3 Ways to Force Unmount in Linux Showing “device is busy”

Updated August 8, 2019By Bobbin ZachariahLINUX HOWTOTROUBLESHOOTING

When you do an NFS mount, it sometimes shows "device is busy” status, in such case we need to perform force unmount in a graceful way. There are different ways and options we can try out if normal nfs unmount fails.

Scenario

In our scenario, we have created /var/linoxide directory for the mount. When we try to umount the remote partition, we have an error message. Good to read on NFS Mount Options in Linux.

You can all the mounted folders with the df command

# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/vda1 20G 1.3G 18G 7% /
devtmpfs 236M 0 236M 0% /dev
tmpfs 245M 0 245M 0% /dev/shm
tmpfs 245M 8.4M 237M 4% /run
tmpfs 245M 0 245M 0% /sys/fs/cgroup
tmpfs 49M 0 49M 0% /run/user/0
10.128.20.241:/var/linoxide 20G 1.3G 18G 7% /mnt/nfs/linoxide_srv
10.128.20.241:/home 20G 1.3G 18G 7% /mnt/nfs/home_srv

In the last two lines, you can see mounted folders on the client. Below example shows the unmount fails because the device is busy

# umount /mnt/nfs/linoxide_srv/
umount.nfs4: /mnt/nfs/linoxide_srv: device is busy

1) With lsof

The lsof (list open files) command displays a list of all open files and the processes associated with them on a specific file system, directory, or device. By default, it lists all files, shared libraries, and directories that are currently open and provides as much information as possible about each of them. The output gives us some information such as the PID, USER so that we can use a pipe to filter its output.

# lsof /mnt/nfs/linoxide_srv/
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
bash 24098 root cwd DIR 253,1 4096 519062 /mnt/nfs/linoxide_srv
bash 24125 root cwd DIR 253,1 4096 519062 /mnt/nfs/linoxide_srv
vim 24144 linoxide cwd DIR 253,1 4096 519062 /mnt/nfs/linoxide_srv

You can see that we have the PID of process which uses the mounted folder, we see the commands in execution, the user who executes the command. It is possible to kill the busy process but take care of the executed command. You can see vim command which means that a file is being edited by the linoxide user. So if we kill the process, his progress will be lost. Suppose that we have informed him, let's see the result

# lsof /mnt/nfs/linoxide_srv/
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
bash 24098 root cwd DIR 253,1 4096 519062 /mnt/nfs/linoxide_srv
bash 24125 root cwd DIR 253,1 4096 519062 /mnt/nfs/linoxide_srv

You can look that our user has stopped his modification but we still have bash command in execution but we don't know why. We can now kill the two processes with kill command. Be sure to don't miss the pid of the process to kill.

Now we will kill the first bash process

# kill -9 24098

We can verify the result

# lsof /mnt/nfs/linoxide_srv/
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
bash 24125 root cwd DIR 253,1 4096 519062 /mnt/nfs/linoxide_srv

We can see that one process is killed

# kill -9 24125

Now let's verify for the second process

# lsof /mnt/nfs/linoxide_srv/

Now let's try to unmount the folder

# umount /mnt/nfs/linoxide_srv/
umount: /mnt/nfs/linoxide_srv/: not mounted

It seems that kill the process has automatically unmounted the folder but let's check with df command

# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/vda1 20G 1.3G 18G 7% /
devtmpfs 236M 0 236M 0% /dev
tmpfs 245M 0 245M 0% /dev/shm
tmpfs 245M 8.3M 237M 4% /run
tmpfs 245M 0 245M 0% /sys/fs/cgroup
tmpfs 49M 0 49M 0% /run/user/0
10.128.20.241:/home 20G 1.3G 18G 7% /mnt/nfs/home_srv

The folder /mnt/nfs/linoxide_srv has been unmounted as we want.

2) With fuser

The fuser (find user processes) command helps to identify processes that are preventing you from unmounting file systems. It finds user processes that are associated with whatever files, directories, or file system mount points that you supply as command-line arguments.

# fuser /mnt/nfs/linoxide_srv/
/mnt/nfs/linoxide_srv: 24191c

We can use fuser command with -m option which lists all the processes accessing the files or mount point on the file system and the -v option which shows a result like ps command with PID, user and the executed command.

# fuser -mv /mnt/nfs/linoxide_srv/
USER PID ACCESS COMMAND
/mnt/nfs/linoxide_srv:
root kernel mount /mnt/nfs/home_srv
root 24191 ..c.. bash
root 24275 ..c.. bash
linoxide 24290 ..c.. vim

You can see the command in execution. We must prevent our linoxide user to save his work.

# fuser -mv /mnt/nfs/linoxide_srv/
USER PID ACCESS COMMAND
/mnt/nfs/linoxide_srv:
root kernel mount /mnt/nfs/home_srv
root 24191 ..c.. bash
root 24275 ..c.. bash

With fuser command, it is possible to directly kill the process in execution with -k option without kill command

# fuser -kmv /mnt/nfs/linoxide_srv/
USER PID ACCESS COMMAND
/mnt/nfs/linoxide_srv:
root kernel mount /mnt/nfs/home_srv
root 24191 ..c.. bash
root 24275 ..c.. bash

Check the result

# fuser -mv /mnt/nfs/linoxide_srv/
USER PID ACCESS COMMAND
/mnt/nfs/linoxide_srv:
root kernel mount /mnt/nfs/home_srv

It seems that only the mount is in execution. Let's try to unmount the folder

# umount /mnt/nfs/linoxide_srv/

We don't have error message. Check the mount point

# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/vda1 20G 1.3G 18G 7% /
devtmpfs 236M 0 236M 0% /dev
tmpfs 245M 0 245M 0% /dev/shm
tmpfs 245M 8.3M 237M 4% /run
tmpfs 245M 0 245M 0% /sys/fs/cgroup
tmpfs 49M 0 49M 0% /run/user/0
10.128.20.241:/home 20G 1.3G 18G 7% /mnt/nfs/home_srv

We can see that the /mnt/nfs/linoxide_srv folder has been unmounted as we want.

3) Lazy unmount

umount command has an -l option to perform a lazy unmount. The mount will be removed from the filesystem namespace (so you won't see it under /mnt/nfs/linoxide anymore) but it stays mounted, so programs accessing it can continue to do so. When the last program accessing it exits, the unmount will actually occur.

# fuser -mv /mnt/nfs/linoxide_srv/
USER PID ACCESS COMMAND
/mnt/nfs/linoxide_srv:
root kernel mount /mnt/nfs/home_srv
root 24366 ..c.. bash
root 24381 ..c.. bash
linoxide 24398 ..c.. vim

We can see that the folder is busy. Now let's try to do a lazy unmount

# umount -l /mnt/nfs/linoxide_srv/

We don't have an error message. We will check if the command was being executed without error

# echo $?
0

Now let's check the mount point

# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/vda1 20G 1.3G 18G 7% /
devtmpfs 236M 0 236M 0% /dev
tmpfs 245M 0 245M 0% /dev/shm
tmpfs 245M 8.4M 237M 4% /run
tmpfs 245M 0 245M 0% /sys/fs/cgroup
tmpfs 49M 0 49M 0% /run/user/0
10.128.20.241:/home 20G 1.3G 18G 7% /mnt/nfs/home_srv

We can see that the mount point /mnt/nfs/linoxide_srv doesn't appear again but as we said earlier, for example, our linoxide user is still modifying his file, can create new files, etc. On the server, we can see the file that the user is modifying.

We can need to unmount a partition because of an emergency or simply to remove a device but a problem can occur because that device is busy. It is important to examine every process on the system before taking a decision for the method to resolve the problem. The lsof and fuser commands make it easy to identify the processes that are preventing you from unmounting a file system.

Read Also:

3 Ways to Force Unmount in Linux Showing “device is busy”的更多相关文章

  1. Linux在device is busy处理

    在Linux管理umount设备时,时常会遇到"device is busy", 假设umount一个文件系统碰到这样的情况.而且你并没有在所需卸载的文件夹下.那么非常可能实用户或 ...

  2. 5 Ways to Send Email From Linux Command Line

    https://tecadmin.net/ways-to-send-email-from-linux-command-line/ We all know the importance of email ...

  3. Linux umount设备时出现device is busy解决方法

    在Linux中,有时使用umount命令去卸载LV或文件时,可能出现umount: xxx: device is busy的情况,如下案例所示 [root@DB-Server u06]# vgdisp ...

  4. [platform]linux platform device/driver(三)--Platform Device和Platform_driver注册过程之代码对比

    转自:http://blog.csdn.net/thl789/article/details/6723350 Linux 2.6的设备驱动模型中,所有的device都是通过Bus相连.device_r ...

  5. linux umount 提示device is busy 的解决

    linux umount 提示"device is busy" 终极解决 为了干净地关闭或热交换 UNIX 或类 UNIX 系统上的存储硬件,必须能够卸载使用此设备上的存储的所有文件系统.但是,如果正 ...

  6. Linux 环境下umount, 报 device is busy 的问题分析与解决方法

    在Linux环境中,有时候需要挂载外部目录或硬盘等,但当想umount时,却提示类似“umount:/home/oracle-server/backup:device is busy”这种提示. 出现 ...

  7. Linux DTS(Device Tree Source)设备树详解之二(dts匹配及发挥作用的流程篇)【转】

    转自:https://blog.csdn.net/radianceblau/article/details/74722395 版权声明:本文为博主原创文章,未经博主允许不得转载.如本文对您有帮助,欢迎 ...

  8. I.MX6 Linux I2C device& driver hacking

    /******************************************************************************************* * I.MX6 ...

  9. Linux内核device结构体分析

    1.前言 Linux内核中的设备驱动模型,是建立在sysfs设备文件系统和kobject上的,由总线(bus).设备(device).驱动(driver)和类(class)所组成的关系结构,在底层,L ...

随机推荐

  1. Sublime Text3安装LESS

    Sublime Text3安装LESS 1.Sublime Text3利用Package Control安装LESS插件.LESS2CSS插件 2.去node官网下载node.js http://no ...

  2. 屏蔽组合键[CTRL+N]

    https://www.cnblogs.com/gaodu2003/archive/2011/05/05/2037229.html …… const  _KeyPressMask=$80000000; ...

  3. PAT(B) 1045 快速排序(C)

    题目链接:1045 快速排序 (25 point(s)) 参考博客:1045 快速排序 (25 point(s))繁星蓝雨 题目描述 著名的快速排序算法里有一个经典的划分过程:我们通常采用某种方法取一 ...

  4. Jmeter_数据库

    1.准备一个有测试数据表的mysql数据库 2.在测试计划面板点击“浏览..." 按钮,将你的JDBC驱动添加进来.         需要安装插件   mysql-connector-jav ...

  5. LOJ2074/2157 JSOI2016/POI2011 Lightning Conductor 决策单调性DP

    传送门 我们相当于要求出\(f_i = \max\limits_{j=1}^{n} (a_j + \sqrt{|i-j|})\).这个绝对值太烦人了,考虑对于\(i>j\)和\(i<j\) ...

  6. 笔谈runloop(一)

    关于runloop熟悉而又陌生,熟悉的是在iOS开发的过程中线程的执行就跟runloop扯上关系了,陌生的是runloop到底是个什么东西.去公司面试的时候,很多公司的面试人员会问这个问题.runlo ...

  7. c#指定长度切割字符串,返回数组

    public List<string> subStringByCount(string text, int count) { ;//开始索引 ;//结束索引 double count_va ...

  8. 微信小程序实现下拉刷新上拉加载

    代码片段:https://developers.weixin.qq.com/s/K9VbWZmy7e8C

  9. TCP_Wrappers基础知识介绍

    1. TCP_Wrappers基础知识介绍 TCP_Wrappers是在 Solaris, HP_UX以及 Linux中广泛流行的免费软件.它被设计为一个介于外来服务请求和系统服务回应的中间处理软件. ...

  10. 听说你知道什么是锁 --JAVA

    I.java中的锁 1.1 什么是锁 ​ 在计算机科学中,锁(lock)与互斥(mutex)是一种同步机制,用于在许多线程执行时对资源的限制. ​ 锁通常需要硬件支持才可以有效实施.这种支持通常采用一 ...