前几天，网站出现Many connections的问题，进入mysql,show full processlist发现有154个进程，晕....直接service mysqld restart
但是不能启动，出现了“Timeout error occurred trying to start MySQL Daemon”问题，百度搜索了一下，说
可能是磁盘空间不够了。
# df -lh
#查看磁盘使用情况
发现根目录满了，于是
# du -s /* | sort -nr
#查看根目录下下文件大小，并按大小排序
# du -sh /var/*
#查看某目录下的文件、目录大小
#rm -rf ***.tar.gz
OK.....
===================================================================
关于df:
#man df | col -bx > /moushu/shell_man/df.txt
NAME
df - report file system disk space usage
SYNOPSIS
df [OPTION]... [FILE]...
DESCRIPTION
This manual page documents the GNU version of df. df displays the
amount of disk space available on the file system containing each file
name argument. If no file name is given, the space available on all
currently mounted file systems is shown. Disk space is shown in 1K
blocks by default, unless the environment variable POSIXLY_CORRECT is
set, in which case 512-byte blocks are used.
If an argument is the absolute file name of a disk device node contain-
ing a mounted file system, df shows the space available on that file
system rather than on the file system containing the device node (which
is always the root file system). This version of df cannot show the
space available on unmounted file systems, because on most kinds of
systems doing so requires very nonportable intimate knowledge of file
system structures.
OPTIONS
Show information about the file system on which each FILE resides, or
all file systems by default.
Mandatory arguments to long options are mandatory for short options
. too.
-a, --all
include dummy file systems
-B, --block-size=SIZE
use SIZE-byte blocks
--direct
show statistics for a file instead of mount point
--total
produce a grand total
-h, --human-readable
print sizes in human readable format (e.g., 1K 234M 2G)
-H, --si
likewise, but use powers of 1000 not 1024
-i, --inodes
list inode information instead of block usage
-k like --block-size=1K
-l, --local
limit listing to local file systems
--no-sync
do not invoke sync before getting usage info (default)
-P, --portability
use the POSIX output format
--sync invoke sync before getting usage info
-t, --type=TYPE
limit listing to file systems of type TYPE
-T, --print-type
print file system type
-x, --exclude-type=TYPE
limit listing to file systems not of type TYPE
-v (ignored)
--help display this help and exit
--version
output version information and exit
Display values are in units of the first available SIZE from
--block-size, and the DF_BLOCK_SIZE, BLOCK_SIZE and BLOCKSIZE environ-
ment variables. Otherwise, units default to 1024 bytes (or 512 if
POSIXLY_CORRECT is set).
SIZE may be (or may be an integer optionally followed by) one of fol-
lowing: KB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G, T,
P, E, Z, Y.
中文参考资料：
http://vbird.dic.ksu.edu.tw/linux_basic/0230filesystem_2.php
http://www.cnblogs.com/peida/archive/2012/12/07/2806483.html
关于du:
#man du | col -bx > /moushu/shell_man/du.txt
NAME
du - estimate file space usage
SYNOPSIS
du [OPTION]... [FILE]...
du [OPTION]... --files0-from=F
DESCRIPTION
Summarize disk usage of each FILE, recursively for directories.
Mandatory arguments to long options are mandatory for short options
too.
-a, --all
write counts for all files, not just directories
--apparent-size
print apparent sizes, rather than disk usage; although the
apparent size is usually smaller, it may be larger due to holes
in (‘sparse’) files, internal fragmentation, indirect blocks,
and the like
-B, --block-size=SIZE
use SIZE-byte blocks
-b, --bytes
equivalent to ‘--apparent-size --block-size=1’
-c, --total
produce a grand total
-D, --dereference-args
dereference only symlinks that are listed on the command line
--files0-from=F
summarize disk usage of the NUL-terminated file names specified
in file F; If F is - then read names from standard input
-H equivalent to --dereference-args (-D)
-h, --human-readable
print sizes in human readable format (e.g., 1K 234M 2G)
--si like -h, but use powers of 1000 not 1024
-k like --block-size=1K
-l, --count-links
count sizes many times if hard linked
-m like --block-size=1M
-L, --dereference
dereference all symbolic links
-P, --no-dereference
don’t follow any symbolic links (this is the default)
-0, --null
end each output line with 0 byte rather than newline
-S, --separate-dirs
do not include size of subdirectories
-s, --summarize
display only a total for each argument
-x, --one-file-system
skip directories on different file systems
-X, --exclude-from=FILE
exclude files that match any pattern in FILE
--exclude=PATTERN
exclude files that match PATTERN
--max-depth=N
print the total for a directory (or file, with --all) only if it
is N or fewer levels below the command line argument;
--max-depth=0 is the same as --summarize
--time show time of the last modification of any file in the directory,
or any of its subdirectories
--time=WORD
show time as WORD instead of modification time: atime, access,
use, ctime or status
--time-style=STYLE
show times using style STYLE: full-iso, long-iso, iso, +FORMAT
FORMAT is interpreted like ‘date’
--help display this help and exit
--version
output version information and exit
Display values are in units of the first available SIZE from
--block-size, and the DU_BLOCK_SIZE, BLOCK_SIZE and BLOCKSIZE environ-
ment variables. Otherwise, units default to 1024 bytes (or 512 if
POSIXLY_CORRECT is set).
SIZE may be (or may be an integer optionally followed by) one of fol-
lowing: KB 1000, K 1024, MB 1000*1000, M 1024*1024, and so on for G, T,
P, E, Z, Y.
PATTERNS
PATTERN is a shell pattern (not a regular expression). The pattern ?
matches any one character, whereas * matches any string (composed of
zero, one or multiple characters). For example, *.o will match any
files whose names end in .o. Therefore, the command
du --exclude='*.o'
will skip all files and subdirectories ending in .o (including the file
.o itself).
中文参考资料：
http://vbird.dic.ksu.edu.tw/linux_basic/0230filesystem_2.php
http://www.cnblogs.com/peida/archive/2012/12/10/2810755.html