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Commands by mpb from sorted by
Terminal - Commands by mpb - 41 results
# cd $partition; dd if=/dev/zero of=ShredUnusedBlocks bs=512M; shred -vzu ShredUnusedBlocks
2009-06-21 14:17:22
User: mpb
Functions: cd dd shred

This command securely erases all the unused blocks on a partition.

The unused blocks are the "free space" on the partition.

Some of these blocks will contain data from previously deleted files.

You might want to use this if you are given access to an old computer and you do not know its provenance.

The command could be used while booted from a LiveCD to clear freespace space on old HD.

On modern Linux LiveCDs, the "ntfs-3g" system provides ReadWrite access to NTFS partitions thus enabling this method to also be used on Wind'ohs drives.

NB depending on the size of the partition, this command could take a while to complete.

shred -vzu /tmp/junk-file-to-be-shredded
<<<"k=1024; m=k*k; g=k*m; g" bc
2009-06-17 10:35:10
User: mpb

There are two ways to use "here documents" with bash to fill stdin:

The following example shows use with the "bc" command.

a) Using a delimiter at the end of data:

less-than less-than eeooff bc

> k=1024

> m=k*k

> g=k*m

> g

> eeooff


b) using the "inline" verion with three less-than symbols:

less-than less-than less-than "k=1024; m=k*k; g=k*m; g" bc


One nice advantage of using the triple less-than version is that the command can easily be recalled

from command line history and re-executed.

PS: in this "description", I had to use the name "less-than" to represent the less-than symbol because the commandlinefu input text box seems to eat up the real less-than symbols. Odd.

urpmi --auto-update --force # apply all pending updates (Mandriva Linux)
2009-03-28 14:59:26
User: mpb

Update a Mandriva Linux system with any pending updates.

This command needs to be run with root privilege.

Using the "--force" option answers "yes" to any interactive prompts

thus allowing the updates to be left unattended to completion.

NB if there is an update for glibc and/or a new kernel then the system

would need to be rebooted for these to take effect.

A prerequisite for running "urpmi --auto-update" is to have correctly defined

urpmi media sources (which can be done by visiting http://easyurpmi.zarb.org/).

If there are no new updates the the message "Packages are up to date" is shown.

2009-03-28 11:43:21
User: mpb

See: "man pwgen" for full details.

Some Linux distros may not have pwgen included in the base distribution

so you maye have to install it (eg in Mandriva Linux: "urpmi pwgen").

2009-03-28 00:18:39
User: mpb

The vi key sequence !}command will send the file contents from the cursor

to the next blank line as STDOUT to the command specified

and replace that sequence of file lines with the output of the command.

For example: sorting a block of data - !}sort

The sequence !{command will do the same but "upwards" (from the current position towards the start of the file.

netstat -atn | awk ' /tcp/ {printf("%s\n",substr($4,index($4,":")+1,length($4) )) }' | sed -e "s/://g" | sort -rnu | awk '{array [$1] = $1} END {i=32768; again=1; while (again == 1) {if (array[i] == i) {i=i+1} else {print i; again=0}}}'
2009-03-27 20:38:43
User: mpb
Functions: awk netstat sed sort

Some commands (such as netcat) have a port option but how can you know which ports are unused?

# wc -l /var/log/security/writable.today
2009-03-19 12:25:52
User: mpb
Functions: wc

Mandriva Linux includes a security tool called "msec" (configurable via "draksec").

One of the many things it regularily checks for is world writeable files.

If any are found, it writes the list to /var/log/security/writable.today.

"wc -l" simply counts the number of lines in the file.

This number should be low.

Browse through /var/log/security/writable.today and consider if any of those files *need* to be world-writeable (and if not, modify the permissions. eg: "chmod o-w $file").

A large number of world-writeable files may indicate that umask is not correctly set in /etc/profile (or ${HOME}/.bash_profile) but could also indicate poor security configuration or even malicious activity.

vos listvldb | agrep LOCKED -d RWrite | grep RWrite: | awk -F: '{print $2}' | awk '{printf("%s ",$1)} END {printf("\n")}'
2009-03-17 19:55:39
User: mpb
Functions: awk grep

This command shows if there are any locked AFS volumes.

The output is a list of AFS volume IDs (or nothing if there are none locked).

rpm -qa --queryformat '%{installtime} \"%{vendor}\" %{name}-%{version}-%{release} %{installtime:date}\n' | grep "Thu 05 Mar"
2009-03-17 13:38:20
User: mpb
Functions: grep rpm

Find out which RPMs were installed on a particular date.

These would (naturally) include update RPMs.

This example shows searching for "Thu 05 Mar" (with grep).

Alternatively, pipe it to less so you can search inside less (with less's neat text highlighting of the search term):

rpm -qa --queryformat '%{installtime} \"%{vendor}\" %{name}-%{version}-%{release} %{installtime:date}\n' | less # (this example) search term: Thu 05 Mar

play $audio_file
2009-03-17 11:30:02
User: mpb

"play" is part of "SoX"

SoX - Sound eXchange, the Swiss Army knife of audio manipulation.

For details, see: man sox

:!cp % %-
2009-03-17 00:34:24
User: mpb

At the start of a vi session and *before* saving any changes use ":!cp % %-" to make a backup of the current file being edited.

example: vi /data/some/long/path/file

:!cp% %-

creates /data/some/long/path/file-

# indicates a comment in shell
2009-03-16 23:15:33
User: mpb

Using the "#" in shell is surprisingly useful.

Some of the uses I found:

a) As a visible copy buffer in shell history (caveat: do not use for passwords :-)

b) To build complex commands until ready then hit the HOME, DEL, ENTER keys to run it

c) Placing reference data into shell history (search for tags with CTRL-R TAGNAME)

d) Putting aside a "work in progress" command to focus on another task (HOME # ENTER)

rpm -qa --qf '%{SIZE} %{NAME}\n' | sort -nr | nl | head -6 # six largest RPMs
2009-03-15 22:18:17
User: mpb
Functions: head nl rpm sort

Low on disk space? Check the largest installed RPMs for delete canditates.

ls -1 | grep " " | awk '{printf("mv \"%s\" ",$0); gsub(/ /,"_",$0); printf("%s\n",$0)}' | sh # rename filenames: spaces to "_"
2009-03-15 18:42:43
User: mpb
Functions: awk grep ls rename sh

This command converts filenames with embedded spaces in the current directory replacing spaces with the underscore ("_") character.

gcal -K -q GB_EN 2009 # display holidays in UK/England for 2009 (with week numbers)
2009-03-15 10:19:52
User: mpb

NB when you run this gcal command in your shell, holidays are highlighted

but this highlighting does not show in the sample output (above).

To find full details on gcal options: gcal --long-help | less

Example for United States, Pennsylvania:

gcal -K -q US_PA 2009 # display holidays in USA/Pennsylvania for 2009 (with week numbers)

Example for Hong Kong:

gcal -K -q HK 2009 # display holidays in Hong Kong for 2009 (with week numbers)