1：查看CPU負(fù)載--mpstat
mpstat -P ALL [internal [count]]
參數(shù)的含義如下：
-P ALL 表示監(jiān)控所有CPU
internal 相鄰的兩次采樣的間隔時(shí)間
count 采樣的次數(shù)
mpstat命令從/proc/stat獲得數(shù)據(jù)輸出
輸出的含義如下：
CPU 處理器ID
user 在internal時(shí)間段里，用戶態(tài)的CPU時(shí)間（%） ，不包含 nice值為負(fù) 進(jìn)程 ?usr/?total*100
nice 在internal時(shí)間段里，nice值為負(fù)進(jìn)程的CPU時(shí)間（%） ?nice/?total*100
system 在internal時(shí)間段里，核心時(shí)間（%） ?system/?total*100
iowait 在internal時(shí)間段里，硬盤IO等待時(shí)間（%） ?iowait/?total*100
irq 在internal時(shí)間段里，軟中斷時(shí)間（%） ?irq/?total*100
soft 在internal時(shí)間段里，軟中斷時(shí)間（%） ?softirq/?total*100
idle 在internal時(shí)間段里，CPU除去等待磁盤IO操作外的因?yàn)槿魏卧蚨臻e的時(shí)間閑置時(shí)間 （%） ?idle/?total*100
intr/s 在internal時(shí)間段里，每秒CPU接收的中斷的次數(shù) ?intr/?total*100
CPU總的工作時(shí)間total_cur=user+system+nice+idle+iowait+irq+softirq
total_pre=pre_user+ pre_system+ pre_nice+ pre_idle+ pre_iowait+ pre_irq+ pre_softirq
user=user_cur – user_pre
total=total_cur-total_pre
其中_cur 表示當(dāng)前值，_pre表示interval時(shí)間前的值。上表中的所有值可取到兩位小數(shù)點(diǎn)。
2：查看磁盤io情況及CPU負(fù)載--vmstat
usage: vmstat [-V] [-n] [delay [count]]
-V prints version.
-n causes the headers not to be reprinted regularly.
-a print inactive/active page stats.
-d prints disk statistics
-D prints disk table
-p prints disk partition statistics
-s prints vm table
-m prints slabinfo
-S unit size
delay is the delay between updates in seconds.
unit size k:1000 K:1024 m:1000000 M:1048576 (default is K)
count is the number of updates.
vmstat從/proc/stat獲得數(shù)據(jù)
輸出的含義如下:
FIELD DESCRIPTION FOR VM MODE
Procs
r: The number of processes waiting for run time.
b: The number of processes in uninterruptible sleep.
Memory
swpd: the amount of virtual memory used.
free: the amount of idle memory.
buff: the amount of memory used as buffers.
cache: the amount of memory used as cache.
inact: the amount of inactive memory. (-a option)
active: the amount of active memory. (-a option)
Swap
si: Amount of memory swapped in from disk (/s).
so: Amount of memory swapped to disk (/s).
IO
bi: Blocks received from a block device (blocks/s).
bo: Blocks sent to a block device (blocks/s).
System
in: The number of interrupts per second, including the clock.
cs: The number of context switches per second.
CPU
These are percentages of total CPU time.
us: Time spent running non-kernel code. (user time, including nice time)
sy: Time spent running kernel code. (system time)
id: Time spent idle. Prior to Linux 2.5.41, this includes IO-wait time.
wa: Time spent waiting for IO. Prior to Linux 2.5.41, shown as zero.
st: Time spent in involuntary wait. Prior to Linux 2.6.11, shown as zero.
3：查看內(nèi)存使用情況--free
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@Linux /tmp]# free
total used free shared buffers cached
Mem: 255268 238332 16936 0 85540 126384
-/+ buffers/cache: 26408 228860
Swap: 265000 0 265000
Mem：表示物理內(nèi)存統(tǒng)計(jì)
-/+ buffers/cached：表示物理內(nèi)存的緩存統(tǒng)計(jì)
Swap：表示硬盤上交換分區(qū)的使用情況，這里我們不去關(guān)心。
系統(tǒng)的總物理內(nèi)存：255268Kb（256M），但系統(tǒng)當(dāng)前真正可用的內(nèi)存b并不是第一行free 標(biāo)記的 16936Kb，它僅代表未被分配的內(nèi)存。
第1行 Mem：
total：表示物理內(nèi)存總量。
used：表示總計(jì)分配給緩存（包含buffers 與cache ）使用的數(shù)量，但其中可能部分緩存并未實(shí)際使用。
free：未被分配的內(nèi)存。
shared：共享內(nèi)存，一般系統(tǒng)不會(huì)用到，這里也不討論。
buffers：系統(tǒng)分配但未被使用的buffers 數(shù)量。
cached：系統(tǒng)分配但未被使用的cache 數(shù)量。buffer 與cache 的區(qū)別見后面。
total = used + free
第2行 -/+ buffers/cached：
used：也就是第一行中的used - buffers-cached 也是實(shí)際使用的內(nèi)存總量。
free：未被使用的buffers 與cache 和未被分配的內(nèi)存之和，這就是系統(tǒng)當(dāng)前實(shí)際可用內(nèi)存。
free 2= buffers1 + cached1 + free1 //free2為第二行、buffers1等為第一行
buffer 與cache 的區(qū)別
A buffer is something that has yet to be "written" to disk.
A cache is something that has been "read" from the disk and stored for later use
第3行：
對(duì)操作系統(tǒng)來講是Mem的參數(shù).buffers/cached 都是屬于被使用,所以它認(rèn)為free只有16936.
對(duì)應(yīng)用程序來講是(-/+ buffers/cach).buffers/cached 是等同可用的，因?yàn)閎uffer/cached是為了提高文件讀取的性能，當(dāng)應(yīng)用程序需在用到內(nèi)存的時(shí)候，buffer/cached會(huì)很快地被回收。
所以從應(yīng)用程序的角度來說，可用內(nèi)存=系統(tǒng)free memory+buffers+cached.
swap
swap就是LINUX下的虛擬內(nèi)存分區(qū),它的作用是在物理內(nèi)存使用完之后,將磁盤空間(也就是SWAP分區(qū))虛擬成內(nèi)存來使用.
4：查看網(wǎng)卡情況--sar
詳細(xì)見man
4.1：查看網(wǎng)卡流量：sar -n DEV delay count
服務(wù)器網(wǎng)卡最大能承受流量由網(wǎng)卡本身決定，分為10M、10/100自適應(yīng)、100+以及1G網(wǎng)卡，一般普通服務(wù)器用的是百兆，也有用千兆的。
輸出解釋：
IFACE
Name of the network interface for which statistics are reported.
rxpck/s
Total number of packets received per second.
txpck/s
Total number of packets transmitted per second.
rxbyt/s
Total number of bytes received per second.
txbyt/s
Total number of bytes transmitted per second.
rxcmp/s
Number of compressed packets received per second (for cslip etc.).
txcmp/s
Number of compressed packets transmitted per second.
rxmcst/s
Number of multicast packets received per second.
4.2：查看網(wǎng)卡失敗情況：sar -n EDEV delay count
輸出解釋：
IFACE
Name of the network interface for which statistics are reported.
rxerr/s
Total number of bad packets received per second.
txerr/s
Total number of errors that happened per second while transmitting packets.
coll/s
Number of collisions that happened per second while transmitting packets.
rxdrop/s
Number of received packets dropped per second because of a lack of space in linux buffers.
txdrop/s
Number of transmitted packets dropped per second because of a lack of space in linux buffers.
txcarr/s
Number of carrier-errors that happened per second while transmitting packets.
rxfram/s
Number of frame alignment errors that happened per second on received packets.
rxfifo/s
Number of FIFO overrun errors that happened per second on received packets.
txfifo/s
Number of FIFO overrun errors that happened per second on transmitted packets.
5：定位問題進(jìn)程--top, ps
top -d delay，詳細(xì)見man
ps aux 查看進(jìn)程詳細(xì)信息
ps axf 查看進(jìn)程樹
6：查看某個(gè)進(jìn)程與文件關(guān)系--losf
需要root權(quán)限才能看到全部，否則只能看到登錄用戶權(quán)限范圍內(nèi)的內(nèi)容
lsof -p 77//查看進(jìn)程號(hào)為77的進(jìn)程打開了哪些文件
lsof -d 4//顯示使用fd為4的進(jìn)程
lsof abc.txt//顯示開啟文件abc.txt的進(jìn)程
lsof -i :22//顯示使用22端口的進(jìn)程
lsof -i tcp//顯示使用tcp協(xié)議的進(jìn)程
lsof -i tcp:22//顯示使用tcp協(xié)議的22端口的進(jìn)程
lsof +d /tmp//顯示目錄/tmp下被進(jìn)程打開的文件
lsof +D /tmp//同上，但是會(huì)搜索目錄下的目錄，時(shí)間較長
lsof -u username//顯示所屬user進(jìn)程打開的文件
7：查看程序運(yùn)行情況--strace
usage: strace [-dffhiqrtttTvVxx] [-a column] [-e expr] ... [-o file]
[-p pid] ... [-s strsize] [-u username] [-E var=val] ...
[command [arg ...]]
or: strace -c [-e expr] ... [-O overhead] [-S sortby] [-E var=val] ...
[command [arg ...]]
常用選項(xiàng)：
-f：除了跟蹤當(dāng)前進(jìn)程外，還跟蹤其子進(jìn)程。
-c：統(tǒng)計(jì)每一系統(tǒng)調(diào)用的所執(zhí)行的時(shí)間,次數(shù)和出錯(cuò)的次數(shù)等.
-o file：將輸出信息寫到文件file中，而不是顯示到標(biāo)準(zhǔn)錯(cuò)誤輸出（stderr）。
-p pid：綁定到一個(gè)由pid對(duì)應(yīng)的正在運(yùn)行的進(jìn)程。此參數(shù)常用來調(diào)試后臺(tái)進(jìn)程。
8：查看磁盤使用情況--df
test@wolf:~$ df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda1 3945128 1810428 1934292 49% /
udev 745568 80 745488 1% /dev
/dev/sda3 12649960 1169412 10837948 10% /usr/local
/dev/sda4 63991676 23179912 37561180 39% /data
9：查看網(wǎng)絡(luò)連接情況--netstat
常用：netstat -lpn
選項(xiàng)說明：
-p, --programs display PID/Program name for sockets
-l, --listening display listening server sockets
-n, --numeric don't resolve names
-a, --all, --listening display all sockets (default: connected)