commandlinefu.com is the place to record those command-line gems that you return to again and again.
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Every new command is wrapped in a tweet and posted to Twitter. Following the stream is a great way of staying abreast of the latest commands. For the more discerning, there are Twitter accounts for commands that get a minimum of 3 and 10 votes - that way only the great commands get tweeted.
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Wow, didn't really expect you to read this far down. The latest iteration of the site is in open beta. It's a gentle open beta-- not in prime-time just yet. It's being hosted over at UpGuard (link) and you are more than welcome to give it a shot. Couple things:
How to figure out what a program is doing.
-tt detailed timestamps
-f also strace any child processes
-v be very verbose, even with common structures
-o write output to file
-s N capture up to N characters of strings, rather than abbreviating with ...
Batch resize all images to a width of 'X' pixels while maintaing the aspect ratio.
This makes uses of ImageMagick to make life easier.
The above is OK if you not worried about security, as per sshpass man pages:
" The -p option should be considered the least secure of all of sshpass's options. All system users can see the password in the command line with a simple "ps" command."
So, instead what I do is use the -e option:
" -e The password is taken from the environment variable "SSHPASS"."
You need to install "sshpass" for this to work.
apt-get install sshpass
I don't like doing a massive sort on all the directory names just to get a small set of them. the above shows a sorted list of all directories over 1GB. use head as well if you want.
du's "-x" flag limits this to one file system. That's mostly useful when you run it on "/" but don't want "/proc" and "/dev" and so forth. Remember though that it will also exclude "/home" or "/var" if those are separate partitions.
the "-a" option is often useful too, for listing large files as well as large directories. Might be slower.
list the top 15 folders by decreasing size in MB
Another alternative to blkid, lsblk, file -s, cat /proc/paritions, fdisk -l, etc..
This is just a quick and dirty way to play remote audio files *locally* in your PC.
The best way is to mount the remote Music directory into the local FS, say by using sshfs:
sshfs [email protected]:/remote/music/dir/ /mnt/other_pc/
This forces a bonded interface to switch to another slave in the bond as its active slave.
Returns the IP, broadcast, and subnet mask of your interfaces absent any other extraneous info.
I know it's a bit lame, but I've created an alias for this when I *quickly* want to know what a system's IP is. Small amounts of time add up :)
Cleaned up and silent with &>/dev/null at the end.
Execute commands serially on a list of hosts. Each ssh connection is made in the background so that if, after five seconds, it hasn't closed, it will be killed and the script will go on to the next system.
Maybe there's an easier way to set a timeout in the ssh options...
`mount -o remount` doesn't pick up new NFS options (eg. timeo, soft, retrans, etc) so you need to do a full mount/remount cycle. This one-liner makes it quick and easy :) Update your fstab with the new options, then run it.
The lastb command presents you with the history of failed login attempts (stored in /var/log/btmp). The reference file is read/write by root only by default. This can be quite an exhaustive list with lots of bots hammering away at your machine. Sometimes it is more important to see the scale of things, or in this case the volume of failed logins tied to each source IP.
The awk statement determines if the 3rd element is an IP address, and if so increments the running count of failed login attempts associated with it. When done it prints the IP and count.
The sort statement sorts numerically (-n) by column 3 (-k 3), so you can see the most aggressive sources of login attempts. Note that the ':' character is the 2nd column, and that the -n and -k can be combined to -nk.
Please be aware that the btmp file will contain every instance of a failed login unless explicitly rolled over. It should be safe to delete/archive this file after you've processed it.
Use as: $ s host1
Will ssh to remote host upon first invocation. Then use C-a d to detatch. Running "s host1" again will resume the shell session on the remote host. Only useful in LAN environment. You'd want to start the screen on the remote host over a WAN.
Adapted from Hack 34 in Linux Server Hacks 2nd Addition.
Remove old kernels (*-generic and *-generic-pae) via apt-get on debian/ubuntu based systems. Tested on ubuntu 10.04 - 12.04.
Use this the next time you need to come up with a reasonably random bitstring, like for a WPA/WPA2 PSK or something. Takes a continuous stream of bytes coming from /dev/urandom, runs it through od(1), picking a random field ($0 and $1 excluded) from a random line and then prints it.
This command sets the volume for the main PulseAudio "sink" (usually the ALSA output interface) to the maximum, 100% (the 0x10000 in the command). To set it to an arbitrary volume, replace 10000 with the volume you want times 100 (so 75% becomes 7500).
This returns the hardware serial number. Dell calls this the "Service Tag" and it can be used to retrieve warranty information or used for RMA / repairs.