Waxaan kooras ku qaadanayay Linux dhowrkii bilood ee la soo dhaafay iyo hal dhinac oo Linux ah oo had iyo jeer igu wareeray waxay ahayd sida rukhsadyadu u shaqeeyaan. Tusaale ahaan, markii aan fayl galiyay server-kayga hal mar oo uu khalad galay, waxa ii sheegay martigaliyahaygii webka inaan u beddelo oggolaanshaha faylka 755.

Maan garanayn waxa ay taasi ka dhigan tahay, in kasta oo beddelidda oggolaanshaha ay xalisay dhibaatada. Hadda waxaan xaqiiqsaday ogolaanshaha Linux inaysan ahayn kuwa adag, kaliya waa inaad fahanto nidaamka. Maqaalkan, waxaan uga hadli doonaa rukhsadaha Linux heer sare ah waxaanan ku tusi doonaa sida loo isticmaalo amarka chmod si aad u bedesho ogolaanshaha faylalka iyo faylalka.

Oggolaanshaha Linux & Heerarka

Linux , waxaa jira asal ahaan saddex rukhsad oo aad sida caadiga ah ka walwali doonto: akhri, qor oo ful. Dhammaan saddexdan waa kuwo is-sharaxaya. Hadda marka oggolaanshahan lagu dabaqo faylka, waxaa lagu dabaqaa heerar.

Linux waxaa ka jira saddex heer oo ogolaansho : mulkiilaha, kooxda iyo kuwa kale. Milkiilaha waa isticmaalaha leh faylka/folderka, kooxda waxaa ku jira isticmaalayaasha kale ee kooxda faylka iyo kuwa kale oo kaliya waxay matalaan dhammaan isticmaalayaasha kale ee aan ahayn mulkiilaha ama kooxda.

Akhri^(Read) , qor oo ful waxay u taagan yihiin xarfo calaamad ah ama tiro octal ah. Tusaale ahaan, haddii aad ku samayso ls -l hage wata faylal qaar, waxaad arki doontaa astaanta astaanta u ah ogolaanshaha.

Oggolaanshaha waxaa loo qoraa sida soo socota: qaybta ugu horeysa waa xaraf ama xarafka d. Dash macnaheedu waa fayl iyo d waxay u taagan tahay hagaha. Ogow in qaybta ugu horreysa ay sidoo kale noqon karto l haddii magaca faylka uu yahay xiriiriye. Marka xigta, waxaa jira saddex kooxood oo saddex qaybood ah. Qaybta hore ee koox kasta waa wax akhriyi, ka labaadna waa wax qori, ka saddexaadna waa fulinta. Saddexda xabbo ee hore waxaa leh milkiilaha, saddexda xabbadood ee labaadna waxaa leh kooxda, saddexda xabbadoodna waa kuwa kale. Halkan waxaa ah sharraxaad muuqaal ah oo dheeraad ah.

Haddii aad ku aragto meel xaraf ku taal, waxay la macno tahay in mulkiilaha, kooxda ama dhammaan isticmaalayaasha kale aysan haysan oggolaanshahaas. Tusaalaha kore, mulkiilaha, kooxda iyo qof kasta oo kale ayaa akhriyay qor oo fuliyay oggolaanshaha.

Haddii aad eegto wax-soo-saarka amarka ls-l, waxaad ogaan doontaa in faylkayga qoraalka ah uu leeyahay oggolaanshaha soo socda:

-rw-rw-rw-

Tani waxay ka dhigan tahay in qof walba uu haysto ogolaanshaha wax-akhrinta/qorista ee faylka. Waa kan tusaale kale:

drwxr--r--

Marka la eego qaybta hore, waxaan arki karnaa in ogolanshiyaha loogu talagalay hagaha. Mulkiiluhu waxa uu haystaa ogolaanshaha wax-akhrinta/qorista/fulinta, laakiin kooxda iyo isticmaalayaasha kale waxa ay haystaan ​​ogolaansho wax-akhris oo kaliya.

Matalaadda Number Octal

Markaa taasi waa sida ogolaanshaha loogu soo bandhigo Linux iyadoo la adeegsanayo calaamado. Habka labaad ee lagu matali karo ogolaanshaha isku mid ah waa iyadoo la isticmaalayo tirooyinka octal. Marka aan isticmaalno amarka chmod hadhow, waxaad arki doontaa inaad bedeli karto oggolaanshaha adoo isticmaalaya calaamado ama lambaro octal ah.

Marka sidee Linux u matashaa akhrinta, qorista iyo fulinta iyadoo la adeegsanayo tirooyinka octal? Asal ahaan, waxa ay kaliya ku wareejinaysaa lambar ogolaansho kasta sida hoos ku cad.

Ogolaanshaha akhrinta waxaa matalaya 4, qor 2 oo fuliya 1. Waxa kaliya ee ay tahay inaad sameyso waa inaad ku darto iyaga si aad u hesho ogolaanshaha octal. Tusaale ahaan, aan soo qaadanno tusaalaha sare ee uu qof kastaa haysto dhammaan oggolaanshaha:

-rwxrwxrwx

Mulkiiluhu wuxuu leeyahay rwx, markaa waxaanu ku dari doonaa 4 + 2 + 1 si aan u helno qiimaha 7. Waxaan u samaynaa wax la mid ah kooxda iyo wax la mid ah kuwa kale. Qiimaha ugu dambeeya ee octal waa 777. Aynu eegno tusaalaha halka aan kaliya ku siinnay ogolaanshaha wax-akhris/qorista:

-rw-rw-rw-

Lambarka octal ee ugu horreeya wuxuu noqon doonaa 4 + 2 tan iyo markii aan ku darayno akhri iyo qor. Midka labaad wuxuu la mid noqon doonaa lambarka octal ee saddexaad. Halkan waxaan ku haynaa qiimaha ugu dambeeya ee 666.

Haddaba hadda aan isku dayno si kale. Waxaad dhahdaa waxaan rabnaa inaan ogaano waxa ogolaanshaha 755 u taagan yahay? Hagaag, way fududahay in la ogaado haddii aad ku jebiso lambarada gaarka ah. Lambarka koowaad waa 7, kaas oo aan ku heli karno kaliya in lagu daro 4 + 2 + 1, taasoo la micno ah in mulkiiluhu uu akhriyay/qoray/fuliyay ogolaansho. Shan waxaa lagu heli karaa oo kaliya in lagu daro 4 + 1, taasoo la macno ah kooxda iyo isticmaalayaasha kale ayaa akhriyay oo fuliyay rukhsad.

Waxaan rajeyneynaa^(Hopefully) , taasi waa sharraxaad wanaagsan oo ku saabsan sida loogu matalo oggolaanshaha Linux iyadoo la adeegsanayo lambarrada octal. Guud ahaan waa mid toosan.

Isticmaalka chmod si wax looga beddelo oggolaanshaha

Hadda oo aan fahamnay sida loo akhriyo oggolaanshaha, aan ka hadalno sida aan u beddeli karno. Isticmaalka ugu fudud ee ujeedadan loo isticmaalo waa amarka chmod. Waa kan sida ay u shaqeyso Habka ugu wanaagsan ee lagu sharxi karo amarka waa in la maro tusaale.

Aan ku bilowno ogolaanshaha aan kor kaga soo hadalnay, kuwaas oo kala ah:

-rw-rw-rw-

Haddii aan rabno inaan ku darno oggolaanshaha fulinta mulkiilaha, kooxda iyo kuwa kale, waxaan u mari karnaa laba siyaabood. Waxaan isticmaali karnaa habka astaanta ama habka octal-ka. Habka astaanta, waxaanu samayn doonaa kuwan soo socda, sida hoos ku cad:

Amarka saxda ah waa

chmod a+x filename

Hal-ku - ^(–) + waa sida soo socota: xarafka ama xarfaha matalaya milkiilaha ( u ), kooxda ( g ), kale ( o ) ama dhammaan ( a ) oo ay ku xigto ogolaanshaha ( r u akhrinta, w qorista iyo x fulinta).

Tusaalaha kore, waxaan ku daray oggolaanshaha fulinta dhammaan isticmaalayaasha. Natiijada sida aad ku arki karto sawirka kore waa x mulkiilaha, kooxda iyo kuwa kale. Hadda aan nidhaahno waxaan rabay inaan ka saaro qoraalka oo aan fuliyo ogolaanshaha kooxda iyo isticmaalayaasha kale.

Sida aad halkan ku arki karto, waxaan isticmaalay amarka soo socda si aan tan u fuliyo:

chmod go-wx filename

Maadaama aan rabo inaan beddelo oggolaanshaha kooxda iyo kuwa kale, waxaan isticmaalaa xarafka g iyo xarafka o . Waxaan rabaa inaan meesha ka saaro oggolaanshaha, markaa waxaan isticmaalaa calaamadda^(–) . Ugu dambeyntii, waxaan rabaa in aan meesha ka saaro qoraalka oo aan fuliyo ogolaanshaha, markaa waxaan isticmaalaa w iyo x . Halkan waxaa ah miis yar oo anfacaya oo loogu talagalay isticmaalka astaanta:

Markaa taasi waa waxa kaliya ee jira in la isticmaalo habka astaanta. Hadda aan ka hadalno habka octal, kaas oo aan u arko inuu yara fudud yahay. Octal waa fiican sababtoo ah waxaad ku dari kartaa ama ka saari kartaa oggolaanshaha dhammaan hal mar.

Haddii aan ku bilowno oggolaanshaha soo socda faylka, aan aragno sida aan u beddeli karno iyaga oo isticmaalaya habka octal:

-rw-rw-rw-

Kor^(Above) , waxaad arki kartaa inaan adeegsaday amarka soo socda:

chmod 744 filename

Tani waxay asal ahaan odhanaysaa mulkiiluhu wuxuu helayaa ogolaanshaha wax-akhrinta/qorista/fulinta kooxda iyo kuwa kaleba waxay helayaan ogolaanshaha wax-akhrinta oo kaliya. Sida aad arki karto, way fududahay in lagu daro ama laga saaro ogolaanshaha hal amar oo fudud. Aan sii wadno oo nidhaahno waxaan rabaa inaan beddelo oggolaanshaha mar kale.

Hadda waxaan adeegsaday amarkan soo socda, mar kale mid aad u fudud:

chmod 640 filename

Halkan waxaan ku siinay mulkiilaha ogolaanshaha wax-akhrinta/qorista, kooxda wax-akhrinta oo kaliya iyo kooxda kale wax ogolaansho ah. Waxaad isticmaashaa eber si aad u muujiso ogolaansho la'aan. Aad u fudud, eh?

Gebagebadii, tani waa dulmar aad u fudud oo ku saabsan rukhsadaha Linux waxayna ka heli kartaa wax aad uga dhib badan tan, laakiin kuwa bilowga ah, waa meel fiican oo laga bilaabo. Waxaan soo dhejin doonaa maqaalo badan oo ku saabsan ogolaanshaha horumarsan mustaqbalka. Haddii aad wax su'aalo ah qabtid, xor u noqo inaad faallo ka bixiso. Ku raaxayso!

Understanding Linux Permissions and chmod Usage

I’ve been taking a course on Linux for the laѕt few months and оne aspect of Linux that always confused me was how permіssions wоrked. For example, when uploading a file to my web server once аnd getting an error, I was told by my web hоst to change thе file permissions to 755.

I had no clue what that meant, even though changing the permissions fixed the problem. I’ve now realized Linux permissions aren’t all that complicated, you just have to understand the system. In this article, I’ll talk about Linux permissions on a high-level and show you how to use the chmod command to change permissions for files and folders.

Linux Permissions & Levels

In Linux, there are basically three permissions that you will normally have to worry about: read, write and execute. All three of these are pretty self-explanatory. Now when these permissions are applied to a file, they are applied in levels.

There are three levels of permissions in Linux: owner, group and other. The owner is the user who owns the file/folder, the group includes other users in the file’s group and other just represents all other users who are not the owner or in the group.

Read, write and execute are represented as either symbolic characters or as octal numbers. For example, if you do a ls -l in a directory with some files, you’ll see the symbolic character representation of the permissions.

The permissions are written as follows: the first bit is either a dash or the letter d. Dash means it’s a file and d stands for directory. Note that the first bit can also be an l if the file name is a link. Next, there are three groups of three bits. The first bit in each group is for read, the second bit is for write and the third bit is for execute. The first three bits are for the owner, the second three bits are for the group and the third three bits are for other. Here’s a more visual explanation.

If you see a dash in place of a letter, it means that the owner, group or all other users do not have that permission. In the example above, the owner, group and everyone else has read write and execute permissions.

If you look at the output from the ls -l command, you’ll notice that my practice text file has the following permissions:

-rw-rw-rw-

This means that everyone only has read/write permissions for the file. Here’s another example:

drwxr--r--

Looking at the first bit, we can see that the permissions are for a directory. The owner has read/write/execute permissions, but the group and other users only have read permission.

Octal Number Representation

So that’s how permissions are displayed in Linux using symbols. The second way to represent the same permissions is by using octal numbers. When we use the chmod command later on, you’ll see that you can change the permissions using either symbols or octal numbers.

So how does Linux represent read, write and execute using octal numbers? Basically, it just assigns a number to each permission as shown below.

The read permission is represented by 4, write by 2 and execute by 1. All you have to do is add them up to get the octal permission. For example, let’s take the example above where everyone has all permissions:

-rwxrwxrwx

The owner has rwx, so we will add 4 + 2 + 1 to get a value of 7. We do the same thing for group and the same thing for other. The final octal value is 777. Let’s take a look at the example where we only gave read/write permissions:

-rw-rw-rw-

The first octal number will be 4 + 2 since we are adding read and write. The second one will be the same as will the third octal number. Here we have a final octal value of 666.

So now let’s try it the other way. Say we want to know what permissions 755 represents? Well, it’s pretty easy to figure out if you break it down by individual numbers. The first number is 7, which we can only get by adding 4 + 2 + 1, meaning the owner has read/write/execute permission. Five can only be gotten by adding 4 + 1, meaning the group and other users have read and execute permissions.

Hopefully, that’s a good explanation for how to represent permissions in Linux using octal numbers. It’s pretty straight-forward overall.

Using chmod to Modify Permissions

Now that we understand how to read permissions, let’s talk about how we can change them. The easiest utility to use for this purpose is the chmod command. Here’s how it works. The best way to explain the command is to go through an example.

Let’s start with the permissions we talked about above, namely:

-rw-rw-rw-

If we wanted to add the execute permission for owner, group and other, we could go about it in two ways. We could use the symbol method or the octal method. For the symbol method, we would do the following, as shown below:

The exact command is

chmod a+x filename

The syntax is as follows: the letter or letters representing the owner (u), group (g), other (o) or all (a) followed by a + for adding permissions or a – for taking away permissions and then the letter for the permission (r for read, w for write and x for execute).

In the above example, I added the execute permission for all users. The result as you can see in the screenshot above is an x for owner, group and other. Now let’s say I wanted to remove the write and execute permissions for only the group and other users.

As you can see here, I used to the following command to accomplish this:

chmod go-wx filename

Since I want to change the permissions for group and other, I use the letter g and the letter o. I want to remove permissions, so I use the – sign. Finally, I want to remove the write and execute permissions, so I use w and x. Here’s a handy little table for symbol usage:

So that’s all there is to using the symbol method. Now let’s talk about the octal method, which I find to be a bit easier. Octal is nice because you can add or remove permissions all in one go.

If we start with the following permissions on a file, let’s see how we can change them using the octal method:

-rw-rw-rw-

Above, you can see I used the following command:

chmod 744 filename

This basically says the owner gets read/write/execute permission and the group and other gets read permission only. As you can see, it’s easy to add or remove permissions in one simple command. Let’s keep going and say I want to change permissions again.

Now I used the following command, again a very simple one:

chmod 640 filename

Here we have given the owner read/write permissions, the group read permission only and the other group no permissions. You use a zero to denote no permissions. Pretty simple, eh?

In conclusion, this is a very simple overview of Linux permissions and it can get a lot more complicated than this, but for beginners, it’s a good place to start. I’ll be posting more articles on more advanced permissions in the future. If you have any questions, feel free to comment. Enjoy!

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