linux 查看系统信息

一.查看内存信息

可以使用free命令显示系统的物理内存和交换分区的总量，以及已使用的、空闲的、共享的、在内核缓冲内的和被缓存的内存数量。

使用free命令可以显示计算机系统的内存容量。

[root@redhat2 ~]# free --help

free: invalid option -- '-'

usage: free [-b|-k|-m|-g] [-l] [-o] [-t] [-s delay] [-c count] [-V]

-b,-k,-m,-g show output in bytes, KB, MB, or GB

-l show detailed low and high memory statistics

-o use old format (no -/+buffers/cache line)

-t display total for RAM + swap

-s update every [delay] seconds

-c update [count] times

-V display version information and exit

[root@redhat2 ~]#

例1：查看系统的物理内存和交换分区的总量。

[root@redhat2 ~]# free

total       used       free     shared    buffers     cached

Mem:       1592280     368792    1223488          0      51824     122532

-/+ buffers/cache:     194436    1397844

Swap:      3211256          0    3211256

[root@redhat2 ~]#

例2：以MB为单位查看系统的物理内存和交换分区的总量。

[root@redhat2 ~]# free -m

total       used       free     shared    buffers     cached

Mem:          1554        360       1194          0         50        119

-/+ buffers/cache:        189       1365

Swap:         3135          0       3135

[root@redhat2 ~]#

例3：显示物理内存和交换分区的总和。

[root@redhat2 ~]# free -t

total       used       free     shared    buffers     cached

Mem:       1592280     368792    1223488          0      51880     122532

-/+ buffers/cache:     194380    1397900

Swap:      3211256          0    3211256

Total:     4803536     368792    4434744

二.查看磁盘空间占用情况

使用df命令可以显示磁盘的相关信息。检查文件系统的磁盘空间占用情况，利用该命令获取硬盘占用了多少空间、目前还剩下多少空间等相关信息。

[root@redhat2 ~]# df --help

Usage: df [OPTION]... [FILE]...

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

例1:显示系统的磁盘空间使用量。

[root@redhat2 ~]# df

Filesystem           1K-blocks      Used Available Use% Mounted on

/dev/sda3             27499388   6662112  19440388  26% /

tmpfs                   796140        88    796052   1% /dev/shm

/dev/sda1               297485     33069    249056  12% /boot

[root@redhat2 ~]#

例2：以MB或GB为单位显示系统的磁盘空间使用量。

[root@redhat2 ~]# df -h

Filesystem            Size  Used Avail Use% Mounted on

/dev/sda3              27G  6.4G   19G  26% /

tmpfs                 778M   88K  778M   1% /dev/shm

/dev/sda1             291M   33M  244M  12% /boot

[root@redhat2 ~]#

例3：显示ext4文件系统类型磁盘空间使用量。

[root@redhat2 ~]# df -t ext4

Filesystem           1K-blocks      Used Available Use% Mounted on

/dev/sda3             27499388   6662112  19440388  26% /

/dev/sda1               297485     33069    249056  12% /boot

[root@redhat2 ~]#

例4：以MB或GB为单位显示磁盘空间使用量时也显示文件系统类型。

[root@redhat2 ~]# df -hT

Filesystem    Type    Size  Used Avail Use% Mounted on

/dev/sda3     ext4     27G  6.4G   19G  26% /

tmpfs        tmpfs    778M   88K  778M   1% /dev/shm

/dev/sda1     ext4    291M   33M  244M  12% /boot

[root@redhat2 ~]#

例5：显示磁盘空间i节点使用情况。

[root@redhat2 ~]# df -i

Filesystem            Inodes   IUsed   IFree IUse% Mounted on

/dev/sda3            1746240  107517 1638723    7% /

tmpfs                 199035       3  199032    1% /dev/shm

/dev/sda1              76912      39   76873    1% /boot

[root@redhat2 ~]#

三.显示目录或文件的大小

使用du命令可以显示目录或文件的大小。

[root@redhat2 ~]# du --help

Usage: du [OPTION]... [FILE]...

or:  du [OPTION]... --files0-from=F

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

例1：显示文件/root/a.sh的大小。

[root@redhat2 ~]# du /root/a.sh

4       /root/a.sh

[root@redhat2 ~]#

[root@redhat2 ~]# du -h a.sh

4.0K    a.sh

[root@redhat2 ~]#