umount: /tmp: device is busy + Resolved

Guys,

Just check who is accessing the device. Here are the commands to check who are using it.

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lsof |grep /tmp
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You'll get the process ID and kill the processes like kill -9 PID. Here is an example(Second column is PID) :

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root@server [~]# lsof |grep /tmp
mysqld 2579 mysql 4u REG 7,0 0 6098 /tmp/ibZGlGm2 (deleted)
mysqld 2579 mysql 5u REG 7,0 68 6100 /tmp/ibgWnlrp (deleted)
mysqld 2579 mysql 6u REG 7,0 0 6101 /tmp/ib7XB0vM (deleted)
mysqld 2579 mysql 7u REG 7,0 0 6102 /tmp/ibQx1jB9 (deleted)
mysqld 2579 mysql 11u REG 7,0 0 6103 /tmp/ibBSaB7w (deleted)
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Then retry to umount the device like : umount /tmp_device_name //You'll get device from /etc/fstab. This file contains the mounting file system table information after system reboot and /etc/mtab holds the current mounted table information.

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fuser -m /dev/sda3 //You can also get the PID from here also. But note that deleting all the PID related to this device may cause the problem on the system and you may need to restart the machine.
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That's it. Try :)