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Issue
/etc/fstab has been messed up. It is read-only now.
Tried
mount -o remount,rw /
Does not work
Solutions
mount -o remount,rw /dev/sda2 /
Note: Instead of /dev/sda2, use whatever the device is valid for your drive.
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Swap Partition Size
RedHat
RedHat distributions should have a swap partition size of 20% of the available RAM. The minimum amount of RAM is 4GB.
CentOS
CentOS provides the following guidelines:
The swap partition should be twice the amount of RAM if the total RAM amount is below 2GB.
If you have more than 2GB of RAM, then the swap partition should be the size of RAM + 2 GB. For example, use 8GB of swap for 6GB of RAM.
Ubuntu/Debian
Ubuntu has based its swap size recommendations on the use of hibernation.
If you use hibernation, the swap partition should be the same as the amount of RAM plus the square root of the RAM amount.
If you don’t use hibernation:
For less than 1GB of RAM, the swap partition size should be at least the same as the amount of RAM and, at most, double the amount of RAM.
For more than 1GB of RAM, create a swap partition at least equal to the square root of the RAM amount and, at most, double the RAM amount.
swapon Command
swapon –show
Check /proc/swaps File
cat /proc/swaps
Comman to check your swap
free -h
How to Create a Swap Partition
1. Run the fdisk command for the disk you want to partition:
sudo fdisk [disk_path]
Replace [disk_path] with your disk identifier.
2. Type p and press Enter for an overview of the disk.
The output provides information about the available disk space for a new partition. If the last partition ends before the last sector of the hard drive, there is enough space to create a new partition. The output above shows the entire disk space is available for creating a new partition.
3. Type n and press Enter to create a new partition. For partition type, enter p and press Enter.
4. Set the partition number (or keep the default number 1) and press Enter to confirm.
5. Enter the first available sector for the new partition and press Enter. You can also keep the default one offered.
6. Set the last available sector for the partition. You can specify the partition size in KiB, MiB, or GiB units. We will create a swap partition of 1GiB, so the command is:
+1G
7. Press p to verify the partition creation and confirm with Enter.
8. By default, the partition type is 83, while 82 is a partition type identifier for swap space.
Type t and press Enter to change the partition type. Change the value to 82 and press Enter.
9. Verify the change with p and confirm with Enter.
10. fdisk doesn’t make any changes to the disk before confirmation. To proceed with the changes, type w, and press Enter.
12. Update the partition table using the following syntax:
sudo partprobe [disk_path]
13. Use the mkswap command to format the partition for swap space. The command writes a swap signature in the partition, leaving the rest unformatted. The unformatted space stores the memory pages.
Use the following syntax to format the partition and create a swap space:
sudo mkswap [disk_path]
After formatting, the swap partition is created and ready to use.
How to Initialize/Enable a Swap Partition
3. Make Swap Persistent (Optional)
Include the partition in the /etc/fstab file to ensure the swap partition activates on boot.
vi /etc/fstab
Add the following line at the end:
/dev/sdb none swap sw 0 0
Replace /dev/sdb with the path to your swap partition.
How to Change the Size of a Swap Partition
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df -h
Check Disk Usage per User
repquota -a -s
Show only accounts with usage in Gbytes
repquota -a -s | grep G
Check Disk Usage per Partition ignoring links
* You can replace /home with the parition or folder you want to check
Let’s check /home partition
du -hx --max-depth 1 /home
Show only folders with usage in Gbytes
du -hx --max-depth 1 /home | grep G
Check /var partition
du -hx --max-depth 1 /var
Show only folders with usage in Gbytes
du -hx --max-depth 1 /var | grep G
Check Mail folder /var/vmail
du -hx --max-depth 1 /var/vmail
Show only folders with usage in Gbytes
du -hx --max-depth 1 /var/vmail | grep G
Check MySQL folder /var/lib/mysql
du -hx --max-depth 1 /var/lib/mysql
Show only folders with usage in Gbytes
du -hx --max-depth 1 /var/lib/mysql | grep G
Check Backups
du -hx --max-depth 1 /backup
Show only folders with usage in Gbytes
du -hx --max-depth 1 /backup | grep G
Show only daily backup folder with usage in Gbytes
du -hx --max-depth 1 /backup/daily | grep G
Now when you know how to check the partitions and folders here are some useful commands to check files in the folder sorted by size:
ls -lahS /folder/location
Example for MySQL folder /var/lib/mysql/
ls -lahS /var/lib/mysql/
Some useful scripts we already have are checking the most frequent folders:
/var/log/
/usr/local/apache/logs/
/usr/local/apache/domlogs/
/usr/local/cwpsrv/logs/
/tmp
/root
/var/lib/mysql/
/scripts/disk_check
Delete Files
Now when you know how to check, the question is how can you delete or empty files.
Note that you shouldn’t delete files other than logs or backups as all others can crash your server.
Log files are in use by the programs so in case you want to clean big active log files you can’t just delete them as they will remain invisible until you restart the service.
The solution is to empty the file, example:
:> /usr/local/apache/logs/access_log
However all other logs files you can simply delete, examples
rm -f filename
An example case when you have active log files and logrotated which are not active and are renamed with -DATE
Delete single log file NOT currently in use by service
rm -f /var/log/maillog-20211108
Delete all maillog files NOT currently in use by service
rm -f /var/log/maillog-*
Empty active log file which is in use by the service
:> /var/log/maillog
* If you are not sure it’s better to grab a support service and have the experienced sysadmin to check this for you.
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First create a file in /root dir :
cd /root vi clearlog.sh
Then paste this Bash script and save it by press ctrl+x:
#!/bin/bash truncate -s 0 /usr/local/apache/logs/*bytes truncate -s 0 /usr/local/apache/logs/*log truncate -s 0 /usr/local/apache/domlogs/*bytes truncate -s 0 /usr/local/apache/domlogs/*log truncate -s 0 /var/log/messages truncate -s 0 /var/log/maillog truncate -s 0 /var/log/*log truncate -s 0 /opt/alt/*/usr/var/log/php-fpm.log truncate -s 0 /usr/local/cwpsrv/logs/access_log truncate -s 0 /usr/local/cwpsrv/logs/error_log truncate -s 0 /var/log/cron truncate -s 0 /var/log/secure truncate -s 0 /var/log/cwp/services_action.log truncate -s 0 /var/log/cwp/cwp_sslmod.log truncate -s 0 /var/log/cwp/cwp_cron.log truncate -s 0 /var/log/cwp/cwp_backup.log truncate -s 0 /var/log/cwp/activity.log rm -rf /var/log/maillog-* rm -rf /var/log/monit.log-* rm -rf /var/log/spooler-* rm -rf /var/log/messages-* rm -rf /var/log/secure-* rm -rf /var/log/pureftpd.log-* rm -rf /var/log/yum.log-* rm -rf /var/log/monit.log-* rm -rf /var/log/cron-*
Change the permission :
chmod 755 /root/clearlog.sh
Now run this command to run the clear log script:
sh /root/clearlog.sh
Thats it the logs will be cleared you can go and check to the respected locations of the log.
You can also create cron job like below by following solution 2 and create this cron job task according to your needs :
TO run DAILY :
0 0 * * * /usr/bin/sh /root/clearlog.sh
TO run Weekly :
0 0 * * 0 /usr/bin/sh /root/clearlog.sh
TO run Monthly:
0 0 1 * * /usr/bin/sh /root/clearlog.sh
That’s All!
It will save lot’s of space.
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To check DKIM verification:
To check SPF verification: