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

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4
votes
1answer
3k views

Clear unused space with zeros (btrfs)

How to clear unused space with zeros ? (I am asking for tool for btrfs filesystem) I'm looking for something smarter than cat /dev/zero > /mnt/X/big_zero ; sync; rm /mnt/X/big_zero Like ...
26
votes
7answers
36k views

How do I grep recursively through .gz files?

I am using a script to regularly download my gmail messages that compresses the raw .eml into .gz files. The script creates a folder for each day, and then compresses every message into its own file. ...
13
votes
9answers
3k views

Memory problems when compressing and transferring a large number of small files (1TB in total)

I have 5 million files which take up about 1TB of storage space. I need to transfer these files to a third party. What's the best way to do this? I have tried reducing the size using .tar.gz, but ...
1
vote
1answer
38 views

linux unbuffered compression options

I'm working on a embedded system and due to persistent memory restrictions, I need to compress a log file "on the fly". My objective is to have a one liner inside a script, which would look like ...
2
votes
1answer
3k views

Trying to compress avi file using ffmpeg

I used the command below to compress an avi file(using ubuntu) ffmpeg -i input.avi -vcodec msmpeg4v2 output.avi but I am getting these errors Incompatible sample format 's16' for codec 'ac3', ...
1
vote
2answers
28 views

Squashfs minimal compression?

I'd like to create a squashfs image of a directory, but it's a huge one and even minimal compression would be a big win. Is there a way to do something like mksquashfs -1?
2
votes
1answer
21 views

Is there a compression method that supports solid compression and also adding data to the compressed file?

I have a large compressed .tar.xz file containing log files. The compression ratio is very good - but it takes a long time to compress, and if I want to add additional log files to it, I have to ...
1
vote
0answers
19 views

On-the-fly decompression

I have 44 TB worth of gzipped files that are 1.5 GB each when compressed or 2.0 GB when uncompressed. I have a tool that can read only uncompressed files. I would like to avoid the overhead of ...
31
votes
5answers
30k views

Clear unused space with zeros (ext3,ext4)

How to clear unused space with zeros ? (ext3,ext4) I'm looking for something smarter than cat /dev/zero > /mnt/X/big_zero ; sync; rm /mnt/X/big_zero Like FSArchiver is looking for "used space" ...
1
vote
1answer
42 views

log compression using logrotate

I was trying to set compression for jboss log files. The log files I want to compress are console.log and server.log. Compression for console.log is working fine, but server.log I am seeing issues. I ...
58
votes
7answers
40k views

How to XZ a directory with TAR using maximum compression?

So I need to compress a directory with max compression. How can I do it with xz? I mean I will need tar too because I can't compress a directory with only xz. Is there a oneliner to produce e.g. ...
32
votes
5answers
33k views

How to uncompress zlib data in UNIX?

I have created zlib-compressed data in Python, like this: import zlib s = '...' z = zlib.compress(s) with open('/tmp/data', 'w') as f: f.write(z) (or one-liner in shell: echo -n '...' | python2 ...
5
votes
2answers
140 views

How do I layer compression on top of encryption on top of BtrFS, per-file?

BtrFS should support this really, but it doesn't. So ECryptFS looks like it will fill the gap. The only thing is, how would I layer compression on top of this? Reasons for compression on top of ...
0
votes
2answers
63 views

Tar big files in different directories

I have ~20 files, each about 10 GB in size, in different folders that I need to compress into a single tar. It is not practical to copy them all to one location. More precisely, the files are ...
0
votes
1answer
44 views

Compressing files using p7zip from the command-line

I would like to compress four ISO files using 7z into a new archive called ISOs.7z from the command-line on my Sabayon machine. These are the commands I have tried so far (I know none of these specify ...
0
votes
1answer
29 views

Verify files AFTER extracting gzip

I gzip a folder, transfer it to a remote location and then extract it to a folder. The problem is that this machine is a little unreliable and sometimes writes don't succeed and there can be zero-byte ...
1
vote
1answer
541 views

unpigz (and untar) to a specific directory

I know how to gunzip a file to a selected location. But when it comes to utilizing all CPU power, many consider pigz instead of gzip. So, the question is how do I unpigz (and untar) a *.tar.gz file ...
3
votes
2answers
102 views

Extract compressed file by it's header as it is piped from stdout (locally or from remote location)?

I am sending compressed file with piping either local or from a network location. And on the receiving end, I would like to detect the type of compression and use the appropriate decompression utility ...
1
vote
1answer
68 views

How to convert tar.bz2 to .bz2?

I have a file with compression tar.bz2 , I would like to convert it to .bz2 . Is there a command that does this in one shot? I tried the below but no joy ! tar -xvjf US.tar.bz2 US bzip2: ...
1
vote
2answers
492 views

File compression - how to implement in Linux

I would like to be able to compress certain files (that I need to keep, but use rarely) on disk. I noticed that chattr +c flags a file for compression, but it doesn't seem to actually compress files. ...
1
vote
1answer
95 views

Can someone explain what hunzip is for?

I understand what hunspell is for, but I was browsing the source code and the man, and I'm not sure: Does hunzip compress text files or just dictionaries ?
2
votes
1answer
181 views

How to reduce size of a FLAC file without damaging its quality?

I got collection of vinyls which I paid for them to be digitized in FLAC. However my Hard Drive is getting full (91% full as of today) and the smallest of these vinyls is 2.3 GB in size! I would ...
2
votes
3answers
67 views

How can I keep rsync from using encryption and compression for the file transfers after the connection is authorized?

I understand that a secure connection (i.e. ssh) is needed to authorize a connection to the remote server. But after that is authorized can the data be transmitted without encryption and compression ...
5
votes
1answer
123 views

Get compressed size of piped output with gzip?

To get uncompressed size of already compressed file, I can use -l option in gzip utility: gzip -l compressedfile.gz However is there a way to get size of compressed file if I am piping the output? ...
3
votes
2answers
2k views

initramfs image compression other than gzip

can the initramfs image be compressed by a method other than gzip, such as lzma?
22
votes
4answers
2k views

How to know how much space an uncompressed zip will take

Given a (really long) list of zip files, how can you tell the size of them once uncompressed?
38
votes
5answers
30k views

Is it possible to mount a gzip compressed dd image on the fly?

I like create an image backup for the first time I'm backing up a system. After this first time I use rsync to do incremental backups. My usual image backup is as follows: Mount and zero out the ...
0
votes
1answer
52 views

Browser (HTTP client) with support of bzip2 or lzma2 compression?

What browsers (HTTP clients) support HTTP compression using bzip2 or lzma2? (HTTP compression for page requests) I have only heard of Firefox patch, but I am not sure if it actually supports ...
0
votes
1answer
22 views

Generating files of varying variability?

I have used /dev/zero and /dev/random to generate files of certain size. However, is there a way to control variability of generated files? I would like to create few files that would have same ...
6
votes
2answers
7k views

What's the difference between gunzip and unzip?

What is the difference between gunzip and unzip? Tried to search but couldn't find anything relevant with this.
4
votes
3answers
146 views

How can I change the first line of a big gzip file without decompressing all of it?

I currently have a compressed file, A.gz which contains lots of tabulated data, including a header in the first line. I want to create another file, B.gz, which has the same data as the previous file, ...
0
votes
1answer
106 views

What is the highest compression ratio compressor for pdf, djvu, and images

Comments so far have not been specific with the type of files they needed to compress and didn't reach a definitive answer I have a 1 TB hard drive full of pdf,djvu mostly and the rest are images and ...
0
votes
0answers
31 views

How do I create a deflate file suitable for HTTP?

Say I have index.html. How do I obtain index.html.deflate appropriate for serving through HTTP with the "deflate" encoding? I am coding a simple web server and I don't want to implement streaming ...
24
votes
2answers
24k views

Zip everything in current directory

I'd like to compress and package everything, including files and folders in current directory, into a single ZIP file on Ubuntu. What would be the most convenient command for this (and name of the ...
19
votes
4answers
6k views

Does tar actually compress files, or just group them together?

I usually assumed that tar was a compression utility, but I am unsure, does it actually compress files, or is it just like an ISO file, a file to hold files?
4
votes
3answers
331 views

Compression / archiving that keeps permissions and file owner?

I know that similar questions have been asked about permissions, but which form of compression or archiving keeps the permissions and file owners of each file and directory? I was considering the ...
11
votes
3answers
671 views

What does the `-C` flag exactly do in `scp`?

I always use either rsync or scp in order to copy file from/to a remote machine. Recently, I discovered in the manual of scp (man scp) the flag -C -C Compression enable. Passes the -C flag to ...
0
votes
0answers
191 views

where to compress=lzo, btrfs with virtual disk images, with their vm's internally using btrfs

I've been using compress=lzo on my btrfs volumes, because I read this fast compression method actually increases drive performance. (Haven't tested myself.) I'm starting to use ...
2
votes
2answers
2k views

Mount compressed tar file and update it

How do I mount a .tar.gz file, update it (add new files, edit files), and then unmount it such that changes are reflected in the original compressed file? I'm open to other compression formats if no ...
3
votes
4answers
1k views

Is it possible to make a .tar.gz file directly from stdin? Or, I need to tar together already gzipped files

I'm going to tell you exactly what I need in order to clarify the cryptic question in the title. I'm currently making scheduled MySQL backups of all my databases with something like: mysqldump ... | ...
1
vote
2answers
727 views

How strong is the encryption of a zip file in Linux Mint

Zip encryption has had often a bad reputation of being weak, but some would argue that a zip file encrypted using certain algorithms (such as by using AES), together with strong password, is really ...
0
votes
1answer
97 views

Can I use lzma compression, without using “tar”, on OSX 10.10.3?

I kind of think of OSX as Unix by another name. But, if I need to move this to the Apple forum, please tell me! I can create tar files compressed using lzma as such: $ ls ./DbDumps alpha.dmp ...
6
votes
3answers
395 views

Does gz compression ratio improve over time?

I have some process that creates a stream of millions of highly similar lines. I'm piping this to gz. Does the compression ratio improve over time in such a setup? I.e. is the compression ratio better ...
0
votes
2answers
38 views

How to open compressed file in less mode [duplicate]

How do I open a compressed file in less mode. I am able to grep using zgrep and using zcatI can open, but the file is big I want to open in less mode.
7
votes
3answers
478 views

Can tarring files improve compression?

Can tarring a bunch of files together improve compression with the standard tools, e.g. gzip, bzip2, xz? I've long thought this to be the case but never tested it out. If we have 2 copies of the same ...
0
votes
1answer
393 views

Compress multiple files and keep their name?

I have hundreds of .csv files that I need to compress into one file each. It should look like this originalname.csv.gz
1
vote
0answers
21 views

Pipe gzip output to Bluetooth transfer?

How do I pipe gzip output to Bluetooth transfer? I am able to send send file over Bluetooth using this command: bluetooth-sendto --device=12:23:35:96:45:45 file.tar However, piping gzip didn't ...
2
votes
1answer
53 views

lrzip compression does not shrink random data

I'm trying to shrink down some big files around 3.0 GB each and I decided to use lrzip after seeing a few benchmarks and such however is it something I'm doing wrong or something as whenever I run ...
6
votes
2answers
3k views

What's the difference between tar.gz and tar.Z?

The downloads on this page, e.g. of NetCDF C/C++/Fortran 4.1.3, show tar.Z and tar.gz formats. The tar.Z doesn't even have a configure file in it. What is it used for?
2
votes
1answer
59 views

appendable and greppable archive on CentOS to hold many log files (logrotate on steroids)

I have a bunch of applications on a CentOS 6.3 box, which generate daily logs (text files with a very similar content) in this vein: /data/logs/app/my-2014-06-29.log ...