Use of SWAP Space in Linux ..???

Q.1 What is SWAP Space?

Answer:

Swap space in Linux is used when the amount of physical memory (RAM) is full. If the system needs more memory resources and the RAM is full, inactive pages in memory are moved to the swap space. While swap space can help machines with a small amount of RAM, it should not be considered a replacement for more RAM. Swap space is located on hard drives, which have a slower access time than physical memory.

Q2. What is swap id

Answer:

82

Q3.What are the steps to create SWAP files or Partition?

Answer:

1> - Create swap partition or file

2> - Write special signature using “mkswap”

3> - Activate swap space by “swapon –a” command

4> - Add swap entry into /etc/fstab file

Q4.  How you will create swap file of size 4 GB and explain swap file entry in /etc/fstab file?

Answer:

Step1: Use “dd” command to create swap file.

Step2: dd if=/dev/zero  of=/SWAPFILE  bs=1024  count=4

Step3: mkswap /SWAPFILE

Step4: swapon –a

Step5: Entry into /etc/fstab file.

/SWAPFILE   swap   swap   defaults   0   0

Q5.  Tell me the steps to remove the swap file?

Answer:

1) Firstly disable the swap file by “swapoff” command.

2) Remove Swap file entry from /etc/fstab file.

3)Now remove the swap file by “rm” command.

Q6.How to Clear Swap Space in Linux?

Answer:

If you want to clear Swap space, you may like to run the below command.

# swapoff -a && swapon -a

Q7.How to Check Swap Space in Linux using /proc/swaps file.?
Answer:
Type the following cat command to see total and used swap size:

# cat /proc/swaps 

Sample outputs:

Filename				Type		Size	Used	Priority
/dev/sda3                               partition	6291448	65680	0

Q8.How to Check Swap Space in Linux using grep command.?
Answer:

#grep Swap /proc/meminfo

SwapCached:            0 kB
SwapTotal:        524284 kB
SwapFree:         524284 kB

Q9. How to check swap size in Linux using vmstat command.?
Answer:
Type the following vmstat command:

# vmstat

# vmstat 1 5

Sample outputs:

procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
 1  9 1209512 101352   1504 127980    0    3    11    20   60   55  3  1 95  1
 2 11 1209640 101292   1508 134132  844  424  5608   964 23280 15012  2  8 20 70
 0 10 1210052 108132   1532 125764  648  660 10548   916 22237 18103  3 10 11 77
 1 13 1209892 106484   1500 128052  796  240 10484   980 24024 12692  2  8 24 67
 1  9 1209332 113412   1500 124028 1608  168  2472   620 28854 13761  2  8 20 70

Note down the following output from swap field:


si: Amount of memory swapped in from disk (/s).

so: Amount of memory swapped to disk (/s).

Q10. How to check swap size in Linux using free command.?
Answer:
#free -h

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