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