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Path: content/Tips/Linux/Filesystems.md

Filesystems

Reducing wasted space

Older systems (and maybe some new ones) will reserve 5% of space for root. This is sort of useful on small root disks but if you have a 10TB data drive it's daft to have 500GB unusable. Set the percentage reserved to 1% with this:

tune2fs -m 1 /dev/sda1

m can be zero.

Reload partition table

If you add a disk to a system, eg in VMWare, KVM or in cloud, you may need to rescan the partitions:

partprobe or partx -a /dev/sdX

The old school way is to poke the scsi driver with something like this:

New disks: echo "- - -" >> /sys/class/scsi_host/host0/scan (there may be a host1, host2 etc)

Resized disks: echo 1 >> /sys/class/block/sd?/device/rescan (replace ? with the letter of your drive)

To Sum all file sizes over 'n' days old

find . -type f -mtime +356 -printf '%s\n' | awk '{a+=$1;} END {printf "%.1f GB\n", a/2**30;}'

EG to get file that are 1 year, 6 months, 3 months and one month old:

for i in 365 180 90 30
> do
> echo -n "$i == " ;
> find . -type f -mtime +$i -printf '%s\n' | awk '{a+=$1;} END {printf "%.1f GB\n", a/2**30;}'
> done

Setting date format in ls

Getting a consistent date stamp from ls can be done with the --time-styles= option. eg ls -lR --time-style=+%s will always return epoc. By default the style depends on the age of the file.

Links in this section

Filesystems
SSH
Systemd
VI

Last updated : 14 November 2024