The purpose of this blog

The purpose of this blog is to post fixes for common linux or unix command line problems including the command line on Mac OS X.

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ZFS syntax (updated)

Introduction ZFS is an alternative filesystem. It allows RAID, deduplication and compression. You create a collection of drives as a 'pool'. That's useful if you want many drives as one big drive. Suppose you have two spare drives, sdc1 and sdd1. To make them into one big drive with deduplication and no compression, do this. Deduplication = where it doesn't make multiple copies of identical files, just marks them as copies. Creating a ZFS pool (drive collection) zpool create -f zfspool /dev/sdc1  /dev/sdd1 zfs set compression= off  zfspool zfs set dedup= on  zfspool zpool list df -h you'll see it is mounted as /zfspool A zfs snapshot  is a read-only copy of  zfs  file system or volume. They consume no extra space in the  zfs  pool and can be created instantly. They can be used to save a state of file system at particular point of time and can later be rolled back to exactly same state.  LVM is similar to ZFS but doesn't offer all these other features. (In my e
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/var/log/journal taking up lots of space

 If /var/log/journal is taking up too much space, you can clear it and prevent it growing too big again. Prevention: vi /etc/systemd/journald.conf   Look for: SystemMaxUse=2000M Or similar, and set it to a lower value Then: service systemd-journald restart Clearing once-off: journalctl --vacuum-time=2d assuming for example you want to clear everything before two days ago.
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throttle traffic on apache

sudo apt install apache2-utils sudo apt install libapache2-mod-evasive vi /etc/apache2/mods-enabled/evasive.conf service apache restart edit it and set values as per below or whatever else you like, the time quantities are seconds     DOSSiteInterval     1     DOSBlockingPeriod   10     #DOSLogDir           "/var/lock/mod_evasive"
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