "\n\n"
47 //usage: "Unmount file systems\n"
48 //usage: IF_FEATURE_UMOUNT_ALL(
49 //usage: "\n -a Unmount all file systems" IF_FEATURE_MTAB_SUPPORT(" in /etc/mtab")
51 //usage: IF_FEATURE_MTAB_SUPPORT(
52 //usage: "\n -n Don't erase /etc/mtab entries"
54 //usage: "\n -r Try to remount devices as read-only if mount is busy"
55 //usage: "\n -l Lazy umount (detach filesystem)"
56 //usage: "\n -f Force umount (i.e., unreachable NFS server)"
57 //usage: IF_FEATURE_MOUNT_LOOP(
58 //usage: "\n -d Free loop device if it has been used"
61 //usage:#define umount_example_usage
62 //usage: "$ umount /dev/hdc1\n"
65 #include <sys/mount.h>
67 # define MNT_DETACH 0x00000002
70 #include "common_bufsiz.h"
72 #if defined(__dietlibc__)
73 // TODO: This does not belong here.
74 /* 16.12.2006, Sampo Kellomaki (sampo@iki.fi)
75 * dietlibc-0.30 does not have implementation of getmntent_r() */
76 static struct mntent *getmntent_r(FILE* stream, struct mntent* result,
77 char* buffer UNUSED_PARAM, int bufsize UNUSED_PARAM)
79 struct mntent* ment = getmntent(stream);
80 return memcpy(result, ment, sizeof(*ment));
84 /* ignored: -v -t -i */
85 #define OPTION_STRING "fldnra" "vt:i"
86 #define OPT_FORCE (1 << 0) // Same as MNT_FORCE
87 #define OPT_LAZY (1 << 1) // Same as MNT_DETACH
88 #define OPT_FREELOOP (1 << 2)
89 #define OPT_NO_MTAB (1 << 3)
90 #define OPT_REMOUNT (1 << 4)
91 #define OPT_ALL (ENABLE_FEATURE_UMOUNT_ALL ? (1 << 5) : 0)
93 int umount_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
94 int umount_main(int argc UNUSED_PARAM, char **argv)
100 int status = EXIT_SUCCESS;
105 struct mtab_list *next;
108 opt = getopt32(argv, OPTION_STRING, &fstype);
112 // MNT_FORCE and MNT_DETACH (from linux/fs.h) must match
113 // OPT_FORCE and OPT_LAZY.
114 BUILD_BUG_ON(OPT_FORCE != MNT_FORCE || OPT_LAZY != MNT_DETACH);
115 doForce = opt & (OPT_FORCE|OPT_LAZY);
117 /* Get a list of mount points from mtab. We read them all in now mostly
118 * for umount -a (so we don't have to worry about the list changing while
119 * we iterate over it, or about getting stuck in a loop on the same failing
120 * entry. Notice that this also naturally reverses the list so that -a
121 * umounts the most recent entries first. */
124 // If we're umounting all, then m points to the start of the list and
125 // the argument list should be empty (which will match all).
126 fp = setmntent(bb_path_mtab_file, "r");
129 bb_error_msg_and_die("can't open '%s'", bb_path_mtab_file);
131 setup_common_bufsiz();
132 while (getmntent_r(fp, &me, bb_common_bufsiz1, COMMON_BUFSIZE)) {
133 /* Match fstype (fstype==NULL matches always) */
134 if (!fstype_matches(me.mnt_type, fstype))
136 m = xzalloc(sizeof(*m));
138 m->device = xstrdup(me.mnt_fsname);
139 m->dir = xstrdup(me.mnt_dir);
145 // If we're not umounting all, we need at least one argument.
146 if (!(opt & OPT_ALL) && !fstype) {
152 // Loop through everything we're supposed to umount, and do so.
158 // Do we already know what to umount this time through the loop?
160 path = xstrdup(m->dir);
161 // For umount -a, end of mtab means time to exit.
162 else if (opt & OPT_ALL)
164 // Use command line argument (and look it up in mtab list)
169 path = xmalloc_realpath(zapit);
171 for (m = mtl; m; m = m->next)
172 if (strcmp(path, m->dir) == 0 || strcmp(path, m->device) == 0)
176 // If we couldn't find this sucker in /etc/mtab, punt by passing our
177 // command line argument straight to the umount syscall. Otherwise,
178 // umount the directory even if we were given the block device.
179 if (m) zapit = m->dir;
181 // umount from util-linux 2.22.2 does not do this:
182 // umount -f uses umount2(MNT_FORCE) immediately,
183 // not trying umount() first.
184 // (Strangely, umount -fl ignores -f: it is equivalent to umount -l.
185 // We do pass both flags in this case)
187 // Let's ask the thing nicely to unmount.
188 curstat = umount(zapit);
190 // Unmount with force and/or lazy flags, if necessary.
191 if (curstat && doForce)
193 curstat = umount2(zapit, doForce);
195 // If still can't umount, maybe remount read-only?
197 if ((opt & OPT_REMOUNT) && errno == EBUSY && m) {
198 // Note! Even if we succeed here, later we should not
199 // free loop device or erase mtab entry!
200 const char *msg = "%s busy - remounted read-only";
201 curstat = mount(m->device, zapit, NULL, MS_REMOUNT|MS_RDONLY, NULL);
203 msg = "can't remount %s read-only";
204 status = EXIT_FAILURE;
206 bb_error_msg(msg, m->device);
208 status = EXIT_FAILURE;
209 bb_perror_msg("can't unmount %s", zapit);
212 // De-allocate the loop device. This ioctl should be ignored on
213 // any non-loop block devices.
214 if (ENABLE_FEATURE_MOUNT_LOOP && (opt & OPT_FREELOOP) && m)
216 if (ENABLE_FEATURE_MTAB_SUPPORT && !(opt & OPT_NO_MTAB) && m)
220 // Find next matching mtab entry for -a or umount /dev
221 // Note this means that "umount /dev/blah" will unmount all instances
222 // of /dev/blah, not just the most recent.
224 while ((m = m->next) != NULL)
225 // NB: if m is non-NULL, path is non-NULL as well
226 if ((opt & OPT_ALL) || strcmp(path, m->device) == 0)
232 // Free mtab list if necessary
233 if (ENABLE_FEATURE_CLEAN_UP) {