Copy Text From a File in Terminal

Posted on May 20, 2018 by curiouscat

If you just want to quickly copy the text of a file to the clipboard while in terminal you can just use:

cat [filename]

That will display the full text of the file to the terminal and you can just highlight the text and copy.

One case where this can be useful is as a quick and simple way to copy text to the clipboard of your laptop when you ssh into a remote server. If contents of the file are larger than a screen it can be difficult to scroll and copy the text you want to copy without using the cat command.

As a reminder: The intention for this site is quick and easy sample code and syntax reminders. I frequently forget the basic syntax of some thing I don’t use frequently and at times find it hard to find the simple basic information I want.

Some Quick cli Syntax for Postgres

Posted on May 24, 2016 by curiouscat

How to Dump SQL result to a text file using cli

> psql -U postgres -d [database_name] -c ‘SELECT * FROM users’

How to exit postgres command-line utility psql
Type \q and then press ENTER to quit psql

Reset Root Password on MySQL Database
Notice that in PostgreSQL superuser is called postres (not root). If you forgot superuser password, you can reset it this way:

edit file pg_hba.conf

> sudo vim /etc/postgresql/9.3/main/pg_hba.conf

and find there a line similar to:

# TYPE  DATABASE        USER            ADDRESS                 METHOD
local   all             postgres                                md5

md5 here means that postgres asks for password. If there is this line then replace
md5 with peer, if there is no this line then add it

local   all             postgres                                peer

save the file, exit and reload postgresql service to pick up the updated configuration:

> sudo service postgresql reload

Then you should be able to get access to psql without providing a password this way:

> sudo -u postgres psql

In psql you can change user password using this command:

ALTER USER postgres PASSWORD 'new password';

PostgreSQL performance and monitoring

switch current database

\connect database_name or \c database_name

you can user autocomplete by pressing [tab]

list tables in current database

\dt

create a new database and import tables, data from a dump
in psql

CREATE DATABASE some_database

create a dump (in terminal)

> pg_dump dbname > outfile

You may notice that no password is used. That is because with Postgres you can setup a password file that is used to verify your access as such:

> vim ~/.pgpass

Then (format is hostname:port:database:username:password):

localhost:5432:mydbname:postgres:mypass
[ctrl-x] then confirm with y, then hit [enter]

save and exit

> chmod 600 ~/.pgpass

restore a dump (in terminal)

> psql dbname < infile

more details on dump-restore

create a user (it sql)

CREATE USER tester WITH PASSWORD 'test_password';
GRANT ALL PRIVILEGES ON DATABASE "test_database" to tester;

notice difference in quotation marks – in first case it must be single quotation mark ‘ and in the second case – double quotation mark “, otherwise PostgreSQL raises a syntax error

restart PostgreSQL

> sudo service postgresql restart

other regular service actions available too – [force-reload, reload, start, status, stop]

Also for Nginx (unrelated to this post really), Restart Nginx

sudo service nginx restart
other regular service actions available too – [force-reload, reload, start, status, stop]
reload only reloads configuration files, without stopping a service (which restart does)

Locking and Unlocking a User in Ubuntu

Posted on February 19, 2016 by curiouscat

To lock a user in Ubuntu sudo usermod –expiredate 1 [username] Substitute the user’s username where username is shown below.

[code]sudo usermod –expiredate 1 username[/code]

This also can be shortened to

[code]sudo usermod -e 1 username[/code]

To unlock a user

[code]sudo usermod -e -1 username[/code]

This will disable the user both from accessing via password and from accessing via a private key.

You can also expire a user at a future date using

[code]sudo usermod -e YYYY-MM-DD username[/code]

To expire a password and force a user to enter a new password

[code]sudo passwd -e YYYY-MM-DD username[/code]

How to Manually Run Cron Tasks

Posted on September 27, 2015 by curiouscat

To manually run cron tasks you can use the run-parts command in Linux.

So to run your cron-weekly, for example, to test that a fix you just made runs without error (this is what I just did, in fact)

run-parts /etc/cron-weekly

run-parts will run all the executables in a directory (you must point at the directory). So if you have several files in cron-weekly to run, you can’t just point to one of the files.

You may run into environmental differences running the script as a different user than the cron test runs at, so you can run as that user if needed. You need to be aware this is a quick and simple way of testing part of the process but it doesn’t do a perfect job of testing if it works as a cron task. But it will let you catch some failures quickly and fix them in time for the actual cron task to run. So do check that the everything works after the real cron job runs.

This is just the kind of thing I said I would put in this blog. Simple stuff but things I forget – so I put it here to remember and maybe help out others, like me, that need really basic tips.

If you have a cron task item (or have setup the whole task this way) that is just a script and you just want to test that 1 item you may run the script directly. For example (for a Linux shell script):

sh /etc/cron.weekly/your_crontask_script.sh

Compare WordPress Files on Server to Proper WordPress Version

Posted on November 18, 2014 by curiouscat

Sadly one of the hassles in managing your own WordPress blog is dealing with people that use your blog to serve spam content. These hacks can insert spam links into your pages and posts or create spam directories that are completely their own content on your domain.

There are many issues to deal with in re-establishing control of your server; but that isn’t the scope of this post.

This is just a tips if you are troubleshooting to try and determine what is going on. Often your server has been hacked to allow uploaded php pages to be added or for WordPress php files to be edited.

One way to track down if the files have been changed or new ones added is to compare the WordPress files on your server to the current files for a fresh WordPress install. This assumes your blog is using the current version, which hopefully it is because on the big improvement WordPress made is to make those updates automatic. That greatly reduces the chance to have WordPress be the vector to infecting your server. If you were using a older version then just compare to the field for that version from the WordPress server.

If you don’t have a current backup I would make a backup before I tried this. Obviously, don’t make any deletions or changes to your server unless you understand what you are doing. You can create big problems for yourself.

You can use the diff command to view the difference between WordPress on your sever and the fresh install from WordPress. I install the new WordPress in a new directory outside public_html. At the cli on a Ubuntu/Linux server:

[code]sudo wget http://wordpress.org/wordpress-4.0.zip
unzip wordpress-4.0.zip
diff -rq wordpress ../public_html/[/code]

wordpress-4.0.zip – replace with whatever the version is you are using.
../public_html/blog/ – replace with the path to your blog

Continue reading →

How to Dump SQL Result to a Text File Using cli

Posted on September 15, 2014 by curiouscat

Just a quick tip on how to dump a sql result to a txt file.

mysql -e “select * from [table]” -u[user] -p [database] > sqlresult.txt

For example:

[bash]mysql -e "select * from orders where product_id = 15" -uroot -p > sqlresult.txt[/bash]

Reset Root Password on MySQL Database

Posted on August 15, 2014 by curiouscat

How to reset the root password on a MySQL database.

Stop mysql using this command:

[bash]sudo /etc/init.d/mysql stop[/bash]

Because you are not checking user privledges at this point, it’s safest to disable networking. Then, start the mysqld demon process using the –skip-grant-tables option using

[bash]sudo /usr/sbin/mysqld –skip-grant-tables –skip-networking &[/bash]

Next, start the mysql client process using this command:

[bash]mysql -u root[/bash]

from the mysql prompt execute this command to be able to change any password

[bash]FLUSH PRIVILEGES;[/bash]

Then reset/update your password

[bash]SET PASSWORD FOR root@’localhost’ = PASSWORD(‘password’);[/bash]

Rsync to copy Files Between Servers and Computers

Posted on June 28, 2014 by curiouscat

I found rsync when I wanted to use scp to copy files to a server but not overwrite files already there. Rsync is actually more efficient no matter what (it seems) but it is really great if there are a bunch of duplicate files (Rsync will just skip them).

To copy files from your current computer to a server:

rsync -azv -r ssh [directory] [username]@remotehost:[location]

[bash]$ sudo rsync -azv -e ssh directory-on-my-computer/ [email protected]:~/files/go/here[/bash]

a = archive mode
z = compress file data
v = verbose
r = recurse through subdirectories and copy all of them

Compressing file data saves bandwidth so if that is an issue it is another big win over scp. And in my reading it seems rsync can restart a broken file transfer in process (while scp you have to redo the whole file transfer).

To copy from the server to your computer just reverse the order of the locations. And you can even just put in two addresses not on your current computer and copy between then.

As a reminder, I realize this blog is made up of stuff that is obvious to a large number of people. It is really aimed at me (so I can quickly find what I found before), and to a lessor extent others like me (who use cli some but are not system administrators or programmers to any significant extent).

Don’t Copy-Paste Directly from Website to Terminal

Posted on April 8, 2013 by curiouscat

Good reminder and discussion on Hacker News about the danger of copy-paste from a website into terminal.

When copying from a website it is easy for hidden text to be included in the clipboard. If you paste that into terminal it can be executed before you see the code. Including new line commands in the copied text will automatically execute the commands (in most terminal applications).

The best solution is to paste the clipboard content into something to view the text before pasting into clipboard. The best way is probably to recopy it. I use this double copy method to get rid of formatting I don’t want (when the clipboard includes things like font styling info you don’t want – not relavent when pasting into terminal but the pasting [into say vim, which won’t include the extra formatting details] and recopying part is similar). It may be possible to have text hidden (write it in a way where it won’t show up on the screen but is in the clipboard – using some tricky unicode characters or something).

Some people put # before pasting into clipboard but that only protects the first “line.” Any new lines could still be run without you seeing them.

The discussion warns against a malicious website intentionally creating a problem but if you paste in multiple lines there is also just the danger from the lines executing immediately when you wanted to edit the line before it was executed.

Making Sure You Don’t Run Out of Space on Your VPS

Posted on February 6, 2013 by curiouscat

Over the years I have had web sites I work on go down because the server ran out of space (when I wasn’t responsible for the system administration). Well today I had it happen for some sites on one of my servers.

I have a remote monitoring service so I was notified when the sites were unavailable. Looking in the error logs I could see I ran out of space, which is a fairly lame error to make, I think. I cleared up some space quickly and things were in working order again.

A few tips from this experience. To see data on space used and available space from the command line (linux/ubuntu) use the df command.

[bash]df[/bash]

You could check that occasionally to see if anything strange is going on. But it is better to use something like Nagios to monitor the server and provide notice if usage goes past certain points is wise (75%, 80%…).

I found a nice way to find large files (that may be possible to delete to free up space)

[bash]sudo find . -mount -ls | awk ‘{print $7, $11}’ | sort -rn > large_file_list[/bash]

If you get an error with the file creation, you can log in as root (su) or create the file first and then it can overwrite the existing file.

It is smart to have log rotate setup for logs. I didn’t have it setup for every log. To create a file to keep track of all your logs for domains you can do the following. Create a file in the logrotate directory so it is run per your settings.

[bash]sudo vim /etc/logrotate.d/virtualhosts[/bash]

This article from Slicehost provide details on options, a simple setup is to include text such as this in the file created in the line above.

[bash]/var/www/domain1.com/logs/*log /var/www/domain2.com/logs/*log {
rotate 14
daily
compress
delaycompress
sharedscripts
postrotate
/usr/sbin/apache2ctl graceful > /dev/null
endscript
}[/bash]