服务器磁盘满无法释放空间解析及解决

Posted 2022-10-26 henrylinux

硬盘显示被写满，但是用du -sh /*查看时占用硬盘空间之和还远小于硬盘大小

使用df -h查看，磁盘空间确实是满的，即找不到硬盘分区是怎么被写满的。

了解前因后果后，得知，这台WEB服务器的日志文件被删除了，目的是想清除日志文件占用的大量磁盘空间，但是当文件在一直被 写入的这个过程中，我们是无法彻底的删除的。

因此产生了这样的一个问题，下面我来模拟一下：

[root@oldboyedu test]# dd if=/dev/zero of=/dev/sdc bs=10M count=10
10+0 records in
10+0 records out
104857600 bytes (105 MB) copied, 2.18347 s, 48.0 MB/s
[root@oldboyedu test]# ll -hi /dev/sdc
48657 -rw-r--r--. 1 root root 100M Jul 14 19:08 /dev/sdc
[root@oldboyedu test]# mkfs -t ext4 /dev/sdc
mke2fs 1.41.12 (17-May-2010)
/dev/sdc is not a block special device.
Proceed anyway? (y,n) y
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
25688 inodes, 102400 blocks
5120 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=67371008
13 block groups
8192 blocks per group, 8192 fragments per group
1976 inodes per group
Superblock backups stored on blocks: 
    8193, 24577, 40961, 57345, 73729

Writing inode tables: done                            
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 22 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@oldboyedu test]# tune2fs -c -1 /dev/sdc
tune2fs 1.41.12 (17-May-2010)
Setting maximal mount count to -1
[root@oldboyedu test]# mkdir /log
[root@oldboyedu test]# mount -o loop /dev/sdc /log
[root@oldboyedu log]# dd if=/dev/zero of=/log/1.txt bs=10M count=8
8+0 records in
8+0 records out
83886080 bytes (84 MB) copied, 0.287821 s, 291 MB/s
[root@oldboyedu log]# echo "dddd">>1.txt
[root@oldboyedu log]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        19G  1.5G   17G   8% /
tmpfs           491M     0  491M   0% /dev/shm
/dev/sda1       190M   35M  146M  19% /boot
/dev/sdc         93M   82M  6.4M  93% /log

 

我重新打开一个终端执行以下命令：

[root@oldboyedu ~]# tail -f /log/1.txt
dddd

 

然后准备删除，查看结果

[root@oldboyedu log]# rm 1.txt -f
[root@oldboyedu log]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        19G  1.5G   17G   8% /
tmpfs           491M     0  491M   0% /dev/shm
/dev/sda1       190M   35M  146M  19% /boot
/dev/sdc         93M   82M  6.4M  93% /log
[root@oldboyedu log]# ll
total 12
drwx------. 2 root root 12288 Jul 14 19:11 lost+found
[root@oldboyedu log]# du -sh /log
13K    /log
[root@oldboyedu log]# du -sh /log/*
12K    /log/lost+found
[root@oldboyedu log]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        19G  1.5G   17G   8% /
tmpfs           491M     0  491M   0% /dev/shm
/dev/sda1       190M   35M  146M  19% /boot
/dev/sdc         93M   82M  6.4M  93% /log
[root@oldboyedu log]# lsof |grep deleted
tail      3029      root    3r      REG                7,0 83886085         12 /log/1.txt (deleted)
[root@oldboyedu log]# kill -15 3029
[root@oldboyedu log]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        19G  1.5G   17G   8% /
tmpfs           491M     0  491M   0% /dev/shm
/dev/sda1       190M   35M  146M  19% /boot
/dev/sdc         93M  1.6M   87M   2% /log
[root@oldboyedu log]# lsof |grep deleted
[root@oldboyedu log]#