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38
basics/hard_links.md
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38
basics/hard_links.md
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---
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title: "hard links"
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tags: [ "basics", "links" ]
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---
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A hard link is one file which exists in multiple locations.
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Each file has an ID, which is kept on the hard disk's partition.
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Each hard link has the same ID, because they are the same file.
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This ID is called the 'inode'.
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Create a file, and a hard link:
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```bash
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fortune > $file_1
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mkdir -p x/y/z/
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ln $file_1 x/y/z/$file_2
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```
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Have a long look at the file with the `-l` flag, and check the inode with `-i`:
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```bash
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ls -li $file_1 x/y/z/$file_2
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```
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Since they are the same file, you can make a change to one, and it changes both:
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```bash
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fortune | tee x/y/z/$file_2
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cat $file_1
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cat x/y/z/$file_2
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```
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# Danger Zone
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- hard links will not work on directories, only standard files and fifos.
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- `git` will destroy and remake files, so it will not respect hard links.
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- Files cannot have a hard link on another disk partition, because the inode is stored on each partition.
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@ -1,19 +1,9 @@
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---
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title: "links"
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tags: [ "Documentation", "Basics" ]
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tags: [ "basics", "links" ]
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---
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Link from X to Y.
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```bash
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ln -s X ../otherdir/Y
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```
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If you want a hard link, this will make a single file exist in two locations.
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If it is deleted in one location, it continues to exist in the other.
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```bash
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ln *X* *Y*
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```
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Both files must be on the same hard drive, as they have the same inode (check this with `ls -i file`).
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There are two types:
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- [Soft links](soft_links.md)
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- [Hard links](hard_links.md)
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72
basics/soft_links.md
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72
basics/soft_links.md
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---
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title: "soft links"
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tags: [ "basics", "links" ]
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---
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A soft link is a file which says how to go to another file.
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When a program encounters a soft link, it will make a guess at whether it should ignore it, or try to get to that file.
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To make a soft link to a file in the current directory, linking is easy:
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```bash
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fortune > $file_1
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ln -s $file_1 $link_1
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```
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Now imagine your directory looks like this:
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```
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dir_0/
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├── dir_1
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│ └── file_1
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├── dir_2
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│ └── file_1
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├── file_1
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└── link_1
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```
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Inside `dir_1`, making a soft link to `dir_0/file_1` would mean putting the directions to that file:
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```bash
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cd dir_1
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ln -s ../file_1 link_1
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```
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The real content of the file is just '`../file_1`, so making it from another directory would mean writing exactly the same address to that file:
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```bash
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ln -s ../file_1 dir_2/link_2
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```
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Both symlinks are identical, except for the name.
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```
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dir_0/
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├── dir_1
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│ ├── file_1
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│ └── link_1 <-- This one points to ../file_1
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├── dir_2
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│ ├── file_1
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│ └── link_2 <-- This one points to ../file_1 as well.
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└── file_2
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```
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Since it's just an address, you can delete the original file, then make another.
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```bash
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rm file_1
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ls -l dir_1/
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fortune > file_1
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cat dir_2/link_2
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fortune | tee -a file_1
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cat dir_1/link_1
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```
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Last, let's make a link from `dir_2/link_2` to `dir_1/file_1` (this will delete the old link):
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```bash
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ln -s -f ../dir_1/file_1 dir_2/link_2
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cat dir_2/link_2
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```
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@ -68,3 +68,11 @@ ntpq -p
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Usually this is run as a service, so just start that service.
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# Force Reset
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If your clock drifts too far from the right time, it will not reset happily.
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For it to reset like this:
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```bash
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sudo ntpd -q -g -x -n
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```
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@ -22,6 +22,7 @@ And overwrite all metadata:
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```bash
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exiftool -all= -overwrite_original -ext jpg .
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```
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(NB: This does not work on pdf data. See [here](pdf_erasure.md) for erasing all pdf data)
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Or just GPS data:
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@ -36,3 +37,4 @@ identify -verbose
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```
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25
data/pdf_erasure.md
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data/pdf_erasure.md
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---
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title: "PDF Metadata Erasure"
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tags: [ "Documentation", "Metadata", "Ghost Script" ]
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---
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Make a text file called 'pdfmark.txt'.
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```text
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[ /Title ()
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/Author ()
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/Subject ()
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/Creator ()
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/ModDate ()
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/Producer ()
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/Keywords ()
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/CreationDate ()
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/DOCINFO pdfmark
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```
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Then run:
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```bash
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gs -o output.pdf -sDEVICE=pdfwrite "$FILE".pdf pdfmark.txt
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```
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19
system/deduplicate.md
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19
system/deduplicate.md
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---
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title: "deduplicate"
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tags: [ "system", "deduplicate", "duplicates", "maintenance" ]
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---
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`rdfind`: find duplicate files, then delete them, or turn them into links.
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Ask if a directory has duplicates (`rdfind` will not delete anything):
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```bash
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rdfind $dir
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$EDITOR results.txt
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```
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Replace the duplicated files with [hard links](../basics/hard_links.md).
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```bash
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rdfind -makehardlinks true $dir
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```
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