Solve Linux NFS umount 'device is busy' and 'df-H' hang

The backups of the company's development, testing, and quasi-production databases are all nfs-mounted nas disks and local disks of backup hosts. Recently, after the nas permission is adjusted, the nfs mount point is dropped. Df-h does not see the mounted nas and causes hang operation.

1. 'df-H' hang
[Root @ develop119 ~] # Df-h
File System capacity used available % mount point
/Dev/sda5 34G 10G 22G 32%/
/Dev/sda7 76G 68G 4.1G 95%/oradata
/Dev/sda3 34G 29G 2.9G 91%/u01
/Dev/sda2 48G 24G 22G 52%/bakcup
/Dev/sda1 145 M 12 M 126 M 9%/boot
Tmpfs 3.9G 0 3.9G 0%/dev/shm
192.168.101.119:/nfs_backup
197G, 89G, 99G, 48%/bakcup/expdp_bk/dmp
After df-h, you cannot view the mount point when operating hang. After checking/etc/fatab, you find that automatic mounting is not set at startup.


Solution:
View mount points:
[Root @ develop119 ~] # Cat/proc/mounts
Rootfs/rootfs rw 0 0
/Dev/root/ext3 rw, data = ordered 0 0
/Dev tmpfs rw 0 0
/Proc rw 0 0
/Sys sysfs rw 0 0
/Proc/bus/usb usbfs rw 0 0
Devpts/dev/pts devpts rw 0 0
/Dev/sda7/oradata ext3 rw, data = ordered 0 0
/Dev/sda3/u01 ext3 rw, data = ordered 0 0
/Dev/sda2/bakcup ext3 rw, data = ordered 0 0
/Dev/sda1/boot ext3 rw, data = ordered 0 0
Tmpfs/dev/shm tmpfs rw 0 0
None/proc/sys/fs/binfmt_misc rw 0 0
Sunrpc/var/lib/nfs/rpc_pipefs rw 0 0
/Etc/auto. misc/misc autofs rw, fd = 7, pgrp = 2854, timeout = 300, minproto = 5, maxproto = 5, indirect 0 0
-Hosts/net autofs rw, fd = 13, pgrp = 2854, timeout = 300, minproto = 5, maxproto = 5, indirect 0 0
192.168.101.119:/nfs_backup/bakcup/expdp_bk/dmp nfs rw, vers = 3, rsize = 262144, wsize = 262144, hard, proto = tcp, timeo = 600, retrans = 2, sec = sys, addr = 192.168.101.119 0 0
172.16.7.241:/db_bak/mnt nfs rw, vers = 3, rsize = 32768, wsize = 32768, hard, proto = tcp, timeo = 600, retrans = 2, sec = sys, addr = 172.16.7.241 0 0

The directory where the nas disk is mounted Is/mnt.

Umount mount point
[Root @ develop119 ~] # Umount-lf/mnt
[Root @ develop119 ~] # Df-h
File System capacity used available % mount point
/Dev/sda5 34G 10G 22G 32%/
/Dev/sda7 76G 68G 4.1G 95%/oradata
/Dev/sda3 34G 29G 2.9G 91%/u01
/Dev/sda2 48G 24G 22G 52%/bakcup
/Dev/sda1 145 M 12 M 126 M 9%/boot
Tmpfs 3.9G 0 3.9G 0%/dev/shm
192.168.101.119:/nfs_backup
197G, 89G, 99G, 48%/bakcup/expdp_bk/dmp
[Root @ develop119 ~] #

Ii. umount 'device is busy'
[Root @ mysql10 ~] # Umount/mnt/
Umount:/mnt: device is busy

Umount:/mnt: device is busy

 

Solve device is busy:
[Root @ mysql10 ~] # Fuser-k/mnt/-- fuser command shows the PID of the process accessing a file.-k is the process that uses kill to access the file.
[Root @ mysql10 ~] # Umount/mnt/
[Root @ mysql10 ~] # Df-h
Filesystem Size Used Avail Use % Mounted on
/Dev/mapper/VolGroup00-LogVol00
229 GB 111G 107G 51%/
/Dev/sda1 99 M 13 M 82 M 14%/boot
Tmpfs 3.9G 0 3.9G 0%/dev/shm

Iii. Restart portmap and nfs on the nfs server and then re-mount
/Etc/init. d/portmap restart or service portmap restart
/Etc/init. d/nfs restart or service nfs restart

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