Ctrl + A Go to the top of the line you are typing.
Ctrl + E Go to the end of the line you are typing.
Ctrl + L Clear the screen.
Ctrl + U Clears the screen before the cursor. If you are at the end of the line, clears the entire line.
Ctrl + R allows you to search through previously used commands.
Ctrl + C Stop whatever you are doing.
Ctrl + D Exit the current shell.
Ctrl + Z starts the suspension in the background whatever you are doing.
Ctrl + W Delete the word before the cursor is.
Ctrl + K Clear the line after the cursor.
Ctrl + T Reverses the last two characters before the cursor.
Esc + T Swap the last two words before the cursor.
Alt + F Move cursor forward one word in the current row.
Alt + B Move cursor back one word in the current row.
Tab Auto-Complete the names of files and folders.
Paste Ctrl + Y (as in copy and paste) all the text before the cursor.

Note: Some of these commands do not work if shell access is via telnet, or SSH session if the keyboard is a particular configuratain

When we install spamassassin on our mail server we have installed a script used to download the rules to improve the capture of email spam coming to our server.

The script is called sa-update . Below we report a simple crontab entry to be included in your linux box to call every day at 7:00 and the script to keep up to date with the rules of your spamassassin.

0 7 *** / usr / bin / sa-update-D-updatedir / etc / mail / spamassassin /

Remember to also restart the spamassassin service after the update with the command:

/ Etc / init.d / spamassassin restart

or

/ Etc / init.d / spamd restart

NOTE: Commands and locations can vary from distro to distro, but for the sysadmin should not be difficult to find the correct position. In case of difficulty please contact us or leave a comment.

Often you have to put hand to full-bodied configuration files where we can make do with a handful of parameters. In these cases we can remove all the unnecessary fluff simply using the command shown below:

# Grep-v "^ #" / etc / my.conf | sed-e '/ ^ $ / d'> / etc / my_new.conf

or you can use this alternative:

# Cat / etc / my.conf | sed '/ * # / d / ^ * $ / d'> / etc / my_new.conf

Remember to my_new.conf to overwrite the original file after checking the contents.

Show all rpm packages installed:

# Rpm-qa

Query the db rpm filtering out all packets containing the string 'httpd':

# Rpm-qa | grep httpd

Obtaining information about a specific package installed, eg:

# Rpm-qi httpd

Display the list of files provided by a package installed, eg:

# Rpm-ql httpd

Display only the list of configuration files provided by a package installed:

# Rpm-qc httpd

Get information on the documentation provided by a package:

# Rpm-qc httpd

Display the list of dependencies required for a package:

# Rpm-q httpd-whatrequires

Show capability provided by a package:

# Rpm-q httpd-whatprovides

Show scripts started during installation / removal:

# Rpm-q httpd-scripts

Show history of revisions of the package:

# Rpm-q httpd-changelog

Check out which package owns a given file:

# Rpm-qf / etc / httpd / conf / httpd.conf

Display the list of files provided by a package not yet installed:

# Rpm-qp-2.0.52-3.i386.rpm httpd-l

Fedora / RedHat, sign all packets with a digital private GPG key. To import the public-key using the following command:

# Rpm-import / media / cdrom / RPM-GPG-KEY

To verify the integrity of a package before proceeding with the installation, especially if it is downloaded from the Internet, run the next command:

# Rpm-checksig package_name.rpm

To verify all packages installed on your system:

# Rpm-qa gpg-pubkey

Install a binary package:

# Rpm-ivh package_name.rpm

Install a binary package ignoring dependencies requests:

# Rpm-ivh-nodeeps package_name.rpm

Install a binary package by sending the automatic resolution of dependencies:

# Rpm-ivh-aid package_name.rpm

Upgrading a package without changing configuration files:

# Rpm-U package_name.rpm

Updating a package only if it is already installed:

# Rpm-F package_name.rpm

Rimuore a rpm package:

# Rpm-e package_name

Check file size, permissions, type, owner, group, MD5 checksum and last modification on the RPM database:

# Rpm-V httpd

Check all packages installed on your system - use with caution, the system engages in an extreme way:

# Rpm-Va

Verifying a package not installed:

# Rpm-Vp httpd-2.0.52-3.i386.rpm

This command allows you to extract files from the package to be converted into a stream and then cpio to extract the executable from the package:

# Httpd-2.0.52-3.i386.rpm rpm2cpio | cpio-extract-make-directories * bin *

Installing a source package i386.

Step 1:

# Rpmbuild-rebuild nome_pacchetto.src.rpm

Step 2:

# Rpm-ivh / usr/src/redhat/RPMS/i386/nome_pacchetto.rpm

Installing a source package i386 (alternative procedure).

Step 1:

# Rpmbuild-recompile nome_pacchetto.src.rpm

Step 2:

# Rpmbuild-bb / usr / src / redhat / SPECS / nome_pacchetto.spec

Step 3:

# Rpm-ivh / usr/src/redhat/RPMS/i386/nome_pacchetto.rpm

Creating a rpm package from source.
We want to create a package from source application example. We download the source from the internet with wget:

# Wget http://www.example.org/dl/example-2.0.0.tar.gz

# Cp example-2.0.0.tar.gz / usr / src / redhat / SOURCE

# Cd / usr / src / redhat / SOURCE

# Example-2.0.0.tar.gz tar xzf

Check if directory exists within the unzipped file. 'Spec', which contains the specifications for the creation of the track, and copy it to / usr / src / redhat / SPEC:

Example.spec # cp / usr / src / redhat / SPEC / example.spec

If the file. Spec does not exist can be created. Finally, prepare the filling for the creation of the new rpm:

# Cd / usr / src / redhat

# Rpmbuild-bb SPECS / snort.spec

Linux systems usually have a preset limit of 1024 files open simultaneously. This limit is indeed quite low in case of machine with high workloads, particularly in the presence of web servers with many different domains and pointers to files and logs.

When you reach the production stage, and you exceed this limit are often strange inconsistency problems. So you better act quickly. Knowing the process-id of our application (eg tomcat or httpd) with the command seguende we examine the number of files that the process is holding open:

lsof-p [process-id] | wc-l

After understanding the problem we can intervene minimally with ulimit. Use the following commands to get information about system settings:

ulimit-Ha

ulimit-Hs

Finally, to revise the maximum simultaneously open files in Linux we can type:

ulimit-n 4000

See also the manpages for more info on the command and all of its options:

man ulimit

If you want to force the file system check to restart our linux box can simply create at the root "/" file forcefsck:

# Cd /

# Touch / forcefsck

# Reboot

For those who come from long experience from RHEL 4.X has certainly had to deal with the command ext2online. This brief note to remember that in RHEL 5.X there is no longer this command. To resize the partition is mounted simply use the command resize2fs. The control automatically detects the status of the partition and behaves accordingly. Below is an example:

[Root @ host ~] # resize2fs / dev/mapper/VolGroup00-LogVol00

resize2fs 1.39 (29-May-2006)
Filesystem at / dev/mapper/VolGroup00-LogVol00 is mounted on /; on-line resizing required
Performing an on-line resize of / dev/mapper/VolGroup00-LogVol00 to 4923392 (4k) blocks.
The filesystem on / dev/mapper/VolGroup00-LogVol00 is now 4923392 blocks long.

Howto Forge on a howto on how to resize the partition EXT2 / 3 without losing data .

When we use the ls command can display the permissions of files in the following format:

-Rw-r-r-1 user group 49296 March 24 2006 file.bin

As they need to display octal permissions on the files themselves recommend this script:

ls-l | awk '{k = 0; for (i = 0; i <= 8; i + +) k + = ((substr ($ 1, i +2.1) ~ / [rwx] /) * 2 ^ (8 -i)) if (k) printf ("% 0th", k) print} '

The command displays + style octal permissions drwxr-xr-x.

If you are satisfied with the result you can make more permanent and easier to use in creating an alias in your shell you used to parameterize and pleasure. For bash you have to edit the file in your home directory ~ /. Bashrc, after logout and login you can use the command 's' to the classic alternately comanto 'ls':

alias l = 'ls-lha-color | awk' {k = 0; for (i = 0; i <= 8; i + +) k + = ((substr ($ 1, i +2.1) ~ / [rwx] / ) * 2 ^ (8-i)) if (k) printf ("% 0th", k); print} '"

Result:

600-134K rw --- 1 user group 21 April 2006 mbox

To get a personalized welcome message after login via ssh simply edit the file / etc / motd.

Optionally you can edit the file / etc / profile to display the date, uptime and other info.