Questions tagged [compression]

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

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34 views

How to prevent btrfs compressing /var

I just installed new instance of Fedora 33 and enabled compression for my root volume via compress=zstd:3 mount option. I enabled compression of /usr with chattr +x /usr. I would like to disable ...
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28 views

How to compress every file in a directory into its own compressed file (files not in current directory)

If the location DATA/AAA/INPUT contains n files (the file names are random job names), I need to create tar files for all the n files in the DATA/AAA/OUTPUT location with a common name format. So, if ...
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1answer
13 views

What is the fastest / best compression for large dar archives

I'm using dar (like tar, but optimized for hard disks) for backing up RAID volumes. They're modest sized for RAIDs, at perhaps 3 - 10 TB. I'm aiming to put the results on 8 TB external drives, but ...
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1answer
63 views

How can you compress images in a PDF?

How can you increase the JPEG compression level on a PDF using batch tools under Linux? Obviously you can use gs -dPDFSETTINGS=/screen or /ebook, but that downsamples the PDF - it reduces the DPI. It'...
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1answer
29 views

compress: No compression — file unchanged

I was trying to compress an image on Linux, specifically using the compress command, and it wasn't working. Can you please advise, based on the output below, what I'm doing wrong and how I could fix ...
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Make Btrfs use all CPUs for compression

I have been playing around with Btrfs and compression, but I have been unable to make Btrfs use all my CPU cores for compressing. The kernel compression processes max out at 8 cores (all running >...
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1answer
43 views

Maximal compression possible with Btrfs

I have been playing around with Btrfs. The maximal compression I have been able to achieve is 30:1 and that is on a file like: yes foo | head -c 10G > file Command line zstd will compress the file ...
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2answers
101 views

got “tar: /path/to/my/dir: Not found in archive” error while verifying created archive

I did compress a directory to .tar.xz archive format with this command: tar --create --verbose --file myArchive.tar.xz /path/to/my/dir then,I tried to check health of created archive with following ...
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how to install BPG encoding

how to install BPG Encoding on google colab( which is similar to linux as I think) My problam is that I have some input images on png format and I want to compress them using BPG
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1answer
103 views

How to unzip the U-boot image?

I have the U-boot image called: rootfs.13cy.initramfs.bzip2.uboot I want to see what's inside of it. Whats dumpimage cmd shows me: dumpimage -l rootfs.13cy.initramfs.bzip2.uboot Image Name: ...
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76 views

“xz : (stdout) : Write error: File too large” while writing a tar archive

I wanted to compress a directory whit size of about 25 GB to .tar.xz format using following command: tar --xz --create --verbose --file myArchive.tar.xz /patch/to/my/dir but got these error lines: xz:...
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1answer
42 views

how to fix “tar: Cannot verify compressed archives” error?

I wanted to compress a directory into .tar.xz format and verify it after writing so I wrote a command like this: tar --xz --create --verbose --verify --file myArchive.tar.xz /patch/to/my/dir but it ...
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1answer
33 views

Updating a large compressed file without creating temp file

I'm trying to figure out a way that I can update a compressed file (currently using zip, but am open to tar/gz/bz derivatives too) on a linux server without creating a temp file for the file to be ...
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1answer
44 views

Lossless ffmpeg recordings with low resource usage

I'm trying to record lossless videos with ffmpeg of My screen My computer audio My microphone audio using this script: MIC="alsa_input.usb-Logitech_Logitech_USB_Headset-00.mono-fallback" ...
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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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3answers
1k 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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1answer
142 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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178 views

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
82 views

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
50 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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101 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
48 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
958 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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93 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
81 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
175 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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56 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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3answers
771 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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28 views

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
75 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
45 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
52 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
90 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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2answers
131 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
79 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
77 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
421 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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483 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
590 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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147 views

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
204 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
44 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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84 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
683 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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47 views

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
822 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
57 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
991 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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2answers
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
475 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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