Comparison between htop and top

In ‘htop’ you can scroll the list vertically and horizontally to see all processes and complete command lines.

In ‘top’ you are subject to a delay for each unassigned key you press (especially annoying when multi-key escape sequences are triggered by accident).

‘htop’ starts faster (‘top’ seems to collect data for a while before displaying anything).

In ‘htop’ you don’t need to type the process number to kill a process, in ‘top’ you do.

In ‘htop’ you don’t need to type the process number or the priority value to renice a process, in ‘top’ you do.

‘htop’ supports mouse operation, ‘top’ doesn’t

‘top’ is older, hence, more used and tested.

Fortunately it is available as binary package for RHEL 5 from rpmforge so the install was quick and painless:

yum install htop

Here is how it looks:

Default colors were not very appropriate for white background so I switched easily (F2-Setup->Colors) to mc colors.

Jul

14

CUPS code is now owned by APPLE

Filed Under Linux, news | Leave a Comment

According to following source.

Apple now owns the CODE ofÂ CUPS.

I hope that this is for good.

Jul

13

How to unlock yourself – Linux screensaver

Filed Under Command line, Fix, Howto, Linux | Leave a Comment

Today I’ve accidentally locked myself with Linux screensaver.

How this happened?

I use English letters for my password, but when I’ve stepped back from my Linux workstation my keyboard group was with group different than English.

As result when I come back and tried to unlock myself I couldn’t enter the correct password.

Solutions:

1. First and simplest solution will be to kill X with Crtl+Alt+Backspace

2. Reboot the PC – Alt+Ctrl+Del

3. Try to fix it

Because I’ve had open and unsaved documents first 2 options will result loss of my work I’ve decided to go with third one.

How I did it:

A requirement is to have another PC and ssh access to main one.

1. Login via ssh to locked PC.

2. Start vnc server under your account

vncserver

Note you will need vnc server installed. How to do it is out of the scope – consult your documentation.

3. Open firewall ports required for VNC or simply shutdown firewall

/etc/init.d/iptables stop

4. On other PC start VNC client and connect to locked one

5. Start keyboard configuration

gnome-keyboard-properties

6. Remove all other layouts except English

7. Now you can return to locked PC and unlock it.

NOTE: This procedure was tested on LAN and CentOS 5.

Jul

11

Fixing Adobe Acrobat Reader “expr: syntax error”

Filed Under error, Fix, Howto, Linux | Leave a Comment

After updating my Linux workstation I found that acroread produces “expr: syntax error” when started.

Quick Googling show me the solution.

Open terminal.
First find where acroread executable script is located – on my machine:
whereis acroread acroread: /usr/bin/acroread /usr/lib/acroread
Then type vi /usr/bin/acroread.
After that type 418G and add *(asterisk) [move cursor after the block press i for insert and *]after second [0-9] block as shown below
Then save the file [Press Esc 2 times and type :wq]
Now you can use acrobat again.

NOTE: This fix is for AdobeReader_enu-7.0.9-1 for Linux. It is not tested on other versions or platforms.

EDIT: How to install AdobeReader_enu-7.0.9-1 in CentOS 5/4.x.

Navigate to adobe.com –> Click on get adobe reader –>Choose .rpm version –>Click on Download –>Either Open with Software Installer or download to disk and install if you need to do it on multiple machines.

Jul

10

Howto change default open with… application in Linux (Gnome)

Filed Under Fix, Howto, Linux | Leave a Comment

Usually on the same system there is different programs that can open the same type of files, but they also have different capabilities.

And “Usually” the program that we are comfortable with is not the one by default.

Here I’ll show you how to fix it:

It is actually very simple. Just open file browser and navigate to file of the same file type that you want to change default program.
Then right click with the mouse and choose properties. You will see similar window:
Then click on Open with tab.
Here you can change default open with program or add new one if it is not into list.
Finally click close. (In contrast with other OS all changes are applied on close and there is no OK button)

That’s it.

Tip: Another way of doing it “Temporarily” is to right click and use open with…

Jul

9

Taking screenshot in CentOS 5 (RHEL 5)

Filed Under Howto, Linux | 1 Comment

When preparing for a post I was challenged by change in GNOME menus.

In CentOS 4.x there was Take screenshot application into menu, but in version 5 this application “disappeared”.

After quick search in documentation I’ve discovered that now I can take screenshot by pressing Print Screen button on my keyboard and if I want only active window I can press Alt+Print Screen

Here is the menu:

Jul

5

Removing user in Linux

Filed Under Command line, Howto, Linux, Unix | Leave a Comment

Today I removed the user in my Linux workstation.

Probably you will say that this is simple task just remove user home directory and his password, but appears that this is not.

First thing is that there is no single command that will do this task for you.

Let’s start:

1. Lock user – this is done with following command:

passwd -l <user_name>

This command will achieve it by changing the password to a value that cannot be matched by any possible encrypted value.

This command is usefull also for temporary disabling user account.

2. Search for and kill any user processes that still run

ps aux | grep -i ^<user_name>

kill -9 <PID number>

where <PID number> is the number in the column just after the user name.

3. Find all files that belong to this user

find / -user <user_name>|less

4. Decision time – decide do you want to keep those files or erase them. My suggestion is to backup them just in case.

5. List and remove any crontab jobs

List user cron jobs:

crontab -u <user_name -l

And if you see any entries remove them:

crontab -u <user_name> -r

6. Remove user from sudoers (if you use sudo)

visudo

7. Check any other applications as remote access, MySQL, Web App.
More extended howto

Jul

5

bash: /bin/rm: Argument list too long – How to fix it (Update 2 )

Filed Under Linux | 14 Comments

Today I’ve decided to cleanup the hard drive on my Linux workstation and “surprisingly” found 8G of temporary files in one folder.

After quick review I’ve decided to erase them with rm command.

For my surprise when running the command:

/bin/rm *.tmp

I got following error message:

bash: /bin/rm: Argument list too long

Conclusion:Even rm command has his limits!

Solution: Get Plumber(Joking)
Actually only Pipe is needed.
By typing following command:

find . -name "*.tmp"|less

You will see list of the files and by replacing less with xargs /bin/rm those files will be erased. Can you skip previous step? Yes you can and it is not required, but you risk to erase a lot of data if you have syntax error.

find . -name "*.tmp"| xargs /bin/rm

find . -name "*.tmp" -print0 | xargs -0 /bin/rm

find . -name "*.tmp" -delete

if you have space in file name.
Depending on the number of files and your system speed after a while all files will be erased.

Done .

UPDATE0:

(Siby) If you get Argument list too long on all commands – probably you should look at you .bashrc file.
More specifically at PATH. Did you modify it to look at subfolders?

UPDATE1:

I’m adding information from the comments to main post. Thanks to “Scriptster” and “Swynndla”

UPDATE2:

Another solution is to use -delete option applied to find command.

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Comparison between htop and top

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