Skip to content

Filesystem

Jump to bottom
GradedJestRisk edited this page Jan 21, 2026 · 9 revisions

Overview

List:

  • add to path : export PATH=$PATH:PATH_TO_ADD
  • Show (physical) location : pwd -P
  • Change owner : chown OWNER FILE
  • Soft link : ln --symbolic TARGET LINK_NAME
  • Create folder : mkdir FOLDER_NAME
  • Delete file : rm FILE_NAME
  • Delete folder : rmdir FOLDER_NAME
  • Delete folder and contained files : rm --recursive --force HEAD_FOLDER_NAME
  • Find file by name : find STARTING_PATH -name FILTER

Basics

Block size

  • drive block size is 512 bytes
  • OS block size is 4096 bytes (4 kbytes)

To find the count of drive blocks a file use

stat $FILE

You get 707 976 blocks for 362 479 616 bytes, which are roughly 512 bytes blocks.

 File: base/16384/16385
  Size: 362479616 	Blocks: 707976     IO Block: 4096   regular file

Reference

You can't use ls to get the block count, unless you pass the block-size parameter which is clumsy.

ls -ls --block-size=4K

Reference

To find if blocks are contiguous on the filesystem

sudo hdparm --fibmap  $FILE

You get a list of blocks spans, eg 16, then 49 136

 filesystem blocksize 4096, begins at LBA 0; assuming 512 byte sectors.
 byte_offset  begin_LBA    end_LBA    sectors
           0  526071904  526071919         16
        8192  755184728  755233863      49136
    25165824  692322304  692355071      32768
    41943040   27770880   27820031      49152
    67108864   27869184   27918335      49152

To check if a file is fragmented, this is located in non-continuous block, you need the extent count. A extent is a block-contiguous set.

To get extent count

filefrag -v $FILE

You get 32 here

Filesystem type is: ef53
File size of /var/lib/docker/volumes/sandbox_postgresql_data/_data/base/16384/16401 is 362479616 (88496 blocks of 4096 bytes)
 ext:     logical_offset:        physical_offset: length:   expected: flags:
   0:        0..    1023:  105417728.. 105418751:   1024:            
   1:     1024..    2047:  105431040.. 105432063:   1024:  105418752:
   2:     2048..    4095:   67688448..  67690495:   2048:  105432064:
   3:     4096..    6143:   67594240..  67596287:   2048:   67690496
  (..)
  31:    88064..   88495:   87228416..  87228847:    432:   67880960: last,eof
/var/lib/docker/volumes/sandbox_postgresql_data/_data/base/16384/16401: 32 extents found

Reference

Structure

Frequent

  • /snap : containerized applications
  • /home : user-specific data (not programs)
  • /media : user-specific mounted data (not programs)

All

Mount

View mount points

# df or # mount

Mount

Step 1: Get UUID

Input sudo blkid /dev/sda1

Output /dev/md127: LABEL="data" UUID="13f99b52-(..)-a6a47f400303" TYPE="ext4"

Step 2: Mount

# sudo mount --uuid DEVICE_UUID -t TYPE -o OPTIONS DESTINATION_DIR

Unmount

Grateful # sudo umount DESTINATION_DIR -l

Forceful # sudo umount -f DESTINATION_DIR

List (ls)

General:

  • list: -l (l for list)
  • sort ** default is alphanumeric, ignoring hidden file dot prefix ** reverse order: -r (r for reverse) ** by modification time, newest first : -t
  • include hidden files: ** include: -a (a for all) ** sort them first LC_COLLATE=C ls -a
  • show file type: -F ** / : directory ** * : executable ** @ : symbolic link *** others (IPC) **** | : pipe **** = : socket **** > : door

enhance output

List

  • in list
  • directories blue and DIRECTORY_NAME/
  • readable size
  • print only file modification date and file name
  • aligned

Gives alias ls='ls -lFh --color=always | awk '''{print $5,$6,$7,$8,$9}''' | column -t'

Backup

https://phoenixnap.com/kb/linux-create-partition

List:

  • identity your device, eg. sdd
  • create partition table on device ** "sudo parted" ** select device: "select /dev/sdd" ** check for existing partition: "print" ** if any partition, remove it using its number: "rm 1" ** create partition table: "mklabel gpt" ** check: print should display "Partition Table: gpt"
  • create partition ** "mkpart primary ext4 1MB 1000GB" ** check with "print": ext4 partiton shall exist ** save with "quit"
  • create file system ** sudo mkfs.ext4 /dev/sdd1 ** check message is "Writing superblocks and filesystem accounting information: done"
  • mount ** create mountpoint: mkdir $HOME/mountpoint ** mount read/write for ?: "sudo mount --types auto --options rw /dev/sdd1 $HOME/backup" ** try writing a file: "touch $HOME/backup/test"
  • copy files ** cp *** create folder: "sudo mkdir $HOME/backup/2022-11-21" *** copy directory tree: "sudo cp --recursive $HOME/data $HOME/backup/2022-11-21" *** monitor with glances ** give user access to files (current owner is root) *** easy: "chown username $HOME/backup" *** read/write for everyone: "chmod --recursive a=rw $HOME/backup/2022-11-21" *** read/write for specific user: "setfacl --recursive -m u:username:rwx $HOME/backup/2022-11-21" ** tar https://docstore.mik.ua/orelly/unix3/upt/ch10_13.htm ** rsync

locally

cp

Copy

  • recursively
  • preserve timestamp
cp --archive --verbose $SOURCE_FOLDER $DESTINATION_FOLDER

https://unix.stackexchange.com/questions/56047/progress-information-via-pv-for-directory-copy

rsync

Copy

  • recursively
  • preserve timestamp

Display progress for whole transfer, not per-file basis

rsync --archive --info=progress2 $SOURCE_FOLDER $DESTINATION_FOLDER

remotely

ssh

ssh $USERNAME@$HOSTNAME -p$PORT

scp

Tutorial

Use SSH key for authentication or password

Will create target folder if not exists

To copy

  • from a remote server to another remote server
  • folders, recursively
  • preserving timestamp
scp -r -p $SOURCE_USERNAME:/$SOURCE_FOLDER $TARGET_USERNAME@TARGET_HOSTNAME:/$TARGET_FOLDER

To copy

  • from a local server to another remote server
  • folders, recursively
  • preserving timestamp
scp -r -p $SOURCE_FOLDER $TARGET_USERNAME@TARGET_HOSTNAME:/$TARGET_FOLDER

Clone this wiki locally