aggiunge un gruppo
groupadd $group
Tells which group you DON'T belong to (opposite of command "groups")
sed -e "/$USER/d;s/:.*//g" /etc/group | sed -e :a -e '/$/N;s/\n/ /;ta'
aggiunge $username al grupppo
sudo usermod -aG $group $username
list user that can potentially access the system:
cat /etc/passwd | grep /bin/sh cat /etc/passwd | grep -v nologin | grep -v /bin/false
to prevent system user login:
chsh -s /bin/false <username>
mostra le informazioni sui gruppi di un utente
id tony ->uid=1123(tony) gid=1124(developers) groups=1124(developers)
per vedere tutti gli utenti del sistema
cat /etc/passwd
A user who has a valid shell and no password can still log in by non-password-based methods, the most common being an ssh key. A valid shell is necessary to run cron jobs.
cat /etc/shadow
mostra utenti con password
Setup password for user $user:
passwd $user
aggiungere un utente ESISTENTE ad un gruppo
sudo usermod -a -G $group $username sudo usermod -a -G www-data $username id $username groups $username
aggiungere un NUOVO utente ad un gruppo
useradd -g $group $username id tony ->uid=1123(tony) gid=1124(developers) groups=1124(developers) useradd -G $group $username
Create a new user with no shell. Useful to provide other services without giving shell access
useradd -s /usr/sbin/nologin $username
in alternativa
chsh -s /sbin/nologin <username>
assicurarsi che la shell muta esista e se non esistesse crearla
less /etc/shells echo "/usr/sbin/nologin" >> /etc/shells
assicurarsi che l'utente abbia la shell bash, non la shell sh
echo $0 # if "sh" instead of "bash" sudo chsh -s /bin/bash <username>
aggiungere un utente a un gruppo
adduser <username> www-data
oppure
usermod -a -G <groupname> <username>
ensure that the group has write permission:
sudo chown www-data:www-data /var/www/file chmod g+w /var/www/file
List all groups and the user names that were in each group
for u in `cut -f1 -d: /etc/passwd`; do echo -n $u:; groups $u; done | sort
If your program creates directories that behave like /tmp, in that lots of people put things there but shouldn't be able to remove each other's files, then you should set the sticky bit on the directory.You can set the sticky bit on a directory with the chmod command by invoking the following:
% chmod o+t directory
This name is anachronistic; it goes back to a time when setting the sticky bit caused a pro- gram to be retained in main memory even when it was done executing.The pages allocated to the program were "stuck" in memory.
sudo update-rc.d tomcat7 disable 0123456
proc - process information pseudo-file system
man proc 5
basic server monitor script:
$msg .= "<hr>";
$msg .= "<b>DISKS(df):</b>";
$msg .= sprintf('<pre style="font-family: monospace;">%s</pre>', `df -h /`);
$msg .= "<b>RAM(free):</b>";
$msg .= sprintf('<pre style="font-family: monospace;">%s</pre>', `free -h`);
$msg .= "<b>CPU(actual load avg.,5min,10min,currently running processes,last PID):</b>";
$msg .= sprintf('<pre style="font-family: monospace;">%s</pre>', `cat /proc/loadavg`);
To get more details of disk IO, use iostat -x. Again, you want to give it a sampling interval, and ignore the first set of output. iostat also gives you some cpu information but top does that better; let's focus on the Device section:
Device: rrqm/s wrqm/s r/s w/s rsec/s wsec/s avgrq-sz avgqu-sz await svctm %util
sda 9.80 0.20 36.60 0.40 5326.40 4.80 144.09 0.06 1.62 1.41 5.20
There are 3 easy ways to tell if a disk is a probable bottleneck here, and none of them show up without the -x flag, so get in the habit of using that. "avgqu-sz" is the size of the io request queue; if it is large, there are lots of requests waiting in line. "await" is how long (in ms) the average request took to be satisfied (including time enqueued); recall that on non-SSDs, a single seek is between 5 and 10ms. Finally, "%util" is Linux's guess at how fully saturated the device is.
To learn more about per-process CPU and RAM usage, use "top." I won't paste top output here because everyone is so familiar with it, but I will mention a few useful things to know: "P" and "M" toggle between sorting by cpu usage and sorting by memory usage "1" toggles breaking down the CPU summary by CPU core SHR (shared memory) is included in RES (resident memory) Amount of memory belonging to a process that has been swapped out is VIRT - RES a state (S column) of D means the process (or thread, see below) is waiting for disk or network i/o "steal" is how much CPU the hypervisor is giving to another VM in a virtual environment; as virtual provisioning becomes more common, avoiding noisy neighbors is increasingly important
VIRT stands for the virtual size of a process, which is the sum of memory it is actually using, memory it has mapped into itself (for instance the video card's RAM for the X server), files on disk that have been mapped into it (most notably shared libraries), and memory shared with other processes. VIRT represents how much memory the program is able to access at the present moment.
RES stands for the resident size, which is an accurate representation of how much actual physical memory a process is consuming. (This also corresponds directly to the %MEM column.) This will virtually always be less than the VIRT size, since most programs depend on the C library.
SHR indicates how much of the VIRT size is actually sharable (memory or libraries). In the case of libraries, it does not necessarily mean that the entire library is resident. For example, if a program only uses a few functions in a library, the whole library is mapped and will be counted in VIRT and SHR, but only the parts of the library file containing the functions being used will actually be loaded in and be counted under RES.
is your server is swapping? run vmstat with "vmstat sampling-period", e.g.,
vmstat -SM 5
output:
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu----- r b swpd free buff cache si so bi bo in cs us sy id wa st 1 0 0 4428 317 1345 0 0 96 71 199 776 10 2 88 1 0 0 0 0 4428 317 1345 0 0 0 0 225 414 0 0 99 1 0
The first line is your total system average since boot; typically this will not be very useful, since you are interested in what is causing problems NOW. Then you will get one line per sample period; most of the output is self explanatory. The reason to start with vmstat is the "swap" section: si and so are swap in (memory read from disk) and swap out (memory written to disk). si (swap in) and so (swap out). Remember that a little swapping is normal, by default, Linux will swap infrequently used pages of application memory to disk to free up more room for disk caching, even if there is enough ram to accommodate all applications. Numbers in the hundreds or thousands indicate your server is swapping heavily. This consumes a lot of CPU and other server resources and you would get a very (!) significant benefit from adding more memory to your server.
The bi (bytes in) and bo (bytes out) column show disk I/O (including swapping memory to/from disk) on your server.
The us (user), sy (system) and id (idle) show the amount of CPU your server is using. The higher the idle value, the better.
cat /proc/acpi/thermal_zone/THRM/temperature acpi -t
Kill processes that have been running for more than a week
find /proc -user myuser -maxdepth 1 -type d -mtime +7 -exec basename {} \; | xargs kill -9
encript file
openssl des3 -salt -in unencrypted-data.tar -out encrypted-data.tar.des3 gpg --allow-multiple-messages --decrypt-files *
concatenate avi files
avimerge -o output.avi -i file1.avi file2.avi file3.avi
free -h top cat /proc/meminfo
The Linux free command extracts and formats pertinent information from the meminfo file and displays it as follows:
free -h free -mot free -mt
look at is the buffers/cache row used value:This is how much space your applications are currently using. Linux likes to use any spare memory to cache disk blocks(colonna "cached")
ps aux --sort -rss
ps legge la memoria usata dai singoli processi, con l'opzione --sort si indicano campi per cui ordinare, separati da virgola, +/- per ordinamento ascendente discendente
Find Out The Top 10 Memory Consuming Process
ps -auxf | sort -nr -k 4 | head -10
comando linux per monitorare il server:
cat /proc/loadavg 0.22 0.12 0.09 1/68 12621
first three columns measure the CPU and IO utilization( actual, five and 10 minute periods ). The fourth column shows the number of currently running processes and the total number of processes. The last column displays the last process ID used.
Find Out top 10 CPU Consuming Process
ps -auxf | sort -nr -k 3 | head -10
tecnica spiegata da Rasmuss a verona 2009, permette di verificare le operazioni + lente effettuate da un programma come php
Each line in the trace contains the system call name, followed by its arguments in parentheses and its return value.
Run strace against /bin/foo and capture its output to a text file in output.txt:
strace -o output.txt /bin/foo
You can strace the webserver process and see what it's doing. For example, strace php5 fastcgi process, enter:
strace -p 22254 -s 80 -o /tmp/debug.lighttpd.txt
To see only a trace of the open, read system calls, enter :
strace -e trace=open,read -p 22254 -s 80 -o debug.webserver.txt
files aperti da un programma
strace -e trace=open mc
-o filename : Write the trace output to the file filename rather than to screen (stderr).
-p PID : Attach to the process with the process ID pid and begin tracing. The trace may be terminated at any time by a keyboard interrupt signal (hit CTRL-C). strace will respond by detaching itself from the traced process(es) leaving it (them) to continue running. Multiple -p options can be used to attach to up to 32 processes in addition to command (which is optional if at least one -p option is given).
-s SIZE : Specify the maximum string size to print (the default is 32).
w command displays information about the users currently on the machine, and their processes.
w <username>
uptime
w
Hot Key Usage
t Displays summary information off and on.
m Displays memory information
p Display Processor information
A Sorts the display by top consumers of various system resources. Useful for quick identification of performance-hungry tasks on a system.
f Enters an interactive configuration screen for top. Helpful for setting up top for a specific task.
o Enables you to interactively select the ordering within top.
r Issues renice command.
k Issues kill command.
z Turn on or off color/mono
vmstat reports information about processes, memory, paging, block IO, traps, and cpu activity.
vmstat 3
Display Memory Utilization Slabinfo
vmstat -m
Get Information About Active / Inactive Memory Pages
vmstat -a
Find Out Who Is Logged on And What They Are Doing w command displays information about the users currently on the machine, and their processes.
w <username>
iostat - Average CPU Load, Disk Activity The command iostat report Central Processing Unit (CPU) statistics and input/output statistics for devices, partitions and network filesystems (NFS).
iostat
sar command is used to collect, report, and save system activity information. To see network counter, enter:
sar -n DEV | more
To display the network counters from the 24th:
sar -n DEV -f /var/log/sa/sa24 | more
You can also display real time usage using sar:
sar 4 5
spazio disponibile
df -m
spazio usato
du -sh .
molti programmi riferiscono del loro funzionamento a root via email aggiungi un alias di posta per il tuo utente per ricevere al posta inviata a root
nano /etc/aliases root: myuser # root: test@test.com # run update newaliases # reload smtp service postfix restart # test msg echo test | mail -s "test message" root@domain.com
# To run a daemon or any command as root before login, add it to /etc/rc.local @see /etc/init.d/skeleton # ~/.bash_profile will run a command after login # ~/.bashrc will be executed by login shells only # a cron job with @reboot as its time field
date time zone
for t in America/New_York Australia/Perth Japan Asia/Kolkata; do zdump ${t}; done
ffmpeg -y -ss 30 -t 3 -i video1.mkv \ -vf fps=10,scale=320:-1:flags=lanczos,palettegen palette.png ffmpeg -ss 30 -t 3 -i video1.mkv -i palette.png -filter_complex \ "fps=10,scale=320:-1:flags=lanczos[x];[x][1:v]paletteuse" video1.gif
monitor change of file and exec a program each time a file is modified
BASE_DIR=$(cd $(dirname "$0"); pwd)/.. inotifywait -e close_write -m $BASE_DIR/public/* | while read -r directory events filename; do #echo "$filename change!"; $BASE_DIR/bin/compile file $filename done
Partita Iva: 02360450205
Content of this site is licensed under Creative Commons Attribution-Share Alike License.
