clear_memory
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| clear_memory [2023/07/12 00:29] – created wigums | clear_memory [2024/07/23 16:19] (current) – external edit 127.0.0.1 | ||
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| - | Explanation of the above command. | + | ===Explanation of the above command.=== |
| sync will flush the file system buffer. Command Separated by “;” run sequentially. The shell waits for each command to terminate before executing the next command in the sequence. As mentioned in the kernel documentation, | sync will flush the file system buffer. Command Separated by “;” run sequentially. The shell waits for each command to terminate before executing the next command in the sequence. As mentioned in the kernel documentation, | ||
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| If you have to clear the disk cache, the first command is safest in enterprise and production as “...echo 1 > ….” will clear the PageCache only. It is not recommended to use the third option above “...echo 3 >” in production until you know what you are doing, as it will clear pagecache, dentries, and inodes. | If you have to clear the disk cache, the first command is safest in enterprise and production as “...echo 1 > ….” will clear the PageCache only. It is not recommended to use the third option above “...echo 3 >” in production until you know what you are doing, as it will clear pagecache, dentries, and inodes. | ||
| Is it a good idea to free Buffer and Cache in Linux that might be used by Linux Kernel? | Is it a good idea to free Buffer and Cache in Linux that might be used by Linux Kernel? | ||
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| Free Buffer and Cache in Linux | Free Buffer and Cache in Linux | ||
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| Moreover, it will also slow the system for a few seconds while the cache is cleaned and every resource required by OS is loaded again in the disk cache. | Moreover, it will also slow the system for a few seconds while the cache is cleaned and every resource required by OS is loaded again in the disk cache. | ||
| - | Now we will be creating a shell script to auto clear RAM cache daily at 2 am via a cron scheduler task. Create a shell script clearcache.sh and add the following lines. | + | Now we will be creating a shell script to auto clear RAM cache via a cron scheduler task. Create a shell script clearcache.sh and add the following lines. |
| + | |||
| + | < | ||
| + | LOGFILE=/ | ||
| + | |||
| + | LOG() { | ||
| + | msg=" | ||
| + | echo " | ||
| + | } | ||
| + | |||
| + | LOG " | ||
| + | sync; echo 3 > / | ||
| + | LOG " | ||
| - | #!/bin/bash | ||
| - | # Note, we are using "echo 3", but it is not recommended in production instead use "echo 1" | ||
| - | echo "echo 3 > / | ||
| Set execute permission on the clearcache.sh file. | Set execute permission on the clearcache.sh file. | ||
| - | # chmod 755 clearcache.sh | + | < |
| Now you may call the script whenever you are required to clear the ram cache. | Now you may call the script whenever you are required to clear the ram cache. | ||
| Line 43: | Line 54: | ||
| Now set a cron to clear RAM cache every day at 2 am. Open crontab for editing. | Now set a cron to clear RAM cache every day at 2 am. Open crontab for editing. | ||
| - | # crontab -e | + | < |
| + | |||
| + | Append the below line, save and exit to run it at the top of the hour every hour. | ||
| + | |||
| + | < | ||
| - | Append the below line, save and exit to run it at 2 am daily. | ||
| - | 0 2 * * * /path/to/clearcache.sh | + | Think of a situation when you have scheduled the script |
| - | For more details on how to cron a job, you may like to check our article on 11 Cron Scheduling Jobs. | + | At the same time, the scheduled script runs and clears everything in the cache. Now all the users are fetching data from the disk. It will result in a server |
| - | Is it a good idea to auto clear the RAM cache on the production | + | |
| - | Clear RAM Cache on Linux Production Server? | + | |
| - | No! it is not. Think of a situation when you have scheduled the script to clear ram cache every day at 2 am. Every day at 2 am the script is executed and it flushes your RAM cache. One day for whatsoever reason may be more than expected users are online on your website and seeking resources from your server. | ||
| - | At the same time, the scheduled script runs and clears everything in the cache. Now all the users are fetching data from the disk. It will result in a server crash and corrupt the database. So clear ram-cache only when required, and known your footsteps, else you are a Cargo Cult System Administrator. | ||
| How to Clear Swap Space in Linux? | How to Clear Swap Space in Linux? | ||
| If you want to clear Swap space, you may like to run the below command. | If you want to clear Swap space, you may like to run the below command. | ||
| - | # swapoff -a && swapon -a | + | < |
| Also, you may add the above command to a cron script above, after understanding all the associated risks. | Also, you may add the above command to a cron script above, after understanding all the associated risks. | ||
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| Now we will be combining both above commands into one single command to make a proper script to clear RAM Cache and Swap Space. | Now we will be combining both above commands into one single command to make a proper script to clear RAM Cache and Swap Space. | ||
| - | # echo 3 > / | + | < |
| OR | OR | ||
| - | $ su -c "echo 3 >'/ | + | < |
clear_memory.1689121793.txt.gz · Last modified: 2024/07/23 16:19 (external edit)