Questions tagged [compression]

Shrinking (compressing) and restoring (decompressing) of data.

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38 views

The size of my lzma compressed file is different from one system to another using same compression ratio - why?

I have an lzma compressed file that I've extracted from a firmware image (via binwalk) that is X bytes uncompressed and Y bytes compressed. When I try to compress the extracted file again - without ...
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51 views

How to use multi-threading for creating and extracting tar.xz

I use tar -cJvf resultfile.tar.xz files_to_compress to create tar.xz and tar -xzvf resultfile.tar.xz to extract the archive in current directory. How to use multi threading in both cases? I don't ...
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78 views

How do you determine the remaning capacity of a magnetic tape with mt or tar? How much space is in a block?

I am currently trying to back up data onto an LTO-4 tape using mt-st and gnu tar 1.32, but I want to make sure I stop trying to copy things before the tape runs out! LTO-4 nominally has a capacity of ...
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btrfs performance comparison: ssd with compression vs hdd without compression

Has anyone done any r/w performance comparisons using btrfs with compression enabled on an M.2 nvme ssd vs uncompressed hdd?
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1answer
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Need solution to archive a folder excluding all .log and .err files using wildcards

I wish to archive all files and folders under /app/jboss while excluding all .log and .err files. The directory structure under /app/jboss is too vast and complex. Thus a few sample files below should ...
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1answer
39 views

Why won't tar/gzip compress two similar large directories?

A long time ago, before I tried incremental and differential backups, I tried to tar/gzip several similar large (1 GB) directories, but they did not compress any better than tarring and gzipping each ...
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41 views

Compressing pdf files with Ghostscript

I'm using Ghostscript to compress a lot of pdf files with good results. I'm using the option Pavlunin posted here and I'm getting compression without almost losing quality: https://stackoverflow.com/...
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2answers
46 views

Switch all my git repositories to depth 20, to save space?

I know that git clone --depth=20 <repo> is oftentimes much much smaller than git clone. Official docs for --depth. Looks like I've gone a bit crazy with my repos folder, here's the fd piped to ...
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1answer
159 views

Why does zram occupy much more memory compared to its “compressed” value?

I set up zram and made extensive tests inside my Linux machines to measure that it really helps in my scenario. However, I'm very confused that zram seems to use up memory of the whole uncompressed ...
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52 views

pdf black and white compression without losing text recognition

I'm looking for a way to reduce the size of various pdf archives that I have. I have tested lot of programs and mechanisms. I get the best results with the following secuence: pdfimages -png file.pdf ...
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1answer
34 views

pdfinfo optimized

What means optimized in the info pdfinfo shows? pdfinfo file.pdf Tagged: no UserProperties: no Suspects: no Form: none JavaScript: no Pages: 642 Encrypted: ...
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1answer
60 views

How to convert from rar or tgz to squashfs without having to extract to temporary folder?

I enjoy using squashfs for compression because of the simplicity of mounting them as loop devices to access the files inside. I have a lot of rar, tgz and zip files that I would like to convert to ...
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28 views

Clear unused space in KVM Virtual Machine

I have a sparse Virtual Machine. When I boot VM and df I get this /dev/sda1 98G 3.4G 90G 4% / When I check size of qcow2 image ls -sh 6.2G Image.qcow2 Image size should be 3.4G like used ...
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253 views

How to compress .cbr and .cbz files very tightly?

I am wondering how to compress .cbr and .cbz files very tightly to decrease the file size.
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pictures encrypted using seahorse-nautilus do not open after decryption (but thumbnails are visible)

Ok, so here's what happened. As long as I've been using Linux (~2014) you could compress folders and individual files from right-click context menu, while also adding password at the same time. Then ...
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2answers
43 views

Can a pointer point to another pointer instead of a label in DNS compression?

Should DNS clients be worried about the DNS message compression in which pointers may point to another pointer instead of label name? Although doing so seems to be unambiguous, there is not talk about ...
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1answer
41 views

What happens when I create a file in the directory that is being archived with tar?

I have a large directory (80GB) that I want to compress into the archive. What happens, when a new file is created in that directory, while it is being tared? Would new files be included in the ...
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1answer
34 views

Create a rar file with the help of unrar package

The unrar is package is installed in my Arch Linux. I want to create a rar file, so I tried to install rar package from Arch AUR, but the repo is currently unavailable. So, I wonder if it is possible ...
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1answer
31 views

How can I completely zero out all free blocks (deleted files)

I'm making a backup of Raspbian (I know, this isn't the Raspberry Pi SE, but it's a Linux question and it probably isn't just Raspbian that has this problem and BTW, the size of the drive is 128GB). ...
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74 views

Script to convert bit blasted netlist into bus format

I have signals like signal[3]_and_[31] signal[3]_and_[30] signal[3]_and_[29] signal[3]_and_[28] ... signal[3]_and_[0] signal[2]_and_[31] signal[2]_and_[30] signal[2]_and_[29] signal[2]_and_[28] ... ...
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1answer
46 views

Having problem while installing new packages on CentOS 7

I am trying to install unar on CentOS 7 using yum install epel-release then yum install unar commands, but the result is: gnustep-base-libs-1.24.9-1.el7.x86_64: [Errno 5] [Errno 2] No such file or ...
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3answers
47 views

Compress a file into another file, with Gnu/Linux command line

I am trying to take a file containing text, named MyFile, and compress it into a file named MyFileComp, within the same directory. I have tried: gzip MyFile | touch MyFileComp gzip MyFile >> ...
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1answer
74 views

zip/compress a .bin file

I have a .bin file size of 8MB; is it possible to compress it or zip it? Tried with 7z but 8MB -> 7.90 MB so any relevant changes. Is there any other tools? Or simply is it not possible?
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191 views

How to disable compression of initrd.img file of Debian Linux 10 buster

I want to disable compression of /boot/initrd.img file to boot a bit faster. My disk is large enough to accomodate the extra 10MB. To be honest I think that should be the default, who can't afford ...
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1answer
81 views

Auto-compress SFTP file-transfer to reduce network data usage

When downloading /var/log/apache2/other_vhosts_access.log (100 MB) from a distant server to my local computer via SFTP, I noticed that the network transfer was not compressed. Indeed similar ...
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After using `cat` on a binary file, why are letters and numbers left over? [duplicate]

This appears to be an easy concept, but I'm having difficulty finding out what is going on via Google: I have a binary file generated by a C program, example_binary. After using cat example_binary, ...
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1answer
88 views

Compression not working for journald log files

So basically BTRFS transparent compression (zstd:0) isn't working for the log files under /var/log/journal. I don't understand this issue because manually compressing the files (zstd file) gives a ...
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1answer
36 views

How to enable memory compression on SLES12.2?

I can read the: https://www.suse.com/releasenotes/x86_64/SUSE-SLES/12-SP2/#fate-318957 that it can be enabled with a: echo Y > /sys/module/zswap/parameters/enabled Q: but how to make it ...
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40 views

Merge and reduce video file with ffmpeg

I'm trying to merge an opus and webm to single webm video. but at the same time, I also want to reduce the video. I already add some command from this solution. It works from some people but not me. I ...
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2answers
290 views

Archive multiple zip files into one file

How can I combine multiple existing zip files into a single file? I'm asking because I have many PDFs to zip, and I want to leverage parallel to save time in zipping them all up (as in ls ./*.pdf | ...
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What are unzip2dir / unrar2dir

I found some useful extract and compress functions for my .bashrc. But I am struggling to get unzip2dir / unrar2dir to respond. *.zip) unzip2dir $1 ;; *.rar) unrar2dir $1 ;; (unrar2dir: command ...
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1answer
350 views

Difference between gzip -d and zcat

I was wondering what the difference is when decompressing using gzip -d and zcat. Sometimes when I try gzip -d it says unknown suffix -- ignored. However, zcat works perfectly.
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1answer
50 views

Is there an equivalent of zdiff for zstandard

Is there an equivalent of the gzip utility zdiff(1), but for zstandard? I have not been able to find anything in the zstandard repository other than zstdgrep and zstdless.
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1answer
531 views

How to turn on compression for a single file on btrfs?

I'm in the middle of generating a 3 TB drive image with GNU ddrescue, and realizing it will be too big for the target drive (since the empty space is filled with 0xAA instead of 0x00, so instead of ...
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1k views

Make grown extracted tar file small again

I packed and compressed a folder to a .tar.gz archive. After unpacking it was nearly twice as big. du -sh /path/to/old/folder = 263M du -sh /path/to/extracted/folder = 420M I searched a lot ...
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1answer
279 views

Is there a compression tool with an arbitrarily large dictionary?

I am looking for a compression tool with an arbitrarily large dictionary (and "block size"). Let me explain by way of examples. First let us create 32MB random data and then concatenate it to itself ...
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1answer
120 views

How may I emulate the -R feature of “zip”, but in gzip and xz?

The program "zip" has a -R feature which allows one to zip all files with a certain name in a directory tree: zip -r v/s zip -R For example: zip -R bigfile "bigfile" Will zip all of the following: ...
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580 views

zip warning: name not matched compressing folders

I'm trying to backup the whole volume of a drive. I want to have it password-protected This is what I did zip -er archive.zip /Volumes/Storage/ But I'm getting zip warning: name not matched ...
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3answers
1k views

How do I demonstrate the type of kernel compression in practice?

I have to find out the type of compression of the linux kernel of my arch linux system, but I can't find a way to get it more than the theory: now bzip2 (bz), formerly gzip (z). In my computer I run ...
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1answer
91 views

Is the rsync block compression dictionary reset for each file?

Does rsync -z compress blocks of each file without regard to the previous file, or is the compression dictionary reset for each file so that it is handled independently? As an example, consider a ...
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1answer
37 views

Is TLS-level compression with Apache possible?

Apache2 can transfer compressed data by using the deflate filter. However, it does a HTTP-level compression: it sends back a compressed response, and it shows in the response headers to the clients to ...
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1answer
34 views

list directory sizes and compress them

I have a list of directories I want to compress on an ubuntu machine. Is there any tool to automatically calculate the size of the of my folders and copy the size to the name of the compressed file? ...
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1answer
302 views

lz4 compression is only using a single core?

I'm using cat largeFile.iso | lz4 -10 - and it's going quite slowly (30mb/s?). Using htop I see it using only a single core to 100%? Are there any additional parameters I need to specify? I can't ...
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1answer
587 views

Can gzip compress application/octet-stream

Particularly in web, is it possible to compress application/octet-steam, I am serving video files from AWS to a web app and data transfer is very expensive at high scale
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2answers
797 views

bzip2: Check file's decompressed size without actually decompressing it

I have a big bzip2 compressed file and I need to check it's decompressed size without actually decompressing it (similar to gzip -l file.gz or xz -l file.xz). How can this be done using bzip2?
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1answer
131 views

List contents of a tgz archive inside a gz archive

Bit of a weird one - I've got a honeypot running dionaea, which is a tool that consolidates any binaries that were uploaded to the device in single location (/data/dionaea/binaries). However, every ...
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1answer
121 views

7zip client: Compress dirs with method PPMd & compression level Ultra

So today, I am trying to compress multiple folders, of old photos which I want to backup. I've found this article, that says method PPMd, and compression level Ultra, are far better for image ...
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1answer
56 views

/boot running out of space when updating. What now?

I just ran into a serious problem I need to update offline CentOS boxes with fix partition sizes. When updating the process terminates with an error that /boot need 32mb more in order to update. It ...
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1answer
651 views

Using ffmpeg to Compressed a Two Frame Video

I'm trying to use Ubuntu Linux 19.04 to convert an OpenShot video into a more efficient file-size. The video only contains two still images, and 20 minutes of audio, but for each file-type I save-as, ...
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1answer
114 views

How do I pass arguments to lzip through tar?

I want to run tar --lzip -cvf file1.txt file2.txt. But lzip's help page states that by default it does not run at its fullest compression power (the option for which is -9, while the default is -6). I ...

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