80
votes
How to check if an RSA public / private key pair match
Depending on where you get the public key file you are testing, the accepted answer may give false positive results. This is because of the behavior described in the comment by @drewbenn. Specifically,...
57
votes
SSH authorized_keys command option: multiple commands?
You can have only one command per key, because the command is “forced”.
But you can use a wrapper script. The called command gets the original command line as environment variable $...
53
votes
Accepted
Return only a HTTP status code from curl command
You can use the -w parameter to define the format curl outputs. To get the status code and nothing else, use something like this:
$ curl -s -o /dev/null -w "%{http_code}" http://xxx.xxx.xxx
The ...
32
votes
Accepted
How to print the last line of a gz compressed file in the command line?
If you want lines from the tail-end of a file rather than the head-end, use tail instead of head:
$ zcat /var/log/syslog.2.gz | tail -1
Aug 24 07:09:02 myhost rsyslogd: [origin software="rsyslogd" ...
15
votes
SSH authorized_keys command option: multiple commands?
In the great SSH, The Secure Shell: The Definitive Guide book by O'Reilly, in chapter eight, there is a nice example given using a script like the following:
#!/bin/sh
/bin/echo "Welcome!
Your ...
14
votes
How to check if an RSA public / private key pair match
The easiest is to compare fingerprints as the public and private keys have the same. Visual comparison is pretty easy by putting the two commands on same line:
ssh-keygen -l -f PRIVATE_KEY; ssh-keygen ...
13
votes
Accepted
What is difference between */5 and 5 for minute value in crontabs?
5 * * * * means it runs once per hour at five minutes past the hour.
*/5 * * * * means it runs once every five minutes.
The later construct behaves slightly unintuitive if the number does not divide ...
11
votes
Accepted
SSH authorized_keys command option: multiple commands?
No. It is not "allowed" command, but "forced" command (as ForceCommand option).
The only possibility is to use different keys for different commands or read parameters from stdin.
10
votes
How to print the last line of a gz compressed file in the command line?
FWIW: I've developed a command line tool which can make a tail (-t) or even a continuous tail of a gzip file (-T) as it grows. (Many other options available):
https://github.com/circulosmeos/gztool
...
9
votes
Accepted
How to check that all ZFS snapshots within a pool are without holds before destroying that pool
Not sure about how this looked back in 2012 but now you can check the userrefs property:
zfs get userrefs
To list all holds in all pools:
zfs get -Ht snapshot userrefs | grep -v $'\t'0 | cut -d $'\...
6
votes
What is the function in Windows similar to Inode in Linux?
In NTFS file metadata is stored in the MFT records, which is the analog of inode in Windows. Each record has its own unique ID which is the equivalent to inode number. You can check this with fsutil ...
6
votes
Ansible command ignore creates
One very basic solution. In your task:
- name: Do command optionally ignoring create option
command:
cmd: touch /tmp/toto.txt
creates: "{{ ignore_creates | default(false) | bool | ...
5
votes
Nginx enable site command
NGINX
If you're using one of the official upstream packages of nginx from http://nginx.org/packages/, the best way is to navigate to the /etc/nginx/conf.d directory, and rename the affected file from ...
5
votes
Accepted
One liner to check if specific port(s) is/are open
for port in 6379 16379 26379;do nc -zv 127.0.0.1 $port;done
Ofcause, you should use another server to check your firewall from the outside and not from the localhost to be sure that apps are blocked.
5
votes
Accepted
ping: Warning: time of day goes back (-203647us), taking countermeasures
This has happened to me on AMD type processors before, where the clocksource wasn't shared between CPUs (it was set to jiffies for me).
One of the CPU's was a few jiffies ahead of the other causing ...
4
votes
What is /usr/bin/[?
As others pointed out, [ is the shell's condition evaluation utility - test.
In fact, there is a manual page for that!
$ man [
should give you more details about the opening square bracket.
...
4
votes
Accepted
Continuously tailing a rotating log file with date and time in filename
You can create a script to tail the most recent log file in the background and then check regularly for a new log file. If there is a new log file, kill the old process and start tailing the new file. ...
3
votes
Accepted
How to find the ip address of the pc that sent a shutdown command?
Converting my comments/thoughts into an answer.
It appears that you have given all of the students:
Administrative control over all the computers.
Anonymity by allowing them to all share the same ...
3
votes
Is there a global, persistent CMD history?
Yes, it's possible
If all you want to do is save your command line history at the end of every session, here's a simple way to do it:
As other answers indicated, doskey allows you to list the command ...
3
votes
Nginx enable site command
Link with full path:
ln -s /etc/nginx/sites-available/site_1.conf /etc/nginx/sites-enabled/
service nginx reload
3
votes
Accepted
fdisk with a a single command fail in the second execution
After creating a partition, you're moving on to setting the partition type: echo t;. Then, to the next prompt, you're outputting the desired partition type number... but that is not what fdisk is ...
3
votes
Accepted
Azure App Service Plan - Specify App Size with PowerShell
The PowerShell command for this is confusing for two reasons:
The docs are missing the property you need for this, "WorkerSize"
The values for this property don't line up with the actual ...
3
votes
Accepted
Retrieving Active Directory Users with no Email address from a certain group in powershell
Start from the group and get a members list; get the AD user object for each group member; check whether the user has an email address.
Get-ADGroupMember $yourgroup | Get-ADUser -Properties mail | ...
2
votes
Nginx enable site command
Compact ngensite/ngdisite shell scripts
After reading the replies here while setting up a new Debian server, then going off to do some research, I made a couple of readable shell scripts to help me ...
2
votes
Is there a global, persistent CMD history?
I propose using Cygwin with Windows Terminal. It may not be exactly what you want but it works quite well for me. It also probably has some issues that I haven't discovered just yet.
You can integrate ...
2
votes
Remove "Cc: " from mailx command
Change the command sending the email like this:
mail "$To" -s "$Subject" < /dev/null
It will do it for you. If you later decide that you need a Cc: recipient, simply add it with -c switch to the ...
2
votes
Accepted
find command with type and max date age
Read the manual ! See -mtime -2 to get the modifications in the last two days and only concerning the files with -type f
http://man7.org/linux/man-pages/man1/find.1.html
2
votes
SSH authorized_keys command option: multiple commands?
Other approaches use e.g. a restricted shell for the given user or use a wrapper which restrains commands to al files/scripts found in a specific directory, thus allowing to augment the list of ...
2
votes
Accepted
Trouble using powershell output as a variable in batch file
In the FOR command you need escape not only the parenthesis, but the mod (percent) as well. The parens are escaped with ^, the percent by %. Note that this will only work within a batch file, not the ...
2
votes
How to cp files from sources to destination without using alias or non-alias and without getting confirmation/prompts?
Command Without Alias
Any unix command can be prefixed with \ to get the non-alias version.
With Alias
#-(0) :: /dev/shm/test2 > ls
total 0
-rw-------. 1 root 0 Feb 24 16:29 a
-rw-------. 1 root ...
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