Both /etc/mtab and /etc/fstab contain data about mounted volumes, for example:
/etc/mtab/dev/xvda1 / ext4 rw,discard 0 0
proc /proc proc rw,noexec,nosuid,nodev 0 0
...
/etc/fstabLABEL=cloudimg-rootfs / ext4 defaults,discard 0 0
/dev/xvdf /home/ubuntu/logs ext4 rw 0 0
What is the difference between the files?
Unlike many popular programming languages, the popular Oracle Java package is only available using a PPA, not by the official repo.
Why isn't Oracle Java included in the standard Ubuntu repo?
Following the recent heartbleed vulnerability of OpenSSL, I would like to keep my EC2 machines updated on a regular basis. The naive approach would be setting an hourly cron job for security updates (sudo apt-get update && sudo unattended-upgrade).
Are there any risks of doing that? Is there a recommended update mechanism for EC2 machines?
I am trying to change the default shell on Ubuntu server 13.10 on Amazon's AWS (AMI ami-ad184ac4).
I've tried:
~$ chsh -s /bin/zsh
But got:
Password:
chsh: PAM: Authentication failure
I've tried obvious passwords (e.g. ubuntu) but always got the same error message - chsh: PAM: Authentication failure.
Any idea why can't I change the default shell?
How can I define a global shortcuts for copy, cut and paste?
I'm used to Mac's ⌘+C for copy and ⌘+V for paste. They are global, so I can use them interchanging data between CLI and GUI apps.
How can one configure global shortcuts, e.g ⊞ Win+C (copy) and ⊞ Win+V (paste) in Ubuntu 12.04?
Consider the following bash command line, where ^ denotes the cursor location:
svn commit -m very/long/path/to/some/file "[bug 123456] Fix the pixel issue"
^
I'd like to commit a different file with the same message. How can I delete the current word, from cursor location to the next space? Is there also a shortcut for backward deletion, form the cursor to the first space backwards?
Update: ctrl+w erases backwards, but which shortcut erases one word forward?
Consider the following bash prompt, where ^ denotes the prompt location:
$ git commit -am "[bug 123456] Do this and that with the bug"
^
Suppose that I want to commit again to the same bug, with a different commit message. Is there a way to delete the text from the cursor position till the end of line?
I have configured a fancy two-line PS1 bash prompt, with server name, time, user name and other useful variables.
PS1="\n\[\033[1;34m\]\342\226\210\342\226\210 \u @ $SERVER_NAME""$BBlue"" \w""$Color_Off \n\[\033[0;36m\]\342\226\210\342\226\210 \d \t $ \[\033[0;39m\]"
Full Github source here.
The problem is that long lines are often wrapped around themselves, meaning that the new line overlaps the previous one.
The problem is inconsistent: some lines are wrapped correctly, some are not.
Any idea how to fix this?
bc handles numbers as integers:
# echo "100/3" | bc
33
bc -l handles numbers as floating point objects:
# echo "100/3" | bc -l
33.33333333333333333333
Is there a way to limit the number of digits after the decimal point?
I've written this small utility script:
for h in $SERVER_LIST; do ssh $h "uptime"; done
When a new server is added to $SERVER_LIST, the script is stopped with:
The authenticity of host 'blah.blah.blah (10.10.10.10)' can't be established.
RSA key fingerprint is a4:d9:a4:d9:a4:d9a4:d9:a4:d9a4:d9a4:d9a4:d9a4:d9a4:d9.
Are you sure you want to continue connecting (yes/no)?
I've tried yes:
for h in $SERVER_LIST; do yes | ssh $h "uptime"; done
with no luck.
Is there a way to parametrize ssh to automatically accept any new key?
Where does Ubuntu keep the password salt for each user?
Is there a way to add lines to a user's cron via script?
I usually do it using crontab -e, but I would like to automate this task with a shell script.
Consider the following nohup execution:
nohup script.sh > script.out &
Is there a way to log off the terminal, reconnect, bring the process back to foreground and interact with it using the keyboard?
I have scanned a newspaper article which was larger than the scanner glass. Each page was scanned twice: the top and the bottom parts, where the middle part appeared in both images.
Is there a way to quickly match and stitch these scanned images, preferably using CLI? The panorama stitching tools I know require lengthy configuration, which is mostly irrelevant: lens size, focus, angle etc.
Hugin has a solution for this issue, but it isn't practical for batch jobs.
Is it possible to set a new nice level of a running process with a known id?
Does this operation require root access, or just being the owner of the process?
I'm trying to plan my new garden, and want to sketch it professionally - with dimensions of every element in it.
Is there an Ubuntu program for sketching house plans with vectorial elements, like those in the picture above?
When I wake up my laptop (Ubuntu 10.04) from suspension, it does not recognize the available wireless networks. The only way to refresh the list is to disable wireless networking, and than enable it.
Any idea how to force a refresh on the list of wireless networks?
Often, crontab scripts are not executed on schedule or as expected. There are numerous reasons for that:
This community wiki aims to aggregate the top reasons for crontab scripts not being executed as expected. Write each reason in a separate answer.
Please include one reason per answer - details about why it's not executed - and fix(es) for that one reason.
Please write only cron-specific issues, e.g. commands that execute as expected from the shell but execute erroneously by cron.
I have installed an Ubuntu machine with two encrypted LUKS partitions: one for / and one for /home.
I've reinstalled the machine to upgrade to 10.04. Again, the / is installed using LUKS, and I'm able to mount the /home using:
mkdir /media/home
sudo cryptsetup luksOpen /dev/sda2 home
sudo mount -t ext3 /dev/mapper/home /media/home
The problem is, this cryptfs mapper disappears after boot, so I putting the appropriate line in fstab fails.
How do I set the cryptfs to prompt for password and unlock the drive at boot?
Thanks,
Adam
I'm working with many GIS applications under Gnome. It sometimes is very convenient to place one map over another to quickly spot differences.
There used to be a KDE trick to make any window (not just a terminal!) transparent, thereby allowing me to make one map semi-transparent and place it on the window of the other mapping software. Is there a similar trick for Gnome?