Commands by jasonjgw

Commands by jasonjgw (13)

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Suspend an ssh session.

This must be typed before any other characters have been entered on the line. Use fg, as usual, to resume the ssh session.
This is sample output - yours may be different.
4

~ ctrl-z

jasonjgw · 2010-11-21 07:43:40 18
Start delivery of mail queued on a secondary mail server.

This uses fetchmail to issue an etrn command that causes the MTA on the secondary mail server to process the queue for the specified domain. You can also just use telnet or nc to connect to port 25 of the server and then: etrn yourdomain.example.org 250 2.0.0 Queuing for node yourdomain.example.org started Show Sample Output
This is sample output - yours may be different.
```
fetchmail: Queuing for yourdomain.example.org started
fetchmail: Polling secondary-server.example.org
```
0

fetchmail -p etrn --fetchdomains yourdomain.example.org secondary-server.example.org

jasonjgw · 2010-11-20 23:38:09 8
Find broken symlinks in the current directory and its subdirectories.

This is best run as root to avoid permission denials that can produce false positives. Obviously you can specify a directory in the usual way: find -L dirname -type l I can't remember where I read about this or who deserves the credit for it. The find(1) manual page hints strongly toward it, however. Show Sample Output
This is sample output - yours may be different.
```
./linkname
```
4

find -L -type l

jasonjgw · 2010-11-20 07:59:58 8
Encrypt every file in the current directory with 256-bit AES, retaining the original.

The password is stored in the password file, which obviously must be kept secure, encrypted later with gpg, deleted, or whatever you prefer. To decrypt: openssl enc -d -aes-256-cbc -salt -in filename.enc -out filename -pass file:/path/to/password-file Alternative ciphers can be used, of course.
This is sample output - yours may be different.
2

for f in * ; do [ -f $f ] && openssl enc -aes-256-cbc -salt -in $f -out $f.enc -pass file:/tmp/password-file ; done

jasonjgw · 2010-11-20 03:29:16 9
Check hashes of files installed by Debian packages, reporting only errors.
This is sample output - yours may be different.
1

debsums -s

jasonjgw · 2010-11-19 03:33:01 5
Export a directory to all clients via NFSv4, read/write.

This exports a directory to the world in read/write mode. It is useful for quick, temporary NFS exports. Consider restricting the clients to a subnet or to specific hosts for security reasons (the client can be specified before the colon). On the client: mount -t nfs4 hostname:/ /mountpoint To terminate all of the exports (after unmounting on the client): exportfs -u -a Leave out the fsid=0 option if you don't want NFSv4. This works under recent versions of Linux.
This is sample output - yours may be different.
2

exportfs -o fsid=0,rw :/home/jason

jasonjgw · 2010-11-18 10:02:52 4
Create a tar file compressed with xz.

The J option is a recent addition to GNU tar. The xz compression utility is required as well.
This is sample output - yours may be different.
-1

tar cfJ tarfile.tar.xz pathnames

jasonjgw · 2010-11-18 05:34:17 3
Prevent an IPv6 address on an interface from being used as source address of packets.

If two or more IPv6 addresses are assigned to an interface, apply this command to all but the address that you want to use as the source address of outbound packets. This is Linux-specific and requires the iproute package, or equivalent for your distribution.
This is sample output - yours may be different.
1

ip addr change 2001:db8:1:2::ab dev eth0 preferred_lft 0

jasonjgw · 2010-11-18 05:05:15 5
Convert all Microsoft Word files in current directory to HTML.

This requires wvWare, which under Debian is in the wv package. Alternative converters can be used, e.g., jodconverter, which uses OO.O instead (no X server need be running.)
This is sample output - yours may be different.
0

for f in *.doc ; do wvHtml $f ${f%.doc}.html ; done

jasonjgw · 2010-11-18 00:20:54 4
Comment out all lines in a configuration file matching a regexp, creating a backup.
This is sample output - yours may be different.
0

mv -i something.conf{,~} && sed "/regexp/s/^/#/" < something.conf~ > something.conf

jasonjgw · 2010-11-18 00:10:45 5
Create a tar file with the current date in the name.
This is sample output - yours may be different.
3

tar cfz backup-$(date --iso).tar.gz somedirs

jasonjgw · 2010-11-17 23:04:27 6
Remove all untracked files/directories from the working tree of a git repository.
This is sample output - yours may be different.
0

git clean -dfx

jasonjgw · 2010-11-17 23:00:55 4
Count words in a TeX/LaTeX document.
This is sample output - yours may be different.
0

detex document.tex|wc -w

jasonjgw · 2010-11-17 09:00:37 4

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Netstat Connection Check

This command does a tally of concurrent active connections from single IPs and prints out those IPs that have the most active concurrent connections. VERY useful in determining the source of a DoS or DDoS attack.

copy timestamps of files from one location to another - useful when file contents are already synced but timestamps are wrong.

Sometimes when copying files from one place to another, the timestamps get lost. Maybe you forgot to add a flag to preserve timestamps in your copy command. You're sure the files are exactly the same in both locations, but the timestamps of the files in the new home are wrong and you need them to match the source. Using this command, you will get a shell script (/tmp/retime.sh) than you can move to the new location and just execute - it will change the timestamps on all the files and directories to their previous values. Make sure you're in the right directory when you launch it, otherwise all the touch commands will create new zero-length files with those names. Since find's output includes "." it will also change the timestamp of the current directory. Ideally rsync would be the way to handle this - since it only sends changes by default, there would be relatively little network traffic resulting. But rsync has to read the entire file contents on both sides to be sure no bytes have changed, potentially causing a huge amount of local disk I/O on each side. This could be a problem if your files are large. My approach avoids all the comparison I/O. I've seen comments that rsync with the "--size-only" and "--times" options should do this also, but it didn't seem to do what I wanted in my test. With my approach you can review/edit the output commands before running them, so you can tell exactly what will happen. The "tee" command both displays the output on the screen for your review, AND saves it to the file /tmp/retime.sh. Credit: got this idea from Stone's answer at http://serverfault.com/questions/344731/rsync-copying-over-timestamps-only?rq=1, and combined it into one line.

Boot another OS at next startup

scp a good script from host A which has no public access to host C, but with a hop by host B

middlehost allows ssh access from where you are but not securehost. Use nice ssh piping to simulate scp through A => B => C setting up the shell function if left as an exercise for the reader. ;-) Agent forwarding should avoid password typing.

create a progress bar...

A simple way yo do a progress bar like wget.

Swap the two last arguments of the current command line

Say you just typed a long command like this: $ rsync -navupogz --delete /long/path/to/dir_a /very/long/path/to/dir_b but you really want to sync dir_b to dir_a. Instead of rewriting all the command line, just type followed by , and your command line will read $ rsync -navupogz --delete /very/long/path/to/dir_b /long/path/to/dir_a

Convert seconds to [DD:][HH:]MM:SS

Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

a function to find the fastest DNS server

http://public-dns.info gives a list of online dns servers. you need to change the country in url (br in this url) with your country code. this command need some time to ping all IP in list.

Convert seconds to [DD:][HH:]MM:SS

Define words and phrases with google.

This function takes a word or a phrase as arguments and then fetches definitions using Google's "define" syntax. The "nl" and perl portion isn't strictly necessary. It just makes the output a bit more readable, but this also works: $define(){ local y="$@";curl -sA"Opera" "http://www.google.com/search?q=define:${y// /+}"|grep -Po '(?/dev/null;}

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