Can I umount or remount a filesystem, when some process has its working or root directory on it?
Clash Royale CLAN TAG#URR8PPP
If some process has its current working directory or root directory on a mounted filesystem, can I umount/remount that filesystem?
If some process has a read/write file descriptor or read/write/shared mmap of a file on a mounted filesystem, can I remount that filesystem to read-only? If yes, What will happen to these file descriptors and mmaps when you write to them?
linux mount
edited Feb 23 at 15:44
ctrl-alt-delor
12k42561
asked Feb 23 at 12:39
炸鱼薯条德里克炸鱼薯条德里克
5811316
add a comment |
If some process has its current working directory or root directory on a mounted filesystem, can I umount/remount that filesystem?
If some process has a read/write file descriptor or read/write/shared mmap of a file on a mounted filesystem, can I remount that filesystem to read-only? If yes, What will happen to these file descriptors and mmaps when you write to them?
linux mount
edited Feb 23 at 15:44
ctrl-alt-delor
12k42561
asked Feb 23 at 12:39
炸鱼薯条德里克炸鱼薯条德里克
5811316
add a comment |
If some process has its current working directory or root directory on a mounted filesystem, can I umount/remount that filesystem?
If some process has a read/write file descriptor or read/write/shared mmap of a file on a mounted filesystem, can I remount that filesystem to read-only? If yes, What will happen to these file descriptors and mmaps when you write to them?
linux mount
edited Feb 23 at 15:44
ctrl-alt-delor
12k42561
asked Feb 23 at 12:39
炸鱼薯条德里克炸鱼薯条德里克
5811316
If some process has its current working directory or root directory on a mounted filesystem, can I umount/remount that filesystem?
If some process has a read/write file descriptor or read/write/shared mmap of a file on a mounted filesystem, can I remount that filesystem to read-only? If yes, What will happen to these file descriptors and mmaps when you write to them?
linux mount
linux mount
edited Feb 23 at 15:44
ctrl-alt-delor
12k42561
asked Feb 23 at 12:39
炸鱼薯条德里克炸鱼薯条德里克
5811316
edited Feb 23 at 15:44
ctrl-alt-delor
12k42561
asked Feb 23 at 12:39
炸鱼薯条德里克炸鱼薯条德里克
5811316
edited Feb 23 at 15:44
ctrl-alt-delor
12k42561
edited Feb 23 at 15:44
ctrl-alt-delor
12k42561
edited Feb 23 at 15:44
ctrl-alt-delor
12k42561
12k42561
asked Feb 23 at 12:39
炸鱼薯条德里克炸鱼薯条德里克
5811316
asked Feb 23 at 12:39
炸鱼薯条德里克炸鱼薯条德里克
5811316
asked Feb 23 at 12:39
炸鱼薯条德里克炸鱼薯条德里克
5811316
5811316
add a comment |
add a comment |
1 Answer
1
active
oldest
votes
The working directory and root directory of a process are counted as an active reference to the filesystem, the same as an open file. Therefore they prevent the filesystem from being unmounted. The kernel returns a "busy" error.
EBUSY target could not be unmounted because it is busy.
--
man umount
A filesystem can be remounted as read-only if there are no files open for writing. The working directory and root directory of a process are not counted as files open for writing; they do not prevent the filesystem from being remounted as read-only.
EBUSY source cannot be remounted read-only, because it still holds files open for writing.
man mount
There is another case: at least on some filesystems, you cannot remount as read-only if an unlinked file is open, even for reading. Closing a unlinked file allows the space to be reclaimed, but this may require updating filesystem metadata blocks on disk.
The command umount -l (which uses umount2(..., MNT_DETACH)) is able to detach busy filesystems from the mount tree. The filesystem remains active. It will be shut down once the last open file is closed. The documentation does not state whether the shut down happens in the background, or whether you can rely on the filesystem having been shut down cleanly after the last close() call returns.
answered Feb 23 at 12:49
sourcejedisourcejedi
25.2k444110
So, if a filesystem is mounted as rw, while there's no any writable reference to it, it can be re-mounted as ro?
– 炸鱼薯条德里克
Feb 23 at 13:50
@炸鱼薯条德里克 yes, except "if an unlinked file is open, even for reading". I have edited my question better, to try and answer each part of your question. Question upvote for mentioning the root directory of the process, that's a nice detail that does not get mentioned very often :-)
– sourcejedi
Feb 23 at 14:28
add a comment |
Your Answer
StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "106"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);
StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);
else
createEditor();
);
function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: false,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: null,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);
);
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f502515%2fcan-i-umount-or-remount-a-filesystem-when-some-process-has-its-working-or-root%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
1 Answer
1
active
oldest
votes
1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
The working directory and root directory of a process are counted as an active reference to the filesystem, the same as an open file. Therefore they prevent the filesystem from being unmounted. The kernel returns a "busy" error.
EBUSY target could not be unmounted because it is busy.
--
man umount
A filesystem can be remounted as read-only if there are no files open for writing. The working directory and root directory of a process are not counted as files open for writing; they do not prevent the filesystem from being remounted as read-only.
EBUSY source cannot be remounted read-only, because it still holds files open for writing.
man mount
There is another case: at least on some filesystems, you cannot remount as read-only if an unlinked file is open, even for reading. Closing a unlinked file allows the space to be reclaimed, but this may require updating filesystem metadata blocks on disk.
The command umount -l (which uses umount2(..., MNT_DETACH)) is able to detach busy filesystems from the mount tree. The filesystem remains active. It will be shut down once the last open file is closed. The documentation does not state whether the shut down happens in the background, or whether you can rely on the filesystem having been shut down cleanly after the last close() call returns.
answered Feb 23 at 12:49
sourcejedisourcejedi
25.2k444110
So, if a filesystem is mounted as rw, while there's no any writable reference to it, it can be re-mounted as ro?
– 炸鱼薯条德里克
Feb 23 at 13:50
@炸鱼薯条德里克 yes, except "if an unlinked file is open, even for reading". I have edited my question better, to try and answer each part of your question. Question upvote for mentioning the root directory of the process, that's a nice detail that does not get mentioned very often :-)
– sourcejedi
Feb 23 at 14:28
add a comment |
The working directory and root directory of a process are counted as an active reference to the filesystem, the same as an open file. Therefore they prevent the filesystem from being unmounted. The kernel returns a "busy" error.
EBUSY target could not be unmounted because it is busy.
--
man umount
A filesystem can be remounted as read-only if there are no files open for writing. The working directory and root directory of a process are not counted as files open for writing; they do not prevent the filesystem from being remounted as read-only.
EBUSY source cannot be remounted read-only, because it still holds files open for writing.
man mount
There is another case: at least on some filesystems, you cannot remount as read-only if an unlinked file is open, even for reading. Closing a unlinked file allows the space to be reclaimed, but this may require updating filesystem metadata blocks on disk.
The command umount -l (which uses umount2(..., MNT_DETACH)) is able to detach busy filesystems from the mount tree. The filesystem remains active. It will be shut down once the last open file is closed. The documentation does not state whether the shut down happens in the background, or whether you can rely on the filesystem having been shut down cleanly after the last close() call returns.
answered Feb 23 at 12:49
sourcejedisourcejedi
25.2k444110
So, if a filesystem is mounted as rw, while there's no any writable reference to it, it can be re-mounted as ro?
– 炸鱼薯条德里克
Feb 23 at 13:50
@炸鱼薯条德里克 yes, except "if an unlinked file is open, even for reading". I have edited my question better, to try and answer each part of your question. Question upvote for mentioning the root directory of the process, that's a nice detail that does not get mentioned very often :-)
– sourcejedi
Feb 23 at 14:28
add a comment |
The working directory and root directory of a process are counted as an active reference to the filesystem, the same as an open file. Therefore they prevent the filesystem from being unmounted. The kernel returns a "busy" error.
EBUSY target could not be unmounted because it is busy.
--
man umount
A filesystem can be remounted as read-only if there are no files open for writing. The working directory and root directory of a process are not counted as files open for writing; they do not prevent the filesystem from being remounted as read-only.
EBUSY source cannot be remounted read-only, because it still holds files open for writing.
man mount
There is another case: at least on some filesystems, you cannot remount as read-only if an unlinked file is open, even for reading. Closing a unlinked file allows the space to be reclaimed, but this may require updating filesystem metadata blocks on disk.
The command umount -l (which uses umount2(..., MNT_DETACH)) is able to detach busy filesystems from the mount tree. The filesystem remains active. It will be shut down once the last open file is closed. The documentation does not state whether the shut down happens in the background, or whether you can rely on the filesystem having been shut down cleanly after the last close() call returns.
answered Feb 23 at 12:49
sourcejedisourcejedi
25.2k444110
The working directory and root directory of a process are counted as an active reference to the filesystem, the same as an open file. Therefore they prevent the filesystem from being unmounted. The kernel returns a "busy" error.
EBUSY target could not be unmounted because it is busy.
--
man umount
A filesystem can be remounted as read-only if there are no files open for writing. The working directory and root directory of a process are not counted as files open for writing; they do not prevent the filesystem from being remounted as read-only.
EBUSY source cannot be remounted read-only, because it still holds files open for writing.
man mount
There is another case: at least on some filesystems, you cannot remount as read-only if an unlinked file is open, even for reading. Closing a unlinked file allows the space to be reclaimed, but this may require updating filesystem metadata blocks on disk.
The command umount -l (which uses umount2(..., MNT_DETACH)) is able to detach busy filesystems from the mount tree. The filesystem remains active. It will be shut down once the last open file is closed. The documentation does not state whether the shut down happens in the background, or whether you can rely on the filesystem having been shut down cleanly after the last close() call returns.
answered Feb 23 at 12:49
sourcejedisourcejedi
25.2k444110
edited Feb 23 at 14:28
answered Feb 23 at 12:49
sourcejedisourcejedi
25.2k444110
answered Feb 23 at 12:49
sourcejedisourcejedi
25.2k444110
answered Feb 23 at 12:49
sourcejedisourcejedi
25.2k444110
25.2k444110
So, if a filesystem is mounted as rw, while there's no any writable reference to it, it can be re-mounted as ro?
– 炸鱼薯条德里克
Feb 23 at 13:50
@炸鱼薯条德里克 yes, except "if an unlinked file is open, even for reading". I have edited my question better, to try and answer each part of your question. Question upvote for mentioning the root directory of the process, that's a nice detail that does not get mentioned very often :-)
– sourcejedi
Feb 23 at 14:28
add a comment |
So, if a filesystem is mounted as rw, while there's no any writable reference to it, it can be re-mounted as ro?
– 炸鱼薯条德里克
Feb 23 at 13:50
@炸鱼薯条德里克 yes, except "if an unlinked file is open, even for reading". I have edited my question better, to try and answer each part of your question. Question upvote for mentioning the root directory of the process, that's a nice detail that does not get mentioned very often :-)
– sourcejedi
Feb 23 at 14:28
So, if a filesystem is mounted as rw, while there's no any writable reference to it, it can be re-mounted as ro?
– 炸鱼薯条德里克
Feb 23 at 13:50
So, if a filesystem is mounted as rw, while there's no any writable reference to it, it can be re-mounted as ro?
– 炸鱼薯条德里克
Feb 23 at 13:50
@炸鱼薯条德里克 yes, except "if an unlinked file is open, even for reading". I have edited my question better, to try and answer each part of your question. Question upvote for mentioning the root directory of the process, that's a nice detail that does not get mentioned very often :-)
– sourcejedi
Feb 23 at 14:28
@炸鱼薯条德里克 yes, except "if an unlinked file is open, even for reading". I have edited my question better, to try and answer each part of your question. Question upvote for mentioning the root directory of the process, that's a nice detail that does not get mentioned very often :-)
– sourcejedi
Feb 23 at 14:28
add a comment |
Thanks for contributing an answer to Unix & Linux Stack Exchange!
- Please be sure to answer the question. Provide details and share your research!
But avoid …
- Asking for help, clarification, or responding to other answers.
- Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2funix.stackexchange.com%2fquestions%2f502515%2fcan-i-umount-or-remount-a-filesystem-when-some-process-has-its-working-or-root%23new-answer', 'question_page');
);
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown
Required, but never shown