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[problems solution] linux:删除大文件，磁盘没有释放空间

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问题描述#

用tab自动补全报错 No space left on device 

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# cd my-bash: cannot create temp file for here-document: No space left on device
查看磁盘空间，发现/dev/dm-0占用100% 
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# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/dm-0       7.8G  7.8G   20K 100% /
...
用du -h --max-depth / 分析出/var/log文件占用了很大的空间

暴力地用 rm -r /var/log/ 删除,再次查看usr文件,发现var空间下已无log文件 

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# rm -r /var/log/

# du -h --max-depth=1 /var
337M    /var/lib
90M     /var/cache
0       /var/tmp
48M     /var/spool
6.3M    /var/backups
0       /var/local
0       /var/opt
144K    /var/mail
192K    /var/initsh
481M    /var
查看磁盘空间还是却未变 
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# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/dm-0       7.8G  7.8G   20K 100% /
...
## 问题排查与解决 突然想到可能是var/log文件还被占用着，磁盘空间没有成功释放。使用lsof查看 
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# lsof  -u root|grep var/log
rsyslogd  16083 root    5w      REG              253,0    4149248   27063243 /var/log/auth.log (deleted)
rsyslogd  16083 root    6w      REG              253,0 1463746560   27104493 /var/log/syslog (deleted)
rsyslogd  16083 root    7w      REG              253,0 1826508800   27063246 /var/log/messages (deleted)
rsyslogd  16083 root    8w      REG              253,0    3448832   27063245 /var/log/cron.log (deleted)
rsyslogd  16083 root   10w      REG              253,0    2568192   27063241 /var/log/mail.log (deleted)
rsyslogd  16083 root   11w      REG              253,0    2568192   27104495 /var/log/mail.info (deleted)
rsyslogd  16083 root   12w      REG              253,0    2568192   27063239 /var/log/mail.warn (deleted)
rsyslogd  16083 root   13w      REG              253,0    2564096   27063240 /var/log/mail.err (deleted)
rsyslogd  16083 root   14w      REG              253,0    3464038   27063242 /var/log/daemon.log (deleted)
rsyslogd  16083 root   15w      REG              253,0      20480   27063244 /var/log/user.log (deleted)
rsyslogd  16083 root   16w      REG              253,0        528   27104496 /var/log/kern.log (deleted)
rsyslogd  16083 root   17w      REG              253,0        528   27063254 /var/log/debug (deleted)
果然被rsyslogd程序占用中，重启一波rsyslogd，发现成功释放了磁盘空间 
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# /etc/init.d/rsyslog restart

# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/dm-0       7.8G  4.7G  3.1G  61% /

问题思考#

暴力使用rm -r 清除正在被占用的文件例如 var/log，并不会释放磁盘空间。 可以在删除之前 先清空文件，再删除文件 这样能快速释放磁盘空间 

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echo “” > xxx.log
rm -rf xxx.log

如何定期清理#

crontab指令可以定期执行命令, 对于定期清理日志, 当然也要用crontab。具体定期清理方式请阅读 crontab定期执行命令指令,